fix jsonutils macro with generic case object #24429
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metagn
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Thanks for your hard work on this PR! Hint: mm: orc; opt: speed; options: -d:release |
Araq
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Nov 16, 2024
fixes #22479, fixes #24374, depends on #24429 and #24430 When instantiating generic types which directly have nominal types (object, distinct, ref/ptr object but not enums[^1]) as their values, the nominal type is now copied (in the case of ref objects, its child as well) so that it receives a fresh ID and `typeInst` field. Previously this only happened if it contained any generic types in its structure, as is the case for all other types. This solves #22479 and #24374 by virtue of the IDs being unique, which is what destructors check for. Technically types containing generic param fields work for the same reason. There is also the benefit that the `typeInst` field is correct. However issues like #22445 aren't solved because the compiler still uses structural object equality checks for inheritance etc. which could be removed in a later PR. Also fixes a pre-existing issue where destructors bound to object types with generic fields would not error when attempting to define a user destructor after the fact, but the error message doesn't show where the implicit destructor was created now since it was only created for another instance. To do this, a type flag is used that marks the generic type symbol when a generic instance has a destructor created. Reusing `tfCheckedForDestructor` for this doesn't work. Maybe there is a nicer design that isn't an overreliance on the ID mechanism, but the shortcomings of `tyGenericInst` are too ingrained in the compiler to use for this. I thought about maybe adding something like `tyNominalGenericInst`, but it's really much easier if the nominal type itself directly contains the information of its generic parameters, or at least its "symbol", which the design is heading towards. [^1]: See [this test](https://github.com/nim-lang/Nim/blob/21420d8b0976dc034feb90ab2878ae0dd63121ae/lib/std/enumutils.nim#L102) in enumutils. The field symbols `b0`/`b1` always have the uninstantiated type `B` because enum fields don't expect to be generic, so no generic instance of `B` matches its own symbols. Wouldn't expect anyone to use generic enums but maybe someone does.
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split from #24425
The added test did not work previously. The result of
getTypeImplis the uninstantiated AST of the original type symbol, and the macro attempts to use this type for the result. To fix the issue, the providedtypedescargument is used instead.