[PATCH] D11490: [Concepts] Add diagnostic: non template declaration

[Aaron Ballman]

On Fri, Jul 24, 2015 at 2:43 PM, Nathan Wilson <nwilson20 at gmail.com> wrote:
> nwilson created this revision.
> nwilson added reviewers: rsmith, faisalv, fraggamuffin, hubert.reinterpretcast.
> nwilson added a subscriber: cfe-commits.
>
> Adding diagnostic for concepts declared as non template (function or variable)
>
> http://reviews.llvm.org/D11490
>
> Files:
>   include/clang/Basic/DiagnosticSemaKinds.td
>   lib/Sema/SemaDecl.cpp
>   test/SemaCXX/cxx-concept-declaration.cpp
>
> Index: test/SemaCXX/cxx-concept-declaration.cpp
> ===================================================================
> --- test/SemaCXX/cxx-concept-declaration.cpp
> +++ test/SemaCXX/cxx-concept-declaration.cpp
> @@ -15,3 +15,7 @@
>  struct C {
>    template<typename T> static concept bool D3 = true; // expected-error {{concept declarations may only appear in namespace scope}}
>  };
> +
> +concept bool D4() { return true; } // expected-error {{concept can only be applied to a function or variable template definition}}
> +
> +concept bool D5 = true; // expected-error {{concept can only be applied to a function or variable template definition}}
> Index: lib/Sema/SemaDecl.cpp
> ===================================================================
> --- lib/Sema/SemaDecl.cpp
> +++ lib/Sema/SemaDecl.cpp
> @@ -4865,6 +4865,12 @@
>      // C++ Concepts TS [dcl.spec.concept]p1: The concept specifier shall be
>      // applied only to the definition of a function template or variable
>      // template, declared in namespace scope
> +    if (!TemplateParamLists.size()) {
> +      Diag(D.getDeclSpec().getConceptSpecLoc(),
> +           diag::err_concept_decl_non_template);
> +      return nullptr;
> +    }
> +
>      if (!DC->getRedeclContext()->isFileContext()) {
>        Diag(D.getIdentifierLoc(),
>             diag::err_concept_decls_may_only_appear_in_namespace_scope);
> Index: include/clang/Basic/DiagnosticSemaKinds.td
> ===================================================================
> --- include/clang/Basic/DiagnosticSemaKinds.td
> +++ include/clang/Basic/DiagnosticSemaKinds.td
> @@ -1966,6 +1966,8 @@
>    "use __attribute__((visibility(\"hidden\"))) attribute instead">;
>
>  // C++ Concepts TS
> +def err_concept_decl_non_template : Error<
> +  "concept can only be applied to a function or variable template definition">;

Since we are using "concept" as a grammar term, I think we want to
quote it. Similar diagnostics suggest phrasing like:

"'concept' can only appear on a function template or variable template
definition"

This also reduces some ambiguity over how "function or variable template" binds.

~Aaron

>  def err_concept_decls_may_only_appear_in_namespace_scope : Error<
>    "concept declarations may only appear in namespace scope">;
>  def err_function_concept_not_defined : Error<
>
>
>
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