[Concepts] Add diagnostic; invalid specifier on function or variable concept declaration

Summary: Diagnose variable and function concept declarations when an invalid specifier appears

Reviewers: rsmith, aaron.ballman, faisalv, fraggamuffin, hubert.reinterpretcast

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D12435

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@247194 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticSemaKinds.td

@@ -1980,6 +1980,9 @@ def err_var_concept_not_initialized : Error<
   "variable concept declaration must be initialized">;
 def err_function_concept_exception_spec : Error<
   "function concept cannot have exception specification">;
+def err_concept_decl_invalid_specifiers : Error<
+  "%select{variable|function}0 concept cannot be declared "
+  "'%select{thread_local|inline|friend|constexpr}1'">;
 
 // C++11 char16_t/char32_t
 def warn_cxx98_compat_unicode_type : Warning<

lib/Sema/SemaDecl.cpp

@@ -5876,8 +5876,26 @@ Sema::ActOnVariableDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     if (D.getDeclSpec().isConstexprSpecified())
       NewVD->setConstexpr(true);
-    if (D.getDeclSpec().isConceptSpecified())
+    if (D.getDeclSpec().isConceptSpecified()) {
       NewVD->setConcept(true);
+
+      // C++ Concepts TS [dcl.spec.concept]p2: A concept definition shall not
+      // be declared with the thread_local, inline, friend, or constexpr
+      // specifiers, [...]
+      if (D.getDeclSpec().getThreadStorageClassSpec() == TSCS_thread_local) {
+        Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
+             diag::err_concept_decl_invalid_specifiers)
+            << 0 << 0;
+        NewVD->setInvalidDecl(true);
+      }
+
+      if (D.getDeclSpec().isConstexprSpecified()) {
+        Diag(D.getDeclSpec().getConstexprSpecLoc(),
+             diag::err_concept_decl_invalid_specifiers)
+            << 0 << 3;
+        NewVD->setInvalidDecl(true);
+      }
+    }
   }
   // Set the lexical context. If the declarator has a C++ scope specifier, the
@@ -7502,6 +7520,30 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
       // C++ Concepts TS [dcl.spec.concept]p2: Every concept definition is
       // implicity defined to be a constexpr declaration (implicitly inline)
       NewFD->setImplicitlyInline();
+
+      // C++ Concepts TS [dcl.spec.concept]p2: A concept definition shall not
+      // be declared with the thread_local, inline, friend, or constexpr
+      // specifiers, [...]
+      if (isInline) {
+        Diag(D.getDeclSpec().getInlineSpecLoc(),
+             diag::err_concept_decl_invalid_specifiers)
+            << 1 << 1;
+        NewFD->setInvalidDecl(true);
+      }
+
+      if (isFriend) {
+        Diag(D.getDeclSpec().getFriendSpecLoc(),
+             diag::err_concept_decl_invalid_specifiers)
+            << 1 << 2;
+        NewFD->setInvalidDecl(true);
+      }
+
+      if (isConstexpr) {
+        Diag(D.getDeclSpec().getConstexprSpecLoc(),
+             diag::err_concept_decl_invalid_specifiers)
+            << 1 << 3;
+        NewFD->setInvalidDecl(true);
+      }
     }
     // If __module_private__ was specified, mark the function accordingly.

test/CXX/concepts-ts/dcl.dcl/dcl.spec/dcl.concept/p2.cpp

+// RUN:  %clang_cc1 -std=c++14 -fconcepts-ts -x c++ -verify %s
+
+template<typename T> concept thread_local bool VCTL = true; // expected-error {{variable concept cannot be declared 'thread_local'}}
+
+template<typename T> concept constexpr bool VCC = true; // expected-error {{variable concept cannot be declared 'constexpr'}}
+
+template<typename T> concept inline bool FCI() { return true; } // expected-error {{function concept cannot be declared 'inline'}}
+
+struct X {
+  template<typename T> concept friend bool FCF() { return true; } // expected-error {{function concept cannot be declared 'friend'}}
+};
+
+template<typename T> concept constexpr bool FCC() { return true; } // expected-error {{function concept cannot be declared 'constexpr'}}