[WIP] Support #[rustc_on_unimplemented] on methods

compiler/rustc_attr_parsing/src/attributes/diagnostic/on_unimplemented.rs

@@ -16,14 +16,18 @@ impl OnUnimplementedParser {
         let span = cx.attr_span;
         self.span = Some(span);
 
-        if !matches!(cx.target, Target::Trait) {
-            cx.emit_lint(
-                MISPLACED_DIAGNOSTIC_ATTRIBUTES,
-                DiagnosticOnUnimplementedOnlyForTraits,
-                span,
-            );
-            return;
-        }
+        // match cx.target {
+        //     Target::Trait => {}
+        //     Target::Fn => {}
+        //     _ => {
+        //         cx.emit_lint(
+        //             MISPLACED_DIAGNOSTIC_ATTRIBUTES,
+        //             DiagnosticOnUnimplementedOnlyForTraits,
+        //             span,
+        //         );
+        //         return;
+        //     }
+        // }
 
         let Some(items) = parse_list(cx, args, mode) else { return };
 

compiler/rustc_hir/src/attrs/diagnostic.rs

@@ -105,6 +105,20 @@ impl CustomDiagnostic {
 
         self.notes.extend(di.notes.iter().map(|n| n.format(args)))
     }
+
+    pub fn merge(&mut self, other: Self) {
+        if other.message.is_some() {
+            self.message = other.message;
+        }
+        if other.label.is_some() {
+            self.label = other.label;
+        }
+        if other.parent_label.is_some() {
+            self.parent_label = other.parent_label;
+        }
+
+        self.notes.extend(other.notes);
+    }
 }
 
 /// Like [std::fmt::Arguments] this is a string that has been parsed into "pieces",
@@ -248,6 +262,7 @@ impl Filter {
             FlagOrNv::Flag(b) => options.has_flag(*b),
             FlagOrNv::NameValue(NameValue { name, value }) => {
                 let value = value.format(&options.generic_args);
+                tracing::info!(?value);
                 options.contains(*name, value)
             }
         })
@@ -454,6 +469,7 @@ impl FilterOptions {
         }
     }
     pub fn contains(&self, name: Name, value: String) -> bool {
+        tracing::info!(?name, ?value);
         match name {
             Name::SelfUpper => self.self_types.contains(&value),
             Name::FromDesugaring => self.from_desugaring.is_some_and(|ds| ds.matches(&value)),

