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Re-lub also hard union types in simplify #20027

Merged
merged 3 commits into from Apr 4, 2024
Merged

Re-lub also hard union types in simplify #20027

merged 3 commits into from Apr 4, 2024

Commits on Mar 27, 2024

  1. Re-lub also hard union types in simplify 

    Simplify had some elaborate condition that prevented hard union types to be
recomputed with a lub. I am not sure why that was. In the concrete scenario
of i10693.scala, we had an explicitly union result type `B | A` where `A` and `B` are
type parameters. So that is a hard union type. Then `A` was instantiated by `Int | String`
and `B` was instantiated by `String | Int`. Re-forming the lub of that union would
have eliminated one pair, but since the union type was hard tyat was not done. On the
other hand I see no reason why hard unions should not be re-lubbed. Hard unions are
about preventing the widening of or types with a join. I don't see a connection with
avoiding re-lubbing.

Fixes scala#10693
    @odersky
    odersky committed Mar 27, 2024
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  2. Also re-lub unions in widenUnionWithoutNull

    @odersky
    odersky committed Mar 27, 2024
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  3. Add test case supplied by @LucySMartin

    @odersky
    odersky committed Mar 27, 2024
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