Fix #5826: specialize union types to avoid constraint cut #5858
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Blaisorblade
suggested changes
Feb 6, 2019
| @@ -0,0 +1,20 @@ | |||
| class Foo { | |||
| def test[A]: List[Int] | A => Int = { | |||
| case ls: List[Int] => ls.head // error | |||
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We should also make sure to test that GADT matching doesn't infer Int:
case ls: List[_] => ls.head // errorand that List[_] is otherwise still allowed:
case ls: List[_] => ls.length // no error here!| X.widen match { | ||
| case OrType(tp1, tp2) => | ||
| // This case is required to retrofit type inference, | ||
| // which cut constraints in the following two cases: |
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I'm familiar with TypeComparer#either but I'm not sure I get what you are saying...
This case is required to match type inference, which simplifies constraints in the following two cases:
But if that's the reason, what about T1 & T2 <:< T3? Do we need to handle that somehow?
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T1 & T2 <:< T3 is handled in the top-level match on P
Blaisorblade
approved these changes
Feb 7, 2019
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Fix #5826: specialize union types to avoid constraint cut