Add Expr::EvaluateAsLValue which will (believe it or not) try to evaluate an Expr as an LValue.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@68763 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/Expr.h

@@ -229,6 +229,9 @@ public:
   /// must be called on an expression that constant folds to an integer.
   llvm::APSInt EvaluateAsInt(ASTContext &Ctx) const;
 
+  /// EvaluateAsLValue - Evaluate an expression to see if it's a valid LValue.
+  bool EvaluateAsLValue(EvalResult &Result, ASTContext &Ctx) const;
+
   /// isNullPointerConstant - C99 6.3.2.3p3 -  Return true if this is either an
   /// integer constant expression with the value zero, or if this is one that is
   /// cast to void*.

lib/AST/ExprConstant.cpp

@@ -1651,6 +1651,12 @@ bool Expr::Evaluate(EvalResult &Result, ASTContext &Ctx) const {
   return true;
 }
 
+bool Expr::EvaluateAsLValue(EvalResult &Result, ASTContext &Ctx) const {
+  EvalInfo Info(Ctx, Result);
+
+  return EvaluateLValue(this, Result.Val, Info) && !Result.HasSideEffects;
+}
+
 /// isEvaluatable - Call Evaluate to see if this expression can be constant
 /// folded, but discard the result.
 bool Expr::isEvaluatable(ASTContext &Ctx) const {