Rollup merge of #122732 - compiler-errors:coroutine-captures-note, r=nnethercote

Remove redundant coroutine captures note

This note is redundant, since we'll always be printing this "captures the following types..." between *more* descriptive `BuiltinDerivedObligationCause`s.

Please review with whitespace disabled, since I also removed an unnecessary labeled break.

1 files changed, 58 insertions, 60 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index c472f876e66..d19c2bd1f60 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -3209,71 +3209,69 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     }
                 };
 
-                // Don't print the tuple of capture types
-                'print: {
-                    if !is_upvar_tys_infer_tuple {
-                        let ty_str = tcx.short_ty_string(ty, &mut long_ty_file);
-                        let msg = format!("required because it appears within the type `{ty_str}`");
-                        match ty.kind() {
-                            ty::Adt(def, _) => match tcx.opt_item_ident(def.did()) {
-                                Some(ident) => err.span_note(ident.span, msg),
-                                None => err.note(msg),
-                            },
-                            ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => {
-                                // If the previous type is async fn, this is the future generated by the body of an async function.
-                                // Avoid printing it twice (it was already printed in the `ty::Coroutine` arm below).
-                                let is_future = tcx.ty_is_opaque_future(ty);
-                                debug!(
-                                    ?obligated_types,
-                                    ?is_future,
-                                    "note_obligation_cause_code: check for async fn"
-                                );
-                                if is_future
-                                    && obligated_types.last().is_some_and(|ty| match ty.kind() {
-                                        ty::Coroutine(last_def_id, ..) => {
-                                            tcx.coroutine_is_async(*last_def_id)
-                                        }
-                                        _ => false,
-                                    })
-                                {
-                                    break 'print;
-                                }
-                                err.span_note(tcx.def_span(def_id), msg)
+                if !is_upvar_tys_infer_tuple {
+                    let ty_str = tcx.short_ty_string(ty, &mut long_ty_file);
+                    let msg = format!("required because it appears within the type `{ty_str}`");
+                    match ty.kind() {
+                        ty::Adt(def, _) => match tcx.opt_item_ident(def.did()) {
+                            Some(ident) => {
+                                err.span_note(ident.span, msg);
                             }
-                            ty::CoroutineWitness(def_id, args) => {
-                                use std::fmt::Write;
-
-                                // FIXME: this is kind of an unusual format for rustc, can we make it more clear?
-                                // Maybe we should just remove this note altogether?
-                                // FIXME: only print types which don't meet the trait requirement
-                                let mut msg =
-                                    "required because it captures the following types: ".to_owned();
-                                for bty in tcx.coroutine_hidden_types(*def_id) {
-                                    let ty = bty.instantiate(tcx, args);
-                                    write!(msg, "`{ty}`, ").unwrap();
-                                }
-                                err.note(msg.trim_end_matches(", ").to_string())
+                            None => {
+                                err.note(msg);
                             }
-                            ty::Coroutine(def_id, _) => {
-                                let sp = tcx.def_span(def_id);
-
-                                // Special-case this to say "async block" instead of `[static coroutine]`.
-                                let kind = tcx.coroutine_kind(def_id).unwrap();
-                                err.span_note(
-                                    sp,
-                                    with_forced_trimmed_paths!(format!(
-                                        "required because it's used within this {kind:#}",
-                                    )),
-                                )
+                        },
+                        ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => {
+                            // If the previous type is async fn, this is the future generated by the body of an async function.
+                            // Avoid printing it twice (it was already printed in the `ty::Coroutine` arm below).
+                            let is_future = tcx.ty_is_opaque_future(ty);
+                            debug!(
+                                ?obligated_types,
+                                ?is_future,
+                                "note_obligation_cause_code: check for async fn"
+                            );
+                            if is_future
+                                && obligated_types.last().is_some_and(|ty| match ty.kind() {
+                                    ty::Coroutine(last_def_id, ..) => {
+                                        tcx.coroutine_is_async(*last_def_id)
+                                    }
+                                    _ => false,
+                                })
+                            {
+                                // See comment above; skip printing twice.
+                            } else {
+                                err.span_note(tcx.def_span(def_id), msg);
                             }
-                            ty::Closure(def_id, _) => err.span_note(
+                        }
+                        ty::Coroutine(def_id, _) => {
+                            let sp = tcx.def_span(def_id);
+
+                            // Special-case this to say "async block" instead of `[static coroutine]`.
+                            let kind = tcx.coroutine_kind(def_id).unwrap();
+                            err.span_note(
+                                sp,
+                                with_forced_trimmed_paths!(format!(
+                                    "required because it's used within this {kind:#}",
+                                )),
+                            );
+                        }
+                        ty::CoroutineWitness(..) => {
+                            // Skip printing coroutine-witnesses, since we'll drill into
+                            // the bad field in another derived obligation cause.
+                        }
+                        ty::Closure(def_id, _) | ty::CoroutineClosure(def_id, _) => {
+                            err.span_note(
                                 tcx.def_span(def_id),
                                 "required because it's used within this closure",
-                            ),
-                            ty::Str => err.note("`str` is considered to contain a `[u8]` slice for auto trait purposes"),
-                            _ => err.note(msg),
-                        };
-                    }
+                            );
+                        }
+                        ty::Str => {
+                            err.note("`str` is considered to contain a `[u8]` slice for auto trait purposes");
+                        }
+                        _ => {
+                            err.note(msg);
+                        }
+                    };
                 }
 
                 obligated_types.push(ty);