stage2: introduce anonymous struct literals

5 files changed, 287 insertions, 64 deletions

diff --git a/src/Sema.zig b/src/Sema.zig
index c0b49fa473..93dd3c4557 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -7704,7 +7704,7 @@ fn zirHasDecl(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air
     const decl_name = try sema.resolveConstString(block, rhs_src, extra.rhs);
 
     // tuples are structs but they don't have a namespace
-    if (container_type.isTuple()) return Air.Inst.Ref.bool_false;
+    if (container_type.isTupleOrAnonStruct()) return Air.Inst.Ref.bool_false;
     const namespace = container_type.getNamespace() orelse return sema.fail(
         block,
         lhs_src,
@@ -10615,15 +10615,19 @@ fn zirTypeInfo(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
             const layout = struct_ty.containerLayout();
 
             const struct_field_vals = fv: {
-                if (struct_ty.castTag(.tuple)) |payload| {
-                    const field_types = payload.data.types;
+                if (struct_ty.isTupleOrAnonStruct()) {
+                    const tuple = struct_ty.tupleFields();
+                    const field_types = tuple.types;
                     const struct_field_vals = try fields_anon_decl.arena().alloc(Value, field_types.len);
                     for (struct_field_vals) |*struct_field_val, i| {
                         const field_ty = field_types[i];
                         const name_val = v: {
                             var anon_decl = try block.startAnonDecl(src);
                             defer anon_decl.deinit();
-                            const bytes = try std.fmt.allocPrintZ(anon_decl.arena(), "{d}", .{i});
+                            const bytes = if (struct_ty.castTag(.anon_struct)) |payload|
+                                try anon_decl.arena().dupeZ(u8, payload.data.names[i])
+                            else
+                                try std.fmt.allocPrintZ(anon_decl.arena(), "{d}", .{i});
                             const new_decl = try anon_decl.finish(
                                 try Type.Tag.array_u8_sentinel_0.create(anon_decl.arena(), bytes.len),
                                 try Value.Tag.bytes.create(anon_decl.arena(), bytes[0 .. bytes.len + 1]),
@@ -10632,7 +10636,7 @@ fn zirTypeInfo(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Ai
                         };
 
                         const struct_field_fields = try fields_anon_decl.arena().create([5]Value);
-                        const field_val = payload.data.values[i];
+                        const field_val = tuple.values[i];
                         const is_comptime = field_val.tag() != .unreachable_value;
                         const opt_default_val = if (is_comptime) field_val else null;
                         const default_val_ptr = try sema.optRefValue(block, src, field_ty, opt_default_val);
@@ -11631,12 +11635,86 @@ fn finishStructInit(
     return block.addAggregateInit(struct_ty, field_inits);
 }
 
-fn zirStructInitAnon(sema: *Sema, block: *Block, inst: Zir.Inst.Index, is_ref: bool) CompileError!Air.Inst.Ref {
+fn zirStructInitAnon(
+    sema: *Sema,
+    block: *Block,
+    inst: Zir.Inst.Index,
+    is_ref: bool,
+) CompileError!Air.Inst.Ref {
     const inst_data = sema.code.instructions.items(.data)[inst].pl_node;
     const src = inst_data.src();
+    const extra = sema.code.extraData(Zir.Inst.StructInitAnon, inst_data.payload_index);
+    const types = try sema.arena.alloc(Type, extra.data.fields_len);
+    const values = try sema.arena.alloc(Value, types.len);
+    const names = try sema.arena.alloc([]const u8, types.len);
+
+    const opt_runtime_src = rs: {
+        var runtime_src: ?LazySrcLoc = null;
+        var extra_index = extra.end;
+        for (types) |*field_ty, i| {
+            const item = sema.code.extraData(Zir.Inst.StructInitAnon.Item, extra_index);
+            extra_index = item.end;
 
