Rollup merge of rust-lang#83689 - estebank:cool-bears-hot-tip, r=davi…

…dtwco Add more info for common trait resolution and async/await errors * Suggest `Pin::new`/`Box::new`/`Arc::new`/`Box::pin` in more cases * Point at `impl` and type defs introducing requirements on E0277
Dylan-DPC-zz · Mar 31, 2021 · d79d6b3 · d79d6b3
2 parents 4fdac23 + 06b82ab
commit d79d6b3
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diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -2067,7 +2067,14 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
                 // Don't print the tuple of capture types
                 if !is_upvar_tys_infer_tuple {
-                    err.note(&format!("required because it appears within the type `{}`", ty));
+                    let msg = format!("required because it appears within the type `{}`", ty);
+                    match ty.kind() {
+                        ty::Adt(def, _) => match self.tcx.opt_item_name(def.did) {
+                            Some(ident) => err.span_note(ident.span, &msg),
+                            None => err.note(&msg),
+                        },
+                        _ => err.note(&msg),
+                    };
                 }
 
                 obligated_types.push(ty);
@@ -2089,11 +2096,36 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
             ObligationCauseCode::ImplDerivedObligation(ref data) => {
                 let mut parent_trait_ref = self.resolve_vars_if_possible(data.parent_trait_ref);
                 let parent_def_id = parent_trait_ref.def_id();
-                err.note(&format!(
+                let msg = format!(
                     "required because of the requirements on the impl of `{}` for `{}`",
                     parent_trait_ref.print_only_trait_path(),
                     parent_trait_ref.skip_binder().self_ty()
-                ));
+                );
+                let mut candidates = vec![];
+                self.tcx.for_each_relevant_impl(
+                    parent_def_id,
+                    parent_trait_ref.self_ty().skip_binder(),
+                    |impl_def_id| {
+                        candidates.push(impl_def_id);
+                    },
+                );
+                match &candidates[..] {
+                    [def_id] => match self.tcx.hir().get_if_local(*def_id) {
+                        Some(Node::Item(hir::Item {
+                            kind: hir::ItemKind::Impl(hir::Impl { of_trait, self_ty, .. }),
+                            ..
+                        })) => {
+                            let mut spans = Vec::with_capacity(2);
+                            if let Some(trait_ref) = of_trait {
+                                spans.push(trait_ref.path.span);
+                            }
+                            spans.push(self_ty.span);
+                            err.span_note(spans, &msg)
+                        }
+                        _ => err.note(&msg),
+                    },
+                    _ => err.note(&msg),
+                };
 
                 let mut parent_predicate = parent_trait_ref.without_const().to_predicate(tcx);
                 let mut data = data;

diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -987,59 +987,60 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) {
         let mut alt_rcvr_sugg = false;
         if let SelfSource::MethodCall(rcvr) = source {
-            info!(?span, ?item_name, ?rcvr_ty, ?rcvr);
-            if let ty::Adt(..) = rcvr_ty.kind() {
-                // Try alternative arbitrary self types that could fulfill this call.
-                // FIXME: probe for all types that *could* be arbitrary self-types, not
-                // just this list.
-                for (rcvr_ty, post) in &[
-                    (rcvr_ty, ""),
-                    (self.tcx.mk_mut_ref(&ty::ReErased, rcvr_ty), "&mut "),
-                    (self.tcx.mk_imm_ref(&ty::ReErased, rcvr_ty), "&"),
+            debug!(?span, ?item_name, ?rcvr_ty, ?rcvr);
+            // Try alternative arbitrary self types that could fulfill this call.
+            // FIXME: probe for all types that *could* be arbitrary self-types, not
+            // just this list.
+            for (rcvr_ty, post) in &[
+                (rcvr_ty, ""),
+                (self.tcx.mk_mut_ref(&ty::ReErased, rcvr_ty), "&mut "),
+                (self.tcx.mk_imm_ref(&ty::ReErased, rcvr_ty), "&"),
+            ] {
+                for (rcvr_ty, pre) in &[
+                    (self.tcx.mk_lang_item(rcvr_ty, LangItem::OwnedBox), "Box::new"),
+                    (self.tcx.mk_lang_item(rcvr_ty, LangItem::Pin), "Pin::new"),
+                    (self.tcx.mk_diagnostic_item(rcvr_ty, sym::Arc), "Arc::new"),
+                    (self.tcx.mk_diagnostic_item(rcvr_ty, sym::Rc), "Rc::new"),
                 ] {
-                    for (rcvr_ty, pre) in &[
-                        (self.tcx.mk_lang_item(rcvr_ty, LangItem::OwnedBox), "Box::new"),
-                        (self.tcx.mk_lang_item(rcvr_ty, LangItem::Pin), "Pin::new"),
-                        (self.tcx.mk_diagnostic_item(rcvr_ty, sym::Arc), "Arc::new"),
-                        (self.tcx.mk_diagnostic_item(rcvr_ty, sym::Rc), "Rc::new"),
-                    ] {
-                        if let Some(new_rcvr_t) = *rcvr_ty {
-                            if let Ok(pick) = self.lookup_probe(
-                                span,
-                                item_name,
-                                new_rcvr_t,
-                                rcvr,
-                                crate::check::method::probe::ProbeScope::AllTraits,
-                            ) {
-                                debug!("try_alt_rcvr: pick candidate {:?}", pick);
-                                // Make sure the method is defined for the *actual* receiver:
-                                // we don't want to treat `Box<Self>` as a receiver if
-                                // it only works because of an autoderef to `&self`
-                                if pick.autoderefs == 0
-                                    // We don't want to suggest a container type when the missing method is
-                                    // `.clone()`, otherwise we'd suggest `Arc::new(foo).clone()`, which is
-                                    // far from what the user really wants.
-                                    && Some(pick.item.container.id()) != self.tcx.lang_items().clone_trait()
-                                {
-                                    err.span_label(
-                                        pick.item.ident.span,
-                                        &format!(
-                                            "the method is available for `{}` here",
-                                            new_rcvr_t
-                                        ),
-                                    );
-                                    err.multipart_suggestion(
-                                        "consider wrapping the receiver expression with the \
-                                         appropriate type",
-                                        vec![
-                                            (rcvr.span.shrink_to_lo(), format!("{}({}", pre, post)),
-                                            (rcvr.span.shrink_to_hi(), ")".to_string()),
-                                        ],
-                                        Applicability::MaybeIncorrect,
-                                    );
-                                    // We don't care about the other suggestions.
-                                    alt_rcvr_sugg = true;
-                                }
+                    if let Some(new_rcvr_t) = *rcvr_ty {
+                        if let Ok(pick) = self.lookup_probe(
+                            span,
+                            item_name,
+                            new_rcvr_t,
+                            rcvr,
+                            crate::check::method::probe::ProbeScope::AllTraits,
+                        ) {
+                            debug!("try_alt_rcvr: pick candidate {:?}", pick);
+                            let did = Some(pick.item.container.id());
+                            // We don't want to suggest a container type when the missing
+                            // method is `.clone()` or `.deref()` otherwise we'd suggest
+                            // `Arc::new(foo).clone()`, which is far from what the user wants.
+                            let skip = [
+                                self.tcx.lang_items().clone_trait(),
+                                self.tcx.lang_items().deref_trait(),
+                                self.tcx.lang_items().deref_mut_trait(),
+                                self.tcx.lang_items().drop_trait(),
+                            ]
+                            .contains(&did);
+                            // Make sure the method is defined for the *actual* receiver: we don't
+                            // want to treat `Box<Self>` as a receiver if it only works because of
+                            // an autoderef to `&self`
+                            if pick.autoderefs == 0 && !skip {
+                                err.span_label(
+                                    pick.item.ident.span,
+                                    &format!("the method is available for `{}` here", new_rcvr_t),
+                                );
+                                err.multipart_suggestion(
+                                    "consider wrapping the receiver expression with the \
+                                        appropriate type",
+                                    vec![
+                                        (rcvr.span.shrink_to_lo(), format!("{}({}", pre, post)),
+                                        (rcvr.span.shrink_to_hi(), ")".to_string()),
+                                    ],
+                                    Applicability::MaybeIncorrect,
+                                );
+                                // We don't care about the other suggestions.
+                                alt_rcvr_sugg = true;
                             }
                         }
                     }

diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
@@ -765,7 +765,7 @@ unsafe impl<T: ?Sized> Freeze for &mut T {}
 /// [`pin` module]: crate::pin
 #[stable(feature = "pin", since = "1.33.0")]
 #[rustc_on_unimplemented(
-    on(_Self = "std::future::Future", note = "consider using `Box::pin`",),
+    note = "consider using `Box::pin`",
     message = "`{Self}` cannot be unpinned"
 )]
 #[lang = "unpin"]

