Fix #21402: Always allow type member extraction for stable scrutinees in match types. #21700
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smarter
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Oct 4, 2024
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| /* If it is a skolem type, we cannot have class selections nor | ||
| * abstract type selections. If it is an alias, we try to remove | ||
| * any reference to the skolem from the right-hand-side. If that | ||
| * succeeds, we take the result, otherwise we fail as not-specific. | ||
| */ | ||
| def adaptToTriggerNotSpecific(info: Type): Type = info match |
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It looks like the doc comment refers to the code below starting with denot.info match, not to the behavior of the def itself.
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It's about the whole body of the case SkolemType. I added a blank line, which hopefully makes it not misleading anymore?
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Ah I see, usually we write those comments with //.
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I thought /* was just the multi-line version of //, whereas /** is the doc-of-the-def thing.
…inees in match types. Previously, through the various code paths, we basically allowed type member extraction for stable scrutinees if the type member was an alias or a class member. In the alias case, we took the alias, whereas in the class case, we recreated a selection on the stable scrutinee. We did not allow that on abstract type members. We now uniformly do it for all kinds of type members. If the scrutinee is a (non-skolem) stable type, we do not even look at the info of the type member. We directly create a selection to it, which corresponds to what we did before for class members. We only try to dealias type members if the scrutinee type is not a stable type.
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Previously, through the various code paths, we basically allowed type member extraction for stable scrutinees if the type member was an alias or a class member. In the alias case, we took the alias, whereas in the class case, we recreated a selection on the stable scrutinee. We did not allow that on abstract type members.
We now uniformly do it for all kinds of type members. If the scrutinee is a (non-skolem) stable type, we do not even look at the info of the type member. We directly create a selection to it, which corresponds to what we did before for class members.
We only try to dealias type members if the scrutinee type is not a stable type.
Note that this goes against the current spec and should in theory require (yet another) SIP amendment. The core meeting decided a few ago to go for it anyway and "ask for forgiveness" later so that we can have it in 3.6.0 🤷♂️.