Remove redundant explanatory note for type parameters

Author: estebank

src/librustc_trait_selection/traits/error_reporting/mod.rs

@@ -376,7 +376,12 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                             // If it has a custom `#[rustc_on_unimplemented]`
                             // error message, let's display it as the label!
                             err.span_label(span, s.as_str());
-                            err.help(&explanation);
+                            if !matches!(trait_ref.skip_binder().self_ty().kind, ty::Param(_)) {
+                                // When the self type is a type param We don't need to "the trait
+                                // `std::marker::Sized` is not implemented for `T`" as we will point
+                                // at the type param with a label to suggest constraining it.
+                                err.help(&explanation);
+                            }
                         } else {
                             err.span_label(span, explanation);
                         }

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

@@ -21,7 +21,6 @@ LL | trait UncheckedCopy: Sized {
 LL |     + AddAssign<&'static str>
    |       ^^^^^^^^^^^^^^^^^^^^^^^ no implementation for `Self += &'static str`
    |
-   = help: the trait `std::ops::AddAssign<&'static str>` is not implemented for `Self`
 help: consider further restricting `Self`
    |
 LL | trait UncheckedCopy: Sized + std::ops::AddAssign<&'static str> {
@@ -50,7 +49,6 @@ LL | trait UncheckedCopy: Sized {
 LL |     + Display = Self;
    |       ^^^^^^^ `Self` cannot be formatted with the default formatter
    |
-   = help: the trait `std::fmt::Display` is not implemented for `Self`
    = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
 help: consider further restricting `Self`
    |
@@ -69,7 +67,6 @@ LL |     + Display = Self;
 LL | impl<T> UncheckedCopy for T {}
    |         ^^^^^^^^^^^^^ `T` cannot be formatted with the default formatter
    |
-   = 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
 help: consider restricting type parameter `T`
    |
@@ -105,7 +102,6 @@ LL |     + AddAssign<&'static str>
 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`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::ops::AddAssign<&'static str>> UncheckedCopy for T {}

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

@@ -21,7 +21,6 @@ LL | trait UncheckedCopy: Sized {
 LL |     + AddAssign<&'static str>
    |       ^^^^^^^^^^^^^^^^^^^^^^^ no implementation for `Self += &'static str`
    |
-   = help: the trait `std::ops::AddAssign<&'static str>` is not implemented for `Self`
 help: consider further restricting `Self`
    |
 LL | trait UncheckedCopy: Sized + std::ops::AddAssign<&'static str> {
@@ -50,7 +49,6 @@ LL | trait UncheckedCopy: Sized {
 LL |     + Display = Self;
    |       ^^^^^^^ `Self` cannot be formatted with the default formatter
    |
-   = help: the trait `std::fmt::Display` is not implemented for `Self`
    = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
 help: consider further restricting `Self`
    |
@@ -69,7 +67,6 @@ LL |     + Display = Self;
 LL | impl<T> UncheckedCopy for T {}
    |         ^^^^^^^^^^^^^ `T` cannot be formatted with the default formatter
    |
-   = 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
 help: consider restricting type parameter `T`
    |
@@ -105,7 +102,6 @@ LL |     + AddAssign<&'static str>
 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`
 help: consider restricting type parameter `T`
    |
 LL | impl<T: std::ops::AddAssign<&'static str>> UncheckedCopy for T {}

src/test/ui/associated-types/issue-63593.stderr

@@ -6,7 +6,6 @@ LL | trait MyTrait {
 LL |     type This = Self;
    |     ^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
    |
-   = help: the trait `std::marker::Sized` is not implemented for `Self`
 help: consider further restricting `Self`
    |
 LL | trait MyTrait: std::marker::Sized {

src/test/ui/associated-types/trait-with-supertraits-needing-sized-self.stderr

@@ -9,7 +9,6 @@ LL | trait ArithmeticOps: Add<Output=Self> + Sub<Output=Self> + Mul<Output=Self>
 LL | pub trait Add<Rhs = Self> {
    |               --- required by this bound in `std::ops::Add`
    |
-   = help: the trait `std::marker::Sized` is not implemented for `Self`
 help: consider further restricting `Self`
    |
 LL | trait ArithmeticOps: Add<Output=Self> + Sub<Output=Self> + Mul<Output=Self> + Div<Output=Self> + std::marker::Sized {}

