GHC.Rename.Env.extendPatSynEnv does not generate AvailTC

Summary

Usually Haskell records generate AvailTC, associating a list of FieldLabels to fields. However, when record pattern synonyms are renamed, only a flat list of Avail is generated. This makes record-related mechanisms behave differently.

Steps to reproduce

Any record pattern synonyms, such as testsuite/tests/patsyn/should_run/match.hs

Expected behavior

Generate AvailInfo containing AvailTC.

Environment

GHC version used: 8.11.0 (master)

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