Relax comparison between Null and reference types in explicit nulls #23308
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| def f6(s: String | Null): String = s match { | ||
| case s2 => s2 // error | ||
| case null => "other" // error | ||
| case null => "other" | ||
| case s3 => s3 | ||
| } | ||
|
|
||
| def f7(s: String | Null): String = s match { | ||
| case null => "other" | ||
| case null => "other" // error | ||
| case null => "other" | ||
| case s3 => s3 |
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I'm not sure about this test. If we matched null value, then it is clear the following null cases are unreachable?
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I wonder if this is caused by the change here:
https://github.com/scala/scala3/pull/23308/files#diff-9678fa10ff9f7a2cdf71755535b6ef49afd31880e9d159ed4c40a39921d43454R972
That change was in the original PR #19258 . I wonder if it has been subsumed by other changes since then and might no longer be necessary. Without that change, what would break?
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Running scalac tests/explicit-nulls/neg/flow-match.scala -Yexplicit-nulls with checkReachability(m) produces the same compiler output as withoutMode(Mode.safeNulls) { checkReachability(m) }:
-- [E007] Type Mismatch Error: tests\explicit-nulls\neg\flow-match.scala:5:15 --
5 | case s2 => s2 // error
| ^^
| Found: (s2 : String | Null)
| Required: String
|
| longer explanation available when compiling with `-explain`
1 error found
Deleting f6 and re-running causes both changes to warn about unreachability in f7:
-- [E030] Match case Unreachable Warning: tests\explicit-nulls\neg\flow-match.scala:7:9
7 | case null => "other"
| ^^^^
| Unreachable case
1 warning found
An up-to-date version of #19258 with merge conflicts resolved.