Now supports with applications on the RHS when auto implicits are
involved. Auto implicit bound names in patterns now become searches on
the rhs in a with-application (I should write this construct up properly
in a paper some time!)
Elaborate via either === (homogeneous equality) or ~=~ (heterogeneous
equality) both of which are synonyms for Equal. This is to get the Idris
1 behaviour that equality is homogeneous by default to reduce the need
for type annotations, but heterogeneous if that doesn't work.
There's a bit of a trade off here. It would be better to report the
ambiguity but this would lead to a need for (I think) excessive
precision in types which would impact usability. It will always take the
leftmost interface.
Chapter 7 tests added.
Idris 1 will fill in the last metavariables by matching rather than
unification, as a convenience. I still think this is okay, even if it's
a bit hacky, because it's a huge convenience and doesn't affect other
unification problems.
Also abstract over lets in guesses, like in delayed elaborators, to
avoid any difficulties when linearity checking and to make sure that let
bound things don't get reevaluated.
This is enough to get the Chapter 6 TypeDD tests working
Allow matching rather than unification, as long as it doesn't solve any
metavariables on the way. I noticed a potential unification bug on the
way, forgetting to update whether holes are solved when unifying
argument lists.
This was left over from Blodwen (where it was also wrong :)) but the way
we apply metavariables now means we don't need to do anything fancy when
unelaborating them for pretty printing.
This has shown up a problem with 'case' which is hard to fix - since it
works by generating a function with the appropriate type, it's hard to
ensure that let bindings computational behaviour is propagated while
maintaining appropriate dependencies between arguments and keeping the
let so that it only evaluates once. So, I've disabled the computational
behaviour of 'let' inside case blocks. I hope this isn't a big
inconvenience (there are workarounds if it's ever needed, anyway).
Need to add by full name, due to ordering of loading (the name it's
attached to may not be resolved yet!). This doesn't seem to cause any
performance problems but we can revisit if it does.
Don't use the type of a scrutinee to restrict possible patterns, because
it might have been refined by a Rig0 argument that has a missing case.
Instead, generate all the possible cases and check that the generated
ones are impossible (there's no obvious change in performance)
Small change needed to fix one - assume given implicits which are of the
form x@_ arise from types. It's a bit of a hack but I don't think
there's any need for anything more complicated.
Only valid if unifying the pattern at the end doesn't solve any
metavariables. Also when elaborating applications of fromInteger etc to
constants on the LHS we need to be in expression mode, then reduce the
result later.
This was a slight difference from Blodwen that wasn't accounted for -
there might be lets in the nested environment, so when building the
expanded application type, make sure we go under them
This wasn't necessary before, since we always inlined, but since we can
now postpone things longer and don't always inline until much later, we
need to know what names everything refers to earlier.
