[msl-writer] Emit alias types.

This CL adds emission of alias types to the MSL writer. They are output
as `typedef`s.

Bug: tint:8
Change-Id: I18b839ed0238c4636e3975f35f5d88badd412fe4
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/24001
Reviewed-by: David Neto <dneto@google.com>

BUILD.gn

@@ -884,6 +884,7 @@ source_set("tint_unittests_wgsl_writer_src") {
 
 source_set("tint_unittests_msl_writer_src") {
   sources = [
+    "src/writer/msl/generator_impl_alias_type_test.cc",
     "src/writer/msl/generator_impl_array_accessor_test.cc",
     "src/writer/msl/generator_impl_as_test.cc",
     "src/writer/msl/generator_impl_assign_test.cc",

src/CMakeLists.txt

@@ -492,6 +492,7 @@ endif()
 
 if(${TINT_BUILD_MSL_WRITER})
   list(APPEND TINT_TEST_SRCS
+    writer/msl/generator_impl_alias_type_test.cc
     writer/msl/generator_impl_array_accessor_test.cc
     writer/msl/generator_impl_as_test.cc
     writer/msl/generator_impl_assign_test.cc

src/writer/msl/generator_impl.cc

@@ -52,6 +52,15 @@ GeneratorImpl::~GeneratorImpl() = default;
 bool GeneratorImpl::Generate(const ast::Module& module) {
   module_ = &module;
 
+  for (auto* const alias : module.alias_types()) {
+    if (!EmitAliasType(alias)) {
+      return false;
+    }
+  }
+  if (!module.alias_types().empty()) {
+    out_ << std::endl;
+  }
+
   for (const auto& func : module.functions()) {
     if (!EmitFunction(func.get())) {
       return false;
@@ -63,6 +72,17 @@ bool GeneratorImpl::Generate(const ast::Module& module) {
   return true;
 }
 
+bool GeneratorImpl::EmitAliasType(const ast::type::AliasType* alias) {
+  make_indent();
+  out_ << "typedef ";
+  if (!EmitType(alias->type(), "")) {
+    return false;
+  }
+  out_ << " " << alias->name() << ";" << std::endl;
+
+  return true;
+}
+
 bool GeneratorImpl::EmitArrayAccessor(ast::ArrayAccessorExpression* expr) {
   if (!EmitExpression(expr->array())) {
     return false;
@@ -531,7 +551,7 @@ bool GeneratorImpl::EmitType(ast::type::Type* type, const std::string& name) {
       }
       // Array member name will be output with the type
       if (!mem->type()->IsArray()) {
-        out_ << mem->name();
+        out_ << " " << mem->name();
       }
       out_ << ";" << std::endl;
     }

src/writer/msl/generator_impl.h

@@ -40,6 +40,10 @@ class GeneratorImpl : public TextGenerator {
   /// @returns true on successful generation; false otherwise
   bool Generate(const ast::Module& module);
 
+  /// Handles generating an alias
+  /// @param alias the alias to generate
+  /// @returns true if the alias was emitted
+  bool EmitAliasType(const ast::type::AliasType* alias);
   /// Handles an array accessor expression
   /// @param expr the expression to emit
   /// @returns true if the array accessor was emitted

src/writer/msl/generator_impl_alias_type_test.cc

@@ -0,0 +1,73 @@
+// Copyright 2020 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "gtest/gtest.h"
+#include "src/ast/struct.h"
+#include "src/ast/struct_member.h"
+#include "src/ast/struct_member_decoration.h"
+#include "src/ast/struct_member_offset_decoration.h"
+#include "src/ast/type/f32_type.h"
+#include "src/ast/type/i32_type.h"
+#include "src/ast/type/struct_type.h"
+#include "src/writer/msl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace msl {
+namespace {
+
+using MslGeneratorImplTest = testing::Test;
+
+TEST_F(MslGeneratorImplTest, EmitAliasType_F32) {
+  ast::type::F32Type f32;
+  ast::type::AliasType alias("a", &f32);
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitAliasType(&alias)) << g.error();
+  EXPECT_EQ(g.result(), R"(typedef float a;
+)");
+}
+
+TEST_F(MslGeneratorImplTest, EmitAliasType_Struct) {
+  ast::type::I32Type i32;
+  ast::type::F32Type f32;
+
+  ast::StructMemberList members;
+  members.push_back(std::make_unique<ast::StructMember>(
+      "a", &f32, ast::StructMemberDecorationList{}));
+
+  ast::StructMemberDecorationList b_deco;
+  b_deco.push_back(std::make_unique<ast::StructMemberOffsetDecoration>(4));
+  members.push_back(
+      std::make_unique<ast::StructMember>("b", &i32, std::move(b_deco)));
+
+  auto str = std::make_unique<ast::Struct>();
+  str->set_members(std::move(members));
+
+  ast::type::StructType s(std::move(str));
+  ast::type::AliasType alias("a", &s);
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitAliasType(&alias)) << g.error();
+  EXPECT_EQ(g.result(), R"(typedef struct {
+  float a;
+  int b;
+} a;
+)");
+}
+
+}  // namespace
+}  // namespace msl
+}  // namespace writer
+}  // namespace tint