Replace Type::(Is|As)Void with Castable

Change-Id: If8a27c69c91a968a40a982c02b9fcaf9481e60b7
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/34275
Reviewed-by: dan sinclair <dsinclair@chromium.org>

src/ast/type/type.cc

@@ -66,10 +66,6 @@ Type* Type::UnwrapAll() {
   return UnwrapIfNeeded()->UnwrapPtrIfNeeded()->UnwrapIfNeeded();
 }
 
-bool Type::IsVoid() const {
-  return false;
-}
-
 uint64_t Type::MinBufferBindingSize(MemoryLayout) const {
   return 0;
 }
@@ -124,16 +120,6 @@ bool Type::is_integer_scalar_or_vector() {
   return is_unsigned_scalar_or_vector() || is_signed_scalar_or_vector();
 }
 
-const VoidType* Type::AsVoid() const {
-  assert(IsVoid());
-  return static_cast<const VoidType*>(this);
-}
-
-VoidType* Type::AsVoid() {
-  assert(IsVoid());
-  return static_cast<VoidType*>(this);
-}
-
 }  // namespace type
 }  // namespace ast
 }  // namespace tint

src/ast/type/type.h

@@ -23,8 +23,6 @@ namespace tint {
 namespace ast {
 namespace type {
 
-class VoidType;
-
 /// Supported memory layouts for calculating sizes
 enum class MemoryLayout { kUniformBuffer, kStorageBuffer };
 
@@ -35,9 +33,6 @@ class Type : public Castable<Type> {
   Type(Type&&);
   ~Type() override;
 
-  /// @returns true if the type is a void type
-  virtual bool IsVoid() const;
-
   /// @returns the name for this type. The |type_name| is unique over all types.
   virtual std::string type_name() const = 0;
 
@@ -92,12 +87,6 @@ class Type : public Castable<Type> {
   /// @returns true if this type is an integer scalar or vector
   bool is_integer_scalar_or_vector();
 
-  /// @returns the type as a void type
-  const VoidType* AsVoid() const;
-
-  /// @returns the type as a void type
-  VoidType* AsVoid();
-
  protected:
   Type();
 };

src/ast/type/void_type.cc

@@ -24,10 +24,6 @@ VoidType::VoidType(VoidType&&) = default;
 
 VoidType::~VoidType() = default;
 
-bool VoidType::IsVoid() const {
-  return true;
-}
-
 std::string VoidType::type_name() const {
   return "__void";
 }

src/ast/type/void_type.h

@@ -32,9 +32,6 @@ class VoidType : public Castable<VoidType, Type> {
   VoidType(VoidType&&);
   ~VoidType() override;
 
-  /// @returns true if the type is a void type
-  bool IsVoid() const override;
-
   /// @returns the name for this type
   std::string type_name() const override;
 };