Emit member accessor in WGSL generator.

This CL adds MemberAccessor handling into the WGSL generator.

Bug: tint:4
Change-Id: Ib84f9ca1969fec48f167433af957dc1ed4de3415
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17063
Reviewed-by: David Neto <dneto@google.com>

src/CMakeLists.txt

@@ -413,6 +413,7 @@ if(${TINT_BUILD_WGSL_WRITER})
     writer/wgsl/generator_impl_identifier_test.cc
     writer/wgsl/generator_impl_import_test.cc
     writer/wgsl/generator_impl_initializer_test.cc
+    writer/wgsl/generator_impl_member_accessor_test.cc
     writer/wgsl/generator_impl_type_test.cc
     writer/wgsl/generator_impl_variable_test.cc
   )

src/writer/wgsl/generator_impl.cc

@@ -31,6 +31,7 @@
 #include "src/ast/initializer_expression.h"
 #include "src/ast/int_literal.h"
 #include "src/ast/location_decoration.h"
+#include "src/ast/member_accessor_expression.h"
 #include "src/ast/set_decoration.h"
 #include "src/ast/struct.h"
 #include "src/ast/struct_member.h"
@@ -136,6 +137,9 @@ bool GeneratorImpl::EmitExpression(ast::Expression* expr) {
   if (expr->IsInitializer()) {
     return EmitInitializer(expr->AsInitializer());
   }
+  if (expr->IsMemberAccessor()) {
+    return EmitMemberAccessor(expr->AsMemberAccessor());
+  }
 
   error_ = "unknown expression type";
   return false;
@@ -155,6 +159,16 @@ bool GeneratorImpl::EmitArrayAccessor(ast::ArrayAccessorExpression* expr) {
   return true;
 }
 
+bool GeneratorImpl::EmitMemberAccessor(ast::MemberAccessorExpression* expr) {
+  if (!EmitExpression(expr->structure())) {
+    return false;
+  }
+
+  out_ << ".";
+
+  return EmitExpression(expr->member());
+}
+
 bool GeneratorImpl::EmitAs(ast::AsExpression* expr) {
   out_ << "as<";
   if (!EmitType(expr->type())) {

src/writer/wgsl/generator_impl.h

@@ -110,6 +110,10 @@ class GeneratorImpl {
   /// @param expr the initializer expression
   /// @returns true if the expression was emitted
   bool EmitInitializer(ast::InitializerExpression* expr);
+  /// Handles a member accessor expression
+  /// @param expr the member accessor expression
+  /// @returns true if the member accessor was emitted
+  bool EmitMemberAccessor(ast::MemberAccessorExpression* expr);
   /// Handles generating type
   /// @param type the type to generate
   /// @returns true if the type is emitted

src/writer/wgsl/generator_impl_member_accessor_test.cc

@@ -0,0 +1,43 @@
+// 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 <memory>
+
+#include "gtest/gtest.h"
+#include "src/ast/identifier_expression.h"
+#include "src/ast/member_accessor_expression.h"
+#include "src/writer/wgsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace wgsl {
+namespace {
+
+using GeneratorImplTest = testing::Test;
+
+TEST_F(GeneratorImplTest, EmitExpression_MemberAccessor) {
+  auto str = std::make_unique<ast::IdentifierExpression>("str");
+  auto mem = std::make_unique<ast::IdentifierExpression>("mem");
+
+  ast::MemberAccessorExpression expr(std::move(str), std::move(mem));
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitExpression(&expr)) << g.error();
+  EXPECT_EQ(g.result(), "str.mem");
+}
+
+}  // namespace
+}  // namespace wgsl
+}  // namespace writer
+}  // namespace tint