much of the compiler upgraded to new API

lib/std/crypto/tls/Client.zig

@@ -125,9 +125,9 @@ pub const Options = struct {
         /// Verify that the server certificate is authorized by a given ca bundle.
         bundle: Certificate.Bundle,
     },
-    /// If non-null, ssl secrets are logged to this file.  Creating such a log file allows
+    /// If non-null, ssl secrets are logged to this stream.  Creating such a log file allows
     /// other programs with access to that file to decrypt all traffic over this connection.
-    ssl_key_log_file: ?std.fs.File = null,
+    ssl_key_log_file: ?*std.io.BufferedWriter = null,
 };
 
 pub fn InitError(comptime Stream: type) type {

lib/std/io.zig

@@ -282,8 +282,6 @@ pub const Reader = GenericReader;
 pub const Writer = @import("io/Writer.zig");
 
 pub const AnyReader = @import("io/Reader.zig");
-/// Deprecated; to be removed after 0.14.0 is tagged.
-pub const AnyWriter = Writer;
 
 pub const SeekableStream = @import("io/seekable_stream.zig").SeekableStream;
 

lib/std/io/BufferedWriter.zig

@@ -663,9 +663,14 @@ pub fn printValue(
             }
         },
         .error_set => {
-            if (actual_fmt.len != 0) invalidFmtError(fmt, value);
+            if (actual_fmt.len > 0 and actual_fmt.len[0] == 's') {
+                return bw.writeAll(@errorName(value));
+            } else if (actual_fmt.len != 0) {
+                invalidFmtError(fmt, value);
+            } else {
                 try bw.writeAll("error.");
                 return bw.writeAll(@errorName(value));
+            }
         },
         .@"enum" => |enumInfo| {
             try bw.writeAll(@typeName(T));

lib/std/tar.zig

@@ -603,9 +603,10 @@ fn PaxIterator(comptime ReaderType: type) type {
             return null;
         }
 
-        fn readUntil(self: *Self, delimiter: u8) ![]const u8 {
+        fn readUntil(self: *Self, delimiter: u8) anyerror![]const u8 {
-            var fbs: std.io.FixedBufferStream = .{ .buffer = &self.scratch };
+            var fbs: std.io.BufferedWriter = undefined;
-            try self.reader.streamUntilDelimiter(fbs.writer(), delimiter, null);
+            fbs.initFixed(&self.scratch);
+            try self.reader.streamUntilDelimiter(&fbs, delimiter, null);
             return fbs.getWritten();
         }
 

lib/std/zig/Ast.zig

@@ -199,27 +199,24 @@ pub fn parse(gpa: Allocator, source: [:0]const u8, mode: Mode) Allocator.Error!A
 
 /// `gpa` is used for allocating the resulting formatted source code.
 /// Caller owns the returned slice of bytes, allocated with `gpa`.
-pub fn render(tree: Ast, gpa: Allocator) RenderError![]u8 {
+pub fn renderAlloc(tree: Ast, gpa: Allocator) RenderError![]u8 {
-    var buffer = std.ArrayList(u8).init(gpa);
+    var aw: std.io.AllocatingWriter = undefined;
-    defer buffer.deinit();
+    const bw = aw.init(gpa);
+    errdefer aw.deinit();
+    render(tree, gpa, bw, .{}) catch |err| return @errorCast(err); // TODO try @errorCast(...)
+    return aw.toOwnedSlice();
+}
 
-    try tree.renderToArrayList(&buffer, .{});
+pub fn render(tree: Ast, gpa: Allocator, bw: *std.io.BufferedWriter, fixups: Fixups) anyerror!void {
-    return buffer.toOwnedSlice();
+    return @import("./render.zig").renderTree(gpa, bw, tree, fixups);
 }
 
 pub const Fixups = private_render.Fixups;
 
-pub fn renderToArrayList(tree: Ast, buffer: *std.ArrayList(u8), fixups: Fixups) RenderError!void {
-    return @import("./render.zig").renderTree(buffer, tree, fixups);
-}
-
 /// Returns an extra offset for column and byte offset of errors that
 /// should point after the token in the error message.
 pub fn errorOffset(tree: Ast, parse_error: Error) u32 {
-    return if (parse_error.token_is_prev)
+    return if (parse_error.token_is_prev) @intCast(tree.tokenSlice(parse_error.token).len) else 0;
-        @as(u32, @intCast(tree.tokenSlice(parse_error.token).len))
-    else
-        0;
 }
 
 pub fn tokenLocation(self: Ast, start_offset: ByteOffset, token_index: TokenIndex) Location {
@@ -318,254 +315,254 @@ pub fn rootDecls(tree: Ast) []const Node.Index {
     }
 }
 
-pub fn renderError(tree: Ast, parse_error: Error, stream: anytype) !void {
+pub fn renderError(tree: Ast, parse_error: Error, bw: *std.io.BufferedWriter) anyerror!void {
     switch (parse_error.tag) {
         .asterisk_after_ptr_deref => {
             // Note that the token will point at the `.*` but ideally the source
             // location would point to the `*` after the `.*`.
-            return stream.writeAll("'.*' cannot be followed by '*'; are you missing a space?");
+            return bw.writeAll("'.*' cannot be followed by '*'; are you missing a space?");
         },
         .chained_comparison_operators => {
-            return stream.writeAll("comparison operators cannot be chained");
+            return bw.writeAll("comparison operators cannot be chained");
         },
         .decl_between_fields => {
-            return stream.writeAll("declarations are not allowed between container fields");
+            return bw.writeAll("declarations are not allowed between container fields");
         },
         .expected_block => {
-            return stream.print("expected block, found '{s}'", .{
+            return bw.print("expected block, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_block_or_assignment => {
-            return stream.print("expected block or assignment, found '{s}'", .{
+            return bw.print("expected block or assignment, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_block_or_expr => {
-            return stream.print("expected block or expression, found '{s}'", .{
+            return bw.print("expected block or expression, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_block_or_field => {
-            return stream.print("expected block or field, found '{s}'", .{
+            return bw.print("expected block or field, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_container_members => {
-            return stream.print("expected test, comptime, var decl, or container field, found '{s}'", .{
+            return bw.print("expected test, comptime, var decl, or container field, found '{s}'", .{
                 tree.tokenTag(parse_error.token).symbol(),
             });
         },
         .expected_expr => {
-            return stream.print("expected expression, found '{s}'", .{
+            return bw.print("expected expression, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_expr_or_assignment => {
-            return stream.print("expected expression or assignment, found '{s}'", .{
+            return bw.print("expected expression or assignment, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_expr_or_var_decl => {
-            return stream.print("expected expression or var decl, found '{s}'", .{
+            return bw.print("expected expression or var decl, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_fn => {
-            return stream.print("expected function, found '{s}'", .{
+            return bw.print("expected function, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_inlinable => {
-            return stream.print("expected 'while' or 'for', found '{s}'", .{
+            return bw.print("expected 'while' or 'for', found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_labelable => {
-            return stream.print("expected 'while', 'for', 'inline', or '{{', found '{s}'", .{
+            return bw.print("expected 'while', 'for', 'inline', or '{{', found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_param_list => {
-            return stream.print("expected parameter list, found '{s}'", .{
+            return bw.print("expected parameter list, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_prefix_expr => {
-            return stream.print("expected prefix expression, found '{s}'", .{
+            return bw.print("expected prefix expression, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_primary_type_expr => {
-            return stream.print("expected primary type expression, found '{s}'", .{
+            return bw.print("expected primary type expression, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_pub_item => {
-            return stream.writeAll("expected function or variable declaration after pub");
+            return bw.writeAll("expected function or variable declaration after pub");
         },
         .expected_return_type => {
-            return stream.print("expected return type expression, found '{s}'", .{
+            return bw.print("expected return type expression, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_semi_or_else => {
-            return stream.writeAll("expected ';' or 'else' after statement");
+            return bw.writeAll("expected ';' or 'else' after statement");
         },
         .expected_semi_or_lbrace => {
-            return stream.writeAll("expected ';' or block after function prototype");
+            return bw.writeAll("expected ';' or block after function prototype");
         },
         .expected_statement => {
-            return stream.print("expected statement, found '{s}'", .{
+            return bw.print("expected statement, found '{s}'", .{
                 tree.tokenTag(parse_error.token).symbol(),
             });
         },
         .expected_suffix_op => {
-            return stream.print("expected pointer dereference, optional unwrap, or field access, found '{s}'", .{
+            return bw.print("expected pointer dereference, optional unwrap, or field access, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_type_expr => {
-            return stream.print("expected type expression, found '{s}'", .{
+            return bw.print("expected type expression, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_var_decl => {
-            return stream.print("expected variable declaration, found '{s}'", .{
+            return bw.print("expected variable declaration, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_var_decl_or_fn => {
-            return stream.print("expected variable declaration or function, found '{s}'", .{
+            return bw.print("expected variable declaration or function, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_loop_payload => {
-            return stream.print("expected loop payload, found '{s}'", .{
+            return bw.print("expected loop payload, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .expected_container => {
-            return stream.print("expected a struct, enum or union, found '{s}'", .{
+            return bw.print("expected a struct, enum or union, found '{s}'", .{
                 tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev)).symbol(),
             });
         },
         .extern_fn_body => {
-            return stream.writeAll("extern functions have no body");
+            return bw.writeAll("extern functions have no body");
         },
         .extra_addrspace_qualifier => {
-            return stream.writeAll("extra addrspace qualifier");
+            return bw.writeAll("extra addrspace qualifier");
         },
         .extra_align_qualifier => {
-            return stream.writeAll("extra align qualifier");
+            return bw.writeAll("extra align qualifier");
         },
         .extra_allowzero_qualifier => {
-            return stream.writeAll("extra allowzero qualifier");
+            return bw.writeAll("extra allowzero qualifier");
         },
         .extra_const_qualifier => {
-            return stream.writeAll("extra const qualifier");
+            return bw.writeAll("extra const qualifier");
         },
         .extra_volatile_qualifier => {
-            return stream.writeAll("extra volatile qualifier");
+            return bw.writeAll("extra volatile qualifier");
         },
         .ptr_mod_on_array_child_type => {
-            return stream.print("pointer modifier '{s}' not allowed on array child type", .{
+            return bw.print("pointer modifier '{s}' not allowed on array child type", .{
                 tree.tokenTag(parse_error.token).symbol(),
             });
         },
         .invalid_bit_range => {
-            return stream.writeAll("bit range not allowed on slices and arrays");
+            return bw.writeAll("bit range not allowed on slices and arrays");
         },
         .same_line_doc_comment => {
-            return stream.writeAll("same line documentation comment");
+            return bw.writeAll("same line documentation comment");
         },
         .unattached_doc_comment => {
-            return stream.writeAll("unattached documentation comment");
+            return bw.writeAll("unattached documentation comment");
         },
         .test_doc_comment => {
-            return stream.writeAll("documentation comments cannot be attached to tests");
+            return bw.writeAll("documentation comments cannot be attached to tests");
         },
         .comptime_doc_comment => {
-            return stream.writeAll("documentation comments cannot be attached to comptime blocks");
+            return bw.writeAll("documentation comments cannot be attached to comptime blocks");
         },
         .varargs_nonfinal => {
-            return stream.writeAll("function prototype has parameter after varargs");
+            return bw.writeAll("function prototype has parameter after varargs");
         },
         .expected_continue_expr => {
-            return stream.writeAll("expected ':' before while continue expression");
+            return bw.writeAll("expected ':' before while continue expression");
         },
 
         .expected_semi_after_decl => {
-            return stream.writeAll("expected ';' after declaration");
+            return bw.writeAll("expected ';' after declaration");
         },
         .expected_semi_after_stmt => {
-            return stream.writeAll("expected ';' after statement");
+            return bw.writeAll("expected ';' after statement");
         },
         .expected_comma_after_field => {
-            return stream.writeAll("expected ',' after field");
+            return bw.writeAll("expected ',' after field");
         },
         .expected_comma_after_arg => {
-            return stream.writeAll("expected ',' after argument");
+            return bw.writeAll("expected ',' after argument");
         },
         .expected_comma_after_param => {
-            return stream.writeAll("expected ',' after parameter");
+            return bw.writeAll("expected ',' after parameter");
         },
         .expected_comma_after_initializer => {
-            return stream.writeAll("expected ',' after initializer");
+            return bw.writeAll("expected ',' after initializer");
         },
         .expected_comma_after_switch_prong => {
-            return stream.writeAll("expected ',' after switch prong");
+            return bw.writeAll("expected ',' after switch prong");
         },
         .expected_comma_after_for_operand => {
-            return stream.writeAll("expected ',' after for operand");
+            return bw.writeAll("expected ',' after for operand");
         },
         .expected_comma_after_capture => {
-            return stream.writeAll("expected ',' after for capture");
+            return bw.writeAll("expected ',' after for capture");
         },
         .expected_initializer => {
-            return stream.writeAll("expected field initializer");
+            return bw.writeAll("expected field initializer");
         },
         .mismatched_binary_op_whitespace => {
-            return stream.print("binary operator '{s}' has whitespace on one side, but not the other", .{tree.tokenTag(parse_error.token).lexeme().?});
+            return bw.print("binary operator '{s}' has whitespace on one side, but not the other", .{tree.tokenTag(parse_error.token).lexeme().?});
         },
         .invalid_ampersand_ampersand => {
-            return stream.writeAll("ambiguous use of '&&'; use 'and' for logical AND, or change whitespace to ' & &' for bitwise AND");
+            return bw.writeAll("ambiguous use of '&&'; use 'and' for logical AND, or change whitespace to ' & &' for bitwise AND");
         },
         .c_style_container => {
-            return stream.print("'{s} {s}' is invalid", .{
+            return bw.print("'{s} {s}' is invalid", .{
                 parse_error.extra.expected_tag.symbol(), tree.tokenSlice(parse_error.token),
             });
         },
         .zig_style_container => {
-            return stream.print("to declare a container do 'const {s} = {s}'", .{
+            return bw.print("to declare a container do 'const {s} = {s}'", .{
                 tree.tokenSlice(parse_error.token), parse_error.extra.expected_tag.symbol(),
             });
         },
         .previous_field => {
-            return stream.writeAll("field before declarations here");
+            return bw.writeAll("field before declarations here");
         },
         .next_field => {
-            return stream.writeAll("field after declarations here");
+            return bw.writeAll("field after declarations here");
         },
         .expected_var_const => {
-            return stream.writeAll("expected 'var' or 'const' before variable declaration");
+            return bw.writeAll("expected 'var' or 'const' before variable declaration");
         },
         .wrong_equal_var_decl => {
-            return stream.writeAll("variable initialized with '==' instead of '='");
+            return bw.writeAll("variable initialized with '==' instead of '='");
         },
         .var_const_decl => {
-            return stream.writeAll("use 'var' or 'const' to declare variable");
+            return bw.writeAll("use 'var' or 'const' to declare variable");
         },
         .extra_for_capture => {
-            return stream.writeAll("extra capture in for loop");
+            return bw.writeAll("extra capture in for loop");
         },
         .for_input_not_captured => {
-            return stream.writeAll("for input is not captured");
+            return bw.writeAll("for input is not captured");
         },
 
