allow+update deref_into_dyn_supertrait
this commit makes `deref_into_dyn_supertrait` lint allow-by-default, removes future incompatibility (we finally live in a broken world), and changes the wording in the documentation. previously documentation erroneously said that it lints against *usage* of the deref impl, while it actually (since 104742) lints on the impl itself (oooops, my oversight, should have updated it 2+ years ago...)
This commit is contained in:
Waffle Lapkin
parent
bc1d68e389
commit
491599569c
9 changed files with 63 additions and 75 deletions
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@ -1,6 +1,5 @@
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use rustc_hir::{self as hir, LangItem};
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use rustc_middle::ty;
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use rustc_session::lint::FutureIncompatibilityReason;
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use rustc_session::{declare_lint, declare_lint_pass};
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use rustc_span::sym;
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use rustc_trait_selection::traits::supertraits;
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@ -9,12 +8,12 @@ use crate::lints::{SupertraitAsDerefTarget, SupertraitAsDerefTargetLabel};
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use crate::{LateContext, LateLintPass, LintContext};
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declare_lint! {
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/// The `deref_into_dyn_supertrait` lint is output whenever there is a use of the
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/// `Deref` implementation with a `dyn SuperTrait` type as `Output`.
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/// The `deref_into_dyn_supertrait` lint is emitted whenever there is a `Deref` implementation
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/// for `dyn SubTrait` with a `dyn SuperTrait` type as the `Output` type.
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///
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/// These implementations are shadowed by the `trait_upcasting` feature (stabilized since
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/// These implementations are "shadowed" by trait upcasting (stabilized since
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/// CURRENT_RUSTC_VERSION). The `deref` functions is no longer called implicitly, which might
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/// be behavior change compared to previous rustc versions.
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/// change behavior compared to previous rustc versions.
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///
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/// ### Example
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///
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@ -44,15 +43,14 @@ declare_lint! {
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///
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/// ### Explanation
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///
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/// The dyn upcasting coercion feature added a new coercion rules, taking priority
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/// over certain other coercion rules, which caused some behavior change.
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/// The trait upcasting coercion added a new coercion rule, taking priority over certain other
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/// coercion rules, which causes some behavior change compared to older `rustc` versions.
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///
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/// `deref` can be still called explicitly, it just isn't called as part of a deref coercion
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/// (since trait upcasting coercion takes priority).
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pub DEREF_INTO_DYN_SUPERTRAIT,
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Warn,
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"`Deref` implementation usage with a supertrait trait object for output is shadowed by trait upcasting",
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@future_incompatible = FutureIncompatibleInfo {
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reason: FutureIncompatibilityReason::FutureReleaseSemanticsChange,
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reference: "issue #89460 <https://github.com/rust-lang/rust/issues/89460>",
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};
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Allow,
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"`Deref` implementation with a supertrait trait object for output is shadowed by trait upcasting",
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}
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declare_lint_pass!(DerefIntoDynSupertrait => [DEREF_INTO_DYN_SUPERTRAIT]);
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@ -0,0 +1,17 @@
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//@ check-pass
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#![warn(deref_into_dyn_supertrait)]
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use std::ops::Deref;
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trait Bar<T> {}
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trait Foo: Bar<i32> {}
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impl<'a> Deref for dyn Foo + 'a {
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//~^ warn: this `Deref` implementation is covered by an implicit supertrait coercion
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type Target = dyn Bar<u32> + 'a;
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fn deref(&self) -> &Self::Target {
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todo!()
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}
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}
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fn main() {}
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@ -0,0 +1,17 @@
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warning: this `Deref` implementation is covered by an implicit supertrait coercion
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--> $DIR/deref-upcast-shadowing-lint.rs:8:1
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LL | impl<'a> Deref for dyn Foo + 'a {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dyn Foo` implements `Deref<Target = dyn Bar<u32>>` which conflicts with supertrait `Bar<i32>`
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LL |
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LL | type Target = dyn Bar<u32> + 'a;
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| -------------------------------- target type is a supertrait of `dyn Foo`
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note: the lint level is defined here
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--> $DIR/deref-upcast-shadowing-lint.rs:2:9
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LL | #![warn(deref_into_dyn_supertrait)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^^
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warning: 1 warning emitted
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@ -1,4 +1,5 @@
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#![deny(deref_into_dyn_supertrait)]
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//@ check-pass
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#![warn(deref_into_dyn_supertrait)]
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use std::ops::Deref;
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@ -6,8 +7,7 @@ trait Bar<'a> {}
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trait Foo<'a>: Bar<'a> {}
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impl<'a> Deref for dyn Foo<'a> {
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//~^ ERROR this `Deref` implementation is covered by an implicit supertrait coercion
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//~| WARN this will change its meaning in a future release!
