Note [Computing equality on types]

This module implements type equality, notably `eqType`. This is
"definitional equality" or just "equality" for short.

There are several places within GHC that depend on the precise choice of
definitional equality used. If we change that definition, all these places
must be updated. This Note merely serves as a place for all these places
to refer to, so searching for references to this Note will find every place
that needs to be updated.

* See Note [Non-trivial definitional equality] in GHC.Core.TyCo.Rep.

* See Historical Note [Typechecker equality vs definitional equality]
  below