Fails to coerce between newtypes directly

import Data.Coerce
import Data.Type.Coercion

newtype W a = W a
newtype A   = MkA (W A)

a :: Coercion A A
a = Coercion

b :: Coercion a a' -> Coercion a (W a')
b Coercion = Coercion

c :: Coercion A (W A)
c = b a

works just fine but the following fail:

-- • Couldn't match representation of type ‘A’ with that of ‘W A’
--     arising from a use of ‘Coercion’
-- • In the expression: Coercion
--   In an equation for ‘d’: d = Coercion
d :: Coercion A (W A)
d = Coercion

-- • Couldn't match representation of type ‘A’ with that of ‘W A’
--     arising from a use of ‘coerce’
-- • In the expression: coerce
--   In an equation for ‘e’: e = coerce
e :: A -> W A
e = coerce

Trac metadata

Trac field	Value
Version	8.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
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Operating system
Architecture