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Rollup merge of #86657 - jam1garner:future_prelude_false_positive, r=…
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…nikomatsakis

Fix `future_prelude_collision` false positive

Fixes #86633

The lint for checking if method resolution of methods named `try_into` will fail in 2021 edition previously would fire on all inherent methods, however for inherent methods that consume `self`, this takes priority over `TryInto::try_into` due to being inherent, while trait method and methods that take `&self` or `&mut self` don't take priority, and thus aren't affected by this false positive.

This fix is rather simple: simply checking if the inherent method doesn't auto-deref or auto-ref (and thus takes `self`) and if so, prevents the lint from firing.
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JohnTitor authored Jun 28, 2021
2 parents c9ac096 + bf0da44 commit 5028581
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7 changes: 7 additions & 0 deletions compiler/rustc_typeck/src/check/method/prelude2021.rs
Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
{
return;
}

// if it's an inherent `self` method (not `&self` or `&mut self`), it will take
// precedence over the `TryInto` impl, and thus won't break in 2021 edition
if pick.autoderefs == 0 && pick.autoref_or_ptr_adjustment.is_none() {
return;
}

// Inherent impls only require not relying on autoref and autoderef in order to
// ensure that the trait implementation won't be used
self.tcx.struct_span_lint_hir(
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16 changes: 16 additions & 0 deletions src/test/ui/rust-2021/future-prelude-collision-unneeded.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
// edition:2018
// check-pass
#![allow(unused)]
#![deny(future_prelude_collision)]

struct S;

impl S {
fn try_into(self) -> S { S }
}

// See https://github.com/rust-lang/rust/issues/86633
fn main() {
let s = S;
let s2 = s.try_into();
}

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