Do not emit note for projected derived obligations

Author: estebank

src/librustc_middle/traits/mod.rs

@@ -191,6 +191,8 @@ pub enum ObligationCauseCode<'tcx> {
 
     ImplDerivedObligation(DerivedObligationCause<'tcx>),
 
+    DerivedObligation(DerivedObligationCause<'tcx>),
+
     /// Error derived when matching traits/impls; see ObligationCause for more details
     CompareImplMethodObligation {
         item_name: ast::Name,
@@ -263,7 +265,10 @@ impl ObligationCauseCode<'_> {
     // Return the base obligation, ignoring derived obligations.
     pub fn peel_derives(&self) -> &Self {
         let mut base_cause = self;
-        while let BuiltinDerivedObligation(cause) | ImplDerivedObligation(cause) = base_cause {
+        while let BuiltinDerivedObligation(cause)
+        | ImplDerivedObligation(cause)
+        | DerivedObligation(cause) = base_cause
+        {
             base_cause = &cause.parent_code;
         }
         base_cause

src/librustc_middle/traits/structural_impls.rs

@@ -456,6 +456,7 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
             super::ImplDerivedObligation(ref cause) => {
                 tcx.lift(cause).map(super::ImplDerivedObligation)
             }
+            super::DerivedObligation(ref cause) => tcx.lift(cause).map(super::DerivedObligation),
             super::CompareImplMethodObligation {
                 item_name,
                 impl_item_def_id,

src/librustc_trait_selection/traits/error_reporting/on_unimplemented.rs

@@ -134,7 +134,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
 
         match obligation.cause.code {
             ObligationCauseCode::BuiltinDerivedObligation(..)
-            | ObligationCauseCode::ImplDerivedObligation(..) => {}
+            | ObligationCauseCode::ImplDerivedObligation(..)
+            | ObligationCauseCode::DerivedObligation(..) => {}
             _ => {
                 // this is a "direct", user-specified, rather than derived,
                 // obligation.

src/librustc_trait_selection/traits/error_reporting/suggestions.rs

@@ -1135,7 +1135,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         while let Some(code) = next_code {
             debug!("maybe_note_obligation_cause_for_async_await: code={:?}", code);
             match code {
-                ObligationCauseCode::BuiltinDerivedObligation(derived_obligation)
+                ObligationCauseCode::DerivedObligation(derived_obligation)
+                | ObligationCauseCode::BuiltinDerivedObligation(derived_obligation)
                 | ObligationCauseCode::ImplDerivedObligation(derived_obligation) => {
                     let ty = derived_obligation.parent_trait_ref.self_ty();
                     debug!(
@@ -1661,6 +1662,16 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                     obligated_types,
                 );
             }
+            ObligationCauseCode::DerivedObligation(ref data) => {
+                let parent_trait_ref = self.resolve_vars_if_possible(&data.parent_trait_ref);
+                let parent_predicate = parent_trait_ref.without_const().to_predicate();
+                self.note_obligation_cause_code(
+                    err,
+                    &parent_predicate,
+                    &data.parent_code,
+                    obligated_types,
+                );
+            }
             ObligationCauseCode::CompareImplMethodObligation { .. } => {
                 err.note(&format!(
                     "the requirement `{}` appears on the impl method \

src/librustc_trait_selection/traits/wf.rs

@@ -243,7 +243,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                         parent_trait_ref,
                         parent_code: Rc::new(obligation.cause.code.clone()),
                     };
-                    cause.code = traits::ObligationCauseCode::ImplDerivedObligation(derived_cause);
+                    cause.code = traits::ObligationCauseCode::DerivedObligation(derived_cause);
                 }
                 extend_cause_with_original_assoc_item_obligation(
                     tcx,

src/test/ui/associated-type-bounds/bad-bounds-on-assoc-in-trait.stderr

@@ -11,7 +11,6 @@ LL | impl Case1 for S1 {
    |      ^^^^^ `<L1 as Lam<&'a u8>>::App` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
    |
    = help: the trait `for<'a> std::fmt::Debug` is not implemented for `<L1 as Lam<&'a u8>>::App`
-   = note: required because of the requirements on the impl of `for<'a> std::fmt::Debug` for `<<<<S1 as Case1>::C as std::iter::Iterator>::Item as std::iter::Iterator>::Item as Lam<&'a u8>>::App`
 
