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

…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.
rust-lang · Jul 11, 2024 · 27d5db1 · 27d5db1
1 parent e1f45a1
commit 27d5db1
Show file tree

Hide file tree

Showing 4 changed files with 80 additions and 0 deletions.
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs
@@ -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)
@@ -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| {

diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.current.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.current.stderr
@@ -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`.
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.next.stderr b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.next.stderr
@@ -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`.
diff --git a/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.rs b/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.rs
@@ -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
 }