NamedPartsAccumulator: also include bounds of uninstantiated type variables #750
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In 0efa171 I changed the definition of NamedPartsAccumulator to exclude lower bounds as this is required for the implicit search, but NamedPartsAccumulator is also used by Typer#escapingRefs so in the following code: class Foo[T] val z = { class C ??? : Foo[_ >: C] } the type of z was inferred to be Foo[_ >: C] instead of Foo. To avoid this, NamedPartsAccumulator will only exclude lower bounds if the parameter excludeLowerBounds is explicitely set to true. No test because there is no way to detect that a type has escaped, this might be something that could be added to TreeChecker.
…iables
In the following code:
class Foo[T](x: T)
val z = {
class X
new Foo(new X)
}
When we call `Typer#ensureNoLocalRefs` on the block, its type is:
Foo[T] where T <: X
Before this commit, `Typer#escapingRefs` returned the empty set for this
type since T is not instantiated yet, so the type was kept as is, and X escaped:
val z: Foo[X] = {
class X
new Foo(new X)
}
We avoid this by inspecting the bounds of uninstantiated type variables
in `NamedPartsAccumulator` which is used by `Typer#escapingRefs`.
|
I have to think about it. Maybe we should instantiate those type variables that have escaping refs as bounds. |
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I just realized that with the instantiation scheme I proposed in #739 and prototyped in https://github.com/smarter/dotty/commits/fix/tp-instantiation-scheme, this issue does not occur anymore because the type parameters of a method are always instantiated early enough. |
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This PR depends on #749
In the following code:
When we call
Typer#ensureNoLocalRefson the block, its type is:Before this commit,
Typer#escapingRefsreturned the empty set for thistype since
Tis not instantiated yet, so the type was kept as is, andXescaped:We avoid this by inspecting the bounds of uninstantiated type variables
in
NamedPartsAccumulatorwhich is used byTyper#escapingRefs.@odersky : Please review. I'm not sure if this is the proper way to fix this, maybe the instantiation of type parameters could try to avoid types which are not in scope?