compiler/rustc_passes/src/check_attr.rs

@@ -153,7 +153,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 Attribute::Parsed(AttributeKind::Deprecated { span: attr_span, .. }) => {
                     self.check_deprecated(hir_id, *attr_span, target)
                 }
-                Attribute::Parsed(AttributeKind::TargetFeature{ attr_span, ..}) => {
+                Attribute::Parsed(AttributeKind::TargetFeature{ attr_span, .. }) => {
                     self.check_target_feature(hir_id, *attr_span, target, attrs)
                 }
                 Attribute::Parsed(AttributeKind::RustcDumpObjectLifetimeDefaults) => {
@@ -182,28 +182,32 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 }
                 &Attribute::Parsed(AttributeKind::Sanitize { on_set, off_set, rtsan: _, span: attr_span}) => {
                     self.check_sanitize(attr_span, on_set | off_set, span, target);
-                },
+                }
                 Attribute::Parsed(AttributeKind::Link(_, attr_span)) => {
                     self.check_link(hir_id, *attr_span, span, target)
-                },
+                }
                 Attribute::Parsed(AttributeKind::MacroExport { span, .. }) => {
                     self.check_macro_export(hir_id, *span, target)
-                },
+                }
                 Attribute::Parsed(AttributeKind::RustcLegacyConstGenerics{attr_span, fn_indexes}) => {
                     self.check_rustc_legacy_const_generics(item, *attr_span, fn_indexes)
-                },
+                }
                 Attribute::Parsed(AttributeKind::Doc(attr)) => self.check_doc_attrs(attr, hir_id, target),
                 Attribute::Parsed(AttributeKind::EiiImpls(impls)) => {
                      self.check_eii_impl(impls, target)
-                },
+                }
                 Attribute::Parsed(AttributeKind::RustcMustImplementOneOf { attr_span, fn_names }) => {
                     self.check_rustc_must_implement_one_of(*attr_span, fn_names, hir_id,target)
-                },
-                Attribute::Parsed(AttributeKind::OnUnimplemented{directive}) => {self.check_diagnostic_on_unimplemented(hir_id, directive.as_deref())},
-                Attribute::Parsed(AttributeKind::OnConst{span, ..}) => {self.check_diagnostic_on_const(*span, hir_id, target, item)},
+                }
+                Attribute::Parsed(AttributeKind::OnUnimplemented { directive } ) => {
+                    self.check_diagnostic_on_unimplemented(hir_id, directive.as_deref())
+                }
+                Attribute::Parsed(AttributeKind::OnConst{ span, .. }) => {
+                    self.check_diagnostic_on_const(*span, hir_id, target, item)
+                }
                 Attribute::Parsed(AttributeKind::OnMove { directive }) => {
                     self.check_diagnostic_on_move(hir_id, directive.as_deref())
-                },
+                }
                 Attribute::Parsed(
                     // tidy-alphabetical-start
                     AttributeKind::RustcAllowIncoherentImpl(..)
@@ -521,6 +525,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         )
                     }
                 })
+            } else {
+                let node = self.tcx.hir_node(hir_id);
+                tracing::info!(?node);
             }
         }
     }

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

@@ -37,19 +37,37 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         obligation: &PredicateObligation<'tcx>,
         long_ty_path: &mut Option<PathBuf>,
     ) -> CustomDiagnostic {
+        let mut custom = CustomDiagnostic::default();
         if trait_pred.polarity() != ty::PredicatePolarity::Positive {
-            return CustomDiagnostic::default();
+            return custom;
         }
         let (filter_options, format_args) =
             self.on_unimplemented_components(trait_pred, obligation, long_ty_path);
-        if let Some(command) = find_attr!(self.tcx, trait_pred.def_id(), OnUnimplemented {directive, ..} => directive.as_deref()).flatten() {
-            command.eval(
-                Some(&filter_options),
-                &format_args,
+        if let Some(command) = find_attr!(
+            self.tcx,
+            trait_pred.def_id(),
+            OnUnimplemented { directive, .. } => directive.as_deref()
+        )
+        .flatten()
+        {
+            custom = command.eval(Some(&filter_options), &format_args)
+        }
+        if let ObligationCauseCode::FunctionArg { parent_code, .. } = obligation.cause.code()
+            && let ObligationCauseCode::WhereClauseInExpr(def_id, _, _, _) = &**parent_code
+            && let Some(command) = find_attr!(
+                self.tcx,
+                *def_id,
+                OnUnimplemented { directive, .. } => directive.as_deref()
             )
-        } else {
-            CustomDiagnostic::default()
+            .flatten()
+        {
+            tracing::info!("{:#?}", obligation.cause.code());
+            let x = command.eval(Some(&filter_options), &format_args);
+            tracing::info!(?x);
+            custom.merge(x);
         }
+        tracing::info!(?custom);
+        custom
     }
 
     pub(crate) fn on_unimplemented_components(
@@ -250,6 +268,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             .collect();
 
         let format_args = FormatArgs { this, this_sugared, generic_args, item_context };
+        tracing::info!("{filter_options:#?}");
         (filter_options, format_args)
     }
 }

library/core/src/iter/traits/collect.rs

@@ -413,6 +413,13 @@ pub trait Extend<A> {
     /// assert_eq!("abcdef", &message);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_on_unimplemented(
+        message = "can't extend `{Self}` with an iterator of `{A}` items",
+        on(
+            all(Self = "alloc::vec::Vec<&str>", A = "alloc::string::String"),
+            note = "you might have meant to extend a `Vec<String>` or pass in an `Iterator<Item = &str>`"
+        )
+    )]
     fn extend<T: IntoIterator<Item = A>>(&mut self, iter: T);
 