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//~^ warn: this `Deref` implementation is covered by an implicit supertrait coercion
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type Target = dyn Bar<'a>;
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fn deref(&self) -> &Self::Target {
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@ -1,19 +1,17 @@
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error: this `Deref` implementation is covered by an implicit supertrait coercion
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--> $DIR/migrate-lint-deny-regions.rs:8:1
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warning: this `Deref` implementation is covered by an implicit supertrait coercion
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--> $DIR/migrate-lint-deny-regions.rs:9:1
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LL | impl<'a> Deref for dyn Foo<'a> {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dyn Foo<'_>` implements `Deref<Target = dyn Bar<'_>>` which conflicts with supertrait `Bar<'_>`
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...
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LL |
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LL | type Target = dyn Bar<'a>;
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| -------------------------- target type is a supertrait of `dyn Foo<'_>`
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= warning: this will change its meaning in a future release!
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= note: for more information, see issue #89460 <https://github.com/rust-lang/rust/issues/89460>
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note: the lint level is defined here
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--> $DIR/migrate-lint-deny-regions.rs:1:9
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--> $DIR/migrate-lint-deny-regions.rs:2:9
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LL | #![deny(deref_into_dyn_supertrait)]
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LL | #![warn(deref_into_dyn_supertrait)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to 1 previous error
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warning: 1 warning emitted
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@ -1,25 +0,0 @@
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#![deny(deref_into_dyn_supertrait)]
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use std::ops::Deref;
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// issue 89190
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trait A {}
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trait B: A {}
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impl<'a> Deref for dyn 'a + B {
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//~^ ERROR this `Deref` implementation is covered by an implicit supertrait coercion
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//~| WARN this will change its meaning in a future release!
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type Target = dyn A;
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fn deref(&self) -> &Self::Target {
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todo!()
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}
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}
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fn take_a(_: &dyn A) {}
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fn whoops(b: &dyn B) {
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take_a(b)
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}
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fn main() {}
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@ -1,19 +0,0 @@
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error: this `Deref` implementation is covered by an implicit supertrait coercion
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--> $DIR/migrate-lint-deny.rs:9:1
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LL | impl<'a> Deref for dyn 'a + B {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dyn B` implements `Deref<Target = dyn A>` which conflicts with supertrait `A`
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...
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LL | type Target = dyn A;
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| -------------------- target type is a supertrait of `dyn B`
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= warning: this will change its meaning in a future release!
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= note: for more information, see issue #89460 <https://github.com/rust-lang/rust/issues/89460>
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note: the lint level is defined here
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--> $DIR/migrate-lint-deny.rs:1:9
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LL | #![deny(deref_into_dyn_supertrait)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^^
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error: aborting due to 1 previous error
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@ -1,4 +1,5 @@
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//@ check-pass
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#![warn(deref_into_dyn_supertrait)]
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use std::ops::Deref;
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@ -9,8 +10,7 @@ trait Foo: Bar<i32> {
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}
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impl<'a> Deref for dyn Foo + 'a {
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//~^ WARN this `Deref` implementation is covered by an implicit supertrait coercion
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//~| WARN this will change its meaning in a future release!
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//~^ warn: this `Deref` implementation is covered by an implicit supertrait coercion
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type Target = dyn Bar<u32> + 'a;
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fn deref(&self) -> &Self::Target {
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@ -1,15 +1,17 @@
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warning: this `Deref` implementation is covered by an implicit supertrait coercion
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--> $DIR/migrate-lint-different-substs.rs:11:1
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--> $DIR/migrate-lint-different-substs.rs:12:1
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LL | impl<'a> Deref for dyn Foo + 'a {
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `dyn Foo` implements `Deref<Target = dyn Bar<u32>>` which conflicts with supertrait `Bar<i32>`
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...
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LL |
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LL | type Target = dyn Bar<u32> + 'a;
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| -------------------------------- target type is a supertrait of `dyn Foo`
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= warning: this will change its meaning in a future release!
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= note: for more information, see issue #89460 <https://github.com/rust-lang/rust/issues/89460>
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= note: `#[warn(deref_into_dyn_supertrait)]` on by default
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note: the lint level is defined here
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--> $DIR/migrate-lint-different-substs.rs:2:9
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LL | #![warn(deref_into_dyn_supertrait)]
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| ^^^^^^^^^^^^^^^^^^^^^^^^^
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warning: 1 warning emitted
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