Auto merge of rust-lang#81149 - Aaron1011:feature/better-no-method-fo…

…und-err, r=estebank

Avoid describing a method as 'not found' when bounds are unsatisfied

Fixes rust-lang#76267

When there is a single applicable method candidate, but its trait bounds
are not satisfied, we avoid saying that the method is "not found".
Insted, we update the error message to directly mention which bounds are
not satisfied, rather than mentioning them in a note.

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -74,19 +74,18 @@ macro_rules! forward {
         });
     };
 
-    // Forward pattern for &mut self -> &mut Self, with S: Into<MultiSpan>
-    // type parameter. No obvious way to make this more generic.
+    // Forward pattern for &mut self -> &mut Self, with generic parameters.
     (
         $(#[$attrs:meta])*
-        pub fn $n:ident<S: Into<MultiSpan>>(
+        pub fn $n:ident<$($generic:ident: $bound:path),*>(
             &mut self,
             $($name:ident: $ty:ty),*
             $(,)?
         ) -> &mut Self
     ) => {
         $(#[$attrs])*
         forward_inner_docs!(concat!("See [`Diagnostic::", stringify!($n), "()`].") =>
-        pub fn $n<S: Into<MultiSpan>>(&mut self, $($name: $ty),*) -> &mut Self {
+        pub fn $n<$($generic: $bound),*>(&mut self, $($name: $ty),*) -> &mut Self {
             self.0.diagnostic.$n($($name),*);
             self
         });
@@ -398,6 +397,7 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    forward!(pub fn set_primary_message<M: Into<String>>(&mut self, msg: M) -> &mut Self);
     forward!(pub fn set_span<S: Into<MultiSpan>>(&mut self, sp: S) -> &mut Self);
     forward!(pub fn code(&mut self, s: DiagnosticId) -> &mut Self);
 

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -446,6 +446,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
                 }
 
+                let mut label_span_not_found = || {
+                    if unsatisfied_predicates.is_empty() {
+                        err.span_label(span, format!("{item_kind} not found in `{ty_str}`"));
+                    } else {
+                        err.span_label(span, format!("{item_kind} cannot be called on `{ty_str}` due to unsatisfied trait bounds"));
+                    }
+                    self.tcx.sess.trait_methods_not_found.borrow_mut().insert(orig_span);
+                };
+
                 // If the method name is the name of a field with a function or closure type,
                 // give a helping note that it has to be called as `(x.f)(...)`.
                 if let SelfSource::MethodCall(expr) = source {
@@ -501,12 +510,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let field_kind = if is_accessible { "field" } else { "private field" };
                         err.span_label(item_name.span, format!("{}, not a method", field_kind));
                     } else if lev_candidate.is_none() && static_sources.is_empty() {
-                        err.span_label(span, format!("{} not found in `{}`", item_kind, ty_str));
-                        self.tcx.sess.trait_methods_not_found.borrow_mut().insert(orig_span);
+                        label_span_not_found();
                     }
                 } else {
-                    err.span_label(span, format!("{} not found in `{}`", item_kind, ty_str));
-                    self.tcx.sess.trait_methods_not_found.borrow_mut().insert(orig_span);
+                    label_span_not_found();
                 }
 
                 if self.is_fn_ty(&rcvr_ty, span) {
@@ -721,10 +728,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             .map(|(_, path)| path)
                             .collect::<Vec<_>>()
                             .join("\n");
+                        let actual_prefix = actual.prefix_string();
+                        err.set_primary_message(&format!(
+                            "the {item_kind} `{item_name}` exists for {actual_prefix} `{ty_str}`, but its trait bounds were not satisfied"
+                        ));
                         err.note(&format!(
-                            "the method `{}` exists but the following trait bounds were not \
-                             satisfied:\n{}",
-                            item_name, bound_list
+                            "the following trait bounds were not satisfied:\n{bound_list}"
                         ));
                     }
                 }
@@ -742,7 +751,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     );
                 }
 
