Emit assignment statement.

This CL updates the WGSL writer to emit the assignment statement nodes.

Bug: tint:4
Change-Id: I8a52f4e96c61ecb9e97cd3da41f4a1aa718e8d37
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17162
Reviewed-by: David Neto <dneto@google.com>

src/CMakeLists.txt

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 6112a7f..9d55ca8 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -407,6 +407,7 @@
     writer/wgsl/generator_impl_alias_type_test.cc
     writer/wgsl/generator_impl_array_accessor_test.cc
     writer/wgsl/generator_impl_as_test.cc
+    writer/wgsl/generator_impl_assign_test.cc
     writer/wgsl/generator_impl_call_test.cc
     writer/wgsl/generator_impl_cast_test.cc
     writer/wgsl/generator_impl_entry_point_test.cc

src/writer/wgsl/generator_impl.cc

diff --git a/src/writer/wgsl/generator_impl.cc b/src/writer/wgsl/generator_impl.cc
index e0c8fef..7a728e1 100644
--- a/src/writer/wgsl/generator_impl.cc
+++ b/src/writer/wgsl/generator_impl.cc
@@ -19,6 +19,7 @@
 
 #include "src/ast/array_accessor_expression.h"
 #include "src/ast/as_expression.h"
+#include "src/ast/assignment_statement.h"
 #include "src/ast/binding_decoration.h"
 #include "src/ast/bool_literal.h"
 #include "src/ast/builtin_decoration.h"
@@ -34,6 +35,7 @@
 #include "src/ast/member_accessor_expression.h"
 #include "src/ast/relational_expression.h"
 #include "src/ast/set_decoration.h"
+#include "src/ast/statement.h"
 #include "src/ast/struct.h"
 #include "src/ast/struct_member.h"
 #include "src/ast/struct_member_offset_decoration.h"
@@ -639,6 +641,31 @@
   return true;
 }
 
+bool GeneratorImpl::EmitStatement(ast::Statement* stmt) {
+  if (stmt->IsAssign()) {
+    return EmitAssign(stmt->AsAssign());
+  }
+
+  error_ = "unknown statement type";
+  return false;
+}
+
+bool GeneratorImpl::EmitAssign(ast::AssignmentStatement* stmt) {
+  if (!EmitExpression(stmt->lhs())) {
+    return false;
+  }
+
+  out_ << " = ";
+
+  if (!EmitExpression(stmt->rhs())) {
+    return false;
+  }
+
+  out_ << ";";
+
+  return true;
+}
+
 }  // namespace wgsl
 }  // namespace writer
 }  // namespace tint

src/writer/wgsl/generator_impl.h

diff --git a/src/writer/wgsl/generator_impl.h b/src/writer/wgsl/generator_impl.h
index ebb6f7e..7b8f542 100644
--- a/src/writer/wgsl/generator_impl.h
+++ b/src/writer/wgsl/generator_impl.h
@@ -78,6 +78,10 @@
   /// @param expr the as expression
   /// @returns true if the as was emitted
   bool EmitAs(ast::AsExpression* expr);
+  /// Handles an assignment statement
+  /// @param stmt the statement to emit
+  /// @returns true if the statement was emitted successfully
+  bool EmitAssign(ast::AssignmentStatement* stmt);
   /// Handles generating a call expression
   /// @param expr the call expression
   /// @returns true if the call expression is emitted
@@ -118,6 +122,10 @@
   /// @param expr the relational expression
   /// @returns true if the expression was emitted, false otherwise
   bool EmitRelational(ast::RelationalExpression* expr);
+  /// Handles statements
+  /// @param stmt the statement to emit
+  /// @returns true if the statement was emitted
+  bool EmitStatement(ast::Statement* stmt);
   /// Handles generating type
   /// @param type the type to generate
   /// @returns true if the type is emitted

src/writer/wgsl/generator_impl_assign_test.cc

diff --git a/src/writer/wgsl/generator_impl_assign_test.cc b/src/writer/wgsl/generator_impl_assign_test.cc
new file mode 100644
index 0000000..16d973d
--- /dev/null
+++ b/src/writer/wgsl/generator_impl_assign_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 <vector>
+
+#include "gtest/gtest.h"
+#include "src/ast/assignment_statement.h"
+#include "src/ast/identifier_expression.h"
+#include "src/writer/wgsl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace wgsl {
+namespace {
+
+using GeneratorImplTest = testing::Test;
+
+TEST_F(GeneratorImplTest, Emit_Assign) {
+  auto lhs = std::make_unique<ast::IdentifierExpression>("lhs");
+  auto rhs = std::make_unique<ast::IdentifierExpression>("rhs");
+  ast::AssignmentStatement assign(std::move(lhs), std::move(rhs));
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitStatement(&assign)) << g.error();
+  EXPECT_EQ(g.result(), "lhs = rhs;");
+}
+
+}  // namespace
+}  // namespace wgsl
+}  // namespace writer
+}  // namespace tint