diff --git a/src/test/ui/associated-types/impl-wf-cycle-1.stderr b/src/test/ui/associated-types/impl-wf-cycle-1.stderr
@@ -10,7 +10,11 @@ LL | |
 LL | | }
    | |_^
    |
-   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+note: required because of the requirements on the impl of `Grault` for `(T,)`
+  --> $DIR/impl-wf-cycle-1.rs:15:17
+   |
+LL | impl<T: Grault> Grault for (T,)
+   |                 ^^^^^^     ^^^^
    = note: 1 redundant requirements hidden
    = note: required because of the requirements on the impl of `Grault` for `(T,)`
 
@@ -20,7 +24,11 @@ error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
 LL |     type A = ();
    |     ^^^^^^^^^^^^
    |
-   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+note: required because of the requirements on the impl of `Grault` for `(T,)`
+  --> $DIR/impl-wf-cycle-1.rs:15:17
+   |
+LL | impl<T: Grault> Grault for (T,)
+   |                 ^^^^^^     ^^^^
    = note: 1 redundant requirements hidden
    = note: required because of the requirements on the impl of `Grault` for `(T,)`
 
@@ -30,7 +38,11 @@ error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
 LL |     type B = bool;
    |     ^^^^^^^^^^^^^^
    |
-   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+note: required because of the requirements on the impl of `Grault` for `(T,)`
+  --> $DIR/impl-wf-cycle-1.rs:15:17
+   |
+LL | impl<T: Grault> Grault for (T,)
+   |                 ^^^^^^     ^^^^
    = note: 1 redundant requirements hidden
    = note: required because of the requirements on the impl of `Grault` for `(T,)`
 

diff --git a/src/test/ui/associated-types/impl-wf-cycle-2.stderr b/src/test/ui/associated-types/impl-wf-cycle-2.stderr
@@ -10,15 +10,23 @@ LL | |
 LL | | }
    | |_^
    |
-   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+note: required because of the requirements on the impl of `Grault` for `(T,)`
+  --> $DIR/impl-wf-cycle-2.rs:7:17
+   |
+LL | impl<T: Grault> Grault for (T,)
+   |                 ^^^^^^     ^^^^
 
 error[E0275]: overflow evaluating the requirement `<(T,) as Grault>::A == _`
   --> $DIR/impl-wf-cycle-2.rs:11:5
    |
 LL |     type A = ();
    |     ^^^^^^^^^^^^
    |
-   = note: required because of the requirements on the impl of `Grault` for `(T,)`
+note: required because of the requirements on the impl of `Grault` for `(T,)`
+  --> $DIR/impl-wf-cycle-2.rs:7:17
+   |
+LL | impl<T: Grault> Grault for (T,)
+   |                 ^^^^^^     ^^^^
 
 error: aborting due to 2 previous errors
 

diff --git a/src/test/ui/associated-types/issue-44153.stderr b/src/test/ui/associated-types/issue-44153.stderr
@@ -7,7 +7,11 @@ LL |     fn visit() {}
 LL |     <() as Visit>::visit();
    |     ^^^^^^^^^^^^^^^^^^^^ expected `()`, found `&()`
    |
-   = note: required because of the requirements on the impl of `Visit` for `()`
+note: required because of the requirements on the impl of `Visit` for `()`
+  --> $DIR/issue-44153.rs:13:10
+   |
+LL | impl<'a> Visit for () where
+   |          ^^^^^     ^^
 
 error: aborting due to previous error
 

diff --git a/src/test/ui/associated-types/issue-65774-1.stderr b/src/test/ui/associated-types/issue-65774-1.stderr
@@ -13,7 +13,11 @@ error[E0277]: the trait bound `T: MyDisplay` is not satisfied
 LL |         let closure = |config: &mut <S as MPU>::MpuConfig| writer.my_write(&config);
    |                                                                            ^^^^^^^ the trait `MyDisplay` is not implemented for `T`
    |
-   = note: required because of the requirements on the impl of `MyDisplay` for `&mut T`
+note: required because of the requirements on the impl of `MyDisplay` for `&mut T`
+  --> $DIR/issue-65774-1.rs:5:24
+   |
+LL | impl<'a, T: MyDisplay> MyDisplay for &'a mut T { }
+   |                        ^^^^^^^^^     ^^^^^^^^^
    = note: required for the cast to the object type `dyn MyDisplay`
 
