diff --git a/src/AstGen.zig b/src/AstGen.zig
index 3398478266..943d0aad08 100644
--- a/src/AstGen.zig
+++ b/src/AstGen.zig
@@ -1164,6 +1164,10 @@ fn fnProtoExpr(
     const tree = astgen.tree;
     const token_tags = tree.tokens.items(.tag);
 
+    if (fn_proto.name_token) |some| {
+        return astgen.failTok(some, "function type cannot have a name", .{});
+    }
+
     const is_extern = blk: {
         const maybe_extern_token = fn_proto.extern_export_inline_token orelse break :blk false;
         break :blk token_tags[maybe_extern_token] == .keyword_extern;
diff --git a/src/Sema.zig b/src/Sema.zig
index 047d3f84c2..f884684d73 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -2497,18 +2497,6 @@ fn zirEnumDecl(
     extra_index = try mod.scanNamespace(&enum_obj.namespace, extra_index, decls_len, new_decl);
 
     const body = sema.code.extra[extra_index..][0..body_len];
-    if (fields_len == 0) {
-        assert(body.len == 0);
-        if (tag_type_ref != .none) {
-            const ty = try sema.resolveType(block, tag_ty_src, tag_type_ref);
-            if (ty.zigTypeTag() != .Int and ty.zigTypeTag() != .ComptimeInt) {
-                return sema.fail(block, tag_ty_src, "expected integer tag type, found '{}'", .{ty.fmt(sema.mod)});
-            }
-            enum_obj.tag_ty = try ty.copy(new_decl_arena_allocator);
-            enum_obj.tag_ty_inferred = false;
-        }
-        return decl_val;
-    }
     extra_index += body.len;
 
     const bit_bags_count = std.math.divCeil(usize, fields_len, 32) catch unreachable;
@@ -2566,6 +2554,9 @@ fn zirEnumDecl(
             }
             enum_obj.tag_ty = try ty.copy(decl_arena_allocator);
             enum_obj.tag_ty_inferred = false;
+        } else if (fields_len == 0) {
+            enum_obj.tag_ty = try Type.Tag.int_unsigned.create(decl_arena_allocator, 0);
+            enum_obj.tag_ty_inferred = true;
         } else {
             const bits = std.math.log2_int_ceil(usize, fields_len);
             enum_obj.tag_ty = try Type.Tag.int_unsigned.create(decl_arena_allocator, bits);
@@ -3788,6 +3779,7 @@ fn validateStructInit(
     if ((is_comptime or block.is_comptime) and
         (try sema.resolveDefinedValue(block, init_src, struct_ptr)) != null)
     {
+        try sema.resolveStructLayout(block, init_src, struct_ty);
         // In this case the only thing we need to do is evaluate the implicit
         // store instructions for default field values, and report any missing fields.
         // Avoid the cost of the extra machinery for detecting a comptime struct init value.
@@ -3982,6 +3974,7 @@ fn validateStructInit(
         try sema.storePtr2(block, init_src, struct_ptr, init_src, struct_init, init_src, .store);
         return;
     }
+    try sema.resolveStructLayout(block, init_src, struct_ty);
 
     // Our task is to insert `store` instructions for all the default field values.
     for (found_fields) |field_ptr, i| {
@@ -9003,6 +8996,9 @@ fn zirSwitchCond(
         .ErrorSet,
         .Enum,
         => {
+            if (operand_ty.isSlice()) {
+                return sema.fail(block, src, "switch on type '{}'", .{operand_ty.fmt(sema.mod)});
+            }
             if ((try sema.typeHasOnePossibleValue(block, operand_src, operand_ty))) |opv| {
                 return sema.addConstant(operand_ty, opv);
             }
@@ -15849,6 +15845,7 @@ fn finishStructInit(
     }
 
