Add spans to E0277 for impl/trait type/fn obligation disparity

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

@@ -2179,19 +2179,60 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     )
                 });
             }
-            ObligationCauseCode::CompareImplMethodObligation { .. } => {
-                err.note(&format!(
-                    "the requirement `{}` appears on the impl method but not on the corresponding \
-                     trait method",
-                    predicate
-                ));
+            ObligationCauseCode::CompareImplMethodObligation {
+                item_name,
+                trait_item_def_id,
+                ..
+            } => {
+                let msg = format!(
+                    "the requirement `{}` appears on the impl method `{}` but not on the \
+                     corresponding trait method",
+                    predicate, item_name,
+                );
+                let sp = self
+                    .tcx
+                    .opt_item_name(trait_item_def_id)
+                    .map(|i| i.span)
+                    .unwrap_or_else(|| self.tcx.def_span(trait_item_def_id));
+                let mut assoc_span: MultiSpan = sp.into();
+                assoc_span.push_span_label(
+                    sp,
+                    format!("this trait method doesn't have the requirement `{}`", predicate),
+                );
+                if let Some(ident) = self
+                    .tcx
+                    .opt_associated_item(trait_item_def_id)
+                    .and_then(|i| self.tcx.opt_item_name(i.container.id()))
+                {
+                    assoc_span.push_span_label(ident.span, "in this trait".into());
+                }
+                err.span_note(assoc_span, &msg);
             }
-            ObligationCauseCode::CompareImplTypeObligation { .. } => {
-                err.note(&format!(
-                    "the requirement `{}` appears on the associated impl type but not on the \
+            ObligationCauseCode::CompareImplTypeObligation {
+                item_name, trait_item_def_id, ..
+            } => {
+                let msg = format!(
+                    "the requirement `{}` appears on the associated impl type `{}` but not on the \
                      corresponding associated trait type",
-                    predicate
-                ));
+                    predicate, item_name,
+                );
+                let sp = self.tcx.def_span(trait_item_def_id);
+                let mut assoc_span: MultiSpan = sp.into();
+                assoc_span.push_span_label(
+                    sp,
+                    format!(
+                        "this trait associated type doesn't have the requirement `{}`",
+                        predicate,
+                    ),
+                );
+                if let Some(ident) = self
+                    .tcx
+                    .opt_associated_item(trait_item_def_id)
+                    .and_then(|i| self.tcx.opt_item_name(i.container.id()))
+                {
+                    assoc_span.push_span_label(ident.span, "in this trait".into());
+                }
+                err.span_note(assoc_span, &msg);
             }
             ObligationCauseCode::CompareImplConstObligation => {
                 err.note(&format!(

src/test/ui/generic-associated-types/impl_bounds.rs

@@ -6,6 +6,7 @@ trait Foo {
     type A<'a> where Self: 'a;
     type B<'a, 'b> where 'a: 'b;
     type C where Self: Clone;
+    fn d() where Self: Clone;
 }
 
 #[derive(Copy, Clone)]
@@ -19,6 +20,8 @@ impl<T> Foo for Fooy<T> {
     //~| ERROR lifetime bound not satisfied
     type C where Self: Copy = String;
     //~^ ERROR the trait bound `T: Copy` is not satisfied
+    fn d() where Self: Copy {}
+    //~^ ERROR the trait bound `T: Copy` is not satisfied
 }
 
 fn main() {}

src/test/ui/generic-associated-types/impl_bounds.stderr

@@ -1,5 +1,5 @@
 error[E0310]: the parameter type `T` may not live long enough
-  --> $DIR/impl_bounds.rs:15:5
+  --> $DIR/impl_bounds.rs:16:5
    |
 LL |     type A<'a> where Self: 'static = (&'a ());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -8,53 +8,80 @@ LL |     type A<'a> where Self: 'static = (&'a ());
    = note: ...so that the type `Fooy<T>` will meet its required lifetime bounds
 
