[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_valid_line_vector =sizeof(T) <= 16;
+
+  template<typename element_type> requires is_valid_line_vector<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
+    TemplateTypeParmDecl *T = TemplateTypeParmDecl::Create(
+        Context,                          // AST context
+        Context.getTranslationUnitDecl(), // DeclContext
+        SourceLocation(), SourceLocation(),
+        /*depth=*/0,                // Depth in the template parameter list
+        /*position=*/0,             // Position in the template parameter list
+        /*id=*/nullptr,             // Identifier for 'T'
+        /*Typename=*/true,          // Indicates this is a 'typename' or 'class'
+        /*ParameterPack=*/false,    // Not a parameter pack
+        /*HasTypeConstraint=*/false // Has no type constraint
+    );
+
+    T->setDeclContext(DC);
+    T->setReferenced();
----------------
bob80905 wrote:

Setting the decl context is necessary because it puts the decl into the right indentation in the AST dump. Otherwise, I believe the decl would be placed at the same scope as one indentation below the translation unit decl, which is not where the decl belongs.
I'll see if I can get away with removing setReferenced here.

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