         .invalid_byte => {
             const tok_slice = tree.source[tree.tokens.items(.start)[parse_error.token]..];
-            return stream.print("{s} contains invalid byte: '{'}'", .{
+            return bw.print("{s} contains invalid byte: '{'}'", .{
                 switch (tok_slice[0]) {
                     '\'' => "character literal",
                     '"', '\\' => "string literal",
@@ -580,10 +577,10 @@ pub fn renderError(tree: Ast, parse_error: Error, stream: anytype) !void {
             const found_tag = tree.tokenTag(parse_error.token + @intFromBool(parse_error.token_is_prev));
             const expected_symbol = parse_error.extra.expected_tag.symbol();
             switch (found_tag) {
-                .invalid => return stream.print("expected '{s}', found invalid bytes", .{
+                .invalid => return bw.print("expected '{s}', found invalid bytes", .{
                     expected_symbol,
                 }),
-                else => return stream.print("expected '{s}', found '{s}'", .{
+                else => return bw.print("expected '{s}', found '{s}'", .{
                     expected_symbol, found_tag.symbol(),
                 }),
             }

lib/std/zig/AstGen.zig

@@ -11441,10 +11441,13 @@ fn parseStrLit(
     offset: u32,
 ) InnerError!void {
     const raw_string = bytes[offset..];
-    var buf_managed = buf.toManaged(astgen.gpa);
+    const result = r: {
-    const result = std.zig.string_literal.parseWrite(buf_managed.writer(), raw_string);
+        var aw: std.io.AllocatingWriter = undefined;
-    buf.* = buf_managed.moveToUnmanaged();
+        const bw = aw.fromArrayList(astgen.gpa, buf);
-    switch (try result) {
+        defer buf.* = aw.toArrayList();
+        break :r std.zig.string_literal.parseWrite(bw, raw_string) catch |err| return @errorCast(err);
+    };
+    switch (result) {
         .success => return,
         .failure => |err| return astgen.failWithStrLitError(err, token, bytes, offset),
     }
@@ -11493,17 +11496,18 @@ fn appendErrorNodeNotes(
     notes: []const u32,
 ) Allocator.Error!void {
     @branchHint(.cold);
+    const gpa = astgen.gpa;
     const string_bytes = &astgen.string_bytes;
     const msg: Zir.NullTerminatedString = @enumFromInt(string_bytes.items.len);
-    try string_bytes.writer(astgen.gpa).print(format ++ "\x00", args);
+    try string_bytes.print(gpa, format ++ "\x00", args);
     const notes_index: u32 = if (notes.len != 0) blk: {
         const notes_start = astgen.extra.items.len;
-        try astgen.extra.ensureTotalCapacity(astgen.gpa, notes_start + 1 + notes.len);
+        try astgen.extra.ensureTotalCapacity(gpa, notes_start + 1 + notes.len);
         astgen.extra.appendAssumeCapacity(@intCast(notes.len));
         astgen.extra.appendSliceAssumeCapacity(notes);
         break :blk @intCast(notes_start);
     } else 0;
-    try astgen.compile_errors.append(astgen.gpa, .{
+    try astgen.compile_errors.append(gpa, .{
         .msg = msg,
         .node = node.toOptional(),
         .token = .none,
@@ -11587,7 +11591,7 @@ fn appendErrorTokNotesOff(
     const gpa = astgen.gpa;
     const string_bytes = &astgen.string_bytes;
     const msg: Zir.NullTerminatedString = @enumFromInt(string_bytes.items.len);
-    try string_bytes.writer(gpa).print(format ++ "\x00", args);
+    try string_bytes.print(gpa, format ++ "\x00", args);
     const notes_index: u32 = if (notes.len != 0) blk: {
         const notes_start = astgen.extra.items.len;
         try astgen.extra.ensureTotalCapacity(gpa, notes_start + 1 + notes.len);
@@ -11623,7 +11627,7 @@ fn errNoteTokOff(
     @branchHint(.cold);
     const string_bytes = &astgen.string_bytes;
     const msg: Zir.NullTerminatedString = @enumFromInt(string_bytes.items.len);
-    try string_bytes.writer(astgen.gpa).print(format ++ "\x00", args);
+    try string_bytes.print(astgen.gpa, format ++ "\x00", args);
     return astgen.addExtra(Zir.Inst.CompileErrors.Item{
         .msg = msg,
         .node = .none,
@@ -11642,7 +11646,7 @@ fn errNoteNode(
     @branchHint(.cold);
     const string_bytes = &astgen.string_bytes;
     const msg: Zir.NullTerminatedString = @enumFromInt(string_bytes.items.len);
-    try string_bytes.writer(astgen.gpa).print(format ++ "\x00", args);
+    try string_bytes.print(astgen.gpa, format ++ "\x00", args);
     return astgen.addExtra(Zir.Inst.CompileErrors.Item{
         .msg = msg,
         .node = node.toOptional(),
@@ -13888,13 +13892,14 @@ fn emitDbgStmtForceCurrentIndex(gz: *GenZir, lc: LineColumn) !void {
     } });
 }
 
-fn lowerAstErrors(astgen: *AstGen) !void {
+fn lowerAstErrors(astgen: *AstGen) error{OutOfMemory}!void {
     const gpa = astgen.gpa;
     const tree = astgen.tree;
     assert(tree.errors.len > 0);
 
-    var msg: std.ArrayListUnmanaged(u8) = .empty;
+    var msg: std.io.AllocatingWriter = undefined;
-    defer msg.deinit(gpa);
+    const msg_writer = msg.init(gpa);
+    defer msg.deinit();
 
     var notes: std.ArrayListUnmanaged(u32) = .empty;
     defer notes.deinit(gpa);
@@ -13928,20 +13933,20 @@ fn lowerAstErrors(astgen: *AstGen) !void {
             .extra = .{ .offset = bad_off },
         };
         msg.clearRetainingCapacity();
-        try tree.renderError(err, msg.writer(gpa));
+        tree.renderError(err, msg_writer) catch |e| return @errorCast(e); // TODO try @errorCast(...)
-        return try astgen.appendErrorTokNotesOff(tok, bad_off, "{s}", .{msg.items}, notes.items);
+        return try astgen.appendErrorTokNotesOff(tok, bad_off, "{s}", .{msg.getWritten()}, notes.items);
     }
 
     var cur_err = tree.errors[0];
     for (tree.errors[1..]) |err| {
         if (err.is_note) {
-            try tree.renderError(err, msg.writer(gpa));
+            tree.renderError(err, msg_writer) catch |e| return @errorCast(e); // TODO try @errorCast(...)
-            try notes.append(gpa, try astgen.errNoteTok(err.token, "{s}", .{msg.items}));
+            try notes.append(gpa, try astgen.errNoteTok(err.token, "{s}", .{msg.getWritten()}));
         } else {
             // Flush error
             const extra_offset = tree.errorOffset(cur_err);
-            try tree.renderError(cur_err, msg.writer(gpa));
+            tree.renderError(cur_err, msg_writer) catch |e| return @errorCast(e); // TODO try @errorCast(...)
-            try astgen.appendErrorTokNotesOff(cur_err.token, extra_offset, "{s}", .{msg.items}, notes.items);
+            try astgen.appendErrorTokNotesOff(cur_err.token, extra_offset, "{s}", .{msg.getWritten()}, notes.items);
             notes.clearRetainingCapacity();
             cur_err = err;
 
@@ -13954,8 +13959,8 @@ fn lowerAstErrors(astgen: *AstGen) !void {
 
     // Flush error
     const extra_offset = tree.errorOffset(cur_err);
-    try tree.renderError(cur_err, msg.writer(gpa));
+    tree.renderError(cur_err, msg_writer) catch |e| return @errorCast(e); // TODO try @errorCast(...)
-    try astgen.appendErrorTokNotesOff(cur_err.token, extra_offset, "{s}", .{msg.items}, notes.items);
+    try astgen.appendErrorTokNotesOff(cur_err.token, extra_offset, "{s}", .{msg.getWritten()}, notes.items);
 }
 
 const DeclarationName = union(enum) {

lib/std/zig/ZonGen.zig

@@ -452,20 +452,27 @@ fn expr(zg: *ZonGen, node: Ast.Node.Index, dest_node: Zoir.Node.Index) Allocator
     }
 }
 
-fn appendIdentStr(zg: *ZonGen, ident_token: Ast.TokenIndex) !u32 {
+fn appendIdentStr(zg: *ZonGen, ident_token: Ast.TokenIndex) error{ OutOfMemory, BadString }!u32 {
+    const gpa = zg.gpa;
     const tree = zg.tree;
     assert(tree.tokenTag(ident_token) == .identifier);
     const ident_name = tree.tokenSlice(ident_token);
     if (!mem.startsWith(u8, ident_name, "@")) {
         const start = zg.string_bytes.items.len;
-        try zg.string_bytes.appendSlice(zg.gpa, ident_name);
+        try zg.string_bytes.appendSlice(gpa, ident_name);
         return @intCast(start);
-    } else {
+    }
     const offset = 1;
     const start: u32 = @intCast(zg.string_bytes.items.len);
     const raw_string = zg.tree.tokenSlice(ident_token)[offset..];
-        try zg.string_bytes.ensureUnusedCapacity(zg.gpa, raw_string.len);
+    try zg.string_bytes.ensureUnusedCapacity(gpa, raw_string.len);
-        switch (try std.zig.string_literal.parseWrite(zg.string_bytes.writer(zg.gpa), raw_string)) {
+    const result = r: {
+        var aw: std.io.AllocatingWriter = undefined;
+        const bw = aw.fromArrayList(gpa, &zg.string_bytes);
+        defer zg.string_bytes = aw.toArrayList();
+        break :r std.zig.string_literal.parseWrite(bw, raw_string) catch |err| return @errorCast(err);
+    };
+    switch (result) {
         .success => {},
         .failure => |err| {
             try zg.lowerStrLitError(err, ident_token, raw_string, offset);
@@ -482,7 +489,6 @@ fn appendIdentStr(zg: *ZonGen, ident_token: Ast.TokenIndex) !u32 {
         return error.BadString;
     }
     return start;
-    }
 }
 
 /// Estimates the size of a string node without parsing it.
@@ -513,8 +519,8 @@ pub fn strLitSizeHint(tree: Ast, node: Ast.Node.Index) usize {
 pub fn parseStrLit(
     tree: Ast,
     node: Ast.Node.Index,
-    writer: anytype,
+    writer: *std.io.BufferedWriter,
-) error{OutOfMemory}!std.zig.string_literal.Result {
+) anyerror!std.zig.string_literal.Result {
     switch (tree.nodeTag(node)) {
         .string_literal => {
             const token = tree.nodeMainToken(node);
@@ -549,15 +555,21 @@ const StringLiteralResult = union(enum) {
     slice: struct { start: u32, len: u32 },
 };
 
-fn strLitAsString(zg: *ZonGen, str_node: Ast.Node.Index) !StringLiteralResult {
+fn strLitAsString(zg: *ZonGen, str_node: Ast.Node.Index) error{ OutOfMemory, BadString }!StringLiteralResult {
     if (!zg.options.parse_str_lits) return .{ .slice = .{ .start = 0, .len = 0 } };
 
     const gpa = zg.gpa;
     const string_bytes = &zg.string_bytes;
     const str_index: u32 = @intCast(zg.string_bytes.items.len);
     const size_hint = strLitSizeHint(zg.tree, str_node);
-    try string_bytes.ensureUnusedCapacity(zg.gpa, size_hint);
+    try string_bytes.ensureUnusedCapacity(gpa, size_hint);
-    switch (try parseStrLit(zg.tree, str_node, zg.string_bytes.writer(zg.gpa))) {
+    const result = r: {
+        var aw: std.io.AllocatingWriter = undefined;
+        const bw = aw.fromArrayList(gpa, &zg.string_bytes);
+        defer zg.string_bytes = aw.toArrayList();
+        break :r parseStrLit(zg.tree, str_node, bw) catch |err| return @errorCast(err);
+    };
+    switch (result) {
         .success => {},
         .failure => |err| {
             const token = zg.tree.nodeMainToken(str_node);
@@ -805,10 +817,7 @@ fn lowerNumberError(zg: *ZonGen, err: std.zig.number_literal.Error, token: Ast.T
 
 fn errNoteNode(zg: *ZonGen, node: Ast.Node.Index, comptime format: []const u8, args: anytype) Allocator.Error!Zoir.CompileError.Note {
     const message_idx: u32 = @intCast(zg.string_bytes.items.len);
-    const writer = zg.string_bytes.writer(zg.gpa);
+    try zg.string_bytes.print(zg.gpa, format ++ "\x00", args);
-    try writer.print(format, args);
-    try writer.writeByte(0);
-
     return .{
         .msg = @enumFromInt(message_idx),
         .token = .none,
@@ -818,10 +827,7 @@ fn errNoteNode(zg: *ZonGen, node: Ast.Node.Index, comptime format: []const u8, a
 
 fn errNoteTok(zg: *ZonGen, tok: Ast.TokenIndex, comptime format: []const u8, args: anytype) Allocator.Error!Zoir.CompileError.Note {
     const message_idx: u32 = @intCast(zg.string_bytes.items.len);
-    const writer = zg.string_bytes.writer(zg.gpa);
+    try zg.string_bytes.print(zg.gpa, format ++ "\x00", args);
-    try writer.print(format, args);
-    try writer.writeByte(0);
-
     return .{
         .msg = @enumFromInt(message_idx),
         .token = .fromToken(tok),
@@ -862,9 +868,7 @@ fn addErrorInner(
     try zg.error_notes.appendSlice(gpa, notes);
 
     const message_idx: u32 = @intCast(zg.string_bytes.items.len);
-    const writer = zg.string_bytes.writer(zg.gpa);
+    try zg.string_bytes.print(gpa, format ++ "\x00", args);
-    try writer.print(format, args);
-    try writer.writeByte(0);
 
     try zg.compile_errors.append(gpa, .{
         .msg = @enumFromInt(message_idx),
@@ -880,8 +884,9 @@ fn lowerAstErrors(zg: *ZonGen) Allocator.Error!void {
     const tree = zg.tree;
     assert(tree.errors.len > 0);
 