     if (is_ref) {
+        try sema.resolveStructLayout(block, dest_src, struct_ty);
         const target = sema.mod.getTarget();
         const alloc_ty = try Type.ptr(sema.arena, sema.mod, .{
             .pointee_type = struct_ty,
@@ -21895,17 +21892,18 @@ fn unionFieldPtr(
                 if (union_val.isUndef()) {
                     return sema.failWithUseOfUndef(block, src);
                 }
+                const enum_field_index = union_obj.tag_ty.enumFieldIndex(field_name).?;
                 const tag_and_val = union_val.castTag(.@"union").?.data;
                 var field_tag_buf: Value.Payload.U32 = .{
                     .base = .{ .tag = .enum_field_index },
-                    .data = field_index,
+                    .data = @intCast(u32, enum_field_index),
                 };
                 const field_tag = Value.initPayload(&field_tag_buf.base);
                 const tag_matches = tag_and_val.tag.eql(field_tag, union_obj.tag_ty, sema.mod);
                 if (!tag_matches) {
                     const msg = msg: {
                         const active_index = tag_and_val.tag.castTag(.enum_field_index).?.data;
-                        const active_field_name = union_obj.fields.keys()[active_index];
+                        const active_field_name = union_obj.tag_ty.enumFieldName(active_index);
                         const msg = try sema.errMsg(block, src, "access of union field '{s}' while field '{s}' is active", .{ field_name, active_field_name });
                         errdefer msg.destroy(sema.gpa);
                         try sema.addDeclaredHereNote(msg, union_ty);
@@ -21930,12 +21928,11 @@ fn unionFieldPtr(
     if (!initializing and union_obj.layout == .Auto and block.wantSafety() and
         union_ty.unionTagTypeSafety() != null and union_obj.fields.count() > 1)
     {
-        const enum_ty = union_ty.unionTagTypeHypothetical();
         const wanted_tag_val = try Value.Tag.enum_field_index.create(sema.arena, field_index);
-        const wanted_tag = try sema.addConstant(enum_ty, wanted_tag_val);
+        const wanted_tag = try sema.addConstant(union_obj.tag_ty, wanted_tag_val);
         // TODO would it be better if get_union_tag supported pointers to unions?
         const union_val = try block.addTyOp(.load, union_ty, union_ptr);
-        const active_tag = try block.addTyOp(.get_union_tag, enum_ty, union_val);
+        const active_tag = try block.addTyOp(.get_union_tag, union_obj.tag_ty, union_val);
         const ok = try block.addBinOp(.cmp_eq, active_tag, wanted_tag);
         try sema.addSafetyCheck(block, ok, .inactive_union_field);
     }
@@ -21966,9 +21963,10 @@ fn unionFieldVal(
         if (union_val.isUndef()) return sema.addConstUndef(field.ty);
 
         const tag_and_val = union_val.castTag(.@"union").?.data;
+        const enum_field_index = union_obj.tag_ty.enumFieldIndex(field_name).?;
         var field_tag_buf: Value.Payload.U32 = .{
             .base = .{ .tag = .enum_field_index },
-            .data = field_index,
+            .data = @intCast(u32, enum_field_index),
         };
         const field_tag = Value.initPayload(&field_tag_buf.base);
         const tag_matches = tag_and_val.tag.eql(field_tag, union_obj.tag_ty, sema.mod);
@@ -21979,7 +21977,7 @@ fn unionFieldVal(
                 } else {
                     const msg = msg: {
                         const active_index = tag_and_val.tag.castTag(.enum_field_index).?.data;
-                        const active_field_name = union_obj.fields.keys()[active_index];
+                        const active_field_name = union_obj.tag_ty.enumFieldName(active_index);
                         const msg = try sema.errMsg(block, src, "access of union field '{s}' while field '{s}' is active", .{ field_name, active_field_name });
                         errdefer msg.destroy(sema.gpa);
                         try sema.addDeclaredHereNote(msg, union_ty);
@@ -22004,10 +22002,9 @@ fn unionFieldVal(
     if (union_obj.layout == .Auto and block.wantSafety() and
         union_ty.unionTagTypeSafety() != null and union_obj.fields.count() > 1)
     {
-        const enum_ty = union_ty.unionTagTypeHypothetical();
         const wanted_tag_val = try Value.Tag.enum_field_index.create(sema.arena, field_index);
-        const wanted_tag = try sema.addConstant(enum_ty, wanted_tag_val);
-        const active_tag = try block.addTyOp(.get_union_tag, enum_ty, union_byval);
+        const wanted_tag = try sema.addConstant(union_obj.tag_ty, wanted_tag_val);
+        const active_tag = try block.addTyOp(.get_union_tag, union_obj.tag_ty, union_byval);
         const ok = try block.addBinOp(.cmp_eq, active_tag, wanted_tag);
         try sema.addSafetyCheck(block, ok, .inactive_union_field);
     }
@@ -22254,8 +22251,7 @@ fn tupleField(
 