 error[E0277]: `<<T as Case1>::C as std::iter::Iterator>::Item` is not an iterator
   --> $DIR/bad-bounds-on-assoc-in-trait.rs:36:20

src/test/ui/associated-types/defaults-unsound-62211-1.stderr

@@ -53,7 +53,6 @@ LL | impl<T> UncheckedCopy for T {}
    |
    = help: the trait `std::fmt::Display` is not implemented for `T`
    = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
-   = note: required because of the requirements on the impl of `std::fmt::Display` for `<T as UncheckedCopy>::Output`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::fmt::Display> UncheckedCopy for T {}
@@ -71,7 +70,6 @@ LL |     + Deref<Target = str>
 LL | impl<T> UncheckedCopy for T {}
    |         ^^^^^^^^^^^^^ the trait `std::ops::Deref` is not implemented for `T`
    |
-   = note: required because of the requirements on the impl of `std::ops::Deref` for `<T as UncheckedCopy>::Output`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::ops::Deref> UncheckedCopy for T {}
@@ -90,7 +88,6 @@ LL | impl<T> UncheckedCopy for T {}
    |         ^^^^^^^^^^^^^ no implementation for `T += &'static str`
    |
    = help: the trait `std::ops::AddAssign<&'static str>` is not implemented for `T`
-   = note: required because of the requirements on the impl of `std::ops::AddAssign<&'static str>` for `<T as UncheckedCopy>::Output`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::ops::AddAssign<&'static str>> UncheckedCopy for T {}
@@ -108,7 +105,6 @@ LL |     type Output: Copy
 LL | impl<T> UncheckedCopy for T {}
    |         ^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `T`
    |
-   = note: required because of the requirements on the impl of `std::marker::Copy` for `<T as UncheckedCopy>::Output`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::marker::Copy> UncheckedCopy for T {}

src/test/ui/associated-types/defaults-unsound-62211-2.stderr

@@ -53,7 +53,6 @@ LL | impl<T> UncheckedCopy for T {}
    |
    = help: the trait `std::fmt::Display` is not implemented for `T`
    = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
-   = note: required because of the requirements on the impl of `std::fmt::Display` for `<T as UncheckedCopy>::Output`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::fmt::Display> UncheckedCopy for T {}
@@ -71,7 +70,6 @@ LL |     + Deref<Target = str>
 LL | impl<T> UncheckedCopy for T {}
    |         ^^^^^^^^^^^^^ the trait `std::ops::Deref` is not implemented for `T`
    |
-   = note: required because of the requirements on the impl of `std::ops::Deref` for `<T as UncheckedCopy>::Output`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::ops::Deref> UncheckedCopy for T {}
@@ -90,7 +88,6 @@ LL | impl<T> UncheckedCopy for T {}
    |         ^^^^^^^^^^^^^ no implementation for `T += &'static str`
    |
    = help: the trait `std::ops::AddAssign<&'static str>` is not implemented for `T`
-   = note: required because of the requirements on the impl of `std::ops::AddAssign<&'static str>` for `<T as UncheckedCopy>::Output`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::ops::AddAssign<&'static str>> UncheckedCopy for T {}
@@ -108,7 +105,6 @@ LL |     type Output: Copy
 LL | impl<T> UncheckedCopy for T {}
    |         ^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `T`
    |
-   = note: required because of the requirements on the impl of `std::marker::Copy` for `<T as UncheckedCopy>::Output`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::marker::Copy> UncheckedCopy for T {}

src/test/ui/associated-types/issue-43924.stderr

@@ -16,8 +16,6 @@ LL |     type Out: Default + ToString + ?Sized = dyn ToString;
 ...
 LL | impl Foo<u32> for () {}
    |      ^^^^^^^^ the trait `std::default::Default` is not implemented for `(dyn std::string::ToString + 'static)`
-   |
-   = note: required because of the requirements on the impl of `std::default::Default` for `<() as Foo<u32>>::Out`
 
