Remove ast::Variable::constant_id()

The backends now use sem::Variable::ConstantId() instead, since the
AST does not have the correct ID when the parameterless version of the
override attribute is used.

Change-Id: I816295c8b2e4baa1671c9d042920bf001b1b4336
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/50845
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: James Price <jrprice@google.com>

src/ast/variable.cc

@@ -62,14 +62,6 @@ Variable::BindingPoint Variable::binding_point() const {
   return BindingPoint{group, binding};
 }
 
-uint32_t Variable::constant_id() const {
-  if (auto* cid = GetDecoration<OverrideDecoration>(decorations_)) {
-    return cid->value();
-  }
-  TINT_ASSERT(false);
-  return 0;
-}
-
 Variable* Variable::Clone(CloneContext* ctx) const {
   auto src = ctx->Clone(source());
   auto sym = ctx->Clone(symbol());

src/ast/variable.h

@@ -142,10 +142,6 @@ class Variable : public Castable<Variable, Node> {
   /// @returns the binding point information for the variable
   BindingPoint binding_point() const;
 
-  /// @returns the pipeline constant id value for the variable. Assumes that
-  /// this variable has an override decoration.
-  uint32_t constant_id() const;
-
   /// Clones this node and all transitive child nodes using the `CloneContext`
   /// `ctx`.
   /// @param ctx the clone context

src/ast/variable_test.cc

@@ -169,15 +169,6 @@ TEST_F(VariableTest, BindingPointMissingBindingDecoration) {
   EXPECT_EQ(var->binding_point().binding, nullptr);
 }
 
-TEST_F(VariableTest, ConstantId) {
-  auto* var = Var("my_var", ty.i32(), StorageClass::kFunction, nullptr,
-                  DecorationList{
-                      create<OverrideDecoration>(1200),
-                  });
-
-  EXPECT_EQ(var->constant_id(), 1200u);
-}
-
 TEST_F(VariableTest, Decorated_to_str) {
   auto* var = Var("my_var", ty.f32(), StorageClass::kFunction, Expr("expr"),
                   DecorationList{