[PATCH] D11916: [CONCEPTS] Add diagnostic; invalid tag when concept specified

[Aaron Ballman via cfe-commits]

On Mon, Aug 10, 2015 at 3:00 PM, Nathan Wilson <nwilson20 at gmail.com> wrote:
> nwilson created this revision.
> nwilson added reviewers: rsmith, hubert.reinterpretcast, fraggamuffin, faisalv, aaron.ballman.
> nwilson added a subscriber: cfe-commits.
>
> Adding check to emit diagnostic for invalid tag when concept is specified and associated tests.
>
> http://reviews.llvm.org/D11916
>
> 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
> @@ -23,3 +23,13 @@
>  template<typename T>
>  concept bool D6; // expected-error {{variable concept declaration must be initialized}}
>
> +// Tag
> +concept class CC1 {}; // expected-error {{class cannot be marked concept}}
> +concept struct CS1 {}; // expected-error {{struct cannot be marked concept}}
> +concept union CU1 {}; // expected-error {{union cannot be marked concept}}
> +concept enum CE1 {}; // expected-error {{enum cannot be marked concept}}
> +template <typename T> concept class TCC1 {}; // expected-error {{class cannot be marked concept}}
> +template <typename T> concept struct TCS1 {}; // expected-error {{struct cannot be marked concept}}
> +template <typename T> concept union TCU1 {}; // expected-error {{union cannot be marked concept}}
> +
> +extern concept bool ExtC; // expected-error {{'concept' can only appear on the definition of a function template or variable template}}
> Index: lib/Sema/SemaDecl.cpp
> ===================================================================
> --- lib/Sema/SemaDecl.cpp
> +++ lib/Sema/SemaDecl.cpp
> @@ -3662,6 +3662,19 @@
>      return TagD;
>    }
>
> +  if (DS.isConceptSpecified()) {
> +    // C++ Concepts TS [dcl.spec.concept]p1: A concept definition refers to
> +    // either a function concept and its definition or a variable concept and
> +    // its initializer.
> +    if (Tag)
> +      Diag(DS.getConceptSpecLoc(), diag::err_concept_tag)
> +          << GetDiagnosticTypeSpecifierID(DS.getTypeSpecType());
> +    else
> +      Diag(DS.getConceptSpecLoc(), diag::err_concept_decl_non_template);
> +    // Don't emit warnings after this error.
> +    return TagD;
> +  }

I'm not certain I understand why we need two different diagnostics for
this case. I think err_concept_decl_non_template is sufficiently clear
for both.

~Aaron

> +
>    DiagnoseFunctionSpecifiers(DS);
>
>    if (DS.isFriendSpecified()) {
> Index: include/clang/Basic/DiagnosticSemaKinds.td
> ===================================================================
> --- include/clang/Basic/DiagnosticSemaKinds.td
> +++ include/clang/Basic/DiagnosticSemaKinds.td
> @@ -1973,6 +1973,8 @@
>    "function concept declaration must be a definition">;
>  def err_var_concept_not_initialized : Error<
>    "variable concept declaration must be initialized">;
> +def err_concept_tag : Error<
> +  "%select{class|struct|interface|union|enum}0 cannot be marked concept">;
>
>  // C++11 char16_t/char32_t
>  def warn_cxx98_compat_unicode_type : Warning<
>
>