Check for uninhabitedness instead of never #54123
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rust-highfive
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oli-obk
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Sep 11, 2018
| @@ -279,7 +279,8 @@ pub fn create_function_debug_context( | |||
| } | |||
| None => {} | |||
| }; | |||
| 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
| @@ -137,7 +136,7 @@ pub fn declare_fn( | |||
| let fty = FnType::new(cx, sig, &[]); | |||
| let llfn = declare_raw_fn(cx, name, fty.llvm_cconv(), fty.llvm_type(cx)); | |||
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| if cx.layout_of(sig.output()).abi == layout::Abi::Uninhabited { | |||
| if sig.output().conservative_is_uninhabited() { | |||
| @@ -457,7 +457,7 @@ impl FunctionCx<'a, 'll, 'tcx> { | |||
| // we can do what we like. Here, we declare that transmuting | |||
| // 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
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Ah makes sense, still not sure if these PRs can be reviewed independently |
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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. |
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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