[Sema] Fix assertion failure when checking for unused variables in a dependent context.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@316177 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaDecl.cpp

@@ -1724,7 +1724,7 @@ static bool ShouldDiagnoseUnusedDecl(const NamedDecl *D) {
           if (Construct && !Construct->isElidable()) {
             CXXConstructorDecl *CD = Construct->getConstructor();
             if (!CD->isTrivial() && !RD->hasAttr<WarnUnusedAttr>() &&
-                !VD->evaluateValue())
+                (VD->getInit()->isValueDependent() || !VD->evaluateValue()))
               return false;
           }
         }

test/SemaCXX/warn-unused-variables.cpp

@@ -226,4 +226,14 @@ void test(int i) {
   NoLiteral nl2(42);   // no-warning
 }
 }
+
+namespace crash {
+struct a {
+  a(const char *);
+};
+template <typename b>
+void c() {
+  a d(b::e ? "" : "");
+}
+}
 #endif