 error[E0277]: the trait bound `(dyn std::string::ToString + 'static): std::default::Default` is not satisfied
   --> $DIR/issue-43924.rs:11:6
@@ -29,8 +27,6 @@ LL |     type Out: Default + ToString + ?Sized = dyn ToString;
 ...
 LL | impl Foo<u64> for () {}
    |      ^^^^^^^^ the trait `std::default::Default` is not implemented for `(dyn std::string::ToString + 'static)`
-   |
-   = note: required because of the requirements on the impl of `std::default::Default` for `<() as Foo<u64>>::Out`
 
 error: aborting due to 3 previous errors
 

src/test/ui/associated-types/issue-65774-1.stderr

@@ -16,8 +16,6 @@ LL |     type MpuConfig: MyDisplay = T;
 ...
 LL | impl MPU for S { }
    |      ^^^ the trait `MyDisplay` is not implemented for `T`
-   |
-   = note: required because of the requirements on the impl of `MyDisplay` for `<S as MPU>::MpuConfig`
 
 error: aborting due to 2 previous errors
 

src/test/ui/associated-types/issue-65774-2.stderr

@@ -16,8 +16,6 @@ LL |     type MpuConfig: MyDisplay = T;
 ...
 LL | impl MPU for S { }
    |      ^^^ the trait `MyDisplay` is not implemented for `T`
-   |
-   = note: required because of the requirements on the impl of `MyDisplay` for `<S as MPU>::MpuConfig`
 
 error: aborting due to 2 previous errors
 

src/test/ui/associated-types/point-at-type-on-obligation-failure-2.stderr

@@ -8,8 +8,6 @@ LL |     type Assoc: Bar;
 ...
 LL |     type Assoc = bool;
    |                  ^^^^ the trait `Bar` is not implemented for `bool`
-   |
-   = note: required because of the requirements on the impl of `Bar` for `<() as Foo>::Assoc`
 
 error[E0277]: the trait bound `bool: Bar` is not satisfied
   --> $DIR/point-at-type-on-obligation-failure-2.rs:16:18
@@ -19,8 +17,6 @@ LL | trait Baz where Self::Assoc: Bar {
 ...
 LL |     type Assoc = bool;
    |                  ^^^^ the trait `Bar` is not implemented for `bool`
-   |
-   = note: required because of the requirements on the impl of `Bar` for `<() as Baz>::Assoc`
 
 error[E0277]: the trait bound `bool: Bar` is not satisfied
   --> $DIR/point-at-type-on-obligation-failure-2.rs:24:18
@@ -30,8 +26,6 @@ LL | trait Bat where <Self as Bat>::Assoc: Bar {
 ...
 LL |     type Assoc = bool;
    |                  ^^^^ the trait `Bar` is not implemented for `bool`
-   |
-   = note: required because of the requirements on the impl of `Bar` for `<() as Bat>::Assoc`
 
 error: aborting due to 3 previous errors
 

src/test/ui/builtin-superkinds/builtin-superkinds-double-superkind.stderr

@@ -9,7 +9,6 @@ LL | impl <T: Sync+'static> Foo for (T,) { }
    |
    = help: within `(T,)`, the trait `std::marker::Send` is not implemented for `T`
    = note: required because it appears within the type `(T,)`
-   = note: required because of the requirements on the impl of `std::marker::Send` for `(T,)`
 help: consider further restricting this bound
    |
 LL | impl <T: Sync+'static + std::marker::Send> Foo for (T,) { }
@@ -26,7 +25,6 @@ LL | impl <T: Send> Foo for (T,T) { }
    |
    = help: within `(T, T)`, the trait `std::marker::Sync` is not implemented for `T`
    = note: required because it appears within the type `(T, T)`
-   = note: required because of the requirements on the impl of `std::marker::Sync` for `(T, T)`
 help: consider further restricting this bound
    |
 LL | impl <T: Send + std::marker::Sync> Foo for (T,T) { }