-    var msg: std.ArrayListUnmanaged(u8) = .empty;
+    var msg: std.io.AllocatingWriter = undefined;
-    defer msg.deinit(gpa);
+    const msg_bw = msg.init(gpa);
+    defer msg.deinit();
 
     var notes: std.ArrayListUnmanaged(Zoir.CompileError.Note) = .empty;
     defer notes.deinit(gpa);
@@ -889,18 +894,20 @@ fn lowerAstErrors(zg: *ZonGen) Allocator.Error!void {
     var cur_err = tree.errors[0];
     for (tree.errors[1..]) |err| {
         if (err.is_note) {
-            try tree.renderError(err, msg.writer(gpa));
+            tree.renderError(err, msg_bw) catch |e| return @errorCast(e); // TODO: try @errorCast(...)
-            try notes.append(gpa, try zg.errNoteTok(err.token, "{s}", .{msg.items}));
+            try notes.append(gpa, try zg.errNoteTok(err.token, "{s}", .{msg.getWritten()}));
         } else {
             // Flush error
-            try tree.renderError(cur_err, msg.writer(gpa));
+            tree.renderError(cur_err, msg_bw) catch |e| return @errorCast(e); // TODO try @errorCast(...)
             const extra_offset = tree.errorOffset(cur_err);
-            try zg.addErrorTokNotesOff(cur_err.token, extra_offset, "{s}", .{msg.items}, notes.items);
+            try zg.addErrorTokNotesOff(cur_err.token, extra_offset, "{s}", .{msg.getWritten()}, notes.items);
             notes.clearRetainingCapacity();
             cur_err = err;
 
-            // TODO: `Parse` currently does not have good error recovery mechanisms, so the remaining errors could be bogus.
+            // TODO: `Parse` currently does not have good error recovery
-            // As such, we'll ignore all remaining errors for now. We should improve `Parse` so that we can report all the errors.
+            // mechanisms, so the remaining errors could be bogus. As such,
+            // we'll ignore all remaining errors for now. We should improve
+            // `Parse` so that we can report all the errors.
             return;
         }
         msg.clearRetainingCapacity();
@@ -908,8 +915,8 @@ fn lowerAstErrors(zg: *ZonGen) Allocator.Error!void {
 
     // Flush error
     const extra_offset = tree.errorOffset(cur_err);
-    try tree.renderError(cur_err, msg.writer(gpa));
+    tree.renderError(cur_err, msg_bw) catch |e| return @errorCast(e); // TODO try @errorCast(...)
-    try zg.addErrorTokNotesOff(cur_err.token, extra_offset, "{s}", .{msg.items}, notes.items);
+    try zg.addErrorTokNotesOff(cur_err.token, extra_offset, "{s}", .{msg.getWritten()}, notes.items);
 }
 
 const std = @import("std");

lib/std/zig/render.zig

@@ -10,10 +10,6 @@ const primitives = std.zig.primitives;
 const indent_delta = 4;
 const asm_indent_delta = 2;
 
-pub const Error = Ast.RenderError;
-
-const Ais = AutoIndentingStream(std.ArrayList(u8).Writer);
-
 pub const Fixups = struct {
     /// The key is the mut token (`var`/`const`) of the variable declaration
     /// that should have a `_ = foo;` inserted afterwards.
@@ -74,17 +70,17 @@ pub const Fixups = struct {
 
 const Render = struct {
     gpa: Allocator,
-    ais: *Ais,
+    ais: *AutoIndentingStream,
     tree: Ast,
     fixups: Fixups,
 };
 
-pub fn renderTree(buffer: *std.ArrayList(u8), tree: Ast, fixups: Fixups) Error!void {
+pub fn renderTree(gpa: Allocator, bw: *std.io.BufferedWriter, tree: Ast, fixups: Fixups) anyerror!void {
     assert(tree.errors.len == 0); // Cannot render an invalid tree.
-    var auto_indenting_stream = Ais.init(buffer, indent_delta);
+    var auto_indenting_stream: AutoIndentingStream = .init(bw, indent_delta);
     defer auto_indenting_stream.deinit();
     var r: Render = .{
-        .gpa = buffer.allocator,
+        .gpa = gpa,
         .ais = &auto_indenting_stream,
         .tree = tree,
         .fixups = fixups,
@@ -115,7 +111,7 @@ pub fn renderTree(buffer: *std.ArrayList(u8), tree: Ast, fixups: Fixups) Error!v
 }
 
 /// Render all members in the given slice, keeping empty lines where appropriate
-fn renderMembers(r: *Render, members: []const Ast.Node.Index) Error!void {
+fn renderMembers(r: *Render, members: []const Ast.Node.Index) anyerror!void {
     const tree = r.tree;
     if (members.len == 0) return;
     const container: Container = for (members) |member| {
@@ -139,7 +135,7 @@ fn renderMember(
     container: Container,
     decl: Ast.Node.Index,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     if (r.fixups.omit_nodes.contains(decl)) return;
@@ -186,7 +182,7 @@ fn renderMember(
                     if (opt_callconv_expr.unwrap()) |callconv_expr| {
                         if (tree.nodeTag(callconv_expr) == .enum_literal) {
                             if (mem.eql(u8, "@\"inline\"", tree.tokenSlice(tree.nodeMainToken(callconv_expr)))) {
-                                try ais.writer().writeAll("inline ");
+                                try ais.underlying_writer.writeAll("inline ");
                             }
                         }
                     }
@@ -200,7 +196,7 @@ fn renderMember(
                 const lbrace = tree.nodeMainToken(body_node);
                 try renderToken(r, lbrace, .newline);
                 try discardAllParams(r, fn_proto);
-                try ais.writer().writeAll("@trap();");
+                try ais.writeAll("@trap();");
                 ais.popIndent();
                 try ais.insertNewline();
                 try renderToken(r, tree.lastToken(body_node), space); // rbrace
@@ -216,10 +212,9 @@ fn renderMember(
                     const name_ident = param.name_token.?;
                     assert(tree.tokenTag(name_ident) == .identifier);
                     if (r.fixups.unused_var_decls.contains(name_ident)) {
-                        const w = ais.writer();
+                        try ais.writeAll("_ = ");
-                        try w.writeAll("_ = ");
+                        try ais.writeAll(tokenSliceForRender(r.tree, name_ident));
-                        try w.writeAll(tokenSliceForRender(r.tree, name_ident));
+                        try ais.writeAll(";\n");
-                        try w.writeAll(";\n");
                     }
                 }
                 var statements_buf: [2]Ast.Node.Index = undefined;
@@ -310,7 +305,7 @@ fn renderMember(
 }
 
 /// Render all expressions in the slice, keeping empty lines where appropriate
-fn renderExpressions(r: *Render, expressions: []const Ast.Node.Index, space: Space) Error!void {
+fn renderExpressions(r: *Render, expressions: []const Ast.Node.Index, space: Space) anyerror!void {
     if (expressions.len == 0) return;
     try renderExpression(r, expressions[0], space);
     for (expressions[1..]) |expression| {
@@ -319,11 +314,11 @@ fn renderExpressions(r: *Render, expressions: []const Ast.Node.Index, space: Spa
     }
 }
 
-fn renderExpression(r: *Render, node: Ast.Node.Index, space: Space) Error!void {
+fn renderExpression(r: *Render, node: Ast.Node.Index, space: Space) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     if (r.fixups.replace_nodes_with_string.get(node)) |replacement| {
-        try ais.writer().writeAll(replacement);
+        try ais.writeAll(replacement);
         try renderOnlySpace(r, space);
         return;
     } else if (r.fixups.replace_nodes_with_node.get(node)) |replacement| {
@@ -891,11 +886,11 @@ fn renderExpression(r: *Render, node: Ast.Node.Index, space: Space) Error!void {
 
 /// Same as `renderExpression`, but afterwards looks for any
 /// append_string_after_node fixups to apply
-fn renderExpressionFixup(r: *Render, node: Ast.Node.Index, space: Space) Error!void {
+fn renderExpressionFixup(r: *Render, node: Ast.Node.Index, space: Space) anyerror!void {
     const ais = r.ais;
     try renderExpression(r, node, space);
     if (r.fixups.append_string_after_node.get(node)) |bytes| {
-        try ais.writer().writeAll(bytes);
+        try ais.writeAll(bytes);
     }
 }
 
@@ -903,7 +898,7 @@ fn renderArrayType(
     r: *Render,
     array_type: Ast.full.ArrayType,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     const rbracket = tree.firstToken(array_type.ast.elem_type) - 1;
@@ -921,7 +916,7 @@ fn renderArrayType(
     return renderExpression(r, array_type.ast.elem_type, space);
 }
 
-fn renderPtrType(r: *Render, ptr_type: Ast.full.PtrType, space: Space) Error!void {
+fn renderPtrType(r: *Render, ptr_type: Ast.full.PtrType, space: Space) anyerror!void {
     const tree = r.tree;
     const main_token = ptr_type.ast.main_token;
     switch (ptr_type.size) {
@@ -1015,7 +1010,7 @@ fn renderSlice(
     slice_node: Ast.Node.Index,
     slice: Ast.full.Slice,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const after_start_space_bool = nodeCausesSliceOpSpace(tree.nodeTag(slice.ast.start)) or
         if (slice.ast.end.unwrap()) |end| nodeCausesSliceOpSpace(tree.nodeTag(end)) else false;
@@ -1048,7 +1043,7 @@ fn renderAsmOutput(
     r: *Render,
     asm_output: Ast.Node.Index,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     assert(tree.nodeTag(asm_output) == .asm_output);
     const symbolic_name = tree.nodeMainToken(asm_output);
@@ -1074,7 +1069,7 @@ fn renderAsmInput(
     r: *Render,
     asm_input: Ast.Node.Index,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     assert(tree.nodeTag(asm_input) == .asm_input);
     const symbolic_name = tree.nodeMainToken(asm_input);
@@ -1096,14 +1091,14 @@ fn renderVarDecl(
     ignore_comptime_token: bool,
     /// `comma_space` and `space` are used for destructure LHS decls.
     space: Space,
-) Error!void {
+) anyerror!void {
     try renderVarDeclWithoutFixups(r, var_decl, ignore_comptime_token, space);
     if (r.fixups.unused_var_decls.contains(var_decl.ast.mut_token + 1)) {
         // Discard the variable like this: `_ = foo;`
-        const w = r.ais.writer();
+        const ais = r.ais;
-        try w.writeAll("_ = ");
+        try ais.writeAll("_ = ");
-        try w.writeAll(tokenSliceForRender(r.tree, var_decl.ast.mut_token + 1));
+        try ais.writeAll(tokenSliceForRender(r.tree, var_decl.ast.mut_token + 1));
-        try w.writeAll(";\n");
+        try ais.writeAll(";\n");
     }
 }
 
@@ -1114,7 +1109,7 @@ fn renderVarDeclWithoutFixups(
     ignore_comptime_token: bool,
     /// `comma_space` and `space` are used for destructure LHS decls.
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
 
@@ -1226,7 +1221,7 @@ fn renderVarDeclWithoutFixups(
     ais.popIndent();
 }
 
-fn renderIf(r: *Render, if_node: Ast.full.If, space: Space) Error!void {
+fn renderIf(r: *Render, if_node: Ast.full.If, space: Space) anyerror!void {
     return renderWhile(r, .{
         .ast = .{
             .while_token = if_node.ast.if_token,
@@ -1245,7 +1240,7 @@ fn renderIf(r: *Render, if_node: Ast.full.If, space: Space) Error!void {
 
 /// Note that this function is additionally used to render if expressions, with
 /// respective values set to null.
-fn renderWhile(r: *Render, while_node: Ast.full.While, space: Space) Error!void {
+fn renderWhile(r: *Render, while_node: Ast.full.While, space: Space) anyerror!void {
     const tree = r.tree;
 
     if (while_node.label_token) |label| {
@@ -1315,7 +1310,7 @@ fn renderThenElse(
     maybe_error_token: ?Ast.TokenIndex,
     opt_else_expr: Ast.Node.OptionalIndex,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     const then_expr_is_block = nodeIsBlock(tree.nodeTag(then_expr));
@@ -1370,7 +1365,7 @@ fn renderThenElse(
     }
 }
 
-fn renderFor(r: *Render, for_node: Ast.full.For, space: Space) Error!void {
+fn renderFor(r: *Render, for_node: Ast.full.For, space: Space) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     const token_tags = tree.tokens.items(.tag);
@@ -1445,7 +1440,7 @@ fn renderContainerField(
     container: Container,
     field_param: Ast.full.ContainerField,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     var field = field_param;
@@ -1554,7 +1549,7 @@ fn renderBuiltinCall(
     builtin_token: Ast.TokenIndex,
     params: []const Ast.Node.Index,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
 
@@ -1581,7 +1576,7 @@ fn renderBuiltinCall(
             defer r.gpa.free(new_string);
 
             try renderToken(r, builtin_token + 1, .none); // (
-            try ais.writer().print("\"{}\"", .{std.zig.fmtEscapes(new_string)});
+            try ais.print("\"{}\"", .{std.zig.fmtEscapes(new_string)});
             return renderToken(r, str_lit_token + 1, space); // )
         }
     }
@@ -1627,7 +1622,7 @@ fn renderBuiltinCall(
     }
 }
 
-fn renderFnProto(r: *Render, fn_proto: Ast.full.FnProto, space: Space) Error!void {
+fn renderFnProto(r: *Render, fn_proto: Ast.full.FnProto, space: Space) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
 
@@ -1852,7 +1847,7 @@ fn renderSwitchCase(
     r: *Render,
     switch_case: Ast.full.SwitchCase,
     space: Space,
-) Error!void {
+) anyerror!void {
     const ais = r.ais;
     const tree = r.tree;
     const trailing_comma = tree.tokenTag(switch_case.ast.arrow_token - 1) == .comma;
@@ -1914,7 +1909,7 @@ fn renderBlock(
     block_node: Ast.Node.Index,
     statements: []const Ast.Node.Index,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     const lbrace = tree.nodeMainToken(block_node);
@@ -1939,7 +1934,7 @@ fn finishRenderBlock(
     block_node: Ast.Node.Index,
     statements: []const Ast.Node.Index,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     for (statements, 0..) |stmt, i| {
@@ -1967,7 +1962,7 @@ fn renderStructInit(
     struct_node: Ast.Node.Index,
     struct_init: Ast.full.StructInit,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
 
@@ -2038,7 +2033,7 @@ fn renderArrayInit(
     r: *Render,
     array_init: Ast.full.ArrayInit,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     const gpa = r.gpa;
@@ -2139,13 +2134,14 @@ fn renderArrayInit(
 
         const section_exprs = row_exprs[0..section_end];
 
-        var sub_expr_buffer = std.ArrayList(u8).init(gpa);
+        var sub_expr_buffer: std.io.AllocatingWriter = undefined;
+        const sub_expr_buffer_writer = sub_expr_buffer.init(gpa);
         defer sub_expr_buffer.deinit();
 
         const sub_expr_buffer_starts = try gpa.alloc(usize, section_exprs.len + 1);
         defer gpa.free(sub_expr_buffer_starts);
 