     /// Extends a collection with exactly one element.

tests/ui/diagnostic_namespace/on_unimplemented/do_not_accept_options_of_the_internal_rustc_attribute.stderr

@@ -144,14 +144,6 @@ LL | #[diagnostic::on_unimplemented = "Message"]
    |
    = help: only `message`, `note` and `label` are allowed as options
 
-warning: `#[diagnostic::on_unimplemented]` can only be applied to trait definitions
-  --> $DIR/do_not_accept_options_of_the_internal_rustc_attribute.rs:22:1
-   |
-LL | #[diagnostic::on_unimplemented(message = "Not allowed to apply it on a impl")]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `#[warn(misplaced_diagnostic_attributes)]` (part of `#[warn(unknown_or_malformed_diagnostic_attributes)]`) on by default
-
 error[E0277]: trait has `()` and `i32` as params
   --> $DIR/do_not_accept_options_of_the_internal_rustc_attribute.rs:53:15
    |
@@ -212,6 +204,6 @@ note: required by a bound in `takes_baz`
 LL | fn takes_baz(_: impl Baz) {}
    |                      ^^^ required by this bound in `takes_baz`
 
-error: aborting due to 3 previous errors; 19 warnings emitted
+error: aborting due to 3 previous errors; 18 warnings emitted
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/diagnostic_namespace/on_unimplemented/do_not_fail_parsing_on_invalid_options_1.stderr

@@ -16,14 +16,6 @@ LL | #[diagnostic::on_unimplemented(unsupported = "foo")]
    = help: only `message`, `note` and `label` are allowed as options
    = note: `#[warn(malformed_diagnostic_attributes)]` (part of `#[warn(unknown_or_malformed_diagnostic_attributes)]`) on by default
 
-warning: `#[diagnostic::on_unimplemented]` can only be applied to trait definitions
-  --> $DIR/do_not_fail_parsing_on_invalid_options_1.rs:7:1
-   |
-LL | #[diagnostic::on_unimplemented(message = "Baz")]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `#[warn(misplaced_diagnostic_attributes)]` (part of `#[warn(unknown_or_malformed_diagnostic_attributes)]`) on by default
-
 warning: malformed `diagnostic::on_unimplemented` attribute
   --> $DIR/do_not_fail_parsing_on_invalid_options_1.rs:11:50
    |
@@ -159,6 +151,6 @@ note: required by a bound in `take_test`
 LL | fn take_test(_: impl Test) {}
    |                      ^^^^ required by this bound in `take_test`
 
-error: aborting due to 5 previous errors; 8 warnings emitted
+error: aborting due to 5 previous errors; 7 warnings emitted
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/diagnostic_namespace/on_unimplemented/on_impl_trait.stderr

@@ -1,19 +1,13 @@
-warning: `#[diagnostic::on_unimplemented]` can only be applied to trait definitions
-  --> $DIR/on_impl_trait.rs:8:1
-   |
-LL | #[diagnostic::on_unimplemented(message = "blah", label = "blah", note = "blah")]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: `#[warn(misplaced_diagnostic_attributes)]` (part of `#[warn(unknown_or_malformed_diagnostic_attributes)]`) on by default
-
-error[E0277]: the trait bound `{integer}: Alias` is not satisfied
+error[E0277]: blah
   --> $DIR/on_impl_trait.rs:16:9
    |
 LL |     foo(&1);
-   |     --- ^^ the trait `Test` is not implemented for `{integer}`
+   |     --- ^^ blah
    |     |
    |     required by a bound introduced by this call
    |
+   = help: the trait `Test` is not implemented for `{integer}`
+   = note: blah
 help: this trait has no implementations, consider adding one
   --> $DIR/on_impl_trait.rs:6:1
    |
@@ -26,6 +20,6 @@ note: required by a bound in `foo`
 LL | fn foo<T: Alias>(v: &T) {}
    |           ^^^^^ required by this bound in `foo`
 
