Make TAITs and ATPITs capture late-bound lifetimes in scope #122103
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Mar 6, 2024
| @@ -1,8 +1,14 @@ | |||
| error: cannot capture late-bound lifetime in type alias impl trait | |||
| --> $DIR/escaping-bound-var.rs:9:57 | |||
| error: higher kinded lifetime bounds on nested opaque types are not supported yet | |||
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This error message sucks but is improved by #122100. Separated that from this PR for reviewability.
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Alternatively, we could implement this restriction in a far simpler manner by just checking if any late-bound vars are in scope of an opaque via a HIR walker. But given that we may want to support this eventually, and the rest of the compiler is already set up to support this because of RPIT, I'd rather do this the right way. |
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yea, I prefer mirroring RPITs, even if that means we duplicate all the lifetimes from parents only to then immediately always ignore the parent lifetimes @bors r+ |
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☔ The latest upstream changes (presumably #121154) made this pull request unmergeable. Please resolve the merge conflicts. |
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@bors r=oli-obk |
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☔ The latest upstream changes (presumably #122151) made this pull request unmergeable. Please resolve the merge conflicts. |
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@bors r+ |
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…iaskrgr Rollup of 8 pull requests Successful merges: - rust-lang#118623 (Improve std::fs::read_to_string example) - rust-lang#119365 (Add asm goto support to `asm!`) - rust-lang#120608 (Docs for std::ptr::slice_from_raw_parts) - rust-lang#121832 (Add new Tier-3 target: `loongarch64-unknown-linux-musl`) - rust-lang#121938 (Fix quadratic behavior of repeated vectored writes) - rust-lang#122099 (Add `#[inline]` to `BTreeMap::new` constructor) - rust-lang#122103 (Make TAITs and ATPITs capture late-bound lifetimes in scope) - rust-lang#122143 (PassWrapper: update for llvm/llvm-project@a3319371970b) Failed merges: - rust-lang#122076 (Tweak the way we protect in-place function arguments in interpreters) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#122103 - compiler-errors:taits-capture-everything, r=oli-obk Make TAITs and ATPITs capture late-bound lifetimes in scope This generalizes the behavior that RPITs have, where they duplicate their in-scope lifetimes so that they will always *reify* late-bound lifetimes that they capture. This allows TAITs and ATPITs to properly error when they capture in-scope late-bound lifetimes. r? `@oli-obk` cc `@aliemjay` Fixes rust-lang#122093 and therefore rust-lang#120700 (comment)
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Mar 10, 2024
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| // Only check the parent generics, which will ignore any of the | ||
| // duplicated lifetime args that come from reifying late-bounds. | ||
| for (i, arg) in opaque_type_key.args.iter().take(parent_generics.count()).enumerate() { |
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The parent generics are bivariant and can easily be unconstrained lifetime variables. This caused #122307.
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This generalizes the behavior that RPITs have, where they duplicate their in-scope lifetimes so that they will always reify late-bound lifetimes that they capture. This allows TAITs and ATPITs to properly error when they capture in-scope late-bound lifetimes.
r? @oli-obk cc @aliemjay
Fixes #122093 and therefore #120700 (comment)