[AST][RecoveryExpr] Fix a crash on opencl C++.

clang/lib/Sema/SemaDecl.cpp

 
 bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
   // FIXME: Need strict checking.  In C89, we need to check for
   // any assignment, increment, decrement, function-calls, or
   // commas outside of a sizeof.  In C99, it's the same list,
   // except that the aforementioned are allowed in unevaluated
   // expressions.  Everything else falls under the
   // "may accept other forms of constant expressions" exception.
-  // (We never end up here for C++, so the constant expression
-  // rules there don't matter.)
+  //
+  // Regular C++ code will not end up here (exceptions: language extensions,
+  // OpenCL C++ etc), so the constant expression rules there don't matter.
+  if (Init->isValueDependent()) {
+    assert(Init->containsErrors() &&
+           "Dependent code should only occur in error-recovery path.");
+    return true;
+  }
   const Expr *Culprit;
   if (Init->isConstantInitializer(Context, false, &Culprit))
     return false;
   Diag(Culprit->getExprLoc(), diag::err_init_element_not_constant)
     << Culprit->getSourceRange();
   return true;
 }
 

clang/test/SemaOpenCL/recovery-expr.cl

+// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only -cl-std=clc++ -frecovery-ast
+
+void kernel nocrash() {
+  constant int L1 = 0;
+
+  private int *constant L2 = L1++; // expected-error {{read-only variable is not assignable}}
+}