-                if actual.is_enum() {
+                // Don't emit a suggestion if we found an actual method
+                // that had unsatisfied trait bounds
+                if unsatisfied_predicates.is_empty() && actual.is_enum() {
                     let adt_def = actual.ty_adt_def().expect("enum is not an ADT");
                     if let Some(suggestion) = lev_distance::find_best_match_for_name(
                         &adt_def.variants.iter().map(|s| s.ident.name).collect::<Vec<_>>(),
@@ -778,17 +789,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         err.span_label(span, msg);
                     }
                 } else if let Some(lev_candidate) = lev_candidate {
-                    let def_kind = lev_candidate.kind.as_def_kind();
-                    err.span_suggestion(
-                        span,
-                        &format!(
-                            "there is {} {} with a similar name",
-                            def_kind.article(),
-                            def_kind.descr(lev_candidate.def_id),
-                        ),
-                        lev_candidate.ident.to_string(),
-                        Applicability::MaybeIncorrect,
-                    );
+                    // Don't emit a suggestion if we found an actual method
+                    // that had unsatisfied trait bounds
+                    if unsatisfied_predicates.is_empty() {
+                        let def_kind = lev_candidate.kind.as_def_kind();
+                        err.span_suggestion(
+                            span,
+                            &format!(
+                                "there is {} {} with a similar name",
+                                def_kind.article(),
+                                def_kind.descr(lev_candidate.def_id),
+                            ),
+                            lev_candidate.ident.to_string(),
+                            Applicability::MaybeIncorrect,
+                        );
+                    }
                 }
 
                 return Some(err);

compiler/rustc_typeck/src/lib.rs

@@ -60,6 +60,7 @@ This API is completely unstable and subject to change.
 #![feature(bool_to_option)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]
+#![feature(format_args_capture)]
 #![feature(in_band_lifetimes)]
 #![feature(is_sorted)]
 #![feature(nll)]

src/test/ui/associated-types/hr-associated-type-bound-2.rs

@@ -17,5 +17,5 @@ where
 
 fn main() {
     1u32.f("abc");
-    //~^ ERROR no method named `f` found for type `u32` in the current scope
+    //~^ ERROR the method
 }

src/test/ui/associated-types/hr-associated-type-bound-2.stderr

@@ -1,10 +1,10 @@
-error[E0599]: no method named `f` found for type `u32` in the current scope
+error[E0599]: the method `f` exists for type `u32`, but its trait bounds were not satisfied
   --> $DIR/hr-associated-type-bound-2.rs:19:10
    |
 LL |     1u32.f("abc");
-   |          ^ method not found in `u32`
+   |          ^ method cannot be called on `u32` due to unsatisfied trait bounds
    |
-   = note: the method `f` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `<u32 as X<'b>>::U: Clone`
            which is required by `u32: X`
 

src/test/ui/derives/derive-assoc-type-not-impl.stderr

@@ -1,4 +1,4 @@
-error[E0599]: no method named `clone` found for struct `Bar<NotClone>` in the current scope
+error[E0599]: the method `clone` exists for struct `Bar<NotClone>`, but its trait bounds were not satisfied
   --> $DIR/derive-assoc-type-not-impl.rs:18:30
    |
 LL | struct Bar<T: Foo> {
@@ -11,7 +11,7 @@ LL | struct NotClone;
    | ---------------- doesn't satisfy `NotClone: Clone`
 ...
 LL |     Bar::<NotClone> { x: 1 }.clone();
-   |                              ^^^^^ method not found in `Bar<NotClone>`
+   |                              ^^^^^ method cannot be called on `Bar<NotClone>` due to unsatisfied trait bounds
    | 
   ::: $SRC_DIR/core/src/clone.rs:LL:COL
    |
@@ -21,7 +21,7 @@ LL |     fn clone(&self) -> Self;
    |        the method is available for `Arc<Bar<NotClone>>` here
    |        the method is available for `Rc<Bar<NotClone>>` here
    |
-   = note: the method `clone` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `NotClone: Clone`
            which is required by `Bar<NotClone>: Clone`
    = help: items from traits can only be used if the trait is implemented and in scope

src/test/ui/hrtb/issue-30786.migrate.stderr

@@ -1,4 +1,4 @@
-error[E0599]: no method named `filterx` found for struct `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>` in the current scope
+error[E0599]: the method `filterx` exists for struct `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>`, but its trait bounds were not satisfied
   --> $DIR/issue-30786.rs:128:22
    |
 LL | pub struct Map<S, F> {
@@ -8,17 +8,17 @@ LL | pub struct Map<S, F> {
    | doesn't satisfy `_: StreamExt`
 ...
 LL |     let filter = map.filterx(|x: &_| true);
-   |                      ^^^^^^^ method not found in `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>`
+   |                      ^^^^^^^ method cannot be called on `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>` due to unsatisfied trait bounds
    |
-   = note: the method `filterx` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `&'a mut Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: Stream`
            which is required by `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: StreamExt`
            `&'a mut &Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: Stream`
            which is required by `&Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: StreamExt`
            `&'a mut &mut Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: Stream`
            which is required by `&mut Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: StreamExt`
 
