Warn about more than the first unused variable when -Werror is set.

To do this, thread DiagnosticErrorTrap's hasUnrecoverableErrorOccurred through
to Scope.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178294 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Sema/Scope.h

@@ -240,7 +240,11 @@ public:
   void setEntity(void *E) { Entity = E; }
 
   bool hasErrorOccurred() const { return ErrorTrap.hasErrorOccurred(); }
-                           
+
+  bool hasUnrecoverableErrorOccurred() const {
+    return ErrorTrap.hasUnrecoverableErrorOccurred();
+  }
+
   /// isClassScope - Return true if this scope is a class/struct/union scope.
   bool isClassScope() const {
     return (getFlags() & Scope::ClassScope);

lib/Sema/SemaDecl.cpp

@@ -1389,7 +1389,7 @@ void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
     if (!D->getDeclName()) continue;
 
     // Diagnose unused variables in this scope.
-    if (!S->hasErrorOccurred())
+    if (!S->hasUnrecoverableErrorOccurred())
       DiagnoseUnusedDecl(D);
     
     // If this was a forward reference to a label, verify it was defined.

test/Sema/warn-unused-variables-werror.c

@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -Wunused-variable -Werror -verify %s
+
+void f() {
+  int i;  // expected-error{{unused}}
+  int j;  // expected-error{{unused}}
+}