Remove context dependant ! fallback
#148871
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The code supporting it is extremely confusing. At the same time, we have no plans to use this scheme, so there is no value in supporting it.
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I have really low confidence in the never type tests, IMO they require a major refactoring, as a lot of them are based on outdated ideas and features... |
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For the tests, I would expect us to have revisions for edition 2021 and edition 2024 (for the different fallbacks) |
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@jackh726 I'm not sure 2021vs2015 is relevant. But either way, yes, I agree that we should have tests for both current fallback behaviors based on the edition. I'll make a followup which cleans up the tests, wanna make sure that we have relevant and comprehensive tests. |
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the only diagnostic that was using this field specifically сares for the never type fallback, not the integer fallback.
I think in this case the early return is harder to read than just an if. "if fallback hasn't occured we don't do..."
this is about context dependant case which I removed a few commits back
... now that it's always the same for a certain crate
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| // phase of fallback. This means that we only replace | ||
| // inference variables with their underlying opaque types as a | ||
| // last resort. |
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existing, but I do not understand that comment?
Do you understand what this wants to say. It feels like this is a general "if fallback occurred, previously stalled goals may make progress again".
I really don't see how there's anything specific to opaques here.
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I don't get it either .-.
the example below is supposed to explain this, but I still don't get it
| }); | ||
| let unit_obligation = obligation.with(tcx, predicate); | ||
| if self.predicate_may_hold(&unit_obligation) { | ||
| // FIXME: make a new issue for this |
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Can you elaborate on that FIXME? it feels unactionable for anyone who isn't you right now... or maybe just do that if you can xd
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Sure, I opened #148922 and linked it from here. I tried my best to write a good explanation, but it's just confusing :(
| @@ -1,9 +1,8 @@ | |||
| //@ revisions: nofallback fallback | |||
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want to rename the revisions to "unit_fallback never_fallback"?
| fallback_to(self.tcx.types.unit); | ||
| } | ||
| DivergingFallbackBehavior::ContextDependent => { | ||
| if found_infer_var_info.self_in_trait && found_infer_var_info.output { |
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found_infer_var_info is dead code now?
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Did you mean InferVarInfo? Yes, it is. Removed.
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I don't think we need to worry about |
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@rustbot review |
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... and minor cleanup.
r? lcnr