On Tue, Aug 11, 2015 at 8:54 AM, Aaron Ballman <aaron.ball...@gmail.com> wrote:
> On Mon, Aug 10, 2015 at 3:00 PM, Nathan Wilson <nwilso...@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 > This was based on how constexpr handles these checks. Perhaps someone can correct me if I'm wrong, but I believe the idea is that when the `struct` tag exists, for example, we think the user meant to declare a `struct` and not the start of a `concept` declaration. So, the `concept` specifier would be erroneous and we try give a more helpful diagnostic. I would need to add/fix the test case for this, but I tend to think the declaration such as `concept bool;` could be the users intention to try to create a `concept` declaration which is where the err_concept_decl_non_template comes in. > > > + > > 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< > > > > >
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