-    _ = is_ref;
-    return sema.fail(block, src, "TODO: Sema.zirStructInitAnon", .{});
+            names[i] = sema.code.nullTerminatedString(item.data.field_name);
+            const init = sema.resolveInst(item.data.init);
+            field_ty.* = sema.typeOf(init);
+            const init_src = src; // TODO better source location
+            if (try sema.resolveMaybeUndefVal(block, init_src, init)) |init_val| {
+                values[i] = init_val;
+            } else {
+                values[i] = Value.initTag(.unreachable_value);
+                runtime_src = init_src;
+            }
+        }
+        break :rs runtime_src;
+    };
+
+    const tuple_ty = try Type.Tag.anon_struct.create(sema.arena, .{
+        .names = names,
+        .types = types,
+        .values = values,
+    });
+
+    const runtime_src = opt_runtime_src orelse {
+        const tuple_val = try Value.Tag.@"struct".create(sema.arena, values);
+        return sema.addConstantMaybeRef(block, src, tuple_ty, tuple_val, is_ref);
+    };
+
+    try sema.requireRuntimeBlock(block, runtime_src);
+
+    if (is_ref) {
+        const target = sema.mod.getTarget();
+        const alloc = try block.addTy(.alloc, tuple_ty);
+        var extra_index = extra.end;
+        for (types) |field_ty, i_usize| {
+            const i = @intCast(u32, i_usize);
+            const item = sema.code.extraData(Zir.Inst.StructInitAnon.Item, extra_index);
+            extra_index = item.end;
+
+            const field_ptr_ty = try Type.ptr(sema.arena, target, .{
+                .mutable = true,
+                .@"addrspace" = target_util.defaultAddressSpace(target, .local),
+                .pointee_type = field_ty,
+            });
+            if (values[i].tag() == .unreachable_value) {
+                const init = sema.resolveInst(item.data.init);
+                const field_ptr = try block.addStructFieldPtr(alloc, i, field_ptr_ty);
+                _ = try block.addBinOp(.store, field_ptr, init);
+            }
+        }
+
+        return alloc;
+    }
+
+    const element_refs = try sema.arena.alloc(Air.Inst.Ref, types.len);
+    var extra_index = extra.end;
+    for (types) |_, i| {
+        const item = sema.code.extraData(Zir.Inst.StructInitAnon.Item, extra_index);
+        extra_index = item.end;
+        element_refs[i] = sema.resolveInst(item.data.init);
+    }
+
+    return block.addAggregateInit(tuple_ty, element_refs);
 }
 
 fn zirArrayInit(
@@ -11764,8 +11842,10 @@ fn zirArrayInitAnon(
                 .@"addrspace" = target_util.defaultAddressSpace(target, .local),
                 .pointee_type = types[i],
             });
-            const field_ptr = try block.addStructFieldPtr(alloc, i, field_ptr_ty);
-            _ = try block.addBinOp(.store, field_ptr, sema.resolveInst(operand));
+            if (values[i].tag() == .unreachable_value) {
+                const field_ptr = try block.addStructFieldPtr(alloc, i, field_ptr_ty);
+                _ = try block.addBinOp(.store, field_ptr, sema.resolveInst(operand));
+            }
         }
 
         return alloc;
@@ -12126,7 +12206,7 @@ fn zirReify(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.I
                 .size = ptr_size,
                 .mutable = !is_const_val.toBool(),
                 .@"volatile" = is_volatile_val.toBool(),
-                .@"align" = @intCast(u8, alignment_val.toUnsignedInt()), // TODO: Validate this value.
+                .@"align" = @intCast(u16, alignment_val.toUnsignedInt()), // TODO: Validate this value.
                 .@"addrspace" = address_space_val.toEnum(std.builtin.AddressSpace),
                 .pointee_type = try child_ty.copy(sema.arena),
                 .@"allowzero" = is_allowzero_val.toBool(),
@@ -14842,29 +14922,43 @@ fn structFieldVal(
     assert(unresolved_struct_ty.zigTypeTag() == .Struct);
 
     const struct_ty = try sema.resolveTypeFields(block, src, unresolved_struct_ty);
-    if (struct_ty.isTuple()) {
-        return sema.tupleFieldVal(block, src, struct_byval, field_name, field_name_src, struct_ty);
-    }
+    switch (struct_ty.tag()) {
+        .tuple, .empty_struct_literal => return sema.tupleFieldVal(block, src, struct_byval, field_name, field_name_src, struct_ty),
+        .anon_struct => {
+            const anon_struct = struct_ty.castTag(.anon_struct).?.data;
 
