compiler: remove anonymous struct types, unify all tuples

This commit reworks how anonymous struct literals and tuples work.

Previously, an untyped anonymous struct literal
(e.g. `const x = .{ .a = 123 }`) was given an "anonymous struct type",
which is a special kind of struct which coerces using structural
equivalence. This mechanism was a holdover from before we used
RLS / result types as the primary mechanism of type inference. This
commit changes the language so that the type assigned here is a "normal"
struct type. It uses a form of equivalence based on the AST node and the
type's structure, much like a reified (`@Type`) type.

Additionally, tuples have been simplified. The distinction between
"simple" and "complex" tuple types is eliminated. All tuples, even those
explicitly declared using `struct { ... }` syntax, use structural
equivalence, and do not undergo staged type resolution. Tuples are very
restricted: they cannot have non-`auto` layouts, cannot have aligned
fields, and cannot have default values with the exception of `comptime`
fields. Tuples currently do not have optimized layout, but this can be
changed in the future.

This change simplifies the language, and fixes some problematic
coercions through pointers which led to unintuitive behavior.

Resolves: #16865

1 files changed, 32 insertions, 31 deletions

diff --git a/src/codegen/spirv.zig b/src/codegen/spirv.zig
index 46c23d7d53..997771a940 100644
--- a/src/codegen/spirv.zig
+++ b/src/codegen/spirv.zig
@@ -731,13 +731,15 @@ const NavGen = struct {
             .direct => {
                 const result_ty_id = try self.resolveType(Type.bool, .direct);
                 const result_id = self.spv.allocId();
-                const operands = .{
-                    .id_result_type = result_ty_id,
-                    .id_result = result_id,
-                };
                 switch (value) {
-                    true => try section.emit(self.spv.gpa, .OpConstantTrue, operands),
-                    false => try section.emit(self.spv.gpa, .OpConstantFalse, operands),
+                    inline else => |val_ct| try section.emit(
+                        self.spv.gpa,
+                        if (val_ct) .OpConstantTrue else .OpConstantFalse,
+                        .{
+                            .id_result_type = result_ty_id,
+                            .id_result = result_id,
+                        },
+                    ),
                 }
                 return result_id;
             },
@@ -915,7 +917,7 @@ const NavGen = struct {
                 .error_union_type,
                 .simple_type,
                 .struct_type,
-                .anon_struct_type,
+                .tuple_type,
                 .union_type,
                 .opaque_type,
                 .enum_type,
@@ -937,7 +939,7 @@ const NavGen = struct {
                     .undefined,
                     .void,
                     .null,
-                    .empty_struct,
+                    .empty_tuple,
                     .@"unreachable",
                     .generic_poison,
                     => unreachable, // non-runtime values
@@ -1125,7 +1127,7 @@ const NavGen = struct {
 
                         return try self.constructStruct(ty, types.items, constituents.items);
                     },
-                    .anon_struct_type => unreachable, // TODO
+                    .tuple_type => unreachable, // TODO
                     else => unreachable,
                 },
                 .un => |un| {
@@ -1718,7 +1720,7 @@ const NavGen = struct {
             },
             .@"struct" => {
                 const struct_type = switch (ip.indexToKey(ty.toIntern())) {
-                    .anon_struct_type => |tuple| {
+                    .tuple_type => |tuple| {
                         const member_types = try self.gpa.alloc(IdRef, tuple.values.len);
                         defer self.gpa.free(member_types);
 
@@ -2831,18 +2833,12 @@ const NavGen = struct {
                 }
             },
             .vulkan => {
-                const op_result_ty = blk: {
-                    // Operations return a struct{T, T}
-                    // where T is maybe vectorized.
-                    const types = [2]InternPool.Index{ arith_op_ty.toIntern(), arith_op_ty.toIntern() };
-                    const values = [2]InternPool.Index{ .none, .none };
-                    const index = try ip.getAnonStructType(zcu.gpa, pt.tid, .{
-                        .types = &types,
-                        .values = &values,
-                        .names = &.{},
-                    });
-                    break :blk Type.fromInterned(index);
-                };
+                // Operations return a struct{T, T}
+                // where T is maybe vectorized.
+                const op_result_ty: Type = .fromInterned(try ip.getTupleType(zcu.gpa, pt.tid, .{
+                    .types = &.{ arith_op_ty.toIntern(), arith_op_ty.toIntern() },
+                    .values = &.{ .none, .none },
+                }));
                 const op_result_ty_id = try self.resolveType(op_result_ty, .direct);
 
                 const opcode: Opcode = switch (op) {
@@ -4867,7 +4863,7 @@ const NavGen = struct {
                 var index: usize = 0;
 
                 switch (ip.indexToKey(result_ty.toIntern())) {
-                    .anon_struct_type => |tuple| {
+                    .tuple_type => |tuple| {
                         for (tuple.types.get(ip), elements, 0..) |field_ty, element, i| {
                             if ((try result_ty.structFieldValueComptime(pt, i)) != null) continue;
                             assert(Type.fromInterned(field_ty).hasRuntimeBits(zcu));
@@ -6216,15 +6212,20 @@ const NavGen = struct {
             try self.extractField(Type.anyerror, operand_id, eu_layout.errorFieldIndex());
 
         const result_id = self.spv.allocId();
-        const operands = .{
-            .id_result_type = bool_ty_id,
-            .id_result = result_id,
-            .operand_1 = error_id,
-            .operand_2 = try self.constInt(Type.anyerror, 0, .direct),
-        };
         switch (pred) {
-            .is_err => try self.func.body.emit(self.spv.gpa, .OpINotEqual, operands),
-            .is_non_err => try self.func.body.emit(self.spv.gpa, .OpIEqual, operands),
+            inline else => |pred_ct| try self.func.body.emit(
+                self.spv.gpa,
+                switch (pred_ct) {
+                    .is_err => .OpINotEqual,
+                    .is_non_err => .OpIEqual,
+                },
+                .{
+                    .id_result_type = bool_ty_id,
+                    .id_result = result_id,
+                    .operand_1 = error_id,
+                    .operand_2 = try self.constInt(Type.anyerror, 0, .direct),
+                },
+            ),
         }
         return result_id;
     }