This is supported by Idris 1 and is handy for breaking cycles in
modules. To achieve this, we just need to make sure that complete
definitions aren't overwritten with empty definitions on loading.
Checking the let expression in full can break sharing when unifying the
types, and it's unnecessary because we've already checked the type of
the scope unifies with the expected type.
Fixes#63
Elaborate the scope of a let without the computational behaviour,
meaning that `let x = v in e` is equivalent to `(\x => e) v`. This makes
things more consistent (in that let bindings already don't propagate
inside case or with blocks) at the cost of not being able to rely on the
computational behaviour in types. More importantly, it removes a
significant potential source of slowness.
Fixes#58
If you need the computational behaviour, you can use a local function
definition instead.
Fixes#42. If we don't do this, the name is treated in the saem way as
an unbound implicit, which is not what we want, so update with the
method applied to the parameters.
We were only doing implicits, so add auto implicits too. It's slightly
tricky, because we might also have implicits given of the form @{x}
which stands for the next auto implicit.
Fixes#50
Just like all other pi-bound things, if m is an unbound implicit and we
have m ?x = m y as a unification problem, we can conclude ?x = y because
it has to be true for all ms.
This was implemented in Blodwen but I hadn't got around to it yet for
Idris2... fortunately it's a bit easier in Idris2!
Fixes#44
We were only checking parameters, meaning that there were potential
clashes leading to confusing behaviour, and meaning that it was somehow
relevant what the names were in the interface!
Now by marking a method as multiplicity 0, we can explicitly say that
it's compile time only, so we can use it to compute types based on other
erased things - see tests/idris2/interface008 for a small example.
This fixes#8 - at least in that it allows the interface to be expressed
properly now, although the multiplicity annotations mean that
unfortunately it can't be compatible with Idris 1.
A local variable can't be applied to itself when searching (otherwise,
for example, we could end up trying something like id id id id id id etc
forever). So remove it from the environment before searching for its
arguments.
This and the previous patch fix#24. (Or, at least, the minimised cases
reported as part of it!)
We can't begin a search until we know what we're searching for! For some
reason I forgot to add this case, and without it the search space can
explode, or we might find an answer too soon and commit to the wrong
thing!
Fixes#36
This means that even if the relevant parameters aren't used by a method
body, the method can still see what the implicits are (though they will
be 0 multiplicity).
This is relevant to #8, but doesn't really fix it because we still need
a way of saying that methods are 0 multiplicity.
This is part of what we used to have in Enum but I think it's better to
separate the two. Added implementations for Nat, and anything in
Integral/Ord/Neg, so that we get range syntax (at least when its
implemeted) for the most useful cases.
This required a small change to auto implicit search (and I'm still not
sure about this). Now search arguments right to left, because solving
later arguments may resolve earlier arguments by unification and this
can happen in particular when chasing parent interfaces (which may have
fewer parameters).
At least on Linux, \r needs to be in singles quotes as an argument to tr
or it removes all the 'r' instead! Hopefully it also works this way on
Windows...
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).