-    const struct_obj = struct_ty.castTag(.@"struct").?.data;
+            const field_index = for (anon_struct.names) |name, i| {
+                if (mem.eql(u8, name, field_name)) break @intCast(u32, i);
+            } else {
+                return sema.fail(block, field_name_src, "anonymous struct {} has no such field '{s}'", .{
+                    struct_ty, field_name,
+                });
+            };
+            return tupleFieldValByIndex(sema, block, src, struct_byval, field_index, struct_ty);
+        },
+        .@"struct" => {
+            const struct_obj = struct_ty.castTag(.@"struct").?.data;
 
-    const field_index_usize = struct_obj.fields.getIndex(field_name) orelse
-        return sema.failWithBadStructFieldAccess(block, struct_obj, field_name_src, field_name);
-    const field_index = @intCast(u32, field_index_usize);
-    const field = struct_obj.fields.values()[field_index];
+            const field_index_usize = struct_obj.fields.getIndex(field_name) orelse
+                return sema.failWithBadStructFieldAccess(block, struct_obj, field_name_src, field_name);
+            const field_index = @intCast(u32, field_index_usize);
+            const field = struct_obj.fields.values()[field_index];
 
-    if (try sema.resolveMaybeUndefVal(block, src, struct_byval)) |struct_val| {
-        if (struct_val.isUndef()) return sema.addConstUndef(field.ty);
-        if ((try sema.typeHasOnePossibleValue(block, src, field.ty))) |opv| {
-            return sema.addConstant(field.ty, opv);
-        }
+            if (try sema.resolveMaybeUndefVal(block, src, struct_byval)) |struct_val| {
+                if (struct_val.isUndef()) return sema.addConstUndef(field.ty);
+                if ((try sema.typeHasOnePossibleValue(block, src, field.ty))) |opv| {
+                    return sema.addConstant(field.ty, opv);
+                }
 
-        const field_values = struct_val.castTag(.@"struct").?.data;
-        return sema.addConstant(field.ty, field_values[field_index]);
-    }
+                const field_values = struct_val.castTag(.@"struct").?.data;
+                return sema.addConstant(field.ty, field_values[field_index]);
+            }
 
-    try sema.requireRuntimeBlock(block, src);
-    return block.addStructFieldVal(struct_byval, field_index, field.ty);
+            try sema.requireRuntimeBlock(block, src);
+            return block.addStructFieldVal(struct_byval, field_index, field.ty);
+        },
+        else => unreachable,
+    }
 }
 
 fn tupleFieldVal(
@@ -14901,7 +14995,7 @@ fn tupleFieldValByIndex(
     field_index: u32,
     tuple_ty: Type,
 ) CompileError!Air.Inst.Ref {
-    const tuple = tuple_ty.castTag(.tuple).?.data;
+    const tuple = tuple_ty.tupleFields();
     const field_ty = tuple.types[field_index];
 
     if (tuple.values[field_index].tag() != .unreachable_value) {
@@ -18954,8 +19048,8 @@ pub fn typeHasOnePossibleValue(
             return Value.initTag(.empty_struct_value);
         },
 
-        .tuple => {
-            const tuple = ty.castTag(.tuple).?.data;
+        .tuple, .anon_struct => {
+            const tuple = ty.tupleFields();
             for (tuple.values) |val| {
                 if (val.tag() == .unreachable_value) {
                     return null; // non-comptime field
@@ -19583,8 +19677,8 @@ fn typeRequiresComptime(sema: *Sema, block: *Block, src: LazySrcLoc, ty: Type) C
             return sema.typeRequiresComptime(block, src, ty.optionalChild(&buf));
         },
 
