Don't reject dependent range-based for loops in constexpr functions. The loop

variable isn't really uninitialized, it's just not initialized yet.

llvm-svn: 194767

clang/lib/Sema/SemaDeclCXX.cpp

@@ -880,7 +880,7 @@ static bool CheckConstexprDeclStmt(Sema &SemaRef, const FunctionDecl *Dcl,
               diag::err_constexpr_local_var_non_literal_type,
               isa<CXXConstructorDecl>(Dcl)))
           return false;
-        if (!VD->hasInit()) {
+        if (!VD->hasInit() && !VD->isCXXForRangeDecl()) {
           SemaRef.Diag(VD->getLocation(),
                        diag::err_constexpr_local_var_no_init)
             << isa<CXXConstructorDecl>(Dcl);

clang/test/SemaCXX/constant-expression-cxx1y.cpp

@@ -898,3 +898,16 @@ namespace PR17615 {
   };
   constexpr int k = A().r; // expected-error {{constant expression}} expected-note {{in call to}}
 }
+
+namespace PR17331 {
+  template<typename T, unsigned int N>
+  constexpr T sum(const T (&arr)[N]) {
+    T result = 0;
+    for (T i : arr)
+      result += i;
+    return result;
+  }
+
+  constexpr int ARR[] = { 1, 2, 3, 4, 5 };
+  static_assert(sum(ARR) == 15, "");
+}