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Fix problem with comparing Null and value classes #10620

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Merged
merged 1 commit into from
Dec 3, 2020
Merged

Fix problem with comparing Null and value classes #10620

merged 1 commit into from
Dec 3, 2020

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@odersky
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@odersky odersky commented Dec 3, 2020

Consider:

val x: Int = 0 val y: Int | Null = x // during erasure, x is boxed here, and Int | Null becomes Object val z: Int = y

The last line should be an error. But previously

C | Null <: C

succeeded for all classes C since it was deemed incorrectly that Null derivesFrom C.
@odersky
Fix problem with comparing Null and value classes
e8bcc6e 
Consider: ```scala val x: Int = 0 val y: Int | Null = x // during erasure, x is boxed here, and Int | Null becomes Object val z: Int = y ``` The last line should be an error. But previously ``` C | Null <: C ``` succeeded for all classes `C` since it was deemed incorrectly that `Null` derivesFrom `C`.
@odersky odersky requested a review from noti0na1 December 3, 2020 10:12
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noti0na1 approved these changes Dec 3, 2020
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LGTM
@odersky odersky merged commit 0d1e75a into scala:master Dec 3, 2020
@odersky odersky deleted the fix-null-anyval branch December 3, 2020 21:48
@Kordyjan Kordyjan added this to the 3.0.0 milestone Aug 2, 2023
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