4e165c1c99
Instantiate instead of erasing binder when probing param methods Fixes #108836 There is a really old comment saying that a `WhereClauseCandidate` probe candidate "should not contain any inference variables", but I'm not really confident that that comment applies anymore. In contrast, other candidates that we assemble during method probe contain inference variables in their substitutions (e.g. `InherentImplCandidate`)... Since this change is made only to support a nightly feature, I'm happy to gate the new behavior behind this feature flag or discuss it further. r? types