rust/compiler/rustc_hir_analysis
bors 4e1f5d90bc Auto merge of #123468 - compiler-errors:precise-capturing, r=oli-obk
Implement syntax for `impl Trait` to specify its captures explicitly (`feature(precise_capturing)`)

Implements `impl use<'a, 'b, T, U> Sized` syntax that allows users to explicitly list the captured parameters for an opaque, rather than inferring it from the opaque's bounds (or capturing *all* lifetimes under 2024-edition capture rules). This allows us to exclude some implicit captures, so this syntax may be used as a migration strategy for changes due to #117587.

We represent this list of captured params as `PreciseCapturingArg` in AST and HIR, resolving them between `rustc_resolve` and `resolve_bound_vars`. Later on, we validate that the opaques only capture the parameters in this list.

We artificially limit the feature to *require* mentioning all type and const parameters, since we don't currently have support for non-lifetime bivariant generics. This can be relaxed in the future.

We also may need to limit this to require naming *all* lifetime parameters for RPITIT, since GATs have no variance. I have to investigate this. This can also be relaxed in the future.

r? `@oli-obk`

Tracking issue:

- https://github.com/rust-lang/rust/issues/123432
2024-04-16 11:22:35 +00:00
..
src Auto merge of #123468 - compiler-errors:precise-capturing, r=oli-obk 2024-04-16 11:22:35 +00:00
Cargo.toml bump itertools to 0.12 2024-03-08 12:34:05 +03:00
messages.ftl More polishing 2024-04-15 16:45:48 -04:00
README.md rustc_typeck to rustc_hir_analysis 2022-09-27 10:37:23 +02:00

For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.