Add Variable test for invalid initializer.

This CL adds a test to the variable AST node to verify the initializer
is valid.

Bug: tint:11
Change-Id: I95553e8572124e8e2e861b451003e5c9bf6358f1
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/16743
Reviewed-by: Sarah Mashayekhi <sarahmashay@google.com>

src/ast/variable.cc

@@ -44,6 +44,9 @@ bool Variable::IsValid() const {
   if (type_ == nullptr) {
     return false;
   }
+  if (initializer_ && !initializer_->IsValid()) {
+    return false;
+  }
   return true;
 }
 

src/ast/variable_test.cc

@@ -15,6 +15,7 @@
 #include "src/ast/variable.h"
 
 #include "gtest/gtest.h"
+#include "src/ast/identifier_expression.h"
 #include "src/ast/type/f32_type.h"
 #include "src/ast/type/i32_type.h"
 
@@ -69,6 +70,13 @@ TEST_F(VariableTest, IsValid) {
   EXPECT_TRUE(v.IsValid());
 }
 
+TEST_F(VariableTest, IsValid_WithInitializer) {
+  type::I32Type t;
+  Variable v{"my_var", StorageClass::kNone, &t};
+  v.set_initializer(std::make_unique<IdentifierExpression>("ident"));
+  EXPECT_TRUE(v.IsValid());
+}
+
 TEST_F(VariableTest, IsValid_MissinName) {
   type::I32Type t;
   Variable v{"", StorageClass::kNone, &t};
@@ -85,6 +93,13 @@ TEST_F(VariableTest, IsValid_MissingBoth) {
   EXPECT_FALSE(v.IsValid());
 }
 
+TEST_F(VariableTest, IsValid_InvalidInitializer) {
+  type::I32Type t;
+  Variable v{"my_var", StorageClass::kNone, &t};
+  v.set_initializer(std::make_unique<IdentifierExpression>(""));
+  EXPECT_FALSE(v.IsValid());
+}
+
 TEST_F(VariableTest, to_str) {
   type::F32Type t;
   Variable v{"my_var", StorageClass::kFunction, &t};