Throw a type error when using hk-types in unions or intersections #16712
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Throw a type error instead of crashing when using higher-kinded types in unions or intersections. We check kindedness only in PostTyper (to avoid cycles), which means we might get into situations where we coming a higher-kinded type in a union or intersection, which is illegal. In this case we now diagnose the problem with a TypeError instead of failing an assert. However, after Typer we do fail since by then such situations should have been checked by then. Fixeds scala#16696
dwijnand
reviewed
Jan 17, 2023
tests/neg/i16696.check
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| -- Error: tests/neg/i16696.scala:20:27 --------------------------------------------------------------------------------- | ||
| 20 | val boom = BoxMaker[Foo].make(_.foo) // error | ||
| | ^ | ||
| | test2.Foo is not a value type, cannot be used in in intersection R & test2.Foo |
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Ah yes. Good that you spotted! it!
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Throw a type error instead of crashing when using higher-kinded types in unions or intersections.
We check kindedness only in PostTyper (to avoid cycles), which means we might get into situations where we combine a higher-kinded type in a union or intersection, which is illegal. In this case we now diagnose the problem with a TypeError instead of failing an assert. However, after Typer we do fail since by then such situations should have been checked by then.
Fixes #16696