Force the correct type variable to never for method resolution on an adjusted never type - #163450
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Force the correct type variable to never for method resolution on an adjusted never type Fixes the problem described in https://rust-lang.zulipchat.com/#narrow/channel/618216-t-types.2Fcall-for-participation/topic/method.20call.20on.20diverging.20infer.20doesn.27t.20constrain.20to.20never/near/627440568 The reason that the old code didn't work, as far as I understand, is that the subtype constraint `root_ty <: ty` is only evaluated after `ty` is unioned with `&_`, causing a `mismatched type` error when `&_` is then given the subtype constraint. This is fixed by demanding `ty`, rather than `root_ty` to be equal to never. I asked lcnr whether they think there's a way to reproduce this on the old trait solver, they were unsure and I also am. I think to be safe we should backport this to 1.100, since the never type stabilization is in 1.100 and there might be a way to break this code then. r? @lcnr cc @WaffleLapkin
JonathanBrouwer
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Force the correct type variable to never for method resolution on an adjusted never type Fixes the problem described in https://rust-lang.zulipchat.com/#narrow/channel/618216-t-types.2Fcall-for-participation/topic/method.20call.20on.20diverging.20infer.20doesn.27t.20constrain.20to.20never/near/627440568 The reason that the old code didn't work, as far as I understand, is that the subtype constraint `root_ty <: ty` is only evaluated after `ty` is unioned with `&_`, causing a `mismatched type` error when `&_` is then given the subtype constraint. This is fixed by demanding `ty`, rather than `root_ty` to be equal to never. I asked lcnr whether they think there's a way to reproduce this on the old trait solver, they were unsure and I also am. I think to be safe we should backport this to 1.100, since the never type stabilization is in 1.100 and there might be a way to break this code then. r? @lcnr cc @WaffleLapkin
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…uwer Rollup of 15 pull requests Successful merges: - #158936 (Add `std::fs::{Home|Media}Dirs`) - #129036 (Additional NonZero conversions) - #158997 (Avoid recording unnameable `extern crate` aliases in diagnostic metadata) - #161015 (Stabilize `funnel_shifts` (including `const`)) - #161712 (Stabilize `Result::into_{ok,err}`) - #162493 (Add support for -Zsanitizer-cfi-minimal-runtime) - #162655 (next solver: prefer to select impl candidates over global where-clause candidates) - #162862 (Fix intra doc link resolution when a doc comment is composed of both inner and outer doc comment) - #163200 (make `RustaceansAreAwesome` satisfy trait bounds) - #163331 (Move `Arc` and `Rc` into `rcs` mod) - #163427 (implement #![feature(gca_adts)]) - #163428 (do not complain about unstable target features on nightly) - #163444 (Add `stable_rustc` helper in `run-make-support`) - #163447 (Allow using different index types when reading and writing to tables) - #163450 (Force the correct type variable to never for method resolution on an adjusted never type)
JonathanBrouwer
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Force the correct type variable to never for method resolution on an adjusted never type Fixes the problem described in https://rust-lang.zulipchat.com/#narrow/channel/618216-t-types.2Fcall-for-participation/topic/method.20call.20on.20diverging.20infer.20doesn.27t.20constrain.20to.20never/near/627440568 The reason that the old code didn't work, as far as I understand, is that the subtype constraint `root_ty <: ty` is only evaluated after `ty` is unioned with `&_`, causing a `mismatched type` error when `&_` is then given the subtype constraint. This is fixed by demanding `ty`, rather than `root_ty` to be equal to never. I asked lcnr whether they think there's a way to reproduce this on the old trait solver, they were unsure and I also am. I think to be safe we should backport this to 1.100, since the never type stabilization is in 1.100 and there might be a way to break this code then. r? @lcnr cc @WaffleLapkin
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…uwer Rollup of 9 pull requests Successful merges: - #162655 (next solver: prefer to select impl candidates over global where-clause candidates) - #162832 (add `Div` and `Mul` for `Complex<{float}>`) - #162862 (Fix intra doc link resolution when a doc comment is composed of both inner and outer doc comment) - #163024 (Add `Dir` equivalents of `fs::metadata` & `fs::symlink_metadata`) - #163200 (make `RustaceansAreAwesome` satisfy trait bounds) - #163210 (std: split stack overflow module) - #163331 (Move `Arc` and `Rc` into `rcs` mod) - #163183 (Add .seek_read_buf_exact() to std::os::windows::fs::FileExt) - #163450 (Force the correct type variable to never for method resolution on an adjusted never type)
