Reapply "Rename/refactor isIntegerConstantExpression to getIntegerConstantExpression"

Reapply 49e5f603d40083dce9c05796e3cde3a185c3beba
which had been reverted in c94332919bd922032e979b3ae3ced5ca5bdf9650.

Originally reverted because I hadn't updated it in quite a while when I
got around to committing it, so there were a bunch of missing changes to
new code since I'd written the patch.

Reviewers: aaron.ballman

Differential Revision: https://reviews.llvm.org/D76646

1 files changed, 12 insertions, 7 deletions

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 41a4ae4..5f8ad18 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -14892,16 +14892,22 @@ bool Expr::isIntegerConstantExpr(const ASTContext &Ctx,
   return true;
 }
 
-bool Expr::isIntegerConstantExpr(llvm::APSInt &Value, const ASTContext &Ctx,
-                                 SourceLocation *Loc, bool isEvaluated) const {
+Optional<llvm::APSInt> Expr::getIntegerConstantExpr(const ASTContext &Ctx,
+                                                    SourceLocation *Loc,
+                                                    bool isEvaluated) const {
   assert(!isValueDependent() &&
          "Expression evaluator can't be called on a dependent expression.");
 
-  if (Ctx.getLangOpts().CPlusPlus11)
-    return EvaluateCPlusPlus11IntegralConstantExpr(Ctx, this, &Value, Loc);
+  APSInt Value;
+
+  if (Ctx.getLangOpts().CPlusPlus11) {
+    if (EvaluateCPlusPlus11IntegralConstantExpr(Ctx, this, &Value, Loc))
+      return Value;
+    return None;
+  }
 
   if (!isIntegerConstantExpr(Ctx, Loc))
-    return false;
+    return None;
 
   // The only possible side-effects here are due to UB discovered in the
   // evaluation (for instance, INT_MAX + 1). In such a case, we are still
@@ -14915,8 +14921,7 @@ bool Expr::isIntegerConstantExpr(llvm::APSInt &Value, const ASTContext &Ctx,
   if (!::EvaluateAsInt(this, ExprResult, Ctx, SE_AllowSideEffects, Info))
     llvm_unreachable("ICE cannot be evaluated!");
 
-  Value = ExprResult.Val.getInt();
-  return true;
+  return ExprResult.Val.getInt();
 }
 
 bool Expr::isCXX98IntegralConstantExpr(const ASTContext &Ctx) const {