-        var auto_indenting_stream = Ais.init(&sub_expr_buffer, indent_delta);
+        var auto_indenting_stream: AutoIndentingStream = .init(sub_expr_buffer_writer, indent_delta);
         defer auto_indenting_stream.deinit();
         var sub_render: Render = .{
             .gpa = r.gpa,
@@ -2159,13 +2155,13 @@ fn renderArrayInit(
         var single_line = true;
         var contains_newline = false;
         for (section_exprs, 0..) |expr, i| {
-            const start = sub_expr_buffer.items.len;
+            const start = sub_expr_buffer.getWritten().len;
             sub_expr_buffer_starts[i] = start;
 
             if (i + 1 < section_exprs.len) {
                 try renderExpression(&sub_render, expr, .none);
-                const width = sub_expr_buffer.items.len - start;
+                const width = sub_expr_buffer.getWritten().len - start;
-                const this_contains_newline = mem.indexOfScalar(u8, sub_expr_buffer.items[start..], '\n') != null;
+                const this_contains_newline = mem.indexOfScalar(u8, sub_expr_buffer.getWritten()[start..], '\n') != null;
                 contains_newline = contains_newline or this_contains_newline;
                 expr_widths[i] = width;
                 expr_newlines[i] = this_contains_newline;
@@ -2188,7 +2184,7 @@ fn renderArrayInit(
                 ais.popSpace();
 
                 const width = sub_expr_buffer.items.len - start - 2;
-                const this_contains_newline = mem.indexOfScalar(u8, sub_expr_buffer.items[start .. sub_expr_buffer.items.len - 1], '\n') != null;
+                const this_contains_newline = mem.indexOfScalar(u8, sub_expr_buffer.getWritten()[start .. sub_expr_buffer.items.len - 1], '\n') != null;
                 contains_newline = contains_newline or this_contains_newline;
                 expr_widths[i] = width;
                 expr_newlines[i] = contains_newline;
@@ -2199,20 +2195,20 @@ fn renderArrayInit(
                 }
             }
         }
-        sub_expr_buffer_starts[section_exprs.len] = sub_expr_buffer.items.len;
+        sub_expr_buffer_starts[section_exprs.len] = sub_expr_buffer.getWritten().len;
 
         // Render exprs in current section.
         column_counter = 0;
         for (section_exprs, 0..) |expr, i| {
             const start = sub_expr_buffer_starts[i];
             const end = sub_expr_buffer_starts[i + 1];
-            const expr_text = sub_expr_buffer.items[start..end];
+            const expr_text = sub_expr_buffer.getWritten()[start..end];
             if (!expr_newlines[i]) {
-                try ais.writer().writeAll(expr_text);
+                try ais.writeAll(expr_text);
             } else {
                 var by_line = std.mem.splitScalar(u8, expr_text, '\n');
                 var last_line_was_empty = false;
-                try ais.writer().writeAll(by_line.first());
+                try ais.writeAll(by_line.first());
                 while (by_line.next()) |line| {
                     if (std.mem.startsWith(u8, line, "//") and last_line_was_empty) {
                         try ais.insertNewline();
@@ -2220,7 +2216,7 @@ fn renderArrayInit(
                         try ais.maybeInsertNewline();
                     }
                     last_line_was_empty = (line.len == 0);
-                    try ais.writer().writeAll(line);
+                    try ais.writeAll(line);
                 }
             }
 
@@ -2234,7 +2230,7 @@ fn renderArrayInit(
                         try renderToken(r, comma, .space); // ,
                         assert(column_widths[column_counter % row_size] >= expr_widths[i]);
                         const padding = column_widths[column_counter % row_size] - expr_widths[i];
-                        try ais.writer().writeByteNTimes(' ', padding);
+                        try ais.splatByteAll(' ', padding);
 
                         column_counter += 1;
                         continue;
@@ -2265,7 +2261,7 @@ fn renderContainerDecl(
     container_decl_node: Ast.Node.Index,
     container_decl: Ast.full.ContainerDecl,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
 
@@ -2384,7 +2380,7 @@ fn renderAsm(
     r: *Render,
     asm_node: Ast.full.Asm,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
 
@@ -2550,7 +2546,7 @@ fn renderCall(
     r: *Render,
     call: Ast.full.Call,
     space: Space,
-) Error!void {
+) anyerror!void {
     if (call.async_token) |async_token| {
         try renderToken(r, async_token, .space);
     }
@@ -2563,7 +2559,7 @@ fn renderParamList(
     lparen: Ast.TokenIndex,
     params: []const Ast.Node.Index,
     space: Space,
-) Error!void {
+) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
 
@@ -2616,7 +2612,7 @@ fn renderParamList(
 
 /// Render an expression, and the comma that follows it, if it is present in the source.
 /// If a comma is present, and `space` is `Space.comma`, render only a single comma.
-fn renderExpressionComma(r: *Render, node: Ast.Node.Index, space: Space) Error!void {
+fn renderExpressionComma(r: *Render, node: Ast.Node.Index, space: Space) anyerror!void {
     const tree = r.tree;
     const maybe_comma = tree.lastToken(node) + 1;
     if (tree.tokenTag(maybe_comma) == .comma and space != .comma) {
@@ -2629,7 +2625,7 @@ fn renderExpressionComma(r: *Render, node: Ast.Node.Index, space: Space) Error!v
 
 /// Render a token, and the comma that follows it, if it is present in the source.
 /// If a comma is present, and `space` is `Space.comma`, render only a single comma.
-fn renderTokenComma(r: *Render, token: Ast.TokenIndex, space: Space) Error!void {
+fn renderTokenComma(r: *Render, token: Ast.TokenIndex, space: Space) anyerror!void {
     const tree = r.tree;
     const maybe_comma = token + 1;
     if (tree.tokenTag(maybe_comma) == .comma and space != .comma) {
@@ -2642,7 +2638,7 @@ fn renderTokenComma(r: *Render, token: Ast.TokenIndex, space: Space) Error!void
 
 /// Render an identifier, and the comma that follows it, if it is present in the source.
 /// If a comma is present, and `space` is `Space.comma`, render only a single comma.
-fn renderIdentifierComma(r: *Render, token: Ast.TokenIndex, space: Space, quote: QuoteBehavior) Error!void {
+fn renderIdentifierComma(r: *Render, token: Ast.TokenIndex, space: Space, quote: QuoteBehavior) anyerror!void {
     const tree = r.tree;
     const maybe_comma = token + 1;
     if (tree.tokenTag(maybe_comma) == .comma and space != .comma) {
@@ -2674,15 +2670,15 @@ const Space = enum {
     skip,
 };
 
-fn renderToken(r: *Render, token_index: Ast.TokenIndex, space: Space) Error!void {
+fn renderToken(r: *Render, token_index: Ast.TokenIndex, space: Space) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     const lexeme = tokenSliceForRender(tree, token_index);
-    try ais.writer().writeAll(lexeme);
+    try ais.writeAll(lexeme);
     try renderSpace(r, token_index, lexeme.len, space);
 }
 
-fn renderTokenOverrideSpaceMode(r: *Render, token_index: Ast.TokenIndex, space: Space, override_space: Space) Error!void {
+fn renderTokenOverrideSpaceMode(r: *Render, token_index: Ast.TokenIndex, space: Space, override_space: Space) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     const lexeme = tokenSliceForRender(tree, token_index);
@@ -2692,7 +2688,7 @@ fn renderTokenOverrideSpaceMode(r: *Render, token_index: Ast.TokenIndex, space:
     try renderSpace(r, token_index, lexeme.len, space);
 }
 
-fn renderSpace(r: *Render, token_index: Ast.TokenIndex, lexeme_len: usize, space: Space) Error!void {
+fn renderSpace(r: *Render, token_index: Ast.TokenIndex, lexeme_len: usize, space: Space) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
 
@@ -2701,7 +2697,7 @@ fn renderSpace(r: *Render, token_index: Ast.TokenIndex, lexeme_len: usize, space
     if (space == .skip) return;
 
     if (space == .comma and next_token_tag != .comma) {
-        try ais.writer().writeByte(',');
+        try ais.underlying_writer.writeByte(',');
     }
     if (space == .semicolon or space == .comma) ais.enableSpaceMode(space);
     defer ais.disableSpaceMode();
@@ -2712,7 +2708,7 @@ fn renderSpace(r: *Render, token_index: Ast.TokenIndex, lexeme_len: usize, space
     );
     switch (space) {
         .none => {},
-        .space => if (!comment) try ais.writer().writeByte(' '),
+        .space => if (!comment) try ais.writeByte(' '),
         .newline => if (!comment) try ais.insertNewline(),
 
         .comma => if (next_token_tag == .comma) {
@@ -2724,7 +2720,7 @@ fn renderSpace(r: *Render, token_index: Ast.TokenIndex, lexeme_len: usize, space
         .comma_space => if (next_token_tag == .comma) {
             try renderToken(r, token_index + 1, .space);
         } else if (!comment) {
-            try ais.writer().writeByte(' ');
+            try ais.writeByte(' ');
         },
 
         .semicolon => if (next_token_tag == .semicolon) {
@@ -2737,15 +2733,15 @@ fn renderSpace(r: *Render, token_index: Ast.TokenIndex, lexeme_len: usize, space
     }
 }
 
-fn renderOnlySpace(r: *Render, space: Space) Error!void {
+fn renderOnlySpace(r: *Render, space: Space) anyerror!void {
     const ais = r.ais;
     switch (space) {
         .none => {},
-        .space => try ais.writer().writeByte(' '),
+        .space => try ais.writeByte(' '),
         .newline => try ais.insertNewline(),
-        .comma => try ais.writer().writeAll(",\n"),
+        .comma => try ais.writeAll(",\n"),
-        .comma_space => try ais.writer().writeAll(", "),
+        .comma_space => try ais.writeAll(", "),
-        .semicolon => try ais.writer().writeAll(";\n"),
+        .semicolon => try ais.writeAll(";\n"),
         .skip => unreachable,
     }
 }
@@ -2756,13 +2752,13 @@ const QuoteBehavior = enum {
     eagerly_unquote_except_underscore,
 };
 
-fn renderIdentifier(r: *Render, token_index: Ast.TokenIndex, space: Space, quote: QuoteBehavior) Error!void {
+fn renderIdentifier(r: *Render, token_index: Ast.TokenIndex, space: Space, quote: QuoteBehavior) anyerror!void {
     const tree = r.tree;
     assert(tree.tokenTag(token_index) == .identifier);
     const lexeme = tokenSliceForRender(tree, token_index);
 
     if (r.fixups.rename_identifiers.get(lexeme)) |mangled| {
-        try r.ais.writer().writeAll(mangled);
+        try r.ais.writeAll(mangled);
         try renderSpace(r, token_index, lexeme.len, space);
         return;
     }
@@ -2871,15 +2867,15 @@ fn renderQuotedIdentifier(r: *Render, token_index: Ast.TokenIndex, space: Space,
     const lexeme = tokenSliceForRender(tree, token_index);
     assert(lexeme.len >= 3 and lexeme[0] == '@');
 
-    if (!unquote) try ais.writer().writeAll("@\"");
+    if (!unquote) try ais.writeAll("@\"");
     const contents = lexeme[2 .. lexeme.len - 1];
-    try renderIdentifierContents(ais.writer(), contents);
+    try renderIdentifierContents(ais, contents);
-    if (!unquote) try ais.writer().writeByte('\"');
+    if (!unquote) try ais.writeByte('\"');
 
     try renderSpace(r, token_index, lexeme.len, space);
 }
 
-fn renderIdentifierContents(writer: anytype, bytes: []const u8) !void {
+fn renderIdentifierContents(ais: *AutoIndentingStream, bytes: []const u8) !void {
     var pos: usize = 0;
     while (pos < bytes.len) {
         const byte = bytes[pos];
@@ -2892,23 +2888,23 @@ fn renderIdentifierContents(writer: anytype, bytes: []const u8) !void {
                     .success => |codepoint| {
                         if (codepoint <= 0x7f) {
                             const buf = [1]u8{@as(u8, @intCast(codepoint))};
-                            try std.fmt.format(writer, "{}", .{std.zig.fmtEscapes(&buf)});
+                            try ais.print("{}", .{std.zig.fmtEscapes(&buf)});
                         } else {
-                            try writer.writeAll(escape_sequence);
+                            try ais.writeAll(escape_sequence);
                         }
                     },
                     .failure => {
-                        try writer.writeAll(escape_sequence);
+                        try ais.writeAll(escape_sequence);
                     },
                 }
             },
             0x00...('\\' - 1), ('\\' + 1)...0x7f => {
                 const buf = [1]u8{byte};
-                try std.fmt.format(writer, "{}", .{std.zig.fmtEscapes(&buf)});
+                try ais.print("{}", .{std.zig.fmtEscapes(&buf)});
                 pos += 1;
             },
             0x80...0xff => {
-                try writer.writeByte(byte);
+                try ais.writeByte(byte);
                 pos += 1;
             },
         }
@@ -2942,7 +2938,7 @@ fn hasMultilineString(tree: Ast, start_token: Ast.TokenIndex, end_token: Ast.Tok
 
 /// Assumes that start is the first byte past the previous token and
 /// that end is the last byte before the next token.
-fn renderComments(r: *Render, start: usize, end: usize) Error!bool {
+fn renderComments(r: *Render, start: usize, end: usize) anyerror!bool {
     const tree = r.tree;
     const ais = r.ais;
 
@@ -2970,7 +2966,7 @@ fn renderComments(r: *Render, start: usize, end: usize) Error!bool {
             } else if (index == start) {
                 // Otherwise if the first comment is on the same line as
                 // the token before it, prefix it with a single space.
-                try ais.writer().writeByte(' ');
+                try ais.writeByte(' ');
             }
         }
 
@@ -2987,11 +2983,11 @@ fn renderComments(r: *Render, start: usize, end: usize) Error!bool {
             ais.disabled_offset = null;
         } else if (ais.disabled_offset == null and mem.eql(u8, comment_content, "zig fmt: off")) {
             // Write with the canonical single space.
-            try ais.writer().writeAll("// zig fmt: off\n");
+            try ais.writeAll("// zig fmt: off\n");
             ais.disabled_offset = index;
         } else {
             // Write the comment minus trailing whitespace.
-            try ais.writer().print("{s}\n", .{trimmed_comment});
+            try ais.print("{s}\n", .{trimmed_comment});
         }
     }
 
@@ -3005,12 +3001,12 @@ fn renderComments(r: *Render, start: usize, end: usize) Error!bool {
     return index != start;
 }
 
-fn renderExtraNewline(r: *Render, node: Ast.Node.Index) Error!void {
+fn renderExtraNewline(r: *Render, node: Ast.Node.Index) anyerror!void {
     return renderExtraNewlineToken(r, r.tree.firstToken(node));
 }
 
 /// Check if there is an empty line immediately before the given token. If so, render it.
-fn renderExtraNewlineToken(r: *Render, token_index: Ast.TokenIndex) Error!void {
+fn renderExtraNewlineToken(r: *Render, token_index: Ast.TokenIndex) anyerror!void {
     const tree = r.tree;
     const ais = r.ais;
     const token_start = tree.tokenStart(token_index);
@@ -3038,7 +3034,7 @@ fn renderExtraNewlineToken(r: *Render, token_index: Ast.TokenIndex) Error!void {
 