-        .tuple => {
-            const tuple = ty.castTag(.tuple).?.data;
+        .tuple, .anon_struct => {
+            const tuple = ty.tupleFields();
             for (tuple.types) |field_ty, i| {
                 const have_comptime_val = tuple.values[i].tag() != .unreachable_value;
                 if (!have_comptime_val and try sema.typeRequiresComptime(block, src, field_ty)) {
diff --git a/src/Zir.zig b/src/Zir.zig
index b70b41e506..c528380b1d 100644
--- a/src/Zir.zig
+++ b/src/Zir.zig
@@ -2850,7 +2850,9 @@ pub const Inst = struct {
         };
     };
 
-    /// Trailing is an item per field.
+    /// Trailing is an Item per field.
+    /// TODO make this instead array of inits followed by array of names because
+    /// it will be simpler Sema code and better for CPU cache.
     pub const StructInitAnon = struct {
         fields_len: u32,
 
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index 28654b905a..fa29a1aae3 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -958,7 +958,7 @@ pub const DeclGen = struct {
                 // reference, we need to copy it here.
                 gop.key_ptr.* = try t.copy(dg.object.type_map_arena.allocator());
 
-                if (t.isTuple()) {
+                if (t.isTupleOrAnonStruct()) {
                     const tuple = t.tupleFields();
                     const llvm_struct_ty = dg.context.structCreateNamed("");
                     gop.value_ptr.* = llvm_struct_ty; // must be done before any recursive calls
@@ -2104,7 +2104,7 @@ pub const DeclGen = struct {
         var zig_big_align: u32 = 0;
         var llvm_big_align: u32 = 0;
 
-        if (ty.isTuple()) {
+        if (ty.isTupleOrAnonStruct()) {
             const tuple = ty.tupleFields();
             var llvm_field_index: c_uint = 0;
             for (tuple.types) |field_ty, i| {
@@ -5704,7 +5704,7 @@ fn isByRef(ty: Type) bool {
         .Struct => {
             // Packed structs are represented to LLVM as integers.
             if (ty.containerLayout() == .Packed) return false;
-            if (ty.isTuple()) {
+            if (ty.isTupleOrAnonStruct()) {
                 const tuple = ty.tupleFields();
                 var count: usize = 0;
                 for (tuple.values) |field_val, i| {
diff --git a/src/type.zig b/src/type.zig
index 8084da34de..6e58f7a42f 100644
--- a/src/type.zig
+++ b/src/type.zig
@@ -131,6 +131,7 @@ pub const Type = extern union {
             .export_options,
             .extern_options,
             .tuple,
+            .anon_struct,
             => return .Struct,
 
             .enum_full,
@@ -792,6 +793,42 @@ pub const Type = extern union {
 
                 return true;
             },
+            .anon_struct => {
+                const a_struct_obj = a.castTag(.anon_struct).?.data;
+                const b_struct_obj = (b.castTag(.anon_struct) orelse return false).data;
+
+                if (a_struct_obj.types.len != b_struct_obj.types.len) return false;
+
+                for (a_struct_obj.names) |a_name, i| {
+                    const b_name = b_struct_obj.names[i];
+                    if (!std.mem.eql(u8, a_name, b_name)) return false;
+                }
+
+                for (a_struct_obj.types) |a_ty, i| {
+                    const b_ty = b_struct_obj.types[i];
+                    if (!eql(a_ty, b_ty)) return false;
+                }
+
+                for (a_struct_obj.values) |a_val, i| {
+                    const ty = a_struct_obj.types[i];
+                    const b_val = b_struct_obj.values[i];
+                    if (a_val.tag() == .unreachable_value) {
+                        if (b_val.tag() == .unreachable_value) {
+                            continue;
+                        } else {
+                            return false;
+                        }
+                    } else {
+                        if (b_val.tag() == .unreachable_value) {
+                            return false;
+                        } else {
+                            if (!Value.eql(a_val, b_val, ty)) return false;
+                        }
+                    }
+                }
+
+                return true;
+            },
 
