Replace StructMemberDecoration::(Is|As) with Castable

Change-Id: I158194c60a9fe0ea2126ca31a92ad536c92a6388
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/34314
Reviewed-by: dan sinclair <dsinclair@chromium.org>

src/ast/struct_member.cc

@@ -41,7 +41,7 @@ StructMember::~StructMember() = default;
 
 bool StructMember::has_offset_decoration() const {
   for (auto* deco : decorations_) {
-    if (deco->IsOffset()) {
+    if (deco->Is<ast::StructMemberOffsetDecoration>()) {
       return true;
     }
   }
@@ -50,8 +50,8 @@ bool StructMember::has_offset_decoration() const {
 
 uint32_t StructMember::offset() const {
   for (auto* deco : decorations_) {
-    if (deco->IsOffset()) {
-      return deco->AsOffset()->offset();
+    if (auto* offset = deco->As<ast::StructMemberOffsetDecoration>()) {
+      return offset->offset();
     }
   }
   return 0;

src/ast/struct_member_decoration.cc

@@ -32,14 +32,5 @@ DecorationKind StructMemberDecoration::GetKind() const {
   return Kind;
 }
 
-bool StructMemberDecoration::IsOffset() const {
-  return false;
-}
-
-StructMemberOffsetDecoration* StructMemberDecoration::AsOffset() {
-  assert(IsOffset());
-  return static_cast<StructMemberOffsetDecoration*>(this);
-}
-
 }  // namespace ast
 }  // namespace tint

src/ast/struct_member_decoration.h

@@ -24,8 +24,6 @@
 namespace tint {
 namespace ast {
 
-class StructMemberOffsetDecoration;
-
 /// A decoration attached to a struct member
 class StructMemberDecoration
     : public Castable<StructMemberDecoration, Decoration> {
@@ -38,12 +36,6 @@ class StructMemberDecoration
   /// @return the decoration kind
   DecorationKind GetKind() const override;
 
-  /// @returns true if this is an offset decoration
-  virtual bool IsOffset() const;
-
-  /// @returns the decoration as an offset decoration
-  StructMemberOffsetDecoration* AsOffset();
-
  protected:
   /// Constructor
   /// @param source the source of this decoration

src/ast/struct_member_offset_decoration.cc

@@ -21,10 +21,6 @@ StructMemberOffsetDecoration::StructMemberOffsetDecoration(uint32_t offset,
                                                            const Source& source)
     : Base(source), offset_(offset) {}
 
-bool StructMemberOffsetDecoration::IsOffset() const {
-  return true;
-}
-
 StructMemberOffsetDecoration::~StructMemberOffsetDecoration() = default;
 
 void StructMemberOffsetDecoration::to_str(std::ostream& out,

src/ast/struct_member_offset_decoration.h

@@ -34,9 +34,6 @@ class StructMemberOffsetDecoration
   StructMemberOffsetDecoration(uint32_t offset, const Source& source);
   ~StructMemberOffsetDecoration() override;
 
-  /// @returns true if this is an offset decoration
-  bool IsOffset() const override;
-
   /// @returns the offset value
   uint32_t offset() const { return offset_; }
 

src/ast/struct_member_offset_decoration_test.cc

@@ -29,7 +29,7 @@ TEST_F(StructMemberOffsetDecorationTest, Creation) {
 
 TEST_F(StructMemberOffsetDecorationTest, Is) {
   StructMemberOffsetDecoration d{2, Source{}};
-  EXPECT_TRUE(d.IsOffset());
+  EXPECT_TRUE(d.Is<ast::StructMemberOffsetDecoration>());
 }
 
 }  // namespace

src/ast/struct_member_test.cc

@@ -36,7 +36,7 @@ TEST_F(StructMemberTest, Creation) {
   EXPECT_EQ(st.name(), "a");
   EXPECT_EQ(st.type(), &i32);
   EXPECT_EQ(st.decorations().size(), 1u);
-  EXPECT_TRUE(st.decorations()[0]->IsOffset());
+  EXPECT_TRUE(st.decorations()[0]->Is<ast::StructMemberOffsetDecoration>());
   EXPECT_EQ(st.source().range.begin.line, 0u);
   EXPECT_EQ(st.source().range.begin.column, 0u);
   EXPECT_EQ(st.source().range.end.line, 0u);