 /// end_token is the token one past the last doc comment token. This function
 /// searches backwards from there.
-fn renderDocComments(r: *Render, end_token: Ast.TokenIndex) Error!void {
+fn renderDocComments(r: *Render, end_token: Ast.TokenIndex) anyerror!void {
     const tree = r.tree;
     // Search backwards for the first doc comment.
     if (end_token == 0) return;
@@ -3069,7 +3065,7 @@ fn renderDocComments(r: *Render, end_token: Ast.TokenIndex) Error!void {
 }
 
 /// start_token is first container doc comment token.
-fn renderContainerDocComments(r: *Render, start_token: Ast.TokenIndex) Error!void {
+fn renderContainerDocComments(r: *Render, start_token: Ast.TokenIndex) anyerror!void {
     const tree = r.tree;
     var tok = start_token;
     while (tree.tokenTag(tok) == .container_doc_comment) : (tok += 1) {
@@ -3083,7 +3079,7 @@ fn renderContainerDocComments(r: *Render, start_token: Ast.TokenIndex) Error!voi
     }
 }
 
-fn discardAllParams(r: *Render, fn_proto_node: Ast.Node.Index) Error!void {
+fn discardAllParams(r: *Render, fn_proto_node: Ast.Node.Index) anyerror!void {
     const tree = &r.tree;
     const ais = r.ais;
     var buf: [1]Ast.Node.Index = undefined;
@@ -3092,10 +3088,9 @@ fn discardAllParams(r: *Render, fn_proto_node: Ast.Node.Index) Error!void {
     while (it.next()) |param| {
         const name_ident = param.name_token.?;
         assert(tree.tokenTag(name_ident) == .identifier);
-        const w = ais.writer();
+        try ais.writeAll("_ = ");
-        try w.writeAll("_ = ");
+        try ais.writeAll(tokenSliceForRender(r.tree, name_ident));
-        try w.writeAll(tokenSliceForRender(r.tree, name_ident));
+        try ais.writeAll(";\n");
-        try w.writeAll(";\n");
     }
 }
 
@@ -3132,11 +3127,11 @@ fn anythingBetween(tree: Ast, start_token: Ast.TokenIndex, end_token: Ast.TokenI
     return false;
 }
 
-fn writeFixingWhitespace(writer: std.ArrayList(u8).Writer, slice: []const u8) Error!void {
+fn writeFixingWhitespace(bw: *std.io.BufferedWriter, slice: []const u8) anyerror!void {
     for (slice) |byte| switch (byte) {
-        '\t' => try writer.writeAll(" " ** indent_delta),
+        '\t' => try bw.splatByteAll(' ', indent_delta),
         '\r' => {},
-        else => try writer.writeByte(byte),
+        else => try bw.writeByte(byte),
     };
 }
 
@@ -3261,11 +3256,18 @@ fn rowSize(tree: Ast, exprs: []const Ast.Node.Index, rtoken: Ast.TokenIndex) usi
 /// of the appropriate indentation level for them with pushSpace/popSpace.
 /// This should be done whenever a scope that ends in a .semicolon or a
 /// .comma is introduced.
-fn AutoIndentingStream(comptime UnderlyingWriter: type) type {
+const AutoIndentingStream = struct {
-    return struct {
+    underlying_writer: *std.io.BufferedWriter,
-        const Self = @This();
+
-        pub const WriteError = UnderlyingWriter.Error;
+    indent_count: usize = 0,
-        pub const Writer = std.io.Writer(*Self, WriteError, write);
+    indent_delta: usize,
+    indent_stack: std.ArrayList(StackElem),
+    space_stack: std.ArrayList(SpaceElem),
+    space_mode: ?usize = null,
+    disable_indent_committing: usize = 0,
+    current_line_empty: bool = true,
+    /// the most recently applied indent
+    applied_indent: usize = 0,
 
     pub const IndentType = enum {
         normal,
@@ -3282,27 +3284,7 @@ fn AutoIndentingStream(comptime UnderlyingWriter: type) type {
         indent_count: usize,
     };
 
-        underlying_writer: UnderlyingWriter,
+    pub fn init(buffer: *std.ArrayList(u8), indent_delta_: usize) AutoIndentingStream {
-
-        /// Offset into the source at which formatting has been disabled with
-        /// a `zig fmt: off` comment.
-        ///
-        /// If non-null, the AutoIndentingStream will not write any bytes
-        /// to the underlying writer. It will however continue to track the
-        /// indentation level.
-        disabled_offset: ?usize = null,
-
-        indent_count: usize = 0,
-        indent_delta: usize,
-        indent_stack: std.ArrayList(StackElem),
-        space_stack: std.ArrayList(SpaceElem),
-        space_mode: ?usize = null,
-        disable_indent_committing: usize = 0,
-        current_line_empty: bool = true,
-        /// the most recently applied indent
-        applied_indent: usize = 0,
-
-        pub fn init(buffer: *std.ArrayList(u8), indent_delta_: usize) Self {
         return .{
             .underlying_writer = buffer.writer(),
             .indent_delta = indent_delta_,
@@ -3311,65 +3293,102 @@ fn AutoIndentingStream(comptime UnderlyingWriter: type) type {
         };
     }
 
-        pub fn deinit(self: *Self) void {
+    pub fn deinit(self: *AutoIndentingStream) void {
         self.indent_stack.deinit();
         self.space_stack.deinit();
     }
 
-        pub fn writer(self: *Self) Writer {
+    pub fn writeAll(ais: *AutoIndentingStream, bytes: []const u8) anyerror!void {
-            return .{ .context = self };
+        if (bytes.len == 0) return;
+        try ais.applyIndent();
+        if (ais.disabled_offset == null) try ais.underlying_writer.writeAll(bytes);
+        if (bytes[bytes.len - 1] == '\n') ais.resetLine();
     }
 
-        pub fn write(self: *Self, bytes: []const u8) WriteError!usize {
+    pub fn print(ais: *AutoIndentingStream, comptime format: []const u8, args: anytype) anyerror!void {
-            if (bytes.len == 0)
+        comptime assert(format[format.len - 1] != '}');
-                return @as(usize, 0);
+        try ais.applyIndent();
+        if (ais.disabled_offset == null) try ais.underlying_writer.print(format, args);
+        if (format[format.len - 1] == '\n') ais.resetLine();
+    }
 
-            try self.applyIndent();
+    pub fn writeByte(ais: *AutoIndentingStream, byte: u8) anyerror!void {
-            return self.writeNoIndent(bytes);
+        try ais.applyIndent();
+        if (ais.disabled_offset == null) try ais.underlying_writer.writeByte(byte);
+        assert(byte != '\n');
+    }
+
+    pub fn splatByteAll(ais: *AutoIndentingStream, byte: u8, n: usize) anyerror!void {
+        assert(byte != '\n');
+        try ais.applyIndent();
+        if (ais.disabled_offset == null) try ais.underlying_writer.splatByteAll(byte, n);
     }
 
     // Change the indent delta without changing the final indentation level
-        pub fn setIndentDelta(self: *Self, new_indent_delta: usize) void {
+    pub fn setIndentDelta(ais: *AutoIndentingStream, new_indent_delta: usize) void {
-            if (self.indent_delta == new_indent_delta) {
+        if (ais.indent_delta == new_indent_delta) {
             return;
-            } else if (self.indent_delta > new_indent_delta) {
+        } else if (ais.indent_delta > new_indent_delta) {
-                assert(self.indent_delta % new_indent_delta == 0);
+            assert(ais.indent_delta % new_indent_delta == 0);
-                self.indent_count = self.indent_count * (self.indent_delta / new_indent_delta);
+            ais.indent_count = ais.indent_count * (ais.indent_delta / new_indent_delta);
         } else {
             // assert that the current indentation (in spaces) in a multiple of the new delta
-                assert((self.indent_count * self.indent_delta) % new_indent_delta == 0);
+            assert((ais.indent_count * ais.indent_delta) % new_indent_delta == 0);
-                self.indent_count = self.indent_count / (new_indent_delta / self.indent_delta);
+            ais.indent_count = ais.indent_count / (new_indent_delta / ais.indent_delta);
         }
-            self.indent_delta = new_indent_delta;
+        ais.indent_delta = new_indent_delta;
     }
 
-        fn writeNoIndent(self: *Self, bytes: []const u8) WriteError!usize {
+    pub fn insertNewline(ais: *AutoIndentingStream) anyerror!void {
-            if (bytes.len == 0)
+        if (ais.disabled_offset == null) try ais.underlying_writer.writeByte('\n');
-                return @as(usize, 0);
+        ais.resetLine();
-
-            if (self.disabled_offset == null) try self.underlying_writer.writeAll(bytes);
-            if (bytes[bytes.len - 1] == '\n')
-                self.resetLine();
-            return bytes.len;
     }
 
-        pub fn insertNewline(self: *Self) WriteError!void {
+    /// Insert a newline unless the current line is blank
-            _ = try self.writeNoIndent("\n");
+    pub fn maybeInsertNewline(ais: *AutoIndentingStream) anyerror!void {
+        if (!ais.current_line_empty)
+            try ais.insertNewline();
     }
 
-        fn resetLine(self: *Self) void {
+    /// Push an indent that is automatically popped after being applied
-            self.current_line_empty = true;
+    pub fn pushIndentOneShot(ais: *AutoIndentingStream) void {
+        ais.indent_one_shot_count += 1;
+        ais.pushIndent();
+    }
 
-            if (self.disable_indent_committing > 0) return;
+    /// Turns all one-shot indents into regular indents
+    /// Returns number of indents that must now be manually popped
+    pub fn lockOneShotIndent(ais: *AutoIndentingStream) usize {
+        const locked_count = ais.indent_one_shot_count;
+        ais.indent_one_shot_count = 0;
+        return locked_count;
+    }
 
-            if (self.indent_stack.items.len > 0) {
+    /// Push an indent that should not take effect until the next line
+    pub fn pushIndentNextLine(ais: *AutoIndentingStream) void {
+        ais.indent_next_line += 1;
+        ais.pushIndent();
+    }
+
+    /// Checks to see if the most recent indentation exceeds the currently pushed indents
+    pub fn isLineOverIndented(ais: *AutoIndentingStream) bool {
+        if (ais.current_line_empty) return false;
+        return ais.applied_indent > ais.currentIndent();
+    }
+
+    fn resetLine(ais: *AutoIndentingStream) void {
+        ais.current_line_empty = true;
+
+        if (ais.disable_indent_committing > 0) return;
+
+        if (ais.indent_stack.items.len > 0) {
             // By default, we realize the most recent indentation scope.
-                var to_realize = self.indent_stack.items.len - 1;
+            var to_realize = ais.indent_stack.items.len - 1;
 
-                if (self.indent_stack.items.len >= 2 and
+            if (ais.indent_stack.items.len >= 2 and
-                    self.indent_stack.items[to_realize - 1].indent_type == .after_equals and
+                ais.indent_stack.items[to_realize - 1].indent_type == .after_equals and
-                    self.indent_stack.items[to_realize - 1].realized and
+                ais.indent_stack.items[to_realize - 1].realized and
-                    self.indent_stack.items[to_realize].indent_type == .binop)
+                ais.indent_stack.items[to_realize].indent_type == .binop)
             {
                 // If we are in a .binop scope and our direct parent is .after_equals, don't indent.
                 // This ensures correct indentation in the below example:
@@ -3381,104 +3400,91 @@ fn AutoIndentingStream(comptime UnderlyingWriter: type) type {
                 return;
             }
 
-                if (self.indent_stack.items[to_realize].indent_type == .field_access) {
+            if (ais.indent_stack.items[to_realize].indent_type == .field_access) {
                 // Only realize the top-most field_access in a chain.
-                    while (to_realize > 0 and self.indent_stack.items[to_realize - 1].indent_type == .field_access)
+                while (to_realize > 0 and ais.indent_stack.items[to_realize - 1].indent_type == .field_access)
                     to_realize -= 1;
             }
 
-                if (self.indent_stack.items[to_realize].realized) return;
+            if (ais.indent_stack.items[to_realize].realized) return;
-                self.indent_stack.items[to_realize].realized = true;
+            ais.indent_stack.items[to_realize].realized = true;
-                self.indent_count += 1;
+            ais.indent_count += 1;
         }
     }
 
     /// Disables indentation level changes during the next newlines until re-enabled.
-        pub fn disableIndentCommitting(self: *Self) void {
+    pub fn disableIndentCommitting(ais: *AutoIndentingStream) void {
-            self.disable_indent_committing += 1;
+        ais.disable_indent_committing += 1;
     }
 
-        pub fn enableIndentCommitting(self: *Self) void {
+    pub fn enableIndentCommitting(ais: *AutoIndentingStream) void {
-            assert(self.disable_indent_committing > 0);
+        assert(ais.disable_indent_committing > 0);
-            self.disable_indent_committing -= 1;
+        ais.disable_indent_committing -= 1;
     }
 
-        pub fn pushSpace(self: *Self, space: Space) !void {
+    pub fn pushSpace(ais: *AutoIndentingStream, space: Space) !void {
-            try self.space_stack.append(.{ .space = space, .indent_count = self.indent_count });
+        try ais.space_stack.append(.{ .space = space, .indent_count = ais.indent_count });
     }
 
-        pub fn popSpace(self: *Self) void {
+    pub fn popSpace(ais: *AutoIndentingStream) void {
-            _ = self.space_stack.pop();
+        _ = ais.space_stack.pop();
     }
 
     /// Sets current indentation level to be the same as that of the last pushSpace.
-        pub fn enableSpaceMode(self: *Self, space: Space) void {
+    pub fn enableSpaceMode(ais: *AutoIndentingStream, space: Space) void {
-            if (self.space_stack.items.len == 0) return;
+        if (ais.space_stack.items.len == 0) return;
-            const curr = self.space_stack.getLast();
+        const curr = ais.space_stack.getLast();
         if (curr.space != space) return;
-            self.space_mode = curr.indent_count;
+        ais.space_mode = curr.indent_count;
     }
 
-        pub fn disableSpaceMode(self: *Self) void {
+    pub fn disableSpaceMode(ais: *AutoIndentingStream) void {
-            self.space_mode = null;
+        ais.space_mode = null;
     }
 
-        pub fn lastSpaceModeIndent(self: *Self) usize {
+    pub fn lastSpaceModeIndent(ais: *AutoIndentingStream) usize {
-            if (self.space_stack.items.len == 0) return 0;
+        if (ais.space_stack.items.len == 0) return 0;
-            return self.space_stack.getLast().indent_count * self.indent_delta;
+        return ais.space_stack.getLast().indent_count * ais.indent_delta;
-        }
-
-        /// Insert a newline unless the current line is blank
-        pub fn maybeInsertNewline(self: *Self) WriteError!void {
-            if (!self.current_line_empty)
-                try self.insertNewline();
     }
 
