[temp.explicit]p1: constexpr cannot be specified in explicit instantiations.

llvm-svn: 141982

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2412,6 +2412,8 @@ def note_explicit_instantiation_candidate : Note<
   "explicit instantiation candidate function template here %0">;
 def err_explicit_instantiation_inline : Error<
   "explicit instantiation cannot be 'inline'">;
+def err_explicit_instantiation_constexpr : Error<
+  "explicit instantiation cannot be 'constexpr'">;
 def ext_explicit_instantiation_without_qualified_id : Extension<
   "qualifier in explicit instantiation of %q0 requires a template-id "
   "(a typedef is not permitted)">;

clang/lib/Sema/SemaTemplate.cpp

@@ -6165,8 +6165,11 @@ DeclResult Sema::ActOnExplicitInstantiation(Scope *S,
     Diag(D.getDeclSpec().getInlineSpecLoc(),
          diag::err_explicit_instantiation_inline)
       << FixItHint::CreateRemoval(D.getDeclSpec().getInlineSpecLoc());
-
-  // FIXME: check for constexpr specifier.
+  if (D.getDeclSpec().isConstexprSpecified())
+    // FIXME: Add a fix-it to remove the 'constexpr' and add a 'const' if one is
+    // not already specified.
+    Diag(D.getDeclSpec().getConstexprSpecLoc(),
+         diag::err_explicit_instantiation_constexpr);
 
   // C++0x [temp.explicit]p2:
   //   There are two forms of explicit instantiation: an explicit instantiation

clang/test/CXX/temp/temp.spec/temp.explicit/p1-0x.cpp

@@ -5,6 +5,11 @@ struct X {
   void f() {}
 };
 
-template inline void X<int>::f(); // expected-error{{'inline'}}
+template inline void X<int>::f(); // expected-error{{explicit instantiation cannot be 'inline'}}
 
-// FIXME: test constexpr
+template<typename T>
+struct Y {
+  constexpr int f() { return 0; }
+};
+
+template constexpr int Y<int>::f(); // expected-error{{explicit instantiation cannot be 'constexpr'}}