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Previously we believed that reducing type applications did not affect
type inference as long as the reduced type constructor had the same
arity as the unreduced one, for example reducing `Foo[X, Y]` is fine
when `Foo` is defined as:
type Foo[A, B] = Bar[A, B]
but not when it's defined as:
type Foo[A] = Bar[A, A]
But this is not a sufficient condition: the bounds of the type
constructor arguments also matter for type inference, so we need to be
more strict and disallow reductions in cases like:
type Foo[A, B] = Bar[B, A]
and:
type Foo[A, B] = Bar[A, Int]
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