[clang] [HLSL] Add implicit resource element type concepts to AST (PR #112600)

[Joshua Batista via cfe-commits]

================
@@ -323,30 +324,127 @@ struct TemplateParameterListBuilder {
         S.Context, Builder.Record->getDeclContext(), SourceLocation(),
         SourceLocation(), /* TemplateDepth */ 0, Position,
         &S.Context.Idents.get(Name, tok::TokenKind::identifier),
-        /* Typename */ false,
-        /* ParameterPack */ false);
+        /* Typename */ true,
+        /* ParameterPack */ false,
+        /* HasTypeConstraint*/ false);
     if (!DefaultValue.isNull())
       Decl->setDefaultArgument(
           S.Context, S.getTrivialTemplateArgumentLoc(DefaultValue, QualType(),
                                                      SourceLocation()));
-
     Params.emplace_back(Decl);
     return *this;
   }
 
-  BuiltinTypeDeclBuilder &finalizeTemplateArgs() {
+  /*
+  The concept specialization expression (CSE) constructed below is constructed
+  so that it matches the CSE that is constructed when parsing
+  the below C++ code:
+
+  template<typename T>
+  concept is_typed_resource_element_compatible =sizeof(T) <= 16;
+
+  template<typename element_type> requires
+  is_typed_resource_element_compatible<element_type>
+
+  struct RWBuffer {
+      element_type Val;
+  };
+
+  int fn() {
+      RWBuffer<int> Buf;
+  }
+
+  When dumping the AST and filtering for "RWBuffer", the resulting AST
+  structure is what we're trying to construct below, specifically the
+  CSE portion.
+  */
+  ConceptSpecializationExpr *
+  constructConceptSpecializationExpr(Sema &S, ConceptDecl *CD) {
+    ASTContext &Context = S.getASTContext();
+    SourceLocation Loc = Builder.Record->getBeginLoc();
+    DeclarationNameInfo DNI(CD->getDeclName(), Loc);
+    NestedNameSpecifierLoc NNSLoc;
+    DeclContext *DC = Builder.Record->getDeclContext();
+    TemplateArgumentListInfo TALI(Loc, Loc);
+
+    // Assume that the concept decl has just one template parameter
+    // This parameter should have been added when CD was constructed
+    // in getTypedBufferConceptDecl
+    assert(CD->getTemplateParameters()->size() == 1 &&
+           "unexpected concept decl parameter count");
+    TemplateTypeParmDecl *ConceptTTPD = dyn_cast<TemplateTypeParmDecl>(
+        CD->getTemplateParameters()->getParam(0));
+
+    // this fake TemplateTypeParmDecl is used to construct a template argument
+    // that will be used to construct the ImplicitConceptSpecializationDecl
----------------
bob80905 wrote:

It isn't being placed into the AST, the sole reason for its existence is to allow a path to construct a TemplateArgument, and that TemplateArgument will actually be placed into the AST. The fake TemplateTypeParmDecl is otherwise unused and discarded.

https://github.com/llvm/llvm-project/pull/112600