     /// Push default indentation
     /// Doesn't actually write any indentation.
     /// Just primes the stream to be able to write the correct indentation if it needs to.
-        pub fn pushIndent(self: *Self, indent_type: IndentType) !void {
+    pub fn pushIndent(ais: *AutoIndentingStream, indent_type: IndentType) !void {
-            try self.indent_stack.append(.{ .indent_type = indent_type, .realized = false });
+        try ais.indent_stack.append(.{ .indent_type = indent_type, .realized = false });
     }
 
     /// Forces an indentation level to be realized.
-        pub fn forcePushIndent(self: *Self, indent_type: IndentType) !void {
+    pub fn forcePushIndent(ais: *AutoIndentingStream, indent_type: IndentType) !void {
-            try self.indent_stack.append(.{ .indent_type = indent_type, .realized = true });
+        try ais.indent_stack.append(.{ .indent_type = indent_type, .realized = true });
-            self.indent_count += 1;
+        ais.indent_count += 1;
     }
 
-        pub fn popIndent(self: *Self) void {
+    pub fn popIndent(ais: *AutoIndentingStream) void {
-            if (self.indent_stack.pop().?.realized) {
+        if (ais.indent_stack.pop().?.realized) {
-                assert(self.indent_count > 0);
+            assert(ais.indent_count > 0);
-                self.indent_count -= 1;
+            ais.indent_count -= 1;
         }
     }
 
-        pub fn indentStackEmpty(self: *Self) bool {
+    pub fn indentStackEmpty(ais: *AutoIndentingStream) bool {
-            return self.indent_stack.items.len == 0;
+        return ais.indent_stack.items.len == 0;
     }
 
     /// Writes ' ' bytes if the current line is empty
-        fn applyIndent(self: *Self) WriteError!void {
+    fn applyIndent(ais: *AutoIndentingStream) anyerror!void {
-            const current_indent = self.currentIndent();
+        const current_indent = ais.currentIndent();
-            if (self.current_line_empty and current_indent > 0) {
+        if (ais.current_line_empty and current_indent > 0) {
-                if (self.disabled_offset == null) {
+            if (ais.disabled_offset == null) {
-                    try self.underlying_writer.writeByteNTimes(' ', current_indent);
+                try ais.underlying_writer.writeByteNTimes(' ', current_indent);
             }
-                self.applied_indent = current_indent;
+            ais.applied_indent = current_indent;
         }
-            self.current_line_empty = false;
+        ais.current_line_empty = false;
     }
 
-        /// Checks to see if the most recent indentation exceeds the currently pushed indents
+    fn currentIndent(ais: *AutoIndentingStream) usize {
-        pub fn isLineOverIndented(self: *Self) bool {
+        const indent_count = ais.space_mode orelse ais.indent_count;
-            if (self.current_line_empty) return false;
+        return indent_count * ais.indent_delta;
-            return self.applied_indent > self.currentIndent();
     }
-
+};
-        fn currentIndent(self: *Self) usize {
-            const indent_count = self.space_mode orelse self.indent_count;
-            return indent_count * self.indent_delta;
-        }
-    };
-}

lib/std/zig/string_literal.zig

@@ -322,9 +322,9 @@ test parseCharLiteral {
     );
 }
 
-/// Parses `bytes` as a Zig string literal and writes the result to the std.io.Writer type.
+/// Parses `bytes` as a Zig string literal and writes the result to the `std.io.Writer` type.
 /// Asserts `bytes` has '"' at beginning and end.
-pub fn parseWrite(writer: anytype, bytes: []const u8) error{OutOfMemory}!Result {
+pub fn parseWrite(writer: *std.io.BufferedWriter, bytes: []const u8) anyerror!Result {
     assert(bytes.len >= 2 and bytes[0] == '"' and bytes[bytes.len - 1] == '"');
 
     var index: usize = 1;
@@ -340,18 +340,18 @@ pub fn parseWrite(writer: anytype, bytes: []const u8) error{OutOfMemory}!Result
                         if (bytes[escape_char_index] == 'u') {
                             var buf: [4]u8 = undefined;
                             const len = utf8Encode(codepoint, &buf) catch {
-                                return Result{ .failure = .{ .invalid_unicode_codepoint = escape_char_index + 1 } };
+                                return .{ .failure = .{ .invalid_unicode_codepoint = escape_char_index + 1 } };
                             };
                             try writer.writeAll(buf[0..len]);
                         } else {
                             try writer.writeByte(@as(u8, @intCast(codepoint)));
                         }
                     },
-                    .failure => |err| return Result{ .failure = err },
+                    .failure => |err| return .{ .failure = err },
                 }
             },
-            '\n' => return Result{ .failure = .{ .invalid_character = index } },
+            '\n' => return .{ .failure = .{ .invalid_character = index } },
-            '"' => return Result.success,
+            '"' => return .success,
             else => {
                 try writer.writeByte(b);
                 index += 1;
@@ -363,10 +363,12 @@ pub fn parseWrite(writer: anytype, bytes: []const u8) error{OutOfMemory}!Result
 /// Higher level API. Does not return extra info about parse errors.
 /// Caller owns returned memory.
 pub fn parseAlloc(allocator: std.mem.Allocator, bytes: []const u8) ParseError![]u8 {
-    var buf = std.ArrayList(u8).init(allocator);
+    var buf: std.io.AllocatingWriter = undefined;
+    const bw = buf.init(allocator);
     defer buf.deinit();
-
+    // TODO try @errorCast(...)
-    switch (try parseWrite(buf.writer(), bytes)) {
+    const result = parseWrite(bw, bytes) catch |err| return @errorCast(err);
+    switch (result) {
         .success => return buf.toOwnedSlice(),
         .failure => return error.InvalidLiteral,
     }

src/Air/print.zig

@@ -1,6 +1,5 @@
 const std = @import("std");
 const Allocator = std.mem.Allocator;
-const fmtIntSizeBin = std.fmt.fmtIntSizeBin;
 
 const build_options = @import("build_options");
 const Zcu = @import("../Zcu.zig");
@@ -25,20 +24,20 @@ pub fn write(air: Air, stream: anytype, pt: Zcu.PerThread, liveness: ?Air.Livene
 
     // zig fmt: off
     stream.print(
-        \\# Total AIR+Liveness bytes: {}
+        \\# Total AIR+Liveness bytes: {Bi}
-        \\# AIR Instructions:         {d} ({})
+        \\# AIR Instructions:         {d} ({Bi})
-        \\# AIR Extra Data:           {d} ({})
+        \\# AIR Extra Data:           {d} ({Bi})
-        \\# Liveness tomb_bits:       {}
+        \\# Liveness tomb_bits:       {Bi}
-        \\# Liveness Extra Data:      {d} ({})
+        \\# Liveness Extra Data:      {d} ({Bi})
-        \\# Liveness special table:   {d} ({})
+        \\# Liveness special table:   {d} ({Bi})
         \\
     , .{
-        fmtIntSizeBin(total_bytes),
+        total_bytes,
-        air.instructions.len, fmtIntSizeBin(instruction_bytes),
+        air.instructions.len, instruction_bytes,
-        air.extra.items.len, fmtIntSizeBin(extra_bytes),
+        air.extra.items.len, extra_bytes,
-        fmtIntSizeBin(tomb_bytes),
+        tomb_bytes,
-        if (liveness) |l| l.extra.len else 0, fmtIntSizeBin(liveness_extra_bytes),
+        if (liveness) |l| l.extra.len else 0, liveness_extra_bytes,
-        if (liveness) |l| l.special.count() else 0, fmtIntSizeBin(liveness_special_bytes),
+        if (liveness) |l| l.special.count() else 0, liveness_special_bytes,
     }) catch return;
     // zig fmt: on
 

src/Builtin.zig

@@ -51,7 +51,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
     const zig_backend = opts.zig_backend;
 
     @setEvalBranchQuota(4000);
-    try buffer.writer().print(
+    try buffer.print(
         \\const std = @import("std");
         \\/// Zig version. When writing code that supports multiple versions of Zig, prefer
         \\/// feature detection (i.e. with `@hasDecl` or `@hasField`) over version checks.
@@ -89,10 +89,10 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
         const index = @as(std.Target.Cpu.Feature.Set.Index, @intCast(index_usize));
         const is_enabled = target.cpu.features.isEnabled(index);
         if (is_enabled) {
-            try buffer.writer().print("        .{p_},\n", .{std.zig.fmtId(feature.name)});
+            try buffer.print("        .{p_},\n", .{std.zig.fmtId(feature.name)});
         }
     }
-    try buffer.writer().print(
+    try buffer.print(
         \\    }}),
         \\}};
         \\pub const os: std.Target.Os = .{{
@@ -104,7 +104,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
 
     switch (target.os.versionRange()) {
         .none => try buffer.appendSlice(" .none = {} },\n"),
-        .semver => |semver| try buffer.writer().print(
+        .semver => |semver| try buffer.print(
             \\ .semver = .{{
             \\        .min = .{{
             \\            .major = {},
@@ -127,7 +127,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
             semver.max.minor,
             semver.max.patch,
         }),
-        .linux => |linux| try buffer.writer().print(
+        .linux => |linux| try buffer.print(
             \\ .linux = .{{
             \\        .range = .{{
             \\            .min = .{{
@@ -164,7 +164,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
 
             linux.android,
         }),
-        .hurd => |hurd| try buffer.writer().print(
+        .hurd => |hurd| try buffer.print(
             \\ .hurd = .{{
             \\        .range = .{{
             \\            .min = .{{
@@ -198,7 +198,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
             hurd.glibc.minor,
             hurd.glibc.patch,
         }),
-        .windows => |windows| try buffer.writer().print(
+        .windows => |windows| try buffer.print(
             \\ .windows = .{{
             \\        .min = {c},
             \\        .max = {c},
@@ -217,7 +217,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
     );
 
     if (target.dynamic_linker.get()) |dl| {
-        try buffer.writer().print(
+        try buffer.print(
             \\    .dynamic_linker = .init("{s}"),
             \\}};
             \\
@@ -237,7 +237,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
     // knows libc will provide it, and likewise c.zig will not export memcpy.
     const link_libc = opts.link_libc;
 
-    try buffer.writer().print(
+    try buffer.print(
         \\pub const object_format: std.Target.ObjectFormat = .{p_};
         \\pub const mode: std.builtin.OptimizeMode = .{p_};
         \\pub const link_libc = {};
@@ -269,7 +269,7 @@ pub fn append(opts: @This(), buffer: *std.ArrayList(u8)) Allocator.Error!void {
     });
 
     if (target.os.tag == .wasi) {
-        try buffer.writer().print(
+        try buffer.print(
             \\pub const wasi_exec_model: std.builtin.WasiExecModel = .{p_};
             \\
         , .{std.zig.fmtId(@tagName(opts.wasi_exec_model))});

src/Package/Fetch.zig

@@ -1643,10 +1643,8 @@ fn dumpHashInfo(all_files: []const *const HashedFile) !void {
     const w = bw.writer();
 
     for (all_files) |hashed_file| {
-        try w.print("{s}: {s}: {s}\n", .{
+        try w.print("{s}: {x}: {s}\n", .{
-            @tagName(hashed_file.kind),
+            @tagName(hashed_file.kind), &hashed_file.hash, hashed_file.normalized_path,
-            std.fmt.fmtSliceHexLower(&hashed_file.hash),
-            hashed_file.normalized_path,
         });
     }
 

src/Package/Fetch/git.zig

@@ -127,7 +127,7 @@ pub const Oid = union(Format) {
     ) @TypeOf(writer).Error!void {
         _ = fmt;
         _ = options;
-        try writer.print("{}", .{std.fmt.fmtSliceHexLower(oid.slice())});
+        try writer.print("{x}", .{oid.slice()});
     }
 
     pub fn slice(oid: *const Oid) []const u8 {

src/Zcu/PerThread.zig

@@ -477,11 +477,8 @@ pub fn updateZirRefs(pt: Zcu.PerThread) Allocator.Error!void {
                     if (std.zig.srcHashEql(old_hash, new_hash)) {
                         break :hash_changed;
                     }
-                    log.debug("hash for (%{d} -> %{d}) changed: {} -> {}", .{
+                    log.debug("hash for (%{d} -> %{d}) changed: {x} -> {x}", .{
-                        old_inst,
+                        old_inst, new_inst, &old_hash, &new_hash,
-                        new_inst,
-                        std.fmt.fmtSliceHexLower(&old_hash),
-                        std.fmt.fmtSliceHexLower(&new_hash),
                     });
                 }
                 // The source hash associated with this instruction changed - invalidate relevant dependencies.

src/arch/x86_64/encoder.zig

@@ -1205,9 +1205,9 @@ pub const Vex = struct {
 fn expectEqualHexStrings(expected: []const u8, given: []const u8, assembly: []const u8) !void {
     assert(expected.len > 0);
     if (std.mem.eql(u8, expected, given)) return;
-    const expected_fmt = try std.fmt.allocPrint(testing.allocator, "{x}", .{std.fmt.fmtSliceHexLower(expected)});
+    const expected_fmt = try std.fmt.allocPrint(testing.allocator, "{x}", .{expected});
     defer testing.allocator.free(expected_fmt);
-    const given_fmt = try std.fmt.allocPrint(testing.allocator, "{x}", .{std.fmt.fmtSliceHexLower(given)});
+    const given_fmt = try std.fmt.allocPrint(testing.allocator, "{x}", .{given});
     defer testing.allocator.free(given_fmt);
     const idx = std.mem.indexOfDiff(u8, expected_fmt, given_fmt).?;
     const padding = try testing.allocator.alloc(u8, idx + 5);

src/fmt.zig

@@ -190,41 +190,7 @@ pub fn run(
     }
 }
 
-const FmtError = error{
+fn fmtPath(fmt: *Fmt, file_path: []const u8, check_mode: bool, dir: fs.Dir, sub_path: []const u8) anyerror!void {
-    SystemResources,
-    OperationAborted,
-    IoPending,
-    BrokenPipe,
-    Unexpected,
-    WouldBlock,
-    Canceled,
-    FileClosed,
-    DestinationAddressRequired,
-    DiskQuota,
-    FileTooBig,
-    MessageTooBig,
-    InputOutput,
-    NoSpaceLeft,
-    AccessDenied,
-    OutOfMemory,
-    RenameAcrossMountPoints,
-    ReadOnlyFileSystem,
-    LinkQuotaExceeded,
-    FileBusy,
-    EndOfStream,
-    Unseekable,
-    NotOpenForWriting,
-    UnsupportedEncoding,
-    InvalidEncoding,
-    ConnectionResetByPeer,
-    SocketNotConnected,
-    LockViolation,
-    NetNameDeleted,
-    InvalidArgument,
-    ProcessNotFound,
-} || fs.File.OpenError;
-
-fn fmtPath(fmt: *Fmt, file_path: []const u8, check_mode: bool, dir: fs.Dir, sub_path: []const u8) FmtError!void {
     fmtPathFile(fmt, file_path, check_mode, dir, sub_path) catch |err| switch (err) {
         error.IsDir, error.AccessDenied => return fmtPathDir(fmt, file_path, check_mode, dir, sub_path),
         else => {
@@ -241,7 +207,7 @@ fn fmtPathDir(
     check_mode: bool,
     parent_dir: fs.Dir,
     parent_sub_path: []const u8,
-) FmtError!void {
+) anyerror!void {
     var dir = try parent_dir.openDir(parent_sub_path, .{ .iterate = true });
     defer dir.close();
 
