Use the most recent previous decl to check if inline is added after a definition

[rnk]

Summary

This affects this test case:

void foo();
template <typename T> class C {
  friend void foo();
};
inline void foo() {}
C<int> c;

Here, we instantiate the foo friend decl and add it to foo's redecl
chain. However, our previous decl pointer happens to reference the first
declaration of foo, which is not marked inline. When we check to see if
foo was already defined, we implicitly search all previous decls. We
should do the same for the inline check, instead of just checking this
particular previous decl.

[rnk]

• Add alternate test case not relying on r233817

[rsmith]

LGTM

cfe/trunk/lib/Sema/SemaDeclCXX.cpp

bool Sema::MergeCXXFunctionDecl(FunctionDecl *New, FunctionDecl *Old,
   // C++11 [dcl.constexpr]p1: If any declaration of a function or function
   // template has a constexpr specifier then all its declarations shall
   // contain the constexpr specifier.
   if (New->isConstexpr() != Old->isConstexpr()) {
     Diag(New->getLocation(), diag::err_constexpr_redecl_mismatch)
       << New << New->isConstexpr();
     Diag(Old->getLocation(), diag::note_previous_declaration);
     Invalid = true;
-  } else if (!Old->isInlined() && New->isInlined() && Old->isDefined(Def)) {
+  } else if (!Old->getMostRecentDecl()->isInlined() && New->isInlined() &&
+             Old->isDefined(Def)) {
     // C++11 [dcl.fcn.spec]p4:
     //   If the definition of a function appears in a translation unit before its
     //   first declaration as inline, the program is ill-formed.
     Diag(New->getLocation(), diag::err_inline_decl_follows_def) << New;
     Diag(Def->getLocation(), diag::note_previous_definition);
     Invalid = true;
   }
 

cfe/trunk/test/SemaTemplate/friend.cpp

namespace PR6770 {
 
   template<typename T> void f1(T, T);
   template <class T>
   void f() {
     friend class f; // expected-error{{'friend' used outside of class}}
     friend class f1; // expected-error{{'friend' used outside of class}}
   }
 }
+
+namespace friend_redecl_inline {
+// We had a bug where instantiating the foo friend declaration would check the
+// defined-ness of the most recent decl while checking if the canonical decl was
+// inlined.
+void foo();
+void bar();
+template <typename T>
+class C {
+  friend void foo();
+  friend inline void bar();
+};
+inline void foo() {}
+inline void bar() {}
+C<int> c;
+}