src/test/ui/builtin-superkinds/builtin-superkinds-in-metadata.stderr

@@ -11,7 +11,6 @@ LL | pub trait RequiresRequiresShareAndSend : RequiresShare + Send { }
    |
    = help: within `X<T>`, the trait `std::marker::Send` is not implemented for `T`
    = note: required because it appears within the type `X<T>`
-   = note: required because of the requirements on the impl of `std::marker::Send` for `X<T>`
 help: consider further restricting this bound
    |
 LL | impl <T:Sync+'static + std::marker::Send> RequiresRequiresShareAndSend for X<T> { }

src/test/ui/builtin-superkinds/builtin-superkinds-simple.stderr

@@ -8,7 +8,6 @@ LL | impl Foo for std::rc::Rc<i8> { }
    |      ^^^ `std::rc::Rc<i8>` cannot be sent between threads safely
    |
    = help: the trait `std::marker::Send` is not implemented for `std::rc::Rc<i8>`
-   = note: required because of the requirements on the impl of `std::marker::Send` for `std::rc::Rc<i8>`
 
 error: aborting due to previous error
 

src/test/ui/builtin-superkinds/builtin-superkinds-typaram-not-send.stderr

@@ -8,7 +8,6 @@ LL | impl <T: Sync+'static> Foo for T { }
    |                        ^^^ `T` cannot be sent between threads safely
    |
    = help: the trait `std::marker::Send` is not implemented for `T`
-   = note: required because of the requirements on the impl of `std::marker::Send` for `T`
 help: consider further restricting this bound
    |
 LL | impl <T: Sync+'static + std::marker::Send> Foo for T { }

src/test/ui/dst/dst-sized-trait-param.stderr

@@ -9,7 +9,6 @@ LL | impl Foo<[isize]> for usize { }
    |
    = help: the trait `std::marker::Sized` is not implemented for `[isize]`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-   = note: required because of the requirements on the impl of `std::marker::Sized` for `[isize]`
 
 error[E0277]: the size for values of type `[usize]` cannot be known at compilation time
   --> $DIR/dst-sized-trait-param.rs:10:6
@@ -22,7 +21,6 @@ LL | impl Foo<isize> for [usize] { }
    |
    = help: the trait `std::marker::Sized` is not implemented for `[usize]`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-   = note: required because of the requirements on the impl of `std::marker::Sized` for `[usize]`
 
 error: aborting due to 2 previous errors
 

src/test/ui/generics/issue-61631-default-type-param-can-reference-self-in-trait.stderr

@@ -9,7 +9,6 @@ LL | impl Tsized for () {}
    |
    = help: the trait `std::marker::Sized` is not implemented for `[()]`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-   = note: required because of the requirements on the impl of `std::marker::Sized` for `[()]`
 
 error: aborting due to previous error
 

src/test/ui/impl-bounds-checking.stderr

@@ -6,8 +6,6 @@ LL | trait Getter<T: Clone2> {
 ...
 LL | impl Getter<isize> for isize {
    |      ^^^^^^^^^^^^^ the trait `Clone2` is not implemented for `isize`
-   |
-   = note: required because of the requirements on the impl of `Clone2` for `isize`
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-10412.stderr

@@ -57,7 +57,6 @@ LL | impl<'self> Serializable<str> for &'self str {
    |
    = help: the trait `std::marker::Sized` is not implemented for `str`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-   = note: required because of the requirements on the impl of `std::marker::Sized` for `str`
 
 error: aborting due to 9 previous errors
 

src/test/ui/issues/issue-43784-associated-type.stderr

@@ -4,7 +4,6 @@ error[E0277]: the trait bound `T: std::marker::Copy` is not satisfied
 LL |     type Assoc = T;
    |                  ^ the trait `std::marker::Copy` is not implemented for `T`
    |
-   = note: required because of the requirements on the impl of `std::marker::Copy` for `<T as Complete>::Assoc`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::marker::Copy> Complete for T {