src/test/ui/async-await/issue-70818.stderr

@@ -7,7 +7,6 @@ LL |
 LL |     async { (ty, ty1) }
    |     ------------------- this returned value is of type `impl std::future::Future`
    |
-   = help: within `impl std::future::Future`, the trait `std::marker::Send` is not implemented for `U`
 note: captured value is not `Send`
   --> $DIR/issue-70818.rs:6:18
    |

src/test/ui/bad/bad-method-typaram-kind.stderr

@@ -4,7 +4,6 @@ error[E0277]: `T` cannot be sent between threads safely
 LL |     1.bar::<T>();
    |       ^^^ `T` cannot be sent between threads safely
    |
-   = help: the trait `std::marker::Send` is not implemented for `T`
 help: consider further restricting this bound
    |
 LL | fn foo<T:'static + std::marker::Send>() {

src/test/ui/bound-suggestions.stderr

@@ -4,7 +4,6 @@ error[E0277]: `impl Sized` doesn't implement `std::fmt::Debug`
 LL |     println!("{:?}", t);
    |                      ^ `impl Sized` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
    |
-   = help: the trait `std::fmt::Debug` is not implemented for `impl Sized`
    = note: required by `std::fmt::Debug::fmt`
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider further restricting this bound
@@ -18,7 +17,6 @@ error[E0277]: `T` doesn't implement `std::fmt::Debug`
 LL |     println!("{:?}", t);
    |                      ^ `T` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
    |
-   = help: the trait `std::fmt::Debug` is not implemented for `T`
    = note: required by `std::fmt::Debug::fmt`
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider restricting type parameter `T`
@@ -32,7 +30,6 @@ error[E0277]: `T` doesn't implement `std::fmt::Debug`
 LL |     println!("{:?}", t);
    |                      ^ `T` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
    |
-   = help: the trait `std::fmt::Debug` is not implemented for `T`
    = note: required by `std::fmt::Debug::fmt`
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider further restricting this bound
@@ -46,7 +43,6 @@ error[E0277]: `Y` doesn't implement `std::fmt::Debug`
 LL |     println!("{:?} {:?}", x, y);
    |                              ^ `Y` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
    |
-   = help: the trait `std::fmt::Debug` is not implemented for `Y`
    = note: required by `std::fmt::Debug::fmt`
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider further restricting type parameter `Y`
@@ -60,7 +56,6 @@ error[E0277]: `X` doesn't implement `std::fmt::Debug`
 LL |     println!("{:?}", x);
    |                      ^ `X` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
    |
-   = help: the trait `std::fmt::Debug` is not implemented for `X`
    = note: required by `std::fmt::Debug::fmt`
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider further restricting this bound
@@ -74,7 +69,6 @@ error[E0277]: `X` doesn't implement `std::fmt::Debug`
 LL |     println!("{:?}", x);
    |                      ^ `X` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
    |
-   = help: the trait `std::fmt::Debug` is not implemented for `X`
    = note: required by `std::fmt::Debug::fmt`
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider further restricting type parameter `X`

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

@@ -7,7 +7,6 @@ LL |
 LL | impl <T: Sync+'static> Foo for (T,) { }
    |                        ^^^ `T` cannot be sent between threads safely
    |
-   = help: within `(T,)`, the trait `std::marker::Send` is not implemented for `T`
    = note: required because it appears within the type `(T,)`
 help: consider further restricting this bound
    |
@@ -23,7 +22,6 @@ LL | trait Foo : Send+Sync { }
 LL | impl <T: Send> Foo for (T,T) { }
    |                ^^^ `T` cannot be shared between threads safely
    |
-   = help: within `(T, T)`, the trait `std::marker::Sync` is not implemented for `T`
    = note: required because it appears within the type `(T, T)`
 help: consider further restricting this bound
    |

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

@@ -9,7 +9,6 @@ LL | impl <T:Sync+'static> RequiresRequiresShareAndSend for X<T> { }
 LL | pub trait RequiresRequiresShareAndSend : RequiresShare + Send { }
    |                                                          ---- required by this bound in `trait_superkinds_in_metadata::RequiresRequiresShareAndSend`
    |
-   = help: within `X<T>`, the trait `std::marker::Send` is not implemented for `T`
    = note: required because it appears within the type `X<T>`
 help: consider further restricting this bound
    |