 error: aborting due to 2 previous errors

diff --git a/src/test/ui/async-await/issue-72590-type-error-sized.stderr b/src/test/ui/async-await/issue-72590-type-error-sized.stderr
@@ -17,7 +17,11 @@ LL |     async fn frob(self) {}
    |                   ^^^^ doesn't have a size known at compile-time
    |
    = help: within `Foo`, the trait `Sized` is not implemented for `str`
-   = note: required because it appears within the type `Foo`
+note: required because it appears within the type `Foo`
+  --> $DIR/issue-72590-type-error-sized.rs:5:8
+   |
+LL | struct Foo {
+   |        ^^^
    = help: unsized fn params are gated as an unstable feature
 help: function arguments must have a statically known size, borrowed types always have a known size
    |

diff --git a/src/test/ui/async-await/pin-needed-to-poll-2.rs b/src/test/ui/async-await/pin-needed-to-poll-2.rs
@@ -0,0 +1,48 @@
+use std::{
+    future::Future,
+    pin::Pin,
+    marker::Unpin,
+    task::{Context, Poll},
+};
+
+struct Sleep(std::marker::PhantomPinned);
+
+impl Future for Sleep {
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Ready(())
+    }
+}
+
+impl Drop for Sleep {
+    fn drop(&mut self) {}
+}
+
+fn sleep() -> Sleep {
+    Sleep(std::marker::PhantomPinned)
+}
+
+
+struct MyFuture {
+    sleep: Sleep,
+}
+
+impl MyFuture {
+    fn new() -> Self {
+        Self {
+            sleep: sleep(),
+        }
+    }
+}
+
+impl Future for MyFuture {
+    type Output = ();
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Pin::new(&mut self.sleep).poll(cx)
+        //~^ ERROR `PhantomPinned` cannot be unpinned
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/async-await/pin-needed-to-poll-2.stderr b/src/test/ui/async-await/pin-needed-to-poll-2.stderr
@@ -0,0 +1,17 @@
+error[E0277]: `PhantomPinned` cannot be unpinned
+  --> $DIR/pin-needed-to-poll-2.rs:43:9
+   |
+LL |         Pin::new(&mut self.sleep).poll(cx)
+   |         ^^^^^^^^ within `Sleep`, the trait `Unpin` is not implemented for `PhantomPinned`
+   |
+   = note: consider using `Box::pin`
+note: required because it appears within the type `Sleep`
+  --> $DIR/pin-needed-to-poll-2.rs:8:8
+   |
+LL | struct Sleep(std::marker::PhantomPinned);
+   |        ^^^^^
+   = note: required by `Pin::<P>::new`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/src/test/ui/block-result/issue-22645.stderr b/src/test/ui/block-result/issue-22645.stderr
@@ -6,7 +6,11 @@ LL |   b + 3
    |
    = help: the following implementations were found:
              <f64 as Scalar>
-   = note: required because of the requirements on the impl of `Add<{integer}>` for `Bob`
+note: required because of the requirements on the impl of `Add<{integer}>` for `Bob`
+  --> $DIR/issue-22645.rs:8:19
+   |
+LL | impl<RHS: Scalar> Add <RHS> for Bob {
+   |                   ^^^^^^^^^     ^^^
 
 error[E0308]: mismatched types
   --> $DIR/issue-22645.rs:15:3

diff --git a/src/test/ui/builtin-superkinds/builtin-superkinds-in-metadata.stderr b/src/test/ui/builtin-superkinds/builtin-superkinds-in-metadata.stderr
@@ -9,7 +9,11 @@ LL | impl <T:Sync+'static> RequiresRequiresShareAndSend for X<T> { }
 LL | pub trait RequiresRequiresShareAndSend : RequiresShare + Send { }
    |                                                          ---- required by this bound in `RequiresRequiresShareAndSend`
    |
-   = note: required because it appears within the type `X<T>`
+note: required because it appears within the type `X<T>`
+  --> $DIR/builtin-superkinds-in-metadata.rs:9:8
+   |
+LL | struct X<T>(T);
+   |        ^
 help: consider further restricting this bound
    |
 LL | impl <T:Sync+'static + Send> RequiresRequiresShareAndSend for X<T> { }