Remember the TyApply is always on a Rho #1081
Merged
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This is an invariant I realized we were losing. since
(forall x. C[x])[y] == (forall x. C[x, y])
we can always push formal out of TyApply and keep the left hand side a Rho type.This makes it easier to reason about the types, but also does a minor performance improvement in Infer since we can leverage that the left is a Rho without having to pattern match again.