Skip to content

Commit

Permalink
Auto merge of #123468 - compiler-errors:precise-capturing, r=oli-obk
Browse files Browse the repository at this point in the history
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:

- rust-lang/rust#123432
  • Loading branch information
bors committed Apr 16, 2024
2 parents ac174ae + 735f2c6 commit dd0da10
Showing 1 changed file with 10 additions and 1 deletion.
11 changes: 10 additions & 1 deletion clippy_utils/src/ast_utils.rs
Original file line number Diff line number Diff line change
Expand Up @@ -709,7 +709,8 @@ pub fn eq_ty(l: &Ty, r: &Ty) -> bool {
(Tup(l), Tup(r)) => over(l, r, |l, r| eq_ty(l, r)),
(Path(lq, lp), Path(rq, rp)) => both(lq, rq, eq_qself) && eq_path(lp, rp),
(TraitObject(lg, ls), TraitObject(rg, rs)) => ls == rs && over(lg, rg, eq_generic_bound),
(ImplTrait(_, lg), ImplTrait(_, rg)) => over(lg, rg, eq_generic_bound),
(ImplTrait(_, lg, lc), ImplTrait(_, rg, rc)) =>
over(lg, rg, eq_generic_bound) && both(lc, rc, |lc, rc| over(lc.0.as_slice(), rc.0.as_slice(), eq_precise_capture)),
(Typeof(l), Typeof(r)) => eq_expr(&l.value, &r.value),
(MacCall(l), MacCall(r)) => eq_mac_call(l, r),
_ => false,
Expand Down Expand Up @@ -770,6 +771,14 @@ pub fn eq_generic_bound(l: &GenericBound, r: &GenericBound) -> bool {
}
}

pub fn eq_precise_capture(l: &PreciseCapturingArg, r: &PreciseCapturingArg) -> bool {
match (l, r) {
(PreciseCapturingArg::Lifetime(l), PreciseCapturingArg::Lifetime(r)) => l.ident == r.ident,
(PreciseCapturingArg::Arg(l, _), PreciseCapturingArg::Arg(r, _)) => l.segments[0].ident == r.segments[0].ident,
_ => false,
}
}

fn eq_term(l: &Term, r: &Term) -> bool {
match (l, r) {
(Term::Ty(l), Term::Ty(r)) => eq_ty(l, r),
Expand Down

0 comments on commit dd0da10

Please sign in to comment.