Do not mention associated items when they introduce an obligation

Author: estebank

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

@@ -1958,15 +1958,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     region, object_ty,
                 ));
             }
-            ObligationCauseCode::ItemObligation(item_def_id) => {
-                let item_name = tcx.def_path_str(item_def_id);
-                let msg = format!("required by `{}`", item_name);
-                let sp = tcx
-                    .hir()
-                    .span_if_local(item_def_id)
-                    .unwrap_or_else(|| tcx.def_span(item_def_id));
-                let sp = tcx.sess.source_map().guess_head_span(sp);
-                err.span_note(sp, &msg);
+            ObligationCauseCode::ItemObligation(_item_def_id) => {
+                // We hold the `DefId` of the item introducing the obligation, but displaying it
+                // doesn't add user usable information. It always point at an associated item.
             }
             ObligationCauseCode::BindingObligation(item_def_id, span) => {
                 let item_name = tcx.def_path_str(item_def_id);

compiler/rustc_typeck/src/check/compare_method.rs

@@ -232,7 +232,6 @@ fn compare_predicate_entailment<'tcx>(
                 span,
                 impl_m_hir_id,
                 ObligationCauseCode::CompareImplMethodObligation {
-                    item_name: impl_m.ident.name,
                     impl_item_def_id: impl_m.def_id,
                     trait_item_def_id: trait_m.def_id,
                 },

src/test/ui/allocator/not-an-allocator.stderr

@@ -6,11 +6,6 @@ LL | #[global_allocator]
 LL | static A: usize = 0;
    | ^^^^^^^^^^^^^^^^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
-note: required by `std::alloc::GlobalAlloc::alloc`
-  --> $SRC_DIR/core/src/alloc/global.rs:LL:COL
-   |
-LL |     unsafe fn alloc(&self, layout: Layout) -> *mut u8;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
@@ -21,11 +16,6 @@ LL | #[global_allocator]
 LL | static A: usize = 0;
    | ^^^^^^^^^^^^^^^^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
-note: required by `std::alloc::GlobalAlloc::dealloc`
-  --> $SRC_DIR/core/src/alloc/global.rs:LL:COL
-   |
-LL |     unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
@@ -36,11 +26,6 @@ LL | #[global_allocator]
 LL | static A: usize = 0;
    | ^^^^^^^^^^^^^^^^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
-note: required by `std::alloc::GlobalAlloc::realloc`
-  --> $SRC_DIR/core/src/alloc/global.rs:LL:COL
-   |
-LL |     unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `usize: GlobalAlloc` is not satisfied
@@ -51,11 +36,6 @@ LL | #[global_allocator]
 LL | static A: usize = 0;
    | ^^^^^^^^^^^^^^^^^^^^ the trait `GlobalAlloc` is not implemented for `usize`
    |
-note: required by `std::alloc::GlobalAlloc::alloc_zeroed`
-  --> $SRC_DIR/core/src/alloc/global.rs:LL:COL
-   |
-LL |     unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: this error originates in the attribute macro `global_allocator` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 4 previous errors

src/test/ui/associated-consts/associated-const-array-len.stderr

@@ -3,12 +3,6 @@ error[E0277]: the trait bound `i32: Foo` is not satisfied
    |
 LL | const X: [i32; <i32 as Foo>::ID] = [0, 1, 2];
    |                ^^^^^^^^^^^^^^^^ the trait `Foo` is not implemented for `i32`
-   |
-note: required by `Foo::ID`
-  --> $DIR/associated-const-array-len.rs:2:5
-   |
-LL |     const ID: usize;
-   |     ^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/associated-consts/issue-63496.stderr

