Commit 59cb44a3 authored by Joachim Breitner's avatar Joachim Breitner
Browse files

Explain why TcAxiomInstCo carries [TcCoercion], and not [TcType]

parent da66a8df
......@@ -90,6 +90,12 @@ differences
- TcSubCo is not applied as deep as done with mkSubCo
Reason: they'll get established when we desugar to Coercion
* TcAxiomInstCo has a [TcCoercion] parameter, and not a [Type] parameter.
This differs from the formalism, but corresponds to AxiomInstCo (see
[Coercion axioms applied to coercions]).
Why can't we use [TcType] here, in code not relevant for the simplifier?
Because of coercionToTcCoercion.
\begin{code}
data TcCoercion
= TcRefl Role TcType
......
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