             // we can't compare these based on tags because it wouldn't detect if,
             // for example, a was resolved into .@"struct" but b was one of these tags.
@@ -1062,6 +1099,20 @@ pub const Type = extern union {
                     field_val.hash(field_ty, hasher);
                 }
             },
+            .anon_struct => {
+                const struct_obj = ty.castTag(.anon_struct).?.data;
+                std.hash.autoHash(hasher, std.builtin.TypeId.Struct);
+                std.hash.autoHash(hasher, struct_obj.types.len);
+
+                for (struct_obj.types) |field_ty, i| {
+                    const field_name = struct_obj.names[i];
+                    const field_val = struct_obj.values[i];
+                    hasher.update(field_name);
+                    hashWithHasher(field_ty, hasher);
+                    if (field_val.tag() == .unreachable_value) continue;
+                    field_val.hash(field_ty, hasher);
+                }
+            },
 
             // we can't hash these based on tags because they wouldn't match the expanded version.
             .call_options,
@@ -1279,6 +1330,26 @@ pub const Type = extern union {
                     .values = values,
                 });
             },
+            .anon_struct => {
+                const payload = self.castTag(.anon_struct).?.data;
+                const names = try allocator.alloc([]const u8, payload.names.len);
+                const types = try allocator.alloc(Type, payload.types.len);
+                const values = try allocator.alloc(Value, payload.values.len);
+                for (payload.names) |name, i| {
+                    names[i] = try allocator.dupe(u8, name);
+                }
+                for (payload.types) |ty, i| {
+                    types[i] = try ty.copy(allocator);
+                }
+                for (payload.values) |val, i| {
+                    values[i] = try val.copy(allocator);
+                }
+                return Tag.anon_struct.create(allocator, .{
+                    .names = names,
+                    .types = types,
+                    .values = values,
+                });
+            },
             .function => {
                 const payload = self.castTag(.function).?.data;
                 const param_types = try allocator.alloc(Type, payload.param_types.len);
@@ -1533,6 +1604,26 @@ pub const Type = extern union {
                     try writer.writeAll("}");
                     return;
                 },
+                .anon_struct => {
+                    const anon_struct = ty.castTag(.anon_struct).?.data;
+                    try writer.writeAll("struct{");
+                    for (anon_struct.types) |field_ty, i| {
+                        if (i != 0) try writer.writeAll(", ");
+                        const val = anon_struct.values[i];
+                        if (val.tag() != .unreachable_value) {
+                            try writer.writeAll("comptime ");
+                        }
+                        try writer.writeAll(anon_struct.names[i]);
+                        try writer.writeAll(": ");
+                        try field_ty.format("", .{}, writer);
+                        if (val.tag() != .unreachable_value) {
+                            try writer.writeAll(" = ");
+                            try val.format("", .{}, writer);
+                        }
+                    }
+                    try writer.writeAll("}");
+                    return;
+                },
                 .single_const_pointer => {
                     const pointee_type = ty.castTag(.single_const_pointer).?.data;
                     try writer.writeAll("*const ");
@@ -2020,8 +2111,8 @@ pub const Type = extern union {
                 return payload.error_set.hasRuntimeBits() or payload.payload.hasRuntimeBits();
             },
 
-            .tuple => {
-                const tuple = ty.castTag(.tuple).?.data;
+            .tuple, .anon_struct => {
+                const tuple = ty.tupleFields();
                 for (tuple.types) |field_ty, i| {
                     const val = tuple.values[i];
                     if (val.tag() != .unreachable_value) continue; // comptime field
@@ -2292,8 +2383,8 @@ pub const Type = extern union {
                 return big_align;
             },
 
-            .tuple => {
-                const tuple = self.castTag(.tuple).?.data;
+            .tuple, .anon_struct => {
+                const tuple = self.tupleFields();
                 var big_align: u32 = 0;
                 for (tuple.types) |field_ty, i| {
                     const val = tuple.values[i];
@@ -2375,7 +2466,7 @@ pub const Type = extern union {
             .void,
             => 0,
 
-            .@"struct", .tuple => switch (self.containerLayout()) {
+            .@"struct", .tuple, .anon_struct => switch (self.containerLayout()) {
                 .Packed => {
                     const struct_obj = self.castTag(.@"struct").?.data;
                     var buf: Type.Payload.Bits = undefined;
@@ -2575,6 +2666,13 @@ pub const Type = extern union {
             .bound_fn => unreachable,
 
