coerce can cause compiler to loop

This program causes GHC to loop at compile time

{-# LANGUAGE ScopedTypeVariables #-}
import Data.Coerce
coerce' :: Coercible b a => a -> b
coerce' = coerce (\x -> x :: b) :: forall a b. Coercible b a => a -> b

I encountered this trying to use a similar construction in

https://github.com/glguy/profunctors/blob/coerce/src/Data/Profunctor/Unsafe.hs

I'm not absolutely certain about what aspect of this snippet is looping the compiler, but it's pretty small.

Trac metadata

Trac field	Value
Version	7.10.1-rc1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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