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List:       cfe-commits
Subject:    Re: [PATCH] D11490: [Concepts] Add diagnostic: non template declaration
From:       Aaron Ballman <aaron () aaronballman ! com>
Date:       2015-07-24 19:14:47
Message-ID: CAAt6xTvCPSYEQRMa+kHjHqdhOp+uCkZysRvSig5GidB3mzJ8=A () mail ! gmail ! com
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On Fri, Jul 24, 2015 at 2:43 PM, Nathan Wilson <nwilson20@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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