 error[E0478]: lifetime bound not satisfied
-  --> $DIR/impl_bounds.rs:17:5
+  --> $DIR/impl_bounds.rs:18:5
    |
 LL |     type B<'a, 'b> where 'b: 'a = (&'a(), &'b ());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: lifetime parameter instantiated with the lifetime `'b` as defined on the associated item at 17:16
-  --> $DIR/impl_bounds.rs:17:16
+note: lifetime parameter instantiated with the lifetime `'b` as defined on the associated item at 18:16
+  --> $DIR/impl_bounds.rs:18:16
    |
 LL |     type B<'a, 'b> where 'b: 'a = (&'a(), &'b ());
    |                ^^
-note: but lifetime parameter must outlive the lifetime `'a` as defined on the associated item at 17:12
-  --> $DIR/impl_bounds.rs:17:12
+note: but lifetime parameter must outlive the lifetime `'a` as defined on the associated item at 18:12
+  --> $DIR/impl_bounds.rs:18:12
    |
 LL |     type B<'a, 'b> where 'b: 'a = (&'a(), &'b ());
    |            ^^
 
 error[E0478]: lifetime bound not satisfied
-  --> $DIR/impl_bounds.rs:17:5
+  --> $DIR/impl_bounds.rs:18:5
    |
 LL |     type B<'a, 'b> where 'b: 'a = (&'a(), &'b ());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-note: lifetime parameter instantiated with the lifetime `'a` as defined on the associated item at 17:12
-  --> $DIR/impl_bounds.rs:17:12
+note: lifetime parameter instantiated with the lifetime `'a` as defined on the associated item at 18:12
+  --> $DIR/impl_bounds.rs:18:12
    |
 LL |     type B<'a, 'b> where 'b: 'a = (&'a(), &'b ());
    |            ^^
-note: but lifetime parameter must outlive the lifetime `'b` as defined on the associated item at 17:16
-  --> $DIR/impl_bounds.rs:17:16
+note: but lifetime parameter must outlive the lifetime `'b` as defined on the associated item at 18:16
+  --> $DIR/impl_bounds.rs:18:16
    |
 LL |     type B<'a, 'b> where 'b: 'a = (&'a(), &'b ());
    |                ^^
 
 error[E0277]: the trait bound `T: Copy` is not satisfied
-  --> $DIR/impl_bounds.rs:20:5
+  --> $DIR/impl_bounds.rs:21:5
    |
 LL |     type C where Self: Copy = String;
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `T`
    |
    = note: required because of the requirements on the impl of `Copy` for `Fooy<T>`
-   = note: the requirement `Fooy<T>: Copy` appears on the associated impl type but not on the corresponding associated trait type
+note: the requirement `Fooy<T>: Copy` appears on the associated impl type `C` but not on the corresponding associated trait type
+  --> $DIR/impl_bounds.rs:8:5
+   |
+LL | trait Foo {
+   |       --- in this trait
+...
+LL |     type C where Self: Clone;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ this trait associated type doesn't have the requirement `Fooy<T>: Copy`
+help: consider restricting type parameter `T`
+   |
+LL | impl<T: Copy> Foo for Fooy<T> {
+   |       ^^^^^^
+
+error[E0277]: the trait bound `T: Copy` is not satisfied
+  --> $DIR/impl_bounds.rs:23:5
+   |
+LL |     fn d() where Self: Copy {}
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `T`
+   |
+   = note: required because of the requirements on the impl of `Copy` for `Fooy<T>`
+note: the requirement `Fooy<T>: Copy` appears on the impl method `d` but not on the corresponding trait method
+  --> $DIR/impl_bounds.rs:9:8
+   |
+LL | trait Foo {
+   |       --- in this trait
+...
+LL |     fn d() where Self: Clone;
+   |        ^ this trait method doesn't have the requirement `Fooy<T>: Copy`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::marker::Copy> Foo for Fooy<T> {
    |       ^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
 Some errors have detailed explanations: E0277, E0310, E0478.
 For more information about an error, try `rustc --explain E0277`.