Revert "Fix #90970, doesn't address #87437"

This reverts commit ac8cbbd.

Author: Dylan-DPC

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -2,11 +2,10 @@ pub mod on_unimplemented;
 pub mod suggestions;
 
 use super::{
-    DerivedObligationCause, EvaluationResult, FulfillmentContext, FulfillmentError,
-    FulfillmentErrorCode, ImplDerivedObligationCause, MismatchedProjectionTypes, Obligation,
-    ObligationCause, ObligationCauseCode, OnUnimplementedDirective, OnUnimplementedNote,
-    OutputTypeParameterMismatch, Overflow, PredicateObligation, SelectionContext, SelectionError,
-    TraitNotObjectSafe,
+    EvaluationResult, FulfillmentContext, FulfillmentError, FulfillmentErrorCode,
+    MismatchedProjectionTypes, Obligation, ObligationCause, ObligationCauseCode,
+    OnUnimplementedDirective, OnUnimplementedNote, OutputTypeParameterMismatch, Overflow,
+    PredicateObligation, SelectionContext, SelectionError, TraitNotObjectSafe,
 };
 
 use crate::infer::error_reporting::{TyCategory, TypeAnnotationNeeded as ErrorCode};
@@ -661,77 +660,11 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                         } else if !suggested {
                             // Can't show anything else useful, try to find similar impls.
                             let impl_candidates = self.find_similar_impl_candidates(trait_ref);
-                            if !self.report_similar_impl_candidates(
+                            self.report_similar_impl_candidates(
                                 impl_candidates,
                                 trait_ref,
                                 &mut err,
-                            ) {
-                                // This is *almost* equivalent to
-                                // `obligation.cause.code().peel_derives()`, but it gives us the
-                                // trait predicate for that corresponding root obligation. This
-                                // lets us get a derived obligation from a type parameter, like
-                                // when calling `string.strip_suffix(p)` where `p` is *not* an
-                                // implementer of `Pattern<'_>`.
-                                let mut code = obligation.cause.code();
-                                let mut trait_pred = trait_predicate;
-                                let mut peeled = false;
-                                loop {
-                                    match &*code {
-                                        ObligationCauseCode::FunctionArgumentObligation {
-                                            parent_code,
-                                            ..
-                                        } => {
-                                            code = &parent_code;
-                                        }
-                                        ObligationCauseCode::ImplDerivedObligation(
-                                            box ImplDerivedObligationCause {
-                                                derived:
-                                                    DerivedObligationCause {
-                                                        parent_code,
-                                                        parent_trait_pred,
-                                                    },
-                                                ..
-                                            },
-                                        )
-                                        | ObligationCauseCode::BuiltinDerivedObligation(
-                                            DerivedObligationCause {
-                                                parent_code,
-                                                parent_trait_pred,
-                                            },
-                                        )
-                                        | ObligationCauseCode::DerivedObligation(
-                                            DerivedObligationCause {
-                                                parent_code,
-                                                parent_trait_pred,
-                                            },
-                                        ) => {
-                                            peeled = true;
-                                            code = &parent_code;
-                                            trait_pred = *parent_trait_pred;
-                                        }
-                                        _ => break,
-                                    };
-                                }
-                                let def_id = trait_pred.def_id();
-                                // Mention *all* the `impl`s for the *top most* obligation, the
-                                // user might have meant to use one of them, if any found. We skip
-                                // auto-traits or fundamental traits that might not be exactly what
-                                // the user might expect to be presented with. Instead this is
-                                // useful for less general traits.
-                                if peeled
-                                    && !self.tcx.trait_is_auto(def_id)
-                                    && !self.tcx.lang_items().items().contains(&Some(def_id))
-                                {
-                                    let trait_ref = trait_pred.to_poly_trait_ref();
-                                    let impl_candidates =
-                                        self.find_similar_impl_candidates(trait_ref);
-                                    self.report_similar_impl_candidates(
-                                        impl_candidates,
-                                        trait_ref,
-                                        &mut err,
-                                    );
-                                }
-                            }
+                            );
                         }
 
                         // Changing mutability doesn't make a difference to whether we have

src/test/ui/const-generics/generic_const_exprs/issue-85848.stderr

@@ -6,7 +6,6 @@ LL |     writes_to_specific_path(&cap);
    |     |
    |     required by a bound introduced by this call
    |
-   = help: the trait `Delegates<U>` is implemented for `T`
 note: required because of the requirements on the impl of `Contains<(), true>` for `&C`
   --> $DIR/issue-85848.rs:21:12
    |

src/test/ui/impl-trait/cross-return-site-inference.stderr

@@ -7,7 +7,6 @@ LL |     Err("whoops")?;
    |                  ^ the trait `From<&str>` is not implemented for `impl Debug`
    |
    = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
-   = help: the trait `FromResidual<Result<Infallible, E>>` is implemented for `Result<T, F>`
    = note: required because of the requirements on the impl of `FromResidual<Result<Infallible, &str>>` for `Result<(), impl Debug>`
 
 error[E0277]: the trait bound `impl Debug: From<&str>` is not satisfied

src/test/ui/impl-trait/nested_impl_trait.stderr

@@ -52,7 +52,6 @@ error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfie
 LL | fn bad_in_ret_position(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                              ^^^^^^^^^^^^^^^^^^^^^ the trait `From<impl Into<u32>>` is not implemented for `impl Debug`
    |
-   = help: the trait `Into<U>` is implemented for `T`
    = note: required because of the requirements on the impl of `Into<impl Debug>` for `impl Into<u32>`
 
 error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfied
@@ -61,7 +60,6 @@ error[E0277]: the trait bound `impl Debug: From<impl Into<u32>>` is not satisfie
 LL |     fn bad(x: impl Into<u32>) -> impl Into<impl Debug> { x }
    |                                  ^^^^^^^^^^^^^^^^^^^^^ the trait `From<impl Into<u32>>` is not implemented for `impl Debug`
    |
-   = help: the trait `Into<U>` is implemented for `T`
    = note: required because of the requirements on the impl of `Into<impl Debug>` for `impl Into<u32>`
 
 error: aborting due to 8 previous errors

src/test/ui/issues/issue-32709.stderr

@@ -7,7 +7,6 @@ LL |     Err(5)?;
    |           ^ the trait `From<{integer}>` is not implemented for `()`
    |
    = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
-   = help: the trait `FromResidual<Result<Infallible, E>>` is implemented for `Result<T, F>`
    = note: required because of the requirements on the impl of `FromResidual<Result<Infallible, {integer}>>` for `Result<i32, ()>`
 
 error: aborting due to previous error

src/test/ui/kindck/kindck-impl-type-params.stderr

@@ -80,7 +80,6 @@ error[E0277]: the trait bound `String: Copy` is not satisfied
 LL |     let a = t as Box<dyn Gettable<String>>;
    |             ^ the trait `Copy` is not implemented for `String`
    |
-   = help: the trait `Gettable<T>` is implemented for `S<T>`
 note: required because of the requirements on the impl of `Gettable<String>` for `S<String>`
   --> $DIR/kindck-impl-type-params.rs:14:32
    |
@@ -94,7 +93,6 @@ error[E0277]: the trait bound `Foo: Copy` is not satisfied
 LL |     let a: Box<dyn Gettable<Foo>> = t;
    |                                     ^ the trait `Copy` is not implemented for `Foo`
    |
-   = help: the trait `Gettable<T>` is implemented for `S<T>`
 note: required because of the requirements on the impl of `Gettable<Foo>` for `S<Foo>`
   --> $DIR/kindck-impl-type-params.rs:14:32
    |