Add WGSL writer support for call.

This CL adds call expressions to the WGSL writer support.

Bug: tint:4
Change-Id: I1caa2f5f81ac2e2ab89755c1721e96d44c331853
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17060
Reviewed-by: David Neto <dneto@google.com>

src/CMakeLists.txt

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 8731960..7279687 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_call_test.cc
     writer/wgsl/generator_impl_entry_point_test.cc
     writer/wgsl/generator_impl_identifier_test.cc
     writer/wgsl/generator_impl_import_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 e0257f3..ed3a1bf 100644
--- a/src/writer/wgsl/generator_impl.cc
+++ b/src/writer/wgsl/generator_impl.cc
@@ -22,6 +22,7 @@
 #include "src/ast/binding_decoration.h"
 #include "src/ast/bool_literal.h"
 #include "src/ast/builtin_decoration.h"
+#include "src/ast/call_expression.h"
 #include "src/ast/const_initializer_expression.h"
 #include "src/ast/decorated_variable.h"
 #include "src/ast/float_literal.h"
@@ -122,6 +123,9 @@
   if (expr->IsAs()) {
     return EmitAs(expr->AsAs());
   }
+  if (expr->IsCall()) {
+    return EmitCall(expr->AsCall());
+  }
   if (expr->IsIdentifier()) {
     return EmitIdentifier(expr->AsIdentifier());
   }
@@ -162,6 +166,30 @@
   return true;
 }
 
+bool GeneratorImpl::EmitCall(ast::CallExpression* expr) {
+  if (!EmitExpression(expr->func())) {
+    return false;
+  }
+  out_ << "(";
+
+  bool first = true;
+  const auto& params = expr->params();
+  for (const auto& param : params) {
+    if (!first) {
+      out_ << ", ";
+    }
+    first = false;
+
+    if (!EmitExpression(param.get())) {
+      return false;
+    }
+  }
+
+  out_ << ")";
+
+  return true;
+}
+
 bool GeneratorImpl::EmitInitializer(ast::InitializerExpression* expr) {
   if (expr->IsConstInitializer()) {
     return EmitConstInitializer(expr->AsConstInitializer());

src/writer/wgsl/generator_impl.h

diff --git a/src/writer/wgsl/generator_impl.h b/src/writer/wgsl/generator_impl.h
index 25203d9..d03b8f6 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 generating a call expression
+  /// @param expr the call expression
+  /// @returns true if the call expression is emitted
+  bool EmitCall(ast::CallExpression* expr);
   /// Handles generating a const initializer
   /// @param expr the const initializer expression
   /// @returns true if the initializer is emitted

src/writer/wgsl/generator_impl_call_test.cc

diff --git a/src/writer/wgsl/generator_impl_call_test.cc b/src/writer/wgsl/generator_impl_call_test.cc
new file mode 100644
index 0000000..639c231
--- /dev/null
+++ b/src/writer/wgsl/generator_impl_call_test.cc
@@ -0,0 +1,53 @@
+// 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/call_expression.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, EmitExpression_Call_WithoutParams) {
+  auto id = std::make_unique<ast::IdentifierExpression>("my_func");
+  ast::CallExpression call(std::move(id), {});
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitExpression(&call)) << g.error();
+  EXPECT_EQ(g.result(), "my_func()");
+}
+
+TEST_F(GeneratorImplTest, EmitExpression_Call_WithParams) {
+  auto id = std::make_unique<ast::IdentifierExpression>("my_func");
+  std::vector<std::unique_ptr<ast::Expression>> params;
+  params.push_back(std::make_unique<ast::IdentifierExpression>("param1"));
+  params.push_back(std::make_unique<ast::IdentifierExpression>("param2"));
+  ast::CallExpression call(std::move(id), std::move(params));
+
+  GeneratorImpl g;
+  ASSERT_TRUE(g.EmitExpression(&call)) << g.error();
+  EXPECT_EQ(g.result(), "my_func(param1, param2)");
+}
+
+}  // namespace
+}  // namespace wgsl
+}  // namespace writer
+}  // namespace tint