[clang] [clang] [NFC] explicitly check if ParentMap contains key (PR #121736)

[Jay Foad via cfe-commits]

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@@ -78,7 +78,7 @@ static void BuildParentMap(MapTy& M, Stmt* S,
     // The right thing to do is to give the OpaqueValueExpr its syntactic
     // parent, then not reassign that when traversing the semantic expressions.
     OpaqueValueExpr *OVE = cast<OpaqueValueExpr>(S);
-    if (OVMode == OV_Transparent || !M[OVE->getSourceExpr()]) {
+    if (OVMode == OV_Transparent || !M.contains(OVE->getSourceExpr())) {
       M[OVE->getSourceExpr()] = S;
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jayfoad wrote:

Could use `M.find` to avoid the duplicated lookup here?

https://github.com/llvm/llvm-project/pull/121736