Remove type parameter default from FromResidual.

library/core/src/ops/control_flow.rs

@@ -116,7 +116,7 @@ impl<B, C> ops::Try for ControlFlow<B, C> {
 }
 
 #[unstable(feature = "try_trait_v2", issue = "84277")]
-impl<B, C> ops::FromResidual for ControlFlow<B, C> {
+impl<B, C> ops::FromResidual<ControlFlow<B, convert::Infallible>> for ControlFlow<B, C> {
     #[inline]
     fn from_residual(residual: ControlFlow<B, convert::Infallible>) -> Self {
         match residual {

library/core/src/ops/try_trait.rs

@@ -128,7 +128,7 @@ use crate::ops::ControlFlow;
 )]
 #[doc(alias = "?")]
 #[lang = "Try"]
-pub trait Try: FromResidual {
+pub trait Try: FromResidual<Self::Residual> {
     /// The type of the value produced by `?` when *not* short-circuiting.
     #[unstable(feature = "try_trait_v2", issue = "84277")]
     type Output;
@@ -304,7 +304,7 @@ pub trait Try: FromResidual {
 )]
 #[rustc_diagnostic_item = "FromResidual"]
 #[unstable(feature = "try_trait_v2", issue = "84277")]
-pub trait FromResidual<R = <Self as Try>::Residual> {
+pub trait FromResidual<R> {
     /// Constructs the type from a compatible `Residual` type.
     ///
     /// This should be implemented consistently with the `branch` method such
@@ -410,7 +410,7 @@ impl<T> Try for NeverShortCircuit<T> {
     }
 }
 
-impl<T> FromResidual for NeverShortCircuit<T> {
+impl<T> FromResidual<NeverShortCircuitResidual> for NeverShortCircuit<T> {
     #[inline]
     fn from_residual(never: NeverShortCircuitResidual) -> Self {
         match never {}

library/core/src/option.rs

@@ -2495,7 +2495,7 @@ impl<T> ops::Try for Option<T> {
 }
 
 #[unstable(feature = "try_trait_v2", issue = "84277")]
-impl<T> ops::FromResidual for Option<T> {
+impl<T> ops::FromResidual<Option<convert::Infallible>> for Option<T> {
     #[inline]
     fn from_residual(residual: Option<convert::Infallible>) -> Self {
         match residual {

tests/ui/rfcs/rfc-2632-const-trait-impl/ice-119717-constant-lifetime.rs

@@ -3,7 +3,7 @@
 
 use std::ops::FromResidual;
 
-impl<T> const FromResidual for T {
+impl<T> const FromResidual<T> for T {
     //~^ ERROR const `impl` for trait `FromResidual` which is not marked with `#[const_trait]`
     //~| type parameter `T` must be used as the type parameter for some local type
     fn from_residual(t: T) -> _ {

tests/ui/rfcs/rfc-2632-const-trait-impl/ice-119717-constant-lifetime.stderr

@@ -6,16 +6,16 @@ error: using `#![feature(effects)]` without enabling next trait solver globally
 error: const `impl` for trait `FromResidual` which is not marked with `#[const_trait]`
   --> $DIR/ice-119717-constant-lifetime.rs:6:15
    |
-LL | impl<T> const FromResidual for T {
-   |               ^^^^^^^^^^^^
+LL | impl<T> const FromResidual<T> for T {
+   |               ^^^^^^^^^^^^^^^
    |
    = note: marking a trait with `#[const_trait]` ensures all default method bodies are `const`
    = note: adding a non-const method body in the future would be a breaking change
 
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
   --> $DIR/ice-119717-constant-lifetime.rs:6:6
    |
-LL | impl<T> const FromResidual for T {
+LL | impl<T> const FromResidual<T> for T {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
    = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local

tests/ui/rfcs/rfc-2632-const-trait-impl/trait-default-body-stability.rs

@@ -31,7 +31,7 @@ impl const Try for T {
 
 #[stable(feature = "foo", since = "1.0")]
 #[rustc_const_unstable(feature = "const_t_try", issue = "none")]
-impl const FromResidual for T {
+impl const FromResidual<T> for T {
     fn from_residual(t: T) -> T {
         t
     }

tests/ui/rfcs/rfc-2632-const-trait-impl/trait-default-body-stability.stderr

@@ -10,8 +10,8 @@ LL | impl const Try for T {
 error: const `impl` for trait `FromResidual` which is not marked with `#[const_trait]`
   --> $DIR/trait-default-body-stability.rs:34:12
    |
-LL | impl const FromResidual for T {
-   |            ^^^^^^^^^^^^
+LL | impl const FromResidual<T> for T {
+   |            ^^^^^^^^^^^^^^^
    |
    = note: marking a trait with `#[const_trait]` ensures all default method bodies are `const`
    = note: adding a non-const method body in the future would be a breaking change

tests/ui/try-trait/bad-interconversion.stderr

@@ -45,7 +45,7 @@ LL |     Some(Err("hello")?)
    |                      ^ use `.ok()?` if you want to discard the `Result<Infallible, &str>` error information
    |
    = help: the trait `FromResidual<Result<Infallible, &str>>` is not implemented for `Option<u16>`
-   = help: the trait `FromResidual` is implemented for `Option<T>`
+   = help: the trait `FromResidual<Option<Infallible>>` is implemented for `Option<T>`
 
 error[E0277]: the `?` operator can only be used on `Option`s in a function that returns `Option`
   --> $DIR/bad-interconversion.rs:27:33
@@ -56,7 +56,7 @@ LL |     Some(ControlFlow::Break(123)?)
    |                                 ^ this `?` produces `ControlFlow<{integer}, Infallible>`, which is incompatible with `Option<u64>`
    |
    = help: the trait `FromResidual<ControlFlow<{integer}, Infallible>>` is not implemented for `Option<u64>`
-   = help: the trait `FromResidual` is implemented for `Option<T>`
+   = help: the trait `FromResidual<Option<Infallible>>` is implemented for `Option<T>`
 
 error[E0277]: the `?` operator can only be used on `ControlFlow`s in a function that returns `ControlFlow`
   --> $DIR/bad-interconversion.rs:32:39

tests/ui/try-trait/option-to-result.stderr

@@ -20,7 +20,7 @@ LL |     a?;
    |      ^ use `.ok()?` if you want to discard the `Result<Infallible, i32>` error information
    |
    = help: the trait `FromResidual<Result<Infallible, i32>>` is not implemented for `Option<i32>`
-   = help: the trait `FromResidual` is implemented for `Option<T>`
+   = help: the trait `FromResidual<Option<Infallible>>` is implemented for `Option<T>`
 
 error: aborting due to 2 previous errors