fix for nim 2.2, provide all generic params when instantiating Nothing
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The calls to `Nothing` are only given 1 and 2 generic parameters when they both take 3, this compiles due to bugs in Nim. To remove the dependency on this behavior of the Nim compiler, the remaining generic parameters are now provided.
Araq
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Sep 2, 2024
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](https://github.com/nim-lang/Nim/blob/b7b1313d21deb687adab2b4a162e716ba561a26b/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](PMunch/combparser#7) (partial generic instantiation) - merged: [cligen](c-blake/cligen#233) (partial generic instantiation but non-overloaded + template) - merged: [neo](andreaferretti/neo#56) (trying to instantiate template with no generic param)
metagn
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NothingNothing
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@PMunch anything stopping this from getting merged? |
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Oh sorry, not really. I was mostly just waiting for the changes to stabalize and the Nim version to be released. I'll merge it now :) |
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The calls to
Nothingare only given 1 and 2 generic parameters when they both take 3, this compiles due to bugs in Nim. To remove the dependency on this behavior of the Nim compiler, the remaining generic parameters are now provided.