@@ -9,11 +9,6 @@ LL |     fn f() -> ([u8; A::C], [u8; A::C]);
    |
    = note: cannot satisfy `_: A`
    = note: associated constants cannot be accessed directly on a `trait`, they can only be accessed through a specific `impl`
-note: required by `A::C`
-  --> $DIR/issue-63496.rs:2:5
-   |
-LL |     const C: usize;
-   |     ^^^^^^^^^^^^^^^
 
 error[E0283]: type annotations needed
   --> $DIR/issue-63496.rs:4:33
@@ -26,11 +21,6 @@ LL |     fn f() -> ([u8; A::C], [u8; A::C]);
    |
    = note: cannot satisfy `_: A`
    = note: associated constants cannot be accessed directly on a `trait`, they can only be accessed through a specific `impl`
-note: required by `A::C`
-  --> $DIR/issue-63496.rs:2:5
-   |
-LL |     const C: usize;
-   |     ^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 

src/test/ui/associated-item/issue-48027.stderr

@@ -9,11 +9,6 @@ LL |     fn return_n(&self) -> [u8; Bar::X];
    |
    = note: cannot satisfy `_: Bar`
    = note: associated constants cannot be accessed directly on a `trait`, they can only be accessed through a specific `impl`
-note: required by `Bar::X`
-  --> $DIR/issue-48027.rs:2:5
-   |
-LL |     const X: usize;
-   |     ^^^^^^^^^^^^^^^
 
 error[E0038]: the trait `Bar` cannot be made into an object
   --> $DIR/issue-48027.rs:6:6

src/test/ui/associated-types/associated-types-bound-failure.stderr

@@ -6,11 +6,6 @@ LL |     ToInt::to_int(&g.get())
    |     |
    |     required by a bound introduced by this call
    |
-note: required by `ToInt::to_int`
-  --> $DIR/associated-types-bound-failure.rs:6:5
-   |
-LL |     fn to_int(&self) -> isize;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
 help: consider further restricting the associated type
    |
 LL |     where G : GetToInt, <G as GetToInt>::R: ToInt

src/test/ui/associated-types/associated-types-unconstrained.stderr

@@ -5,11 +5,6 @@ LL |     let x: isize = Foo::bar();
    |                    ^^^^^^^^ cannot infer type
    |
    = note: cannot satisfy `_: Foo`
-note: required by `Foo::bar`
-  --> $DIR/associated-types-unconstrained.rs:5:5
-   |
-LL |     fn bar() -> isize;
-   |     ^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/associated-types/issue-44153.stderr

@@ -9,11 +9,6 @@ note: required because of the requirements on the impl of `Visit` for `()`
    |
 LL | impl<'a> Visit for () where
    |          ^^^^^     ^^
-note: required by `Visit::visit`
-  --> $DIR/issue-44153.rs:6:5
-   |
-LL |     fn visit() {}
-   |     ^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/async-await/issue-61076.rs

@@ -42,12 +42,10 @@ async fn bar() -> Result<(), ()> {
     foo()?; //~ ERROR the `?` operator can only be applied to values that implement `Try`
     //~^ NOTE the `?` operator cannot be applied to type `impl Future<Output = Result<(), ()>>`
     //~| HELP the trait `Try` is not implemented for `impl Future<Output = Result<(), ()>>`
-    //~| NOTE required by `branch`
     //~| HELP consider `await`ing on the `Future`
     //~| NOTE in this expansion of desugaring of operator `?`
     //~| NOTE in this expansion of desugaring of operator `?`
     //~| NOTE in this expansion of desugaring of operator `?`
-    //~| NOTE in this expansion of desugaring of operator `?`
     Ok(())
 }
 
@@ -67,12 +65,10 @@ async fn baz() -> Result<(), ()> {
     t?; //~ ERROR the `?` operator can only be applied to values that implement `Try`
     //~^ NOTE the `?` operator cannot be applied to type `T`
     //~| HELP the trait `Try` is not implemented for `T`
-    //~| NOTE required by `branch`
     //~| HELP consider `await`ing on the `Future`
     //~| NOTE in this expansion of desugaring of operator `?`
     //~| NOTE in this expansion of desugaring of operator `?`
     //~| NOTE in this expansion of desugaring of operator `?`
-    //~| NOTE in this expansion of desugaring of operator `?`
 
 
     let _: i32 = tuple().0; //~ ERROR no field `0`