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Allows #[diagnostic::do_not_recommend] to supress trait impls in su…
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…ggestions as well

This commit changes the error reporting mechanism for not implemented
traits to skip impl marked as `#[diagnostic::do_not_recommend]` in the
help part of the error message ("the following other types implement
trait `Foo`:"). The main use case here is to allow crate authors to skip
non-meaningful confusing suggestions. A common example for this are
fully generic impls on tuples.
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weiznich committed Jul 11, 2024
1 parent e1f45a1 commit 27d5db1
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Original file line number Diff line number Diff line change
Expand Up @@ -1776,6 +1776,19 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
true
};

// we filter before checking if `impl_candidates` is empty
// to get the fallback solution if we filtered out any impls
let impl_candidates = impl_candidates
.into_iter()
.cloned()
.filter(|cand| {
!self.tcx.has_attrs_with_path(
cand.impl_def_id,
&[sym::diagnostic, sym::do_not_recommend],
)
})
.collect::<Vec<_>>();

let def_id = trait_ref.def_id();
if impl_candidates.is_empty() {
if self.tcx.trait_is_auto(def_id)
Expand All @@ -1788,6 +1801,12 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
let mut impl_candidates: Vec<_> = self
.tcx
.all_impls(def_id)
// ignore `do_not_recommend` items
.filter(|def_id| {
!self
.tcx
.has_attrs_with_path(*def_id, &[sym::diagnostic, sym::do_not_recommend])
})
// Ignore automatically derived impls and `!Trait` impls.
.filter_map(|def_id| self.tcx.impl_trait_header(def_id))
.filter_map(|header| {
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
error[E0277]: the trait bound `(): Foo` is not satisfied
--> $DIR/supress_suggestions_in_help.rs:23:11
|
LL | check(());
| ----- ^^ the trait `Foo` is not implemented for `()`
| |
| required by a bound introduced by this call
|
= help: the trait `Foo` is implemented for `i32`
note: required by a bound in `check`
--> $DIR/supress_suggestions_in_help.rs:20:18
|
LL | fn check(a: impl Foo) {}
| ^^^ required by this bound in `check`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.
Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
error[E0277]: the trait bound `(): Foo` is not satisfied
--> $DIR/supress_suggestions_in_help.rs:23:11
|
LL | check(());
| ----- ^^ the trait `Foo` is not implemented for `()`
| |
| required by a bound introduced by this call
|
= help: the trait `Foo` is implemented for `i32`
note: required by a bound in `check`
--> $DIR/supress_suggestions_in_help.rs:20:18
|
LL | fn check(a: impl Foo) {}
| ^^^ required by this bound in `check`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.
Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
//@ revisions: current next
//@ ignore-compare-mode-next-solver (explicit revisions)
//@[next] compile-flags: -Znext-solver

#![feature(do_not_recommend)]

trait Foo {}

#[diagnostic::do_not_recommend]
impl<A> Foo for (A,) {}

#[diagnostic::do_not_recommend]
impl<A, B> Foo for (A, B) {}

#[diagnostic::do_not_recommend]
impl<A, B, C> Foo for (A, B, C) {}

impl Foo for i32 {}

fn check(a: impl Foo) {}

fn main() {
check(());
//~^ ERROR the trait bound `(): Foo` is not satisfied
}

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