Commit 22b317b1 authored by Simon Peyton Jones's avatar Simon Peyton Jones
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Comments only: EqVar vs Covar

parent bed4ec57
......@@ -122,14 +122,13 @@ Note [Evidence: EvIds and CoVars]
* An EvId (evidence Id) is a *boxed*, term-level evidence variable
(dictionary, implicit parameter, or equality).
* DictId, IpId, and EqVar are synonyms when we know what kind of
evidence we are talking about. For example, an EqVar has type (t1 ~ t2).
* A CoVar (coercion variable) is an *unboxed* term-level evidence variable
of type (t1 ~# t2). So it's the unboxed version of an EqVar.
* Only CoVars can occur in Coercions (but NB the LCoercion hack; see
Note [LCoercions] in Coercion).
* Only CoVars can occur in Coercions, EqVars appear in TcCoercions.
* DictId, IpId, and EqVar are synonyms when we know what kind of
evidence we are talking about. For example, an EqVar has type (t1 ~ t2).
Note [Kind and type variables]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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