Move the variable stack to a common class.

This Cl extracts the variable stack from the SPIR-V builder and makes it
available as a general class.

Change-Id: I3505d7cc4ec34f78bbc3360b064fa99479fd97d6
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/18701
Reviewed-by: David Neto <dneto@google.com>

src/scope_stack_test.cc

@@ -0,0 +1,94 @@
+// 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 "src/scope_stack.h"
+
+#include "gtest/gtest.h"
+#include "src/ast/variable.h"
+
+namespace tint {
+namespace {
+
+using ScopeStackTest = testing::Test;
+
+TEST_F(ScopeStackTest, Global) {
+  ScopeStack<uint32_t> s;
+  s.set_global("var", 5);
+
+  uint32_t val = 0;
+  EXPECT_TRUE(s.get("var", &val));
+  EXPECT_EQ(val, 5);
+}
+
+TEST_F(ScopeStackTest, Global_SetWithPointer) {
+  ast::Variable v;
+  v.set_name("my_var");
+
+  ScopeStack<ast::Variable*> s;
+  s.set_global("var", &v);
+
+  ast::Variable* v2;
+  EXPECT_TRUE(s.get("var", &v2));
+  EXPECT_EQ(v2->name(), "my_var");
+}
+
+TEST_F(ScopeStackTest, Global_CanNotPop) {
+  ScopeStack<uint32_t> s;
+  s.set_global("var", 5);
+  s.pop_scope();
+
+  uint32_t val = 0;
+  EXPECT_TRUE(s.get("var", &val));
+  EXPECT_EQ(val, 5);
+}
+
+TEST_F(ScopeStackTest, Scope) {
+  ScopeStack<uint32_t> s;
+  s.push_scope();
+  s.set("var", 5);
+
+  uint32_t val = 0;
+  EXPECT_TRUE(s.get("var", &val));
+  EXPECT_EQ(val, 5);
+}
+
+TEST_F(ScopeStackTest, Get_MissingName) {
+  ScopeStack<uint32_t> s;
+  uint32_t ret = 0;
+  EXPECT_FALSE(s.get("val", &ret));
+  EXPECT_EQ(ret, 0);
+}
+
+TEST_F(ScopeStackTest, Has) {
+  ScopeStack<uint32_t> s;
+  s.set_global("var2", 3);
+  s.push_scope();
+  s.set("var", 5);
+
+  EXPECT_TRUE(s.has("var"));
+  EXPECT_TRUE(s.has("var2"));
+}
+
+TEST_F(ScopeStackTest, ReturnsScopeBeforeGlobalFirst) {
+  ScopeStack<uint32_t> s;
+  s.set_global("var", 3);
+  s.push_scope();
+  s.set("var", 5);
+
+  uint32_t ret;
+  EXPECT_TRUE(s.get("var", &ret));
+  EXPECT_EQ(ret, 5);
+}
+
+}  // namespace
+}  // namespace tint