frontend: forbid packed and extern tuples

src/AstGen.zig

@@ -4687,6 +4687,13 @@ fn structDeclInner(
         const container_field = tree.fullContainerField(member_node) orelse continue;
         if (container_field.ast.tuple_like) break true;
     } else false;
+
+    if (is_tuple) switch (layout) {
+        .Auto => {},
+        .Extern => return astgen.failNode(node, "extern tuples are not supported", .{}),
+        .Packed => return astgen.failNode(node, "packed tuples are not supported", .{}),
+    };
+
     if (is_tuple) for (container_decl.ast.members) |member_node| {
         switch (node_tags[member_node]) {
             .container_field_init,

src/Sema.zig

@@ -20391,6 +20391,12 @@ fn reifyStruct(
     const gpa = sema.gpa;
     const ip = &mod.intern_pool;
 
+    if (is_tuple) switch (layout) {
+        .Extern => return sema.fail(block, src, "extern tuples are not supported", .{}),
+        .Packed => return sema.fail(block, src, "packed tuples are not supported", .{}),
+        .Auto => {},
+    };
+
     // Because these three things each reference each other, `undefined`
     // placeholders are used before being set after the struct type gains an
     // InternPool index.

src/codegen/llvm/Builder.zig

@@ -4164,8 +4164,8 @@ pub const WipFunction = struct {
             @memcpy(extra.trail.nextMut(incoming_len, Block.Index, wip), blocks);
             if (wip.builder.useLibLlvm()) {
                 const ExpectedContents = extern struct {
-                    [expected_incoming_len]*llvm.Value,
+                    values: [expected_incoming_len]*llvm.Value,
-                    [expected_incoming_len]*llvm.BasicBlock,
+                    blocks: [expected_incoming_len]*llvm.BasicBlock,
                 };
                 var stack align(@alignOf(ExpectedContents)) =
                     std.heap.stackFallback(@sizeOf(ExpectedContents), wip.builder.gpa);

test/behavior/tuple_declarations.zig

@@ -31,27 +31,6 @@ test "tuple declaration type info" {
         try expect(!info.fields[1].is_comptime);
         try expect(info.fields[1].alignment == @alignOf([]const u8));
     }
-    {
-        const T = packed struct(u32) { u1, u30, u1 };
-        const info = @typeInfo(T).Struct;
-
-        try expect(std.mem.endsWith(u8, @typeName(T), "test.tuple declaration type info.T"));
-
-        try expect(info.layout == .Packed);
-        try expect(info.backing_integer == u32);
-        try expect(info.fields.len == 3);
-        try expect(info.decls.len == 0);
-        try expect(info.is_tuple);
-
-        try expectEqualStrings(info.fields[0].name, "0");
-        try expect(info.fields[0].type == u1);
-
-        try expectEqualStrings(info.fields[1].name, "1");
-        try expect(info.fields[1].type == u30);
-
-        try expectEqualStrings(info.fields[2].name, "2");
-        try expect(info.fields[2].type == u1);
-    }
 }
 
 test "Tuple declaration usage" {

test/cases/compile_errors/reify_struct.zig

@@ -51,7 +51,7 @@ comptime {
             .alignment = 4,
         }},
         .decls = &.{},
-        .is_tuple = true,
+        .is_tuple = false,
     } });
 }
 comptime {
@@ -65,7 +65,7 @@ comptime {
             .alignment = 4,
         }},
         .decls = &.{},
-        .is_tuple = true,
+        .is_tuple = false,
     } });
 }