[clang] [llvm] [HLSL] Add implicit resource element type concepts to AST (PR #116413)

[Justin Bogner via cfe-commits]

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@@ -323,19 +325,117 @@ struct TemplateParameterListBuilder {
     return *this;
   }
 
-  BuiltinTypeDeclBuilder &finalizeTemplateArgs() {
+  // The concept specialization expression (CSE) constructed in
+  // constructConceptSpecializationExpr 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 =
+  // __builtin_hlsl_typed_resource_element_compatible<T>
+  //
+  // 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 TemplateTypeParmDecl is the template for the resource, and is
+    // used to construct a template argumentthat will be used
+    // to construct the ImplicitConceptSpecializationDecl
+    TemplateTypeParmDecl *T = TemplateTypeParmDecl::Create(
+        Context,                          // AST context
+        Builder.Record->getDeclContext(), // DeclContext
+        SourceLocation(), SourceLocation(),
+        /*depth=*/0,                // Depth in the template parameter list
+        /*position=*/0,             // Position in the template parameter list
+        /*id=*/nullptr,             // Identifier for 'T'
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bogner wrote:

I get that the parameter names in `TemplateTypeParmDecl::Create` aren't all great, but these comments really should match those names exactly.

https://github.com/llvm/llvm-project/pull/116413