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…uwer Rollup of 9 pull requests Successful merges: - #158997 (Avoid recording unnameable `extern crate` aliases in diagnostic metadata) - #162655 (next solver: prefer to select impl candidates over global where-clause candidates) - #162832 (add `Div` and `Mul` for `Complex<{float}>`) - #162862 (Fix intra doc link resolution when a doc comment is composed of both inner and outer doc comment) - #163200 (make `RustaceansAreAwesome` satisfy trait bounds) - #163210 (std: split stack overflow module) - #163331 (Move `Arc` and `Rc` into `rcs` mod) - #163183 (Add .seek_read_buf_exact() to std::os::windows::fs::FileExt) - #163450 (Force the correct type variable to never for method resolution on an adjusted never type)
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Rollup merge of #163450 - JonathanBrouwer:fix-never, r=lcnr Force the correct type variable to never for method resolution on an adjusted never type Fixes the problem described in https://rust-lang.zulipchat.com/#narrow/channel/618216-t-types.2Fcall-for-participation/topic/method.20call.20on.20diverging.20infer.20doesn.27t.20constrain.20to.20never/near/627440568 The reason that the old code didn't work, as far as I understand, is that the subtype constraint `root_ty <: ty` is only evaluated after `ty` is unioned with `&_`, causing a `mismatched type` error when `&_` is then given the subtype constraint. This is fixed by demanding `ty`, rather than `root_ty` to be equal to never. I asked lcnr whether they think there's a way to reproduce this on the old trait solver, they were unsure and I also am. I think to be safe we should backport this to 1.100, since the never type stabilization is in 1.100 and there might be a way to break this code then. r? @lcnr cc @WaffleLapkin
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…uwer Rollup of 9 pull requests Successful merges: - rust-lang/rust#158997 (Avoid recording unnameable `extern crate` aliases in diagnostic metadata) - rust-lang/rust#162655 (next solver: prefer to select impl candidates over global where-clause candidates) - rust-lang/rust#162832 (add `Div` and `Mul` for `Complex<{float}>`) - rust-lang/rust#162862 (Fix intra doc link resolution when a doc comment is composed of both inner and outer doc comment) - rust-lang/rust#163200 (make `RustaceansAreAwesome` satisfy trait bounds) - rust-lang/rust#163210 (std: split stack overflow module) - rust-lang/rust#163331 (Move `Arc` and `Rc` into `rcs` mod) - rust-lang/rust#163183 (Add .seek_read_buf_exact() to std::os::windows::fs::FileExt) - rust-lang/rust#163450 (Force the correct type variable to never for method resolution on an adjusted never type)
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…uwer Rollup of 9 pull requests Successful merges: - rust-lang/rust#158997 (Avoid recording unnameable `extern crate` aliases in diagnostic metadata) - rust-lang/rust#162655 (next solver: prefer to select impl candidates over global where-clause candidates) - rust-lang/rust#162832 (add `Div` and `Mul` for `Complex<{float}>`) - rust-lang/rust#162862 (Fix intra doc link resolution when a doc comment is composed of both inner and outer doc comment) - rust-lang/rust#163200 (make `RustaceansAreAwesome` satisfy trait bounds) - rust-lang/rust#163210 (std: split stack overflow module) - rust-lang/rust#163331 (Move `Arc` and `Rc` into `rcs` mod) - rust-lang/rust#163183 (Add .seek_read_buf_exact() to std::os::windows::fs::FileExt) - rust-lang/rust#163450 (Force the correct type variable to never for method resolution on an adjusted never type)
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Fixes the problem described in https://rust-lang.zulipchat.com/#narrow/channel/618216-t-types.2Fcall-for-participation/topic/method.20call.20on.20diverging.20infer.20doesn.27t.20constrain.20to.20never/near/627440568
The reason that the old code didn't work, as far as I understand, is that the subtype constraint
root_ty <: tyis only evaluated aftertyis unioned with&_, causing amismatched typeerror when&_is then given the subtype constraint.This is fixed by demanding
ty, rather thanroot_tyto be equal to never.I asked lcnr whether they think there's a way to reproduce this on the old trait solver, they were unsure and I also am.
I think to be safe we should backport this to 1.100, since the never type stabilization is in 1.100 and there might be a way to break this code then.
r? @lcnr
cc @WaffleLapkin