     if (try sema.resolveMaybeUndefVal(block, tuple_src, tuple)) |tuple_val| {
         if (tuple_val.isUndef()) return sema.addConstUndef(field_ty);
-        const field_values = tuple_val.castTag(.aggregate).?.data;
-        return sema.addConstant(field_ty, field_values[field_index]);
+        return sema.addConstant(field_ty, tuple_val.fieldValue(tuple_ty, field_index));
     }
 
     try sema.validateRuntimeElemAccess(block, field_index_src, field_ty, tuple_ty, tuple_src);
@@ -28854,10 +28850,11 @@ pub fn typeHasOnePossibleValue(
 
         .tuple, .anon_struct => {
             const tuple = ty.tupleFields();
-            for (tuple.values) |val| {
-                if (val.tag() == .unreachable_value) {
-                    return null; // non-comptime field
-                }
+            for (tuple.values) |val, i| {
+                const is_comptime = val.tag() != .unreachable_value;
+                if (is_comptime) continue;
+                if ((try sema.typeHasOnePossibleValue(block, src, tuple.types[i])) != null) continue;
+                return null;
             }
             return Value.initTag(.empty_struct_value);
         },
diff --git a/src/print_zir.zig b/src/print_zir.zig
index 579a7970b7..f315d7f014 100644
--- a/src/print_zir.zig
+++ b/src/print_zir.zig
@@ -1721,13 +1721,13 @@ const Writer = struct {
         const body = self.code.extra[extra_index..][0..body_len];
         extra_index += body.len;
 
+        const prev_parent_decl_node = self.parent_decl_node;
+        if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
+        try self.writeBracedDecl(stream, body);
         if (fields_len == 0) {
-            assert(body.len == 0);
-            try stream.writeAll("{}, {})");
+            try stream.writeAll(", {})");
+            self.parent_decl_node = prev_parent_decl_node;
         } else {
-            const prev_parent_decl_node = self.parent_decl_node;
-            if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
-            try self.writeBracedDecl(stream, body);
             try stream.writeAll(", {\n");
 
             self.indent += 2;
diff --git a/src/type.zig b/src/type.zig
index cc6e5706ee..5ff9da8913 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -4979,19 +4979,20 @@ pub const Type = extern union {
                 const s = ty.castTag(.@"struct").?.data;
                 assert(s.haveFieldTypes());
                 for (s.fields.values()) |field| {
-                    if (field.ty.onePossibleValue() == null) {
-                        return null;
-                    }
+                    if (field.is_comptime) continue;
+                    if (field.ty.onePossibleValue() != null) continue;
+                    return null;
                 }
                 return Value.initTag(.empty_struct_value);
             },
 