-error: aborting due to 1 previous error; 1 warning emitted
+error: aborting due to 1 previous error
 
 For more information about this error, try `rustc --explain E0277`.

tests/ui/trait-bounds/vec-extend-unmet-bound.rs

@@ -0,0 +1,23 @@
+fn main() {
+    let mut x = vec!["a", "b", "c"];
+    x.extend([String::from("z")]);
+    //~^ ERROR can't extend `Vec<&str>` with an iterator of `String` items
+    //~| NOTE the trait `Extend<String>` is not implemented for `Vec<&str>`
+    //~| NOTE you might have meant to extend a `Vec<String>` or pass in an `Iterator<Item = &str>`
+    //~| HELP `Vec<T, A>` implements trait `Extend<A>`
+    x.extend(String::from("z"));
+    //~^ ERROR `String` is not an iterator
+    //~| NOTE `String` is not an iterator; try calling `.chars()` or `.bytes()`
+    //~| NOTE required by a bound introduced by this call
+    //~| HELP the trait `Iterator` is not implemented for `String`
+    //~| NOTE required for `String` to implement `IntoIterator`
+    //~| NOTE required by a bound in `extend`
+    x.extend(1);
+    //~^ ERROR `{integer}` is not an iterator
+    //~| NOTE `{integer}` is not an iterator
+    //~| NOTE required by a bound introduced by this call
+    //~| HELP the trait `Iterator` is not implemented for `{integer}`
+    //~| NOTE required for `{integer}` to implement `IntoIterator`
+    //~| NOTE required by a bound in `extend`
+    //~| NOTE if you want to iterate between `start` until a value `end`
+}

tests/ui/trait-bounds/vec-extend-unmet-bound.stderr

@@ -0,0 +1,45 @@
+error[E0277]: can't extend `Vec<&str>` with an iterator of `String` items
+  --> $DIR/vec-extend-unmet-bound.rs:3:7
+   |
+LL |     x.extend([String::from("z")]);
+   |       ^^^^^^ the trait `Extend<String>` is not implemented for `Vec<&str>`
+   |
+   = note: you might have meant to extend a `Vec<String>` or pass in an `Iterator<Item = &str>`
+help: `Vec<T, A>` implements trait `Extend<A>`
+  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
+   |
+   = note: `Extend<T>`
+  ::: $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
+   |
+   = note: `Extend<&T>`
+
+error[E0277]: `String` is not an iterator
+  --> $DIR/vec-extend-unmet-bound.rs:8:14
+   |
+LL |     x.extend(String::from("z"));
+   |       ------ ^^^^^^^^^^^^^^^^^ `String` is not an iterator; try calling `.chars()` or `.bytes()`
+   |       |
+   |       required by a bound introduced by this call
+   |
+   = help: the trait `Iterator` is not implemented for `String`
+   = note: required for `String` to implement `IntoIterator`
+note: required by a bound in `extend`
+  --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
+
+error[E0277]: `{integer}` is not an iterator
+  --> $DIR/vec-extend-unmet-bound.rs:15:14
+   |
+LL |     x.extend(1);
+   |       ------ ^ `{integer}` is not an iterator
+   |       |
+   |       required by a bound introduced by this call
+   |
+   = help: the trait `Iterator` is not implemented for `{integer}`
+   = note: if you want to iterate between `start` until a value `end`, use the exclusive range syntax `start..end` or the inclusive range syntax `start..=end`
+   = note: required for `{integer}` to implement `IntoIterator`
+note: required by a bound in `extend`
+  --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0277`.