[msl-writer] Emit BlockStatement.

This CL adds BlockStatement emission to the MSL backend.

Bug: tint:132
Change-Id: Ie64c02b81760787f6d8aa8833b9756ede3deddf9
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/25608
Reviewed-by: Sarah Mashayekhi <sarahmashay@google.com>

BUILD.gn

@@ -988,6 +988,7 @@ source_set("tint_unittests_msl_writer_src") {
     "src/writer/msl/generator_impl_as_test.cc",
     "src/writer/msl/generator_impl_assign_test.cc",
     "src/writer/msl/generator_impl_binary_test.cc",
+    "src/writer/msl/generator_impl_block_test.cc",
     "src/writer/msl/generator_impl_break_test.cc",
     "src/writer/msl/generator_impl_call_test.cc",
     "src/writer/msl/generator_impl_case_test.cc",

src/CMakeLists.txt

@@ -519,6 +519,7 @@ if(${TINT_BUILD_MSL_WRITER})
     writer/msl/generator_impl_as_test.cc
     writer/msl/generator_impl_assign_test.cc
     writer/msl/generator_impl_binary_test.cc
+    writer/msl/generator_impl_block_test.cc
     writer/msl/generator_impl_break_test.cc
     writer/msl/generator_impl_call_test.cc
     writer/msl/generator_impl_case_test.cc

src/writer/msl/generator_impl.cc

@@ -19,6 +19,7 @@
 #include "src/ast/as_expression.h"
 #include "src/ast/assignment_statement.h"
 #include "src/ast/binary_expression.h"
+#include "src/ast/block_statement.h"
 #include "src/ast/bool_literal.h"
 #include "src/ast/break_statement.h"
 #include "src/ast/call_expression.h"
@@ -1576,6 +1577,33 @@ bool GeneratorImpl::EmitReturn(ast::ReturnStatement* stmt) {
   return true;
 }
 
+bool GeneratorImpl::EmitBlock(ast::BlockStatement* stmt) {
+  make_indent();
+
+  out_ << "{" << std::endl;
+  increment_indent();
+
+  for (const auto& s : *stmt) {
+    if (!EmitStatement(s.get())) {
+      return false;
+    }
+  }
+
+  decrement_indent();
+  make_indent();
+  out_ << "}";
+
+  return true;
+}
+
+bool GeneratorImpl::EmitBlockAndNewline(ast::BlockStatement* stmt) {
+  const bool result = EmitBlock(stmt);
+  if (result) {
+    out_ << std::endl;
+  }
+  return result;
+}
+
 bool GeneratorImpl::EmitStatementBlock(const ast::StatementList& statements) {
   out_ << " {" << std::endl;
 
@@ -1607,6 +1635,9 @@ bool GeneratorImpl::EmitStatement(ast::Statement* stmt) {
   if (stmt->IsAssign()) {
     return EmitAssign(stmt->AsAssign());
   }
+  if (stmt->IsBlock()) {
+    return EmitBlockAndNewline(stmt->AsBlock());
+  }
   if (stmt->IsBreak()) {
     return EmitBreak(stmt->AsBreak());
   }

src/writer/msl/generator_impl.h

@@ -73,6 +73,14 @@ class GeneratorImpl : public TextGenerator {
   /// @param expr the binary expression
   /// @returns true if the expression was emitted, false otherwise
   bool EmitBinary(ast::BinaryExpression* expr);
+  /// Handles a block statement
+  /// @param stmt the statement to emit
+  /// @returns true if the statement was emitted successfully
+  bool EmitBlock(ast::BlockStatement* stmt);
+  /// Handles a block statement with a newline at the end
+  /// @param stmt the statement to emit
+  /// @returns true if the statement was emitted successfully
+  bool EmitBlockAndNewline(ast::BlockStatement* stmt);
   /// Handles a break statement
   /// @param stmt the statement to emit
   /// @returns true if the statement was emitted successfully

src/writer/msl/generator_impl_block_test.cc

@@ -0,0 +1,61 @@
+// 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/block_statement.h"
+#include "src/ast/discard_statement.h"
+#include "src/writer/msl/generator_impl.h"
+
+namespace tint {
+namespace writer {
+namespace msl {
+namespace {
+
+using MslGeneratorImplTest = testing::Test;
+
+TEST_F(MslGeneratorImplTest, Emit_Block) {
+  ast::BlockStatement b;
+  b.append(std::make_unique<ast::DiscardStatement>());
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitStatement(&b)) << g.error();
+  EXPECT_EQ(g.result(), R"(  {
+    discard_fragment();
+  }
+)");
+}
+
+TEST_F(MslGeneratorImplTest, Emit_Block_WithoutNewline) {
+  ast::BlockStatement b;
+  b.append(std::make_unique<ast::DiscardStatement>());
+
+  ast::Module m;
+  GeneratorImpl g(&m);
+  g.increment_indent();
+
+  ASSERT_TRUE(g.EmitBlock(&b)) << g.error();
+  EXPECT_EQ(g.result(), R"(  {
+    discard_fragment();
+  })");
+}
+
+}  // namespace
+}  // namespace msl
+}  // namespace writer
+}  // namespace tint