[clang] [Clang][Sema] Tweak tryCaptureVariable for unevaluated lambdas (PR #93206)

[Younan Zhang via cfe-commits]

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@@ -1576,7 +1576,10 @@ ExprResult Parser::ParseLambdaExpressionAfterIntroducer(
                       TrailingReturnTypeLoc, &DS),
                   std::move(Attributes), DeclEndLoc);
 
-    Actions.ActOnLambdaClosureQualifiers(Intro, MutableLoc);
+    // We have called ActOnLambdaClosureQualifiers for parentheses-less cases
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zyn0217 wrote:

> Yes, we need to set whether the lambda has a mutable keyword as soon as the parameters, if present, are parsed, as that affect the meaning of subsequent id-expressions
> When there are no parens, there can be a noexcept clause for example, and parsing that does requires knowing whether the lambda is mutable, so that we can adjust the type of any reference-to-capture.

Thanks, that makes sense! We currently set `LSI->Mutable` in `ActOnLambdaClosureQualifiers()` , and while I think it's possible to move it out of the function, I'm not opposed to leaving it as-is.

https://github.com/llvm/llvm-project/pull/93206