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05c74d6844
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](21420d8b09/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.
34 lines
801 B
Nim
34 lines
801 B
Nim
discard """
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output: '''
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created Phantom[system.float] with value 1
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created Phantom[system.string] with value 2
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created Phantom[system.byte] with value 3
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destroyed Phantom[system.byte] with value 3
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destroyed Phantom[system.string] with value 2
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destroyed Phantom[system.float] with value 1
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'''
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"""
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# issue #24374
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type Phantom[T] = object
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value: int
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# markerField: T
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proc initPhantom[T](value: int): Phantom[T] =
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doAssert value >= 0
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echo "created " & $Phantom[T] & " with value " & $value
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result = Phantom[T](value: value)
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proc `=wasMoved`[T](x: var Phantom[T]) =
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x.value = -1
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proc `=destroy`[T](x: Phantom[T]) =
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if x.value >= 0:
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echo "destroyed " & $Phantom[T] & " with value " & $x.value
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let
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x = initPhantom[float](1)
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y = initPhantom[string](2)
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z = initPhantom[byte](3)
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