Substantial improvements to coercion optimisation
The main purpose of this patch is to add a bunch of new rules
to the coercion optimiser. They are documented in the (revised)
Appendix of the System FC paper.
Some code has moved about:
- OptCoercion is now a separate module, mainly because it
now uses tcMatchTy, which is defined in Unify, so OptCoercion
must live higehr up in the hierarchy
- Functions that manipulate Kinds has moved from
Type.lhs to Coercion.lhs. Reason: the function typeKind
now needs to call coercionKind. And in any case, a Kind is
a flavour of Type, so it builds on top of Type; indeed Coercions
and Kinds are both flavours of Type.
This change required fiddling with a number of imports, hence
the one-line changes to otherwise-unrelated modules
- The representation of CoTyCons in TyCon has changed. Instead of
an extensional representation (a kind checker) there is now an
intensional representation (namely TyCon.CoTyConDesc). This was
needed for one of the new coercion optimisations.
17 files changed: