ast: Have all decorations derive from base class

This is the first step in unifying the way decorations are parsed - i.e. instead of parsing decorations in different ways based on the predicted grammar that follows, we can parse decorations blocks in a unified way, then later verify what we have is as expected.

`StructDecoration` has been transformed from an `enum class` to a proper class so it can derive from `Decoration`.

Bug: tint:282
Bug: tint:291
Change-Id: Iaf12d266068d03edf695acdf2cd21e6cc3ea8eb3
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/31663
Reviewed-by: dan sinclair <dsinclair@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>

src/reader/spirv/parser_impl.cc

@@ -48,6 +48,7 @@
 #include "src/ast/sint_literal.h"
 #include "src/ast/stride_decoration.h"
 #include "src/ast/struct.h"
+#include "src/ast/struct_block_decoration.h"
 #include "src/ast/struct_decoration.h"
 #include "src/ast/struct_member.h"
 #include "src/ast/struct_member_decoration.h"
@@ -802,9 +803,11 @@ ast::type::Type* ParserImpl::ConvertType(
   if (struct_decorations.size() == 1) {
     const auto decoration = struct_decorations[0][0];
     if (decoration == SpvDecorationBlock) {
-      ast_struct_decorations.push_back(ast::StructDecoration::kBlock);
+      ast_struct_decorations.push_back(
+          std::make_unique<ast::StructBlockDecoration>());
     } else if (decoration == SpvDecorationBufferBlock) {
-      ast_struct_decorations.push_back(ast::StructDecoration::kBlock);
+      ast_struct_decorations.push_back(
+          std::make_unique<ast::StructBlockDecoration>());
       remap_buffer_block_type_.insert(type_id);
     } else {
       Fail() << "struct with ID " << type_id

src/reader/wgsl/parser_impl.cc

@@ -42,6 +42,7 @@
 #include "src/ast/sint_literal.h"
 #include "src/ast/stage_decoration.h"
 #include "src/ast/stride_decoration.h"
+#include "src/ast/struct_block_decoration.h"
 #include "src/ast/struct_member_offset_decoration.h"
 #include "src/ast/switch_statement.h"
 #include "src/ast/type/alias_type.h"
@@ -1524,10 +1525,10 @@ bool ParserImpl::struct_decoration_decl(ast::StructDecorationList& decos) {
   if (has_error()) {
     return false;
   }
-  if (deco == ast::StructDecoration::kNone) {
+  if (deco == nullptr) {
     return true;
   }
-  decos.push_back(deco);
+  decos.emplace_back(std::move(deco));
 
   next();  // Consume the peek of [[
   next();  // Consume the peek from the struct_decoration
@@ -1543,11 +1544,11 @@ bool ParserImpl::struct_decoration_decl(ast::StructDecorationList& decos) {
 
 // struct_decoration
 //  : BLOCK
-ast::StructDecoration ParserImpl::struct_decoration(Token t) {
+std::unique_ptr<ast::StructDecoration> ParserImpl::struct_decoration(Token t) {
   if (t.IsBlock()) {
-    return ast::StructDecoration::kBlock;
+    return std::make_unique<ast::StructBlockDecoration>();
   }
-  return ast::StructDecoration::kNone;
+  return nullptr;
 }
 
 // struct_body_decl

src/reader/wgsl/parser_impl.h

@@ -189,7 +189,7 @@ class ParserImpl {
   /// Parses a `struct_decoration` grammar element
   /// @param t the current token
   /// @returns the struct decoration or StructDecoraton::kNone if none matched
-  ast::StructDecoration struct_decoration(Token t);
+  std::unique_ptr<ast::StructDecoration> struct_decoration(Token t);
   /// Parses a `struct_body_decl` grammar element
   /// @returns the struct members
   ast::StructMemberList struct_body_decl();

src/reader/wgsl/parser_impl_struct_decl_test.cc

@@ -51,7 +51,7 @@ TEST_F(ParserImplTest, StructDecl_ParsesWithDecoration) {
   EXPECT_EQ(s->impl()->members()[0]->name(), "a");
   EXPECT_EQ(s->impl()->members()[1]->name(), "b");
   ASSERT_EQ(s->impl()->decorations().size(), 1u);
-  EXPECT_EQ(s->impl()->decorations()[0], ast::StructDecoration::kBlock);
+  EXPECT_TRUE(s->impl()->decorations()[0]->IsBlock());
 }
 
 TEST_F(ParserImplTest, StructDecl_ParsesWithMultipleDecoration) {
@@ -69,8 +69,8 @@ TEST_F(ParserImplTest, StructDecl_ParsesWithMultipleDecoration) {
   EXPECT_EQ(s->impl()->members()[0]->name(), "a");
   EXPECT_EQ(s->impl()->members()[1]->name(), "b");
   ASSERT_EQ(s->impl()->decorations().size(), 2u);
-  EXPECT_EQ(s->impl()->decorations()[0], ast::StructDecoration::kBlock);
-  EXPECT_EQ(s->impl()->decorations()[1], ast::StructDecoration::kBlock);
+  EXPECT_TRUE(s->impl()->decorations()[0]->IsBlock());
+  EXPECT_TRUE(s->impl()->decorations()[1]->IsBlock());
 }
 
 TEST_F(ParserImplTest, StructDecl_EmptyMembers) {

src/reader/wgsl/parser_impl_struct_decoration_decl_test.cc

@@ -27,7 +27,7 @@ TEST_F(ParserImplTest, StructDecorationDecl_Parses) {
   ASSERT_TRUE(p->struct_decoration_decl(decos));
   ASSERT_FALSE(p->has_error());
   EXPECT_EQ(decos.size(), 1u);
-  EXPECT_EQ(decos[0], ast::StructDecoration::kBlock);
+  EXPECT_TRUE(decos[0]->IsBlock());
 }
 
 TEST_F(ParserImplTest, StructDecorationDecl_MissingAttrRight) {

src/reader/wgsl/parser_impl_struct_decoration_test.cc

@@ -24,7 +24,7 @@ namespace {
 
 struct StructDecorationData {
   const char* input;
-  ast::StructDecoration result;
+  bool is_block;
 };
 inline std::ostream& operator<<(std::ostream& out, StructDecorationData data) {
   out << std::string(data.input);
@@ -40,17 +40,16 @@ TEST_P(StructDecorationTest, Parses) {
 
   auto deco = p->struct_decoration(p->peek());
   ASSERT_FALSE(p->has_error());
-  EXPECT_EQ(deco, params.result);
+  EXPECT_EQ(deco->IsBlock(), params.is_block);
 }
 INSTANTIATE_TEST_SUITE_P(ParserImplTest,
                          StructDecorationTest,
-                         testing::Values(StructDecorationData{
-                             "block", ast::StructDecoration::kBlock}));
+                         testing::Values(StructDecorationData{"block", true}));
 
 TEST_F(ParserImplTest, StructDecoration_NoMatch) {
   auto* p = parser("not-a-stage");
   auto deco = p->struct_decoration(p->peek());
-  ASSERT_EQ(deco, ast::StructDecoration::kNone);
+  ASSERT_EQ(deco, nullptr);
 
   auto t = p->next();
   EXPECT_TRUE(t.IsIdentifier());