@@ -277,7 +243,7 @@ fn fmtPathFile(
     check_mode: bool,
     dir: fs.Dir,
     sub_path: []const u8,
-) FmtError!void {
+) anyerror!void {
     const source_file = try dir.openFile(sub_path, .{});
     var file_closed = false;
     errdefer if (!file_closed) source_file.close();

src/libs/mingw.zig

@@ -388,7 +388,7 @@ pub fn libExists(
 /// This function body is verbose but all it does is test 3 different paths and
 /// see if a .def file exists.
 fn findDef(
-    allocator: Allocator,
+    gpa: Allocator,
     target: *const std.Target,
     zig_lib_directory: Cache.Directory,
     lib_name: []const u8,
@@ -401,7 +401,8 @@ fn findDef(
         else => unreachable,
     };
 
-    var override_path = std.ArrayList(u8).init(allocator);
+    var override_path: std.io.AllocatingWriter = undefined;
+    const override_path_writer = override_path.init(gpa);
     defer override_path.deinit();
 
     const s = path.sep_str;
@@ -410,11 +411,11 @@ fn findDef(
         // Try the archtecture-specific path first.
         const fmt_path = "libc" ++ s ++ "mingw" ++ s ++ "{s}" ++ s ++ "{s}.def";
         if (zig_lib_directory.path) |p| {
-            try override_path.writer().print("{s}" ++ s ++ fmt_path, .{ p, lib_path, lib_name });
+            try override_path_writer.print("{s}" ++ s ++ fmt_path, .{ p, lib_path, lib_name });
         } else {
-            try override_path.writer().print(fmt_path, .{ lib_path, lib_name });
+            try override_path_writer.print(fmt_path, .{ lib_path, lib_name });
         }
-        if (std.fs.cwd().access(override_path.items, .{})) |_| {
+        if (std.fs.cwd().access(override_path.getWritten(), .{})) |_| {
             return override_path.toOwnedSlice();
         } else |err| switch (err) {
             error.FileNotFound => {},
@@ -424,14 +425,14 @@ fn findDef(
 
     {
         // Try the generic version.
-        override_path.shrinkRetainingCapacity(0);
+        override_path.clearRetainingCapacity();
         const fmt_path = "libc" ++ s ++ "mingw" ++ s ++ "lib-common" ++ s ++ "{s}.def";
         if (zig_lib_directory.path) |p| {
-            try override_path.writer().print("{s}" ++ s ++ fmt_path, .{ p, lib_name });
+            try override_path_writer.print("{s}" ++ s ++ fmt_path, .{ p, lib_name });
         } else {
-            try override_path.writer().print(fmt_path, .{lib_name});
+            try override_path_writer.print(fmt_path, .{lib_name});
         }
-        if (std.fs.cwd().access(override_path.items, .{})) |_| {
+        if (std.fs.cwd().access(override_path.getWritten(), .{})) |_| {
             return override_path.toOwnedSlice();
         } else |err| switch (err) {
             error.FileNotFound => {},
@@ -441,14 +442,14 @@ fn findDef(
 
     {
         // Try the generic version and preprocess it.
-        override_path.shrinkRetainingCapacity(0);
+        override_path.clearRetainingCapacity();
         const fmt_path = "libc" ++ s ++ "mingw" ++ s ++ "lib-common" ++ s ++ "{s}.def.in";
         if (zig_lib_directory.path) |p| {
-            try override_path.writer().print("{s}" ++ s ++ fmt_path, .{ p, lib_name });
+            try override_path_writer.print("{s}" ++ s ++ fmt_path, .{ p, lib_name });
         } else {
-            try override_path.writer().print(fmt_path, .{lib_name});
+            try override_path_writer.print(fmt_path, .{lib_name});
         }
-        if (std.fs.cwd().access(override_path.items, .{})) |_| {
+        if (std.fs.cwd().access(override_path.getWritten(), .{})) |_| {
             return override_path.toOwnedSlice();
         } else |err| switch (err) {
             error.FileNotFound => {},

src/link/Coff.zig

@@ -830,8 +830,8 @@ fn debugMem(allocator: Allocator, handle: std.process.Child.Id, pvaddr: std.os.w
     const buffer = try allocator.alloc(u8, code.len);
     defer allocator.free(buffer);
     const memread = try std.os.windows.ReadProcessMemory(handle, pvaddr, buffer);
-    log.debug("to write: {x}", .{std.fmt.fmtSliceHexLower(code)});
+    log.debug("to write: {x}", .{code});
-    log.debug("in memory: {x}", .{std.fmt.fmtSliceHexLower(memread)});
+    log.debug("in memory: {x}", .{memread});
 }
 
 fn writeMemProtected(handle: std.process.Child.Id, pvaddr: std.os.windows.LPVOID, code: []const u8) !void {

src/link/MachO/dyld_info/Trie.zig

@@ -336,9 +336,9 @@ const Edge = struct {
 fn expectEqualHexStrings(expected: []const u8, given: []const u8) !void {
     assert(expected.len > 0);
     if (mem.eql(u8, expected, given)) return;
-    const expected_fmt = try std.fmt.allocPrint(testing.allocator, "{x}", .{std.fmt.fmtSliceHexLower(expected)});
+    const expected_fmt = try std.fmt.allocPrint(testing.allocator, "{x}", .{expected});
     defer testing.allocator.free(expected_fmt);
-    const given_fmt = try std.fmt.allocPrint(testing.allocator, "{x}", .{std.fmt.fmtSliceHexLower(given)});
+    const given_fmt = try std.fmt.allocPrint(testing.allocator, "{x}", .{given});
     defer testing.allocator.free(given_fmt);
     const idx = mem.indexOfDiff(u8, expected_fmt, given_fmt).?;
     const padding = try testing.allocator.alloc(u8, idx + 5);

src/link/Wasm/Flush.zig

@@ -1035,20 +1035,14 @@ pub fn finish(f: *Flush, wasm: *Wasm) !void {
                 var id: [16]u8 = undefined;
                 std.crypto.hash.sha3.TurboShake128(null).hash(binary_bytes.items, &id, .{});
                 var uuid: [36]u8 = undefined;
-                _ = try std.fmt.bufPrint(&uuid, "{s}-{s}-{s}-{s}-{s}", .{
+                _ = try std.fmt.bufPrint(&uuid, "{x}-{x}-{x}-{x}-{x}", .{
-                    std.fmt.fmtSliceHexLower(id[0..4]),
+                    id[0..4], id[4..6], id[6..8], id[8..10], id[10..],
-                    std.fmt.fmtSliceHexLower(id[4..6]),
-                    std.fmt.fmtSliceHexLower(id[6..8]),
-                    std.fmt.fmtSliceHexLower(id[8..10]),
-                    std.fmt.fmtSliceHexLower(id[10..]),
                 });
                 try emitBuildIdSection(gpa, binary_bytes, &uuid);
             },
             .hexstring => |hs| {
                 var buffer: [32 * 2]u8 = undefined;
-                const str = std.fmt.bufPrint(&buffer, "{s}", .{
+                const str = std.fmt.bufPrint(&buffer, "{x}", .{hs.toSlice()}) catch unreachable;
-                    std.fmt.fmtSliceHexLower(hs.toSlice()),
-                }) catch unreachable;
                 try emitBuildIdSection(gpa, binary_bytes, str);
             },
             else => |mode| {

src/main.zig

@@ -65,6 +65,9 @@ pub fn wasi_cwd() std.os.wasi.fd_t {
 
 const fatal = std.process.fatal;
 
+/// This can be global since stdout is a singleton.
+var stdout_buffer: [4096]u8 = undefined;
+
 /// Shaming all the locations that inappropriately use an O(N) search algorithm.
 /// Please delete this and fix the compilation errors!
 pub const @"bad O(N)" = void;
@@ -338,9 +341,7 @@ fn mainArgs(gpa: Allocator, arena: Allocator, args: []const []const u8) !void {
         return cmdInit(gpa, arena, cmd_args);
     } else if (mem.eql(u8, cmd, "targets")) {
         dev.check(.targets_command);
-        const host = std.zig.resolveTargetQueryOrFatal(.{});
+        return @import("print_targets.zig").cmdTargets(arena, cmd_args);
-        const stdout = io.getStdOut().writer();
-        return @import("print_targets.zig").cmdTargets(arena, cmd_args, stdout, &host);
     } else if (mem.eql(u8, cmd, "version")) {
         dev.check(.version_command);
         try std.io.getStdOut().writeAll(build_options.version ++ "\n");
@@ -351,7 +352,7 @@ fn mainArgs(gpa: Allocator, arena: Allocator, args: []const []const u8) !void {
     } else if (mem.eql(u8, cmd, "env")) {
         dev.check(.env_command);
         verifyLibcxxCorrectlyLinked();
-        return @import("print_env.zig").cmdEnv(arena, cmd_args, io.getStdOut().writer());
+        return @import("print_env.zig").cmdEnv(arena, cmd_args);
     } else if (mem.eql(u8, cmd, "reduce")) {
         return jitCmd(gpa, arena, cmd_args, .{
             .cmd_name = "reduce",
@@ -3334,9 +3335,8 @@ fn buildOutputType(
         var bin_digest: Cache.BinDigest = undefined;
         hasher.final(&bin_digest);
 
-        const sub_path = try std.fmt.allocPrint(arena, "tmp" ++ sep ++ "{s}-stdin{s}", .{
+        const sub_path = try std.fmt.allocPrint(arena, "tmp" ++ sep ++ "{x}-stdin{s}", .{
-            std.fmt.fmtSliceHexLower(&bin_digest),
+            &bin_digest, ext.canonicalName(target),
-            ext.canonicalName(target),
         });
         try dirs.local_cache.handle.rename(dump_path, sub_path);
 
@@ -6061,6 +6061,11 @@ fn cmdAstCheck(
 
     const tree = try Ast.parse(arena, source, mode);
 
+    var bw: std.io.BufferedWriter = .{
+        .unbuffered_writer = io.getStdOut().writer(),
+        .buffer = &stdout_buffer,
+    };
+
     switch (mode) {
         .zig => {
             const zir = try AstGen.generate(arena, tree);
@@ -6103,31 +6108,30 @@ fn cmdAstCheck(
                 const extra_bytes = zir.extra.len * @sizeOf(u32);
                 const total_bytes = @sizeOf(Zir) + instruction_bytes + extra_bytes +
                     zir.string_bytes.len * @sizeOf(u8);
-                const stdout = io.getStdOut();
-                const fmtIntSizeBin = std.fmt.fmtIntSizeBin;
                 // zig fmt: off
-                try stdout.writer().print(
+                try bw.print(
-                    \\# Source bytes:       {}
+                    \\# Source bytes:       {Bi}
-                    \\# Tokens:             {} ({})
+                    \\# Tokens:             {} ({Bi})
-                    \\# AST Nodes:          {} ({})
+                    \\# AST Nodes:          {} ({Bi})
-                    \\# Total ZIR bytes:    {}
+                    \\# Total ZIR bytes:    {Bi}
-                    \\# Instructions:       {d} ({})
+                    \\# Instructions:       {d} ({Bi})
                     \\# String Table Bytes: {}
-                    \\# Extra Data Items:   {d} ({})
+                    \\# Extra Data Items:   {d} ({Bi})
                     \\
                 , .{
-                    fmtIntSizeBin(source.len),
+                    source.len,
-                    tree.tokens.len, fmtIntSizeBin(token_bytes),
+                    tree.tokens.len, token_bytes,
-                    tree.nodes.len, fmtIntSizeBin(tree_bytes),
+                    tree.nodes.len, tree_bytes,
-                    fmtIntSizeBin(total_bytes),
+                    total_bytes,
-                    zir.instructions.len, fmtIntSizeBin(instruction_bytes),
+                    zir.instructions.len, instruction_bytes,
-                    fmtIntSizeBin(zir.string_bytes.len),
+                    zir.string_bytes.len,
-                    zir.extra.len, fmtIntSizeBin(extra_bytes),
+                    zir.extra.len, extra_bytes,
                 });
                 // zig fmt: on
             }
 
-            try @import("print_zir.zig").renderAsTextToFile(arena, tree, zir, io.getStdOut());
+            try @import("print_zir.zig").renderAsText(arena, tree, zir, &bw);
+            try bw.flush();
 
             if (zir.hasCompileErrors()) {
                 process.exit(1);
@@ -6154,7 +6158,8 @@ fn cmdAstCheck(
                 fatal("-t option only available in builds of zig with debug extensions", .{});
             }
 
-            try @import("print_zoir.zig").renderToFile(zoir, arena, io.getStdOut());
+            try @import("print_zoir.zig").renderToWriter(zoir, arena, &bw);
+            try bw.flush();
             return cleanExit();
         },
     }
@@ -6275,11 +6280,13 @@ fn detectNativeCpuWithLLVM(
 }
 
 fn printCpu(cpu: std.Target.Cpu) !void {
-    var bw = io.bufferedWriter(io.getStdOut().writer());
+    var bw: std.io.BufferedWriter = .{
-    const stdout = bw.writer();
+        .unbuffered_writer = io.getStdOut().writer(),
+        .buffer = &stdout_buffer,
+    };
 
     if (cpu.model.llvm_name) |llvm_name| {
-        try stdout.print("{s}\n", .{llvm_name});
+        try bw.print("{s}\n", .{llvm_name});
     }
 
     const all_features = cpu.arch.allFeaturesList();
@@ -6288,7 +6295,7 @@ fn printCpu(cpu: std.Target.Cpu) !void {
         const index: std.Target.Cpu.Feature.Set.Index = @intCast(index_usize);
         const is_enabled = cpu.features.isEnabled(index);
         const plus_or_minus = "-+"[@intFromBool(is_enabled)];
-        try stdout.print("{c}{s}\n", .{ plus_or_minus, llvm_name });
+        try bw.print("{c}{s}\n", .{ plus_or_minus, llvm_name });
     }
 
     try bw.flush();
@@ -6356,6 +6363,11 @@ fn cmdDumpZir(
 
     const zir = try Zcu.loadZirCache(arena, f);
 