             .void => 0,
+            .bool, .u1 => 1,
+            .u8, .i8 => 8,
+            .i16, .u16, .f16 => 16,
+            .i32, .u32, .f32 => 32,
+            .i64, .u64, .f64 => 64,
+            .f80 => 80,
+            .u128, .i128, .f128 => 128,
 
             .@"struct" => {
                 const field_count = ty.structFieldCount();
@@ -2595,8 +2693,13 @@ pub const Type = extern union {
                 }
             },
 
-            .tuple => {
-                @panic("TODO bitSize tuples");
+            .tuple, .anon_struct => {
+                const tuple = ty.tupleFields();
+                var total: u64 = 0;
+                for (tuple.types) |field_ty| {
+                    total += field_ty.bitSize(target);
+                }
+                return total;
             },
 
             .enum_simple, .enum_full, .enum_nonexhaustive, .enum_numbered => {
@@ -2608,10 +2711,6 @@ pub const Type = extern union {
                 @panic("TODO bitSize unions");
             },
 
-            .u8, .i8 => 8,
-
-            .bool, .u1 => 1,
-
             .vector => {
                 const payload = ty.castTag(.vector).?.data;
                 const elem_bit_size = payload.elem_type.bitSize(target);
@@ -2634,11 +2733,6 @@ pub const Type = extern union {
                 );
                 return payload.len * 8 * elem_size + payload.elem_type.bitSize(target);
             },
-            .i16, .u16, .f16 => 16,
-            .i32, .u32, .f32 => 32,
-            .i64, .u64, .f64 => 64,
-            .f80 => 80,
-            .u128, .i128, .f128 => 128,
 
             .isize,
             .usize,
@@ -3295,7 +3389,7 @@ pub const Type = extern union {
 
     pub fn containerLayout(ty: Type) std.builtin.TypeInfo.ContainerLayout {
         return switch (ty.tag()) {
-            .tuple, .empty_struct_literal => .Auto,
+            .tuple, .empty_struct_literal, .anon_struct => .Auto,
             .@"struct" => ty.castTag(.@"struct").?.data.layout,
             .@"union" => ty.castTag(.@"union").?.data.layout,
             .union_tagged => ty.castTag(.union_tagged).?.data.layout,
@@ -3369,6 +3463,7 @@ pub const Type = extern union {
             .array_u8 => ty.castTag(.array_u8).?.data,
             .array_u8_sentinel_0 => ty.castTag(.array_u8_sentinel_0).?.data,
             .tuple => ty.castTag(.tuple).?.data.types.len,
+            .anon_struct => ty.castTag(.anon_struct).?.data.types.len,
             .@"struct" => ty.castTag(.@"struct").?.data.fields.count(),
 
             else => unreachable,
@@ -3383,6 +3478,7 @@ pub const Type = extern union {
         return switch (ty.tag()) {
             .vector => @intCast(u32, ty.castTag(.vector).?.data.len),
             .tuple => @intCast(u32, ty.castTag(.tuple).?.data.types.len),
+            .anon_struct => @intCast(u32, ty.castTag(.anon_struct).?.data.types.len),
             else => unreachable,
         };
     }
@@ -3849,8 +3945,8 @@ pub const Type = extern union {
                 return Value.initTag(.empty_struct_value);
             },
 
-            .tuple => {
-                const tuple = ty.castTag(.tuple).?.data;
+            .tuple, .anon_struct => {
+                const tuple = ty.tupleFields();
                 for (tuple.values) |val| {
                     if (val.tag() == .unreachable_value) {
                         return null; // non-comptime field
@@ -4048,8 +4144,8 @@ pub const Type = extern union {
                 return ty.optionalChild(&buf).comptimeOnly();
             },
 