             .tuple, .anon_struct => {
                 const tuple = ty.tupleFields();
-                for (tuple.values) |val| {
-                    if (val.tag() == .unreachable_value) {
-                        return null; // non-comptime field
-                    }
+                for (tuple.values) |val, i| {
+                    const is_comptime = val.tag() != .unreachable_value;
+                    if (is_comptime) continue;
+                    if (tuple.types[i].onePossibleValue() != null) continue;
+                    return null;
                 }
                 return Value.initTag(.empty_struct_value);
             },
diff --git a/test/behavior/enum.zig b/test/behavior/enum.zig
index 9e96163cc0..517414780b 100644
--- a/test/behavior/enum.zig
+++ b/test/behavior/enum.zig
@@ -1170,3 +1170,8 @@ test "switch on an extern enum with negative value" {
         Foo.Bar => return,
     }
 }
+
+test "Non-exhaustive enum with nonstandard int size behaves correctly" {
+    const E = enum(u15) { _ };
+    try expect(@sizeOf(E) == @sizeOf(u15));
+}
diff --git a/test/behavior/packed-struct.zig b/test/behavior/packed-struct.zig
index 9bc1c1f824..bd312e9cda 100644
--- a/test/behavior/packed-struct.zig
+++ b/test/behavior/packed-struct.zig
@@ -564,3 +564,18 @@ test "nested packed struct field access test" {
     try std.testing.expect(arg.g.h == 6);
     try std.testing.expect(arg.g.i == 8);
 }
+
+test "runtime init of unnamed packed struct type" {
+    if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
+    if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
+
+    var z: u8 = 123;
+    try (packed struct {
+        x: u8,
+        pub fn m(s: @This()) !void {
+            try expect(s.x == 123);
+        }
+    }{ .x = z }).m();
+}
diff --git a/test/behavior/tuple.zig b/test/behavior/tuple.zig
index 971e52a0b5..2b715c3b23 100644
--- a/test/behavior/tuple.zig
+++ b/test/behavior/tuple.zig
@@ -301,3 +301,30 @@ test "tuple type with void field" {
     const x = T{{}};
     try expect(@TypeOf(x[0]) == void);
 }
+
+test "zero sized struct in tuple handled correctly" {
+    const State = struct {
+        const Self = @This();
+        data: @Type(.{
+            .Struct = .{
+                .is_tuple = true,
+                .layout = .Auto,
+                .decls = &.{},
+                .fields = &.{.{
+                    .name = "0",
+                    .field_type = struct {},
+                    .default_value = null,
+                    .is_comptime = false,
+                    .alignment = 0,
+                }},
+            },
+        }),
+
+        pub fn do(this: Self) usize {
+            return @sizeOf(@TypeOf(this));
+        }
+    };
+
+    var s: State = undefined;
+    try expect(s.do() == 0);
+}
diff --git a/test/cases/compile_errors/access_inactive_union_field_comptime.zig b/test/cases/compile_errors/access_inactive_union_field_comptime.zig
new file mode 100644
index 0000000000..d990a85f9e
--- /dev/null
+++ b/test/cases/compile_errors/access_inactive_union_field_comptime.zig
@@ -0,0 +1,23 @@
+const Enum = enum(u32) { a, b };
+const TaggedUnion = union(Enum) {
+    b: []const u8,
+    a: []const u8,
+};
+pub export fn entry() void {
+    const result = TaggedUnion{ .b = "b" };
+    _ = result.b;
+    _ = result.a;
+}
+pub export fn entry1() void {
+    const result = TaggedUnion{ .b = "b" };
+    _ = &result.b;
+    _ = &result.a;
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :9:15: error: access of union field 'a' while field 'b' is active
+// :2:21: note: union declared here
+// :14:16: error: access of union field 'a' while field 'b' is active
diff --git a/test/cases/compile_errors/duplicate_field_in_discarded_anon_init.zig b/test/cases/compile_errors/duplicate_field_in_discarded_anon_init.zig
new file mode 100644
index 0000000000..6f850e6fe4
--- /dev/null
+++ b/test/cases/compile_errors/duplicate_field_in_discarded_anon_init.zig
@@ -0,0 +1,10 @@
+pub export fn entry() void {
+    _ = .{ .a = 0, .a = 1 };
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :2:21: error: duplicate field
+// :2:13: note: other field here
diff --git a/test/cases/compile_errors/function_type_named.zig b/test/cases/compile_errors/function_type_named.zig
new file mode 100644
index 0000000000..ad670fe88c
--- /dev/null
+++ b/test/cases/compile_errors/function_type_named.zig
@@ -0,0 +1,7 @@
+const aFunc = fn someFunc(x: i32) void;
+
+// error
+// backend=stage2
+// target=native
+//
+// :1:18: error: function type cannot have a name
diff --git a/test/cases/compile_errors/struct_init_passed_to_type_param.zig b/test/cases/compile_errors/struct_init_passed_to_type_param.zig
new file mode 100644
index 0000000000..b00c27986f
--- /dev/null
+++ b/test/cases/compile_errors/struct_init_passed_to_type_param.zig
@@ -0,0 +1,14 @@
+const MyStruct = struct { x: i32 };
+
+fn hi(comptime T: type) usize {
+    return @sizeOf(T);
+}
+
+export const value = hi(MyStruct{ .x = 12 });
+
+// error
+// backend=stage2
+// target=native
+//
+// :7:33: error: expected type 'type', found 'tmp.MyStruct'
+// :1:18: note: struct declared here
diff --git a/test/cases/compile_errors/switch_on_slice.zig b/test/cases/compile_errors/switch_on_slice.zig
new file mode 100644
index 0000000000..b4644b132c
--- /dev/null
+++ b/test/cases/compile_errors/switch_on_slice.zig
@@ -0,0 +1,13 @@
+pub export fn entry() void {
+    var a: [:0]const u8 = "foo";
+    switch (a) {
+        "--version", "version" => unreachable,
+        else => {},
+    }
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :3:13: error: switch on type '[:0]const u8'