+    var bw: std.io.BufferedWriter = .{
+        .unbuffered_writer = io.getStdOut().writer(),
+        .buffer = &stdout_buffer,
+    };
+
     {
         const instruction_bytes = zir.instructions.len *
             // Here we don't use @sizeOf(Zir.Inst.Data) because it would include
@@ -6364,25 +6376,24 @@ fn cmdDumpZir(
         const extra_bytes = zir.extra.len * @sizeOf(u32);
         const total_bytes = @sizeOf(Zir) + instruction_bytes + extra_bytes +
             zir.string_bytes.len * @sizeOf(u8);
-        const stdout = io.getStdOut();
-        const fmtIntSizeBin = std.fmt.fmtIntSizeBin;
         // zig fmt: off
-        try stdout.writer().print(
+        try bw.print(
-            \\# Total ZIR bytes:    {}
+            \\# Total ZIR bytes:    {Bi}
-            \\# Instructions:       {d} ({})
+            \\# Instructions:       {d} ({Bi})
-            \\# String Table Bytes: {}
+            \\# String Table Bytes: {Bi}
-            \\# Extra Data Items:   {d} ({})
+            \\# Extra Data Items:   {d} ({Bi})
             \\
         , .{
-            fmtIntSizeBin(total_bytes),
+            total_bytes,
-            zir.instructions.len, fmtIntSizeBin(instruction_bytes),
+            zir.instructions.len, instruction_bytes,
-            fmtIntSizeBin(zir.string_bytes.len),
+            zir.string_bytes.len,
-            zir.extra.len, fmtIntSizeBin(extra_bytes),
+            zir.extra.len, extra_bytes,
         });
         // zig fmt: on
     }
 
-    return @import("print_zir.zig").renderAsTextToFile(arena, null, zir, io.getStdOut());
+    try @import("print_zir.zig").renderAsText(arena, null, zir, &bw);
+    try bw.flush();
 }
 
 /// This is only enabled for debug builds.
@@ -6440,13 +6451,15 @@ fn cmdChangelist(
     var inst_map: std.AutoHashMapUnmanaged(Zir.Inst.Index, Zir.Inst.Index) = .empty;
     try Zcu.mapOldZirToNew(arena, old_zir, new_zir, &inst_map);
 
-    var bw = io.bufferedWriter(io.getStdOut().writer());
+    var bw: std.io.BufferedWriter = .{
-    const stdout = bw.writer();
+        .unbuffered_writer = io.getStdOut().writer(),
+        .buffer = &stdout_buffer,
+    };
     {
-        try stdout.print("Instruction mappings:\n", .{});
+        try bw.print("Instruction mappings:\n", .{});
         var it = inst_map.iterator();
         while (it.next()) |entry| {
-            try stdout.print(" %{d} => %{d}\n", .{
+            try bw.print(" %{d} => %{d}\n", .{
                 @intFromEnum(entry.key_ptr.*),
                 @intFromEnum(entry.value_ptr.*),
             });
@@ -6714,13 +6727,10 @@ fn accessFrameworkPath(
 
     for (&[_][]const u8{ ".tbd", ".dylib", "" }) |ext| {
         test_path.clearRetainingCapacity();
-        try test_path.writer().print("{s}" ++ sep ++ "{s}.framework" ++ sep ++ "{s}{s}", .{
+        try test_path.print("{s}" ++ sep ++ "{s}.framework" ++ sep ++ "{s}{s}", .{
-            framework_dir_path,
+            framework_dir_path, framework_name, framework_name, ext,
-            framework_name,
-            framework_name,
-            ext,
         });
-        try checked_paths.writer().print("\n {s}", .{test_path.items});
+        try checked_paths.print("\n {s}", .{test_path.items});
         fs.cwd().access(test_path.items, .{}) catch |err| switch (err) {
             error.FileNotFound => continue,
             else => |e| fatal("unable to search for {s} framework '{s}': {s}", .{
@@ -7033,14 +7043,19 @@ fn cmdFetch(
         try fixups.append_string_after_node.put(gpa, manifest.version_node, dependencies_text);
     }
 
-    var rendered = std.ArrayList(u8).init(gpa);
+    var file = build_root.directory.handle.createFile(Package.Manifest.basename, .{}) catch |err| {
-    defer rendered.deinit();
+        fatal("unable to create {s} file: {s}", .{ Package.Manifest.basename, err });
-    try ast.renderToArrayList(&rendered, fixups);
-
-    build_root.directory.handle.writeFile(.{ .sub_path = Package.Manifest.basename, .data = rendered.items }) catch |err| {
-        fatal("unable to write {s} file: {s}", .{ Package.Manifest.basename, @errorName(err) });
     };
-
+    defer file.close();
+    var buffer: [4096]u8 = undefined;
+    var bw: std.io.BufferedWriter = .{
+        .unbuffered_writer = file.writer(),
+        .buffer = &buffer,
+    };
+    ast.render(gpa, &bw, fixups) catch |err| fatal("failed to render AST to {s}: {s}", .{
+        Package.Manifest.basename, err,
+    });
+    bw.flush() catch |err| fatal("failed to flush {s}: {s}", .{ Package.Manifest.basename, err });
     return cleanExit();
 }
 

src/print_env.zig

@@ -4,7 +4,7 @@ const introspect = @import("introspect.zig");
 const Allocator = std.mem.Allocator;
 const fatal = std.process.fatal;
 
-pub fn cmdEnv(arena: Allocator, args: []const []const u8, stdout: std.fs.File.Writer) !void {
+pub fn cmdEnv(arena: Allocator, args: []const []const u8) !void {
     _ = args;
     const cwd_path = try introspect.getResolvedCwd(arena);
     const self_exe_path = try std.fs.selfExePathAlloc(arena);
@@ -21,10 +21,12 @@ pub fn cmdEnv(arena: Allocator, args: []const []const u8, stdout: std.fs.File.Wr
     const host = try std.zig.system.resolveTargetQuery(.{});
     const triple = try host.zigTriple(arena);
 
-    var bw = std.io.bufferedWriter(stdout);
+    var buffer: [1024]u8 = undefined;
-    const w = bw.writer();
+    var bw: std.io.BufferedWriter = .{
-
+        .buffer = &buffer,
-    var jws = std.json.writeStream(w, .{ .whitespace = .indent_1 });
+        .unbuffered_writer = std.io.getStdOut().writer(),
+    };
+    var jws = std.json.writeStream(bw, .{ .whitespace = .indent_1 });
 
     try jws.beginObject();
 
@@ -55,7 +57,7 @@ pub fn cmdEnv(arena: Allocator, args: []const []const u8, stdout: std.fs.File.Wr
     try jws.endObject();
 
     try jws.endObject();
-    try w.writeByte('\n');
+    try bw.writeByte('\n');
 
     try bw.flush();
 }

src/print_targets.zig

@@ -11,36 +11,36 @@ const assert = std.debug.assert;
 const glibc = @import("libs/glibc.zig");
 const introspect = @import("introspect.zig");
 
-pub fn cmdTargets(
+pub fn cmdTargets(arena: Allocator, args: []const []const u8) anyerror!void {
-    allocator: Allocator,
-    args: []const []const u8,
-    /// Output stream
-    stdout: anytype,
-    native_target: *const Target,
-) !void {
     _ = args;
-    var zig_lib_directory = introspect.findZigLibDir(allocator) catch |err| {
+    const host = std.zig.resolveTargetQueryOrFatal(.{});
+    var buffer: [1024]u8 = undefined;
+    var bw: std.io.BufferedWriter = .{
+        .unbuffered_writer = io.getStdOut().writer(),
+        .buffer = &buffer,
+    };
+    try print(arena, &bw, host);
+    try bw.flush();
+}
+
+fn print(arena: Allocator, output: *std.io.BufferedWriter, host: *const Target) anyerror!void {
+    var zig_lib_directory = introspect.findZigLibDir(arena) catch |err| {
         fatal("unable to find zig installation directory: {s}\n", .{@errorName(err)});
     };
     defer zig_lib_directory.handle.close();
-    defer allocator.free(zig_lib_directory.path.?);
 
     const abilists_contents = zig_lib_directory.handle.readFileAlloc(
-        allocator,
+        arena,
         glibc.abilists_path,
         glibc.abilists_max_size,
     ) catch |err| switch (err) {
         error.OutOfMemory => return error.OutOfMemory,
         else => fatal("unable to read " ++ glibc.abilists_path ++ ": {s}", .{@errorName(err)}),
     };
-    defer allocator.free(abilists_contents);
 
-    const glibc_abi = try glibc.loadMetaData(allocator, abilists_contents);
+    const glibc_abi = try glibc.loadMetaData(arena, abilists_contents);
-    defer glibc_abi.destroy(allocator);
 
-    var bw = io.bufferedWriter(stdout);
+    var sz = std.zon.stringify.serializer(output, .{});
-    const w = bw.writer();
-    var sz = std.zon.stringify.serializer(w, .{});
 
     {
         var root_obj = try sz.beginStruct(.{});
@@ -52,10 +52,9 @@ pub fn cmdTargets(
         {
             var libc_obj = try root_obj.beginTupleField("libc", .{});
             for (std.zig.target.available_libcs) |libc| {
-                const tmp = try std.fmt.allocPrint(allocator, "{s}-{s}-{s}", .{
+                const tmp = try std.fmt.allocPrint(arena, "{s}-{s}-{s}", .{
                     @tagName(libc.arch), @tagName(libc.os), @tagName(libc.abi),
                 });
-                defer allocator.free(tmp);
                 try libc_obj.field(tmp, .{});
             }
             try libc_obj.end();
@@ -64,8 +63,7 @@ pub fn cmdTargets(
         {
             var glibc_obj = try root_obj.beginTupleField("glibc", .{});
             for (glibc_abi.all_versions) |ver| {
-                const tmp = try std.fmt.allocPrint(allocator, "{}", .{ver});
+                const tmp = try std.fmt.allocPrint(arena, "{}", .{ver});
-                defer allocator.free(tmp);
                 try glibc_obj.field(tmp, .{});
             }
             try glibc_obj.end();
@@ -105,21 +103,20 @@ pub fn cmdTargets(
         {
             var native_obj = try root_obj.beginStructField("native", .{});
             {
-                const triple = try native_target.zigTriple(allocator);
+                const triple = try host.zigTriple(arena);
-                defer allocator.free(triple);
                 try native_obj.field("triple", triple, .{});
             }
             {
                 var cpu_obj = try native_obj.beginStructField("cpu", .{});
-                try cpu_obj.field("arch", @tagName(native_target.cpu.arch), .{});
+                try cpu_obj.field("arch", @tagName(host.cpu.arch), .{});
 
-                try cpu_obj.field("name", native_target.cpu.model.name, .{});
+                try cpu_obj.field("name", host.cpu.model.name, .{});
 
                 {
                     var features = try native_obj.beginTupleField("features", .{});
-                    for (native_target.cpu.arch.allFeaturesList(), 0..) |feature, i_usize| {
+                    for (host.cpu.arch.allFeaturesList(), 0..) |feature, i_usize| {
                         const index = @as(Target.Cpu.Feature.Set.Index, @intCast(i_usize));
-                        if (native_target.cpu.features.isEnabled(index)) {
+                        if (host.cpu.features.isEnabled(index)) {
                             try features.field(feature.name, .{});
                         }
                     }
@@ -128,14 +125,13 @@ pub fn cmdTargets(
                 try cpu_obj.end();
             }
 
-            try native_obj.field("os", @tagName(native_target.os.tag), .{});
+            try native_obj.field("os", @tagName(host.os.tag), .{});
-            try native_obj.field("abi", @tagName(native_target.abi), .{});
+            try native_obj.field("abi", @tagName(host.abi), .{});
             try native_obj.end();
         }
 
         try root_obj.end();
     }
 
-    try w.writeByte('\n');
+    try output.writeByte('\n');
-    return bw.flush();
 }

src/print_zoir.zig

@@ -1,13 +1,6 @@
-pub fn renderToFile(zoir: Zoir, arena: Allocator, f: std.fs.File) (std.fs.File.WriteError || Allocator.Error)!void {
+pub fn renderToWriter(zoir: Zoir, arena: Allocator, w: *std.io.BufferedWriter) anyerror!void {
-    var bw = std.io.bufferedWriter(f.writer());
-    try renderToWriter(zoir, arena, bw.writer());
-    try bw.flush();
-}
-
-pub fn renderToWriter(zoir: Zoir, arena: Allocator, w: anytype) (@TypeOf(w).Error || Allocator.Error)!void {
     assert(!zoir.hasCompileErrors());
 
-    const fmtIntSizeBin = std.fmt.fmtIntSizeBin;
     const bytes_per_node = comptime n: {
         var n: usize = 0;
         for (@typeInfo(Zoir.Node.Repr).@"struct".fields) |f| {
@@ -23,22 +16,22 @@ pub fn renderToWriter(zoir: Zoir, arena: Allocator, w: anytype) (@TypeOf(w).Erro
 
     // zig fmt: off
     try w.print(
-        \\# Nodes:              {} ({})
+        \\# Nodes:              {} ({Bi})
-        \\# Extra Data Items:   {} ({})
+        \\# Extra Data Items:   {} ({Bi})
-        \\# BigInt Limbs:       {} ({})
+        \\# BigInt Limbs:       {} ({Bi})
-        \\# String Table Bytes: {}
+        \\# String Table Bytes: {Bi}
-        \\# Total ZON Bytes:    {}
+        \\# Total ZON Bytes:    {Bi}
         \\
     , .{
-        zoir.nodes.len, fmtIntSizeBin(node_bytes),
+        zoir.nodes.len, node_bytes,
-        zoir.extra.len, fmtIntSizeBin(extra_bytes),
+        zoir.extra.len, extra_bytes,
-        zoir.limbs.len, fmtIntSizeBin(limb_bytes),
+        zoir.limbs.len, limb_bytes,
-        fmtIntSizeBin(string_bytes),
+        string_bytes,
-        fmtIntSizeBin(node_bytes + extra_bytes + limb_bytes + string_bytes),
+        node_bytes + extra_bytes + limb_bytes + string_bytes,
     });
     // zig fmt: on
     var pz: PrintZon = .{
-        .w = w.any(),
+        .w = w,
         .arena = arena,
         .zoir = zoir,
         .indent = 0,
@@ -48,7 +41,7 @@ pub fn renderToWriter(zoir: Zoir, arena: Allocator, w: anytype) (@TypeOf(w).Erro
 }
 
 const PrintZon = struct {
-    w: std.io.AnyWriter,
+    w: *std.io.BufferedWriter,
     arena: Allocator,
     zoir: Zoir,
     indent: u32,

src/translate_c.zig

@@ -5905,7 +5905,7 @@ fn parseCPrimaryExpr(c: *Context, m: *MacroCtx, scope: *Scope) ParseError!Node {
             if (slice[0] != '\'' or slice[1] == '\\' or slice.len == 3) {
                 return Tag.char_literal.create(c.arena, try escapeUnprintables(c, m));
             } else {
-                const str = try std.fmt.allocPrint(c.arena, "0x{s}", .{std.fmt.fmtSliceHexLower(slice[1 .. slice.len - 1])});
+                const str = try std.fmt.allocPrint(c.arena, "0x{x}", .{slice[1 .. slice.len - 1]});
                 return Tag.integer_literal.create(c.arena, str);
             }
         },