Normalize MatchAlias in unrollTupleTypes #19565
Conversation
EugeneFlesselle
changed the title
|
Similar to #19199 |
| @@ -443,6 +443,9 @@ object Inlines: | |||
| unrollTupleTypes(tail).map(head :: _) | |||
| case tpe: TermRef if tpe.symbol == defn.EmptyTupleModule => | |||
| Some(Nil) | |||
| case tpRef: TypeRef => tpRef.info match | |||
There was a problem hiding this comment.
The fix works, but I am not sure if this is the correct way to handle MatchAliases.
@sjrd could you have a look at this one?
There was a problem hiding this comment.
It looks reasonable, although usually we would rather expect
case tpe: AppliedType if tpe.isMatchAlias => ... tpe.tryNormalize ...It is a bit suspicious that we directly encounter the tycon here, rather than the surrounding AppliedType. What are tpe and tpe.dealias when we get here on the problematic test case?
There was a problem hiding this comment.
Yes I noticed that for instance isMatchAlias is defined on AppliedTypes.
But in this case, we have tpe := TypeRef(NoPrefix, Alias) which remains the same after dealias since the info of Alias is not a TypeAlias but a MatchAlias. The case is not covered here:
https://github.com/lampepfl/dotty/blob/997103d818ead17d528d320b01edefb8792579ac/compiler/src/dotty/tools/dotc/core/Types.scala#L1438-L1445
I'm not sure whether the normalisation of
MatchAliasshould be done indealias.I suppose it is safer to only add the change in
unrollTupleTypeswhere it is necessary.Fixes #19385