-error[E0599]: no method named `countx` found for struct `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>` in the current scope
+error[E0599]: the method `countx` exists for struct `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>`, but its trait bounds were not satisfied
   --> $DIR/issue-30786.rs:141:24
    |
 LL | pub struct Filter<S, F> {
@@ -28,9 +28,9 @@ LL | pub struct Filter<S, F> {
    | doesn't satisfy `_: StreamExt`
 ...
 LL |     let count = filter.countx();
-   |                        ^^^^^^ method not found in `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>`
+   |                        ^^^^^^ method cannot be called on `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>` due to unsatisfied trait bounds
    |
-   = note: the method `countx` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `&'a mut Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>: Stream`
            which is required by `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>: StreamExt`
            `&'a mut &Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>: Stream`

src/test/ui/hrtb/issue-30786.nll.stderr

@@ -1,4 +1,4 @@
-error[E0599]: no method named `filterx` found for struct `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>` in the current scope
+error[E0599]: the method `filterx` exists for struct `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>`, but its trait bounds were not satisfied
   --> $DIR/issue-30786.rs:128:22
    |
 LL | pub struct Map<S, F> {
@@ -8,17 +8,17 @@ LL | pub struct Map<S, F> {
    | doesn't satisfy `_: StreamExt`
 ...
 LL |     let filter = map.filterx(|x: &_| true);
-   |                      ^^^^^^^ method not found in `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>`
+   |                      ^^^^^^^ method cannot be called on `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>` due to unsatisfied trait bounds
    |
-   = note: the method `filterx` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `&'a mut Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: Stream`
            which is required by `Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: StreamExt`
            `&'a mut &Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: Stream`
            which is required by `&Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: StreamExt`
            `&'a mut &mut Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: Stream`
            which is required by `&mut Map<Repeat, [closure@$DIR/issue-30786.rs:127:27: 127:36]>: StreamExt`
 
-error[E0599]: no method named `countx` found for struct `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>` in the current scope
+error[E0599]: the method `countx` exists for struct `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>`, but its trait bounds were not satisfied
   --> $DIR/issue-30786.rs:141:24
    |
 LL | pub struct Filter<S, F> {
@@ -28,9 +28,9 @@ LL | pub struct Filter<S, F> {
    | doesn't satisfy `_: StreamExt`
 ...
 LL |     let count = filter.countx();
-   |                        ^^^^^^ method not found in `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>`
+   |                        ^^^^^^ method cannot be called on `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>` due to unsatisfied trait bounds
    |
-   = note: the method `countx` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `&'a mut Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>: Stream`
            which is required by `Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>: StreamExt`
            `&'a mut &Filter<Map<Repeat, for<'r> fn(&'r u64) -> &'r u64 {identity::<u64>}>, [closure@$DIR/issue-30786.rs:140:30: 140:42]>: Stream`

src/test/ui/hrtb/issue-30786.rs

@@ -126,8 +126,8 @@ fn variant1() {
     // guess.
     let map = source.mapx(|x: &_| x);
     let filter = map.filterx(|x: &_| true);
-    //[migrate]~^ ERROR no method named `filterx`
-    //[nll]~^^ ERROR no method named `filterx`
+    //[migrate]~^ ERROR the method
+    //[nll]~^^ ERROR the method
 }
 
 fn variant2() {
@@ -139,8 +139,8 @@ fn variant2() {
     let map = source.mapx(identity);
     let filter = map.filterx(|x: &_| true);
     let count = filter.countx();
-    //[migrate]~^ ERROR no method named `countx`
-    //[nll]~^^ ERROR no method named `countx`
+    //[migrate]~^ ERROR the method
+    //[nll]~^^ ERROR the method
 }
 
 fn main() {}

src/test/ui/issues/issue-21596.stderr

@@ -1,12 +1,12 @@
-error[E0599]: no method named `to_string` found for raw pointer `*const u8` in the current scope
+error[E0599]: the method `to_string` exists for raw pointer `*const u8`, but its trait bounds were not satisfied
   --> $DIR/issue-21596.rs:4:22
    |
 LL |     println!("{}", z.to_string());
-   |                      ^^^^^^^^^ method not found in `*const u8`
+   |                      ^^^^^^^^^ method cannot be called on `*const u8` due to unsatisfied trait bounds
    |
    = note: try using `<*const T>::as_ref()` to get a reference to the type behind the pointer: https://doc.rust-lang.org/std/primitive.pointer.html#method.as_ref
    = note: using `<*const T>::as_ref()` on a pointer which is unaligned or points to invalid or uninitialized memory is undefined behavior
-   = note: the method `to_string` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `*const u8: std::fmt::Display`
            which is required by `*const u8: ToString`
 

