Always use a function's decl context when building default arguments. Fixes http://http://llvm.org/pr8479.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@120299 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaExpr.cpp

@@ -3862,7 +3862,15 @@ ExprResult Sema::BuildCXXDefaultArgExpr(SourceLocation CallLoc,
     InstantiatingTemplate Inst(*this, CallLoc, Param, Innermost.first,
                                Innermost.second);
 
-    ExprResult Result = SubstExpr(UninstExpr, ArgList);
+    ExprResult Result;
+    {
+      // C++ [dcl.fct.default]p5:
+      //   The names in the [default argument] expression are bound, and
+      //   the semantic constraints are checked, at the point where the
+      //   default argument expression appears.
+      ContextRAII SavedContext(*this, FD->getDeclContext());
+      Result = SubstExpr(UninstExpr, ArgList);
+    }
     if (Result.isInvalid())
       return ExprError();
 

test/SemaCXX/friend.cpp

@@ -79,3 +79,36 @@ namespace test5 {
 
   struct B { friend void B(); };
 }
+
+// PR8479
+namespace test6_1 {
+  class A {
+   public:
+   private:
+    friend class vectorA;
+    A() {}
+  };
+  class vectorA {
+   public:
+    vectorA(int i, const A& t = A()) {}
+  };
+  void f() {
+    vectorA v(1);
+  }
+}
+namespace test6_2 {
+  template<class T>
+  class vector {
+   public:
+    vector(int i, const T& t = T()) {}
+  };
+  class A {
+   public:
+   private:
+    friend class vector<A>;
+    A() {}
+  };
+  void f() {
+    vector<A> v(1);
+  }
+}