src/test/ui/issues/issue-43784-supertrait.stderr

@@ -4,7 +4,6 @@ error[E0277]: the trait bound `T: std::marker::Copy` is not satisfied
 LL | impl<T> Complete for T {}
    |         ^^^^^^^^ the trait `std::marker::Copy` is not implemented for `T`
    |
-   = note: required because of the requirements on the impl of `std::marker::Copy` for `T`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::marker::Copy> Complete for T {}

src/test/ui/issues/issue-65673.stderr

@@ -11,7 +11,6 @@ LL |     type Ctx = dyn Alias<T>;
    |
    = help: the trait `std::marker::Sized` is not implemented for `(dyn Trait + 'static)`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-   = note: required because of the requirements on the impl of `std::marker::Sized` for `<T as WithType>::Ctx`
 
 error: aborting due to previous error
 

src/test/ui/malformed/malformed-derive-entry.stderr

@@ -27,7 +27,6 @@ LL | #[derive(Copy(Bad))]
 LL | pub trait Copy: Clone {
    |                 ----- required by this bound in `std::marker::Copy`
    |
-   = note: required because of the requirements on the impl of `std::clone::Clone` for `Test1`
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0277]: the trait bound `Test2: std::clone::Clone` is not satisfied
@@ -41,7 +40,6 @@ LL | #[derive(Copy="bad")]
 LL | pub trait Copy: Clone {
    |                 ----- required by this bound in `std::marker::Copy`
    |
-   = note: required because of the requirements on the impl of `std::clone::Clone` for `Test2`
    = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 5 previous errors

src/test/ui/specialization/defaultimpl/specialization-wfcheck.stderr

@@ -7,7 +7,6 @@ LL |
 LL | default impl<U> Foo<'static, U> for () {}
    |                 ^^^^^^^^^^^^^^^ the trait `std::cmp::Eq` is not implemented for `U`
    |
-   = note: required because of the requirements on the impl of `std::cmp::Eq` for `U`
 help: consider restricting type parameter `U`
    |
 LL | default impl<U: std::cmp::Eq> Foo<'static, U> for () {}

src/test/ui/suggestions/missing-assoc-type-bound-restriction.stderr

@@ -28,7 +28,6 @@ LL |     type Assoc = ChildWrapper<T::Assoc>;
    |                  ^^^^^^^^^^^^^^^^^^^^^^ the trait `Child<A>` is not implemented for `<T as Parent>::Assoc`
    |
    = note: required because of the requirements on the impl of `Child<A>` for `ChildWrapper<<T as Parent>::Assoc>`
-   = note: required because of the requirements on the impl of `Child<<ParentWrapper<T> as Parent>::Ty>` for `<ParentWrapper<T> as Parent>::Assoc`
 
 error[E0277]: the trait bound `<T as Parent>::Assoc: Child<A>` is not satisfied
   --> $DIR/missing-assoc-type-bound-restriction.rs:20:5

src/test/ui/traits/cycle-cache-err-60010.stderr

@@ -21,7 +21,6 @@ LL |     type Storage = SalsaStorage;
    = note: required because of the requirements on the impl of `SourceDatabase` for `RootDatabase`
    = note: required because of the requirements on the impl of `Query<RootDatabase>` for `ParseQuery`
    = note: required because it appears within the type `SalsaStorage`
-   = note: required because of the requirements on the impl of `std::marker::Sized` for `<RootDatabase as Database>::Storage`
 
 error: aborting due to 2 previous errors
 

src/test/ui/unsized/unsized-trait-impl-trait-arg.stderr

@@ -11,7 +11,6 @@ LL | impl<X: ?Sized> T2<X> for S4<X> {
    |
    = help: the trait `std::marker::Sized` is not implemented for `X`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-   = note: required because of the requirements on the impl of `std::marker::Sized` for `X`
 
 error: aborting due to previous error
 

src/test/ui/unsized7.stderr

@@ -11,7 +11,6 @@ LL | impl<X: ?Sized + T> T1<X> for S3<X> {
    |
    = help: the trait `std::marker::Sized` is not implemented for `X`
    = note: to learn more, visit <https://doc.rust-lang.org/book/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
-   = note: required because of the requirements on the impl of `std::marker::Sized` for `X`
 
 error: aborting due to previous error