Don't Create `ParamCandidate` When Obligation Contains Errors

[veera-sivarajan]

Fixes #121941

I'm not sure if I understand this correctly but this bug was caused by an error type incorrectly matching against ParamCandidate. This was introduced by the changes made in #72621 (figured using cargo-bisect-rustc).

This PR fixes it by skipping ParamCandidate generation when an error type is involved. Also, this is similar to #73005 but addresses ParamCandidate instead of ImplCandidate.

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[compiler-errors]

Please squash this into one commit. Please also leave a comment that explains what this special case is for, preferably referencing an issue and explaining some motivation behind why the fix works.

@rustbot atuhor

[compiler-errors]

@rustbot author

[veera-sivarajan]

@rustbot ready

[compiler-errors]

@bors r+

[bors]

:pushpin: Commit 96b8225d8dd971bc2ecc7aa12068adcda9a9f20f has been approved by compiler-errors

It is now in the queue for this repository.