fixes#16376
The way the compiler handled generic proc instantiations in calls (like
`foo[int](...)`) up to this point was to instantiate `foo[int]`, create
a symbol for the instantiated proc (or a symchoice for multiple procs
excluding ones with mismatching generic param counts), then perform
overload resolution on this symbol/symchoice. The exception to this was
when the called symbol was already a symchoice node, in which case it
wasn't instantiated and overloading was called directly ([these
lines](b7b1313d21/compiler/semexprs.nim (L3366-L3371))).
This has several problems:
* Templates and macros can't create instantiated symbols, so they
couldn't participate in overloaded explicit generic instantiations,
causing the issue #16376.
* Every single proc that can be instantiated with the given generic
params is fully instantiated including the body. #9997 is about this but
isn't fixed here since the instantiation isn't in a call.
The way overload resolution handles explicit instantiations by itself is
also buggy:
* It doesn't check constraints.
* It allows only partially providing the generic parameters, which makes
sense for implicit generics, but can cause ambiguity in overloading.
Here is how this PR deals with these problems:
* Overload resolution now always handles explicit generic instantiations
in calls, in `initCandidate`, as long as the symbol resolves to a
routine symbol.
* Overload resolution now checks the generic params for constraints and
correct parameter count (ignoring implicit params). If these don't
match, the entire overload is considered as not matching and not
instantiated.
* Special error messages are added for mismatching/missing/extra generic
params. This is almost all of the diff in `semcall`.
* Procs with matching generic parameters now instantiate only the type
of the signature in overload resolution, not the proc itself, which also
works for templates and macros.
Unfortunately we can't entirely remove instantiations because overload
resolution can't handle some cases with uninstantiated types even though
it's resolved in the binding (see the last 2 blocks in
`texplicitgenerics`). There are also some instantiation issues with
default params that #24005 didn't fix but I didn't want this to become
the 3rd huge generics PR in a row so I didn't dive too deep into trying
to fix them. There is still a minor instantiation fix in `semtypinst`
though for subscripts in calls.
Additional changes:
* Overloading of `[]` wasn't documented properly, it somewhat is now
because we need to mention the limitation that it can't be done for
generic procs/types.
* Tests can now enable the new type mismatch errors with just
`-d:testsConciseTypeMismatch` in the command.
Package PRs:
- using fork for now:
[combparser](https://github.com/PMunch/combparser/pull/7) (partial
generic instantiation)
- merged: [cligen](https://github.com/c-blake/cligen/pull/233) (partial
generic instantiation but non-overloaded + template)
- merged: [neo](https://github.com/andreaferretti/neo/pull/56) (trying
to instantiate template with no generic param)
fixes#23186
As explained in #23186, generics can transform `genericProc[int]` into a
call `` `[]`(genericProc, int) `` which causes a problem when
`genericProc` is resemmed, since it is not a resolved generic proc. `[]`
needs unresolved generic procs since `mArrGet` also handles explicit
generic instantiations, so delay the resolved generic proc check to
`semFinishOperands` which is intentionally not called for `mArrGet`.
The root issue for
[t6137](https://github.com/nim-lang/Nim/blob/devel/tests/generics/t6137.nim)
is also fixed (because this change breaks it otherwise), the compiler
doesn't consider the possibility that an assigned generic param can be
an unresolved static value (note the line `if t.kind == tyStatic: s.ast
= t.n` below the change in sigmatch), now it properly errors that it
couldn't instantiate it as it would for a type param. ~~The change in
semtypinst is just for symmetry with the code above it which also gives
a `cannot instantiate` error, it may or may not be necessary/correct.~~
Now removed, I don't think it was correct.
Still possible that this has unintended consequences.
* Fixes implicit and explicit generics
* moved block logic into 'maybeInstantiateGeneric'
* Added more tests
* Update compiler/semexprs.nim
Co-authored-by: Andreas Rumpf <rumpf_a@web.de>