src/test/ui/issues/issue-31173.rs

@@ -11,7 +11,7 @@ pub fn get_tok(it: &mut IntoIter<u8>) {
         //~^ ERROR type mismatch resolving
         //~| expected type `u8`
         //~| found reference `&_`
-        .collect(); //~ ERROR no method named `collect`
+        .collect(); //~ ERROR the method
 }
 
 fn main() {}

src/test/ui/issues/issue-31173.stderr

@@ -7,11 +7,11 @@ LL |         .cloned()
    = note:   expected type `u8`
            found reference `&_`
 
-error[E0599]: no method named `collect` found for struct `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6]>>` in the current scope
+error[E0599]: the method `collect` exists for struct `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6]>>`, but its trait bounds were not satisfied
   --> $DIR/issue-31173.rs:14:10
    |
 LL |         .collect();
-   |          ^^^^^^^ method not found in `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6]>>`
+   |          ^^^^^^^ method cannot be called on `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6]>>` due to unsatisfied trait bounds
    | 
   ::: $SRC_DIR/core/src/iter/adapters/cloned.rs:LL:COL
    |
@@ -23,7 +23,7 @@ LL | pub struct Cloned<I> {
 LL | pub struct TakeWhile<I, P> {
    | -------------------------- doesn't satisfy `<_ as Iterator>::Item = &_`
    |
-   = note: the method `collect` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6]> as Iterator>::Item = &_`
            which is required by `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6]>>: Iterator`
            `Cloned<TakeWhile<&mut std::vec::IntoIter<u8>, [closure@$DIR/issue-31173.rs:6:39: 9:6]>>: Iterator`

src/test/ui/issues/issue-35677.rs

@@ -2,7 +2,7 @@ use std::collections::HashSet;
 
 fn is_subset<T>(this: &HashSet<T>, other: &HashSet<T>) -> bool {
     this.is_subset(other)
-    //~^ ERROR no method named
+    //~^ ERROR the method
 }
 
 fn main() {}

src/test/ui/issues/issue-35677.stderr

@@ -1,10 +1,10 @@
-error[E0599]: no method named `is_subset` found for reference `&HashSet<T>` in the current scope
+error[E0599]: the method `is_subset` exists for reference `&HashSet<T>`, but its trait bounds were not satisfied
   --> $DIR/issue-35677.rs:4:10
    |
 LL |     this.is_subset(other)
-   |          ^^^^^^^^^ method not found in `&HashSet<T>`
+   |          ^^^^^^^^^ method cannot be called on `&HashSet<T>` due to unsatisfied trait bounds
    |
-   = note: the method `is_subset` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `T: Eq`
            `T: Hash`
 

src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref.rs

@@ -1,4 +1,4 @@
 fn main() {
     let _result = &Some(42).as_deref();
-//~^ ERROR no method named `as_deref` found for enum `Option<{integer}>`
+//~^ ERROR the method
 }

src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref.stderr

@@ -1,10 +1,10 @@
-error[E0599]: no method named `as_deref` found for enum `Option<{integer}>` in the current scope
+error[E0599]: the method `as_deref` exists for enum `Option<{integer}>`, but its trait bounds were not satisfied
   --> $DIR/option-as_deref.rs:2:29
    |
 LL |     let _result = &Some(42).as_deref();
-   |                             ^^^^^^^^ help: there is an associated function with a similar name: `as_ref`
+   |                             ^^^^^^^^
    |
-   = note: the method `as_deref` exists but the following trait bounds were not satisfied:
+   = note: the following trait bounds were not satisfied:
            `{integer}: Deref`
            `<{integer} as Deref>::Target = _`
 

src/test/ui/issues/issue-50264-inner-deref-trait/option-as_deref_mut.rs

@@ -1,4 +1,4 @@
 fn main() {
     let _result = &mut Some(42).as_deref_mut();
-//~^ ERROR no method named `as_deref_mut` found for enum `Option<{integer}>`
+//~^ ERROR the method
 }