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Check for uninhabitedness instead of never - #54123
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varkor wants to merge 1 commit into
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oli-obk
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Sep 11, 2018
| }; | ||
| if cx.layout_of(sig.output()).abi == ty::layout::Abi::Uninhabited { | ||
| // Tell LLVM that functions that return uninhabited types will not return. | ||
| if sig.output().conservative_is_uninhabited() { |
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isn't this way more conservative than the layout check? I think this should stay being the layout check. It does not influence type checking, just llvm optimizations
| let llfn = declare_raw_fn(cx, name, fty.llvm_cconv(), fty.llvm_type(cx)); | ||
| if cx.layout_of(sig.output()).abi == layout::Abi::Uninhabited { | ||
| if sig.output().conservative_is_uninhabited() { |
| // into an uninhabited type is impossible, so anything following | ||
| // it must be unreachable. | ||
| assert_eq!(bx.cx.layout_of(sig.output()).abi, layout::Abi::Uninhabited); | ||
| assert!(sig.output().conservative_is_uninhabited()); |
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similarly here, the previous assert was stronger
varkor
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Sep 11, 2018
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oli-obk
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Sep 11, 2018
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Ah makes sense, still not sure if these PRs can be reviewed independently |
varkor
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Sep 11, 2018
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Yeah, in retrospect, the order of dependency would work better flipped. @nikomatsakis: it might make sense to review #54125 directly (as that PR includes the changes here) instead. |
varkor
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Sep 20, 2018
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Closing this PR in favour of merging #54125. |
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Sep 26, 2018
…, r=<try> Less conservative uninhabitedness check Extends the uninhabitedness check to structs, non-empty enums, tuples and arrays. Pulled out of #47291 and #50262. Blocked on #54123. r? @nikomatsakis
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Instead of checking for
!, in many places we can simply check that a type is uninhabited.Pulled out of #47291 and #50262.
r? @nikomatsakis