-            .tuple => {
-                const tuple = ty.castTag(.tuple).?.data;
+            .tuple, .anon_struct => {
+                const tuple = ty.tupleFields();
                 for (tuple.types) |field_ty, i| {
                     const have_comptime_val = tuple.values[i].tag() != .unreachable_value;
                     if (!have_comptime_val and field_ty.comptimeOnly()) return true;
@@ -4350,6 +4446,7 @@ pub const Type = extern union {
             },
             .empty_struct, .empty_struct_literal => return 0,
             .tuple => return ty.castTag(.tuple).?.data.types.len,
+            .anon_struct => return ty.castTag(.anon_struct).?.data.types.len,
             else => unreachable,
         }
     }
@@ -4366,6 +4463,7 @@ pub const Type = extern union {
                 return union_obj.fields.values()[index].ty;
             },
             .tuple => return ty.castTag(.tuple).?.data.types[index],
+            .anon_struct => return ty.castTag(.anon_struct).?.data.types[index],
             else => unreachable,
         }
     }
@@ -4424,8 +4522,8 @@ pub const Type = extern union {
                 return std.mem.alignForwardGeneric(u64, it.offset, it.big_align);
             },
 
-            .tuple => {
-                const tuple = ty.castTag(.tuple).?.data;
+            .tuple, .anon_struct => {
+                const tuple = ty.tupleFields();
 
                 var offset: u64 = 0;
                 var big_align: u32 = 0;
@@ -4700,6 +4798,8 @@ pub const Type = extern union {
         vector,
         /// Possible Value tags for this: @"struct"
         tuple,
+        /// Possible Value tags for this: @"struct"
+        anon_struct,
         pointer,
         single_const_pointer,
         single_mut_pointer,
@@ -4846,6 +4946,7 @@ pub const Type = extern union {
                 .enum_numbered => Payload.EnumNumbered,
                 .empty_struct => Payload.ContainerScope,
                 .tuple => Payload.Tuple,
+                .anon_struct => Payload.AnonStruct,
             };
         }
 
@@ -4869,12 +4970,26 @@ pub const Type = extern union {
     };
 
     pub fn isTuple(ty: Type) bool {
-        return ty.tag() == .tuple or ty.tag() == .empty_struct_literal;
+        return switch (ty.tag()) {
+            .tuple, .empty_struct_literal => true,
+            else => false,
+        };
+    }
+
+    pub fn isTupleOrAnonStruct(ty: Type) bool {
+        return switch (ty.tag()) {
+            .tuple, .empty_struct_literal, .anon_struct => true,
+            else => false,
+        };
     }
 
     pub fn tupleFields(ty: Type) Payload.Tuple.Data {
         return switch (ty.tag()) {
             .tuple => ty.castTag(.tuple).?.data,
+            .anon_struct => .{
+                .types = ty.castTag(.anon_struct).?.data.types,
+                .values = ty.castTag(.anon_struct).?.data.values,
+            },
             .empty_struct_literal => .{ .types = &.{}, .values = &.{} },
             else => unreachable,
         };
@@ -5042,6 +5157,18 @@ pub const Type = extern union {
             };
         };
 
+        pub const AnonStruct = struct {
+            base: Payload = .{ .tag = .anon_struct },
+            data: Data,
+
+            pub const Data = struct {
+                names: []const []const u8,
+                types: []Type,
+                /// unreachable_value elements are used to indicate runtime-known.
+                values: []Value,
+            };
+        };
+
         pub const Union = struct {
             base: Payload,
             data: *Module.Union,
diff --git a/src/value.zig b/src/value.zig
index a740a35b79..5db780c99b 100644
--- a/src/value.zig
+++ b/src/value.zig
@@ -1895,7 +1895,7 @@ pub const Value = extern union {
                 const a_field_vals = a.castTag(.@"struct").?.data;
                 const b_field_vals = b.castTag(.@"struct").?.data;
                 assert(a_field_vals.len == b_field_vals.len);
-                if (ty.isTuple()) {
+                if (ty.isTupleOrAnonStruct()) {
                     const types = ty.tupleFields().types;
                     assert(types.len == a_field_vals.len);
                     for (types) |field_ty, i| {
@@ -2031,7 +2031,7 @@ pub const Value = extern union {
                 }
             },
             .Struct => {
-                if (ty.isTuple()) {
+                if (ty.isTupleOrAnonStruct()) {
                     const fields = ty.tupleFields();
                     for (fields.values) |field_val, i| {
                         field_val.hash(fields.types[i], hasher);