!4594: Fix #19044 by tweaking unification in inst lookup · Merge requests · Glasgow Haskell Compiler / GHC

Richard Eisenberg requested to merge wip/T19044 into master Dec 11, 2020

Commit message:

Fix #19044 by tweaking unification in inst lookup

See Note [Occurs-check in lookup] in GHC.Core.InstEnv

Test case: typecheck/should_compile/T19044

Close #19044

Fix #19044 by tweaking unification in inst lookup

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