Auto merge of #84767 - scottmcm:try_trait_actual, r=lcnr

Implement the new desugaring from `try_trait_v2`

~~Currently blocked on https://github.com/rust-lang/rust/issues/84782, which has a PR in https://github.com/rust-lang/rust/pull/84811~~ Rebased atop that fix.

`try_trait_v2` tracking issue: https://github.com/rust-lang/rust/issues/84277

Unfortunately this is already touching a ton of things, so if you have suggestions for good ways to split it up, I'd be happy to hear them.  (The combination between the use in the library, the compiler changes, the corresponding diagnostic differences, even MIR tests mean that I don't really have a great plan for it other than trying to have decently-readable commits.

r? `@ghost`

~~(This probably shouldn't go in during the last week before the fork anyway.)~~ Fork happened.

5 files changed, 23 insertions, 26 deletions

diff --git a/src/test/ui/try-block/try-block-bad-type.rs b/src/test/ui/try-block/try-block-bad-type.rs
index ef6e690e1bd..30ae96763c0 100644
--- a/src/test/ui/try-block/try-block-bad-type.rs
+++ b/src/test/ui/try-block/try-block-bad-type.rs
@@ -15,8 +15,7 @@ pub fn main() {
     let res: Result<i32, i32> = try { }; //~ ERROR type mismatch
 
     let res: () = try { };
-    //~^ ERROR the trait bound `(): Try` is not satisfied
-    //~| ERROR the trait bound `(): Try` is not satisfied
+    //~^ ERROR a `try` block must return `Result` or `Option`
 
-    let res: i32 = try { 5 }; //~ ERROR the trait bound `i32: Try` is not satisfied
+    let res: i32 = try { 5 }; //~ ERROR a `try` block must return `Result` or `Option`
 }
diff --git a/src/test/ui/try-block/try-block-bad-type.stderr b/src/test/ui/try-block/try-block-bad-type.stderr
index 75a42c0d6b7..ec5e91f10c2 100644
--- a/src/test/ui/try-block/try-block-bad-type.stderr
+++ b/src/test/ui/try-block/try-block-bad-type.stderr
@@ -7,43 +7,40 @@ LL |         Err("")?;
    = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
    = help: the following implementations were found:
              <TryFromSliceError as From<Infallible>>
-   = note: required by `from`
+   = note: required because of the requirements on the impl of `FromResidual<Result<Infallible, &str>>` for `Result<u32, TryFromSliceError>`
+   = note: required by `from_residual`
 
-error[E0271]: type mismatch resolving `<Result<i32, i32> as Try>::Ok == &str`
+error[E0271]: type mismatch resolving `<Result<i32, i32> as Try>::Output == &str`
   --> $DIR/try-block-bad-type.rs:12:9
    |
 LL |         ""
    |         ^^ expected `i32`, found `&str`
 
-error[E0271]: type mismatch resolving `<Result<i32, i32> as Try>::Ok == ()`
+error[E0271]: type mismatch resolving `<Result<i32, i32> as Try>::Output == ()`
   --> $DIR/try-block-bad-type.rs:15:39
    |
 LL |     let res: Result<i32, i32> = try { };
    |                                       ^ expected `i32`, found `()`
 
-error[E0277]: the trait bound `(): Try` is not satisfied
+error[E0277]: a `try` block must return `Result` or `Option` (or another type that implements `Try`)
   --> $DIR/try-block-bad-type.rs:17:25
    |
 LL |     let res: () = try { };
-   |                         ^ the trait `Try` is not implemented for `()`
+   |                         ^ could not wrap the final value of the block as `()` doesn't implement `Try`
    |
-   = note: required by `from_ok`
+   = help: the trait `Try` is not implemented for `()`
+   = note: required by `from_output`
 
-error[E0277]: the trait bound `(): Try` is not satisfied
-  --> $DIR/try-block-bad-type.rs:17:25
-   |
-LL |     let res: () = try { };
-   |                         ^ the trait `Try` is not implemented for `()`
-
-error[E0277]: the trait bound `i32: Try` is not satisfied
-  --> $DIR/try-block-bad-type.rs:21:26
+error[E0277]: a `try` block must return `Result` or `Option` (or another type that implements `Try`)
+  --> $DIR/try-block-bad-type.rs:20:26
    |
 LL |     let res: i32 = try { 5 };
-   |                          ^ the trait `Try` is not implemented for `i32`
+   |                          ^ could not wrap the final value of the block as `i32` doesn't implement `Try`
    |
-   = note: required by `from_ok`
+   = help: the trait `Try` is not implemented for `i32`
+   = note: required by `from_output`
 
-error: aborting due to 6 previous errors
+error: aborting due to 5 previous errors
 
 Some errors have detailed explanations: E0271, E0277.
 For more information about an error, try `rustc --explain E0271`.
diff --git a/src/test/ui/try-block/try-block-in-while.rs b/src/test/ui/try-block/try-block-in-while.rs
index 5d8748f1dd3..69793df525e 100644
--- a/src/test/ui/try-block/try-block-in-while.rs
+++ b/src/test/ui/try-block/try-block-in-while.rs
@@ -4,5 +4,5 @@
 
 fn main() {
     while try { false } {}
-    //~^ ERROR the trait bound `bool: Try` is not satisfied
+    //~^ ERROR a `try` block must
 }
diff --git a/src/test/ui/try-block/try-block-in-while.stderr b/src/test/ui/try-block/try-block-in-while.stderr
index 75a4e8d065c..c83351d5c43 100644
--- a/src/test/ui/try-block/try-block-in-while.stderr
+++ b/src/test/ui/try-block/try-block-in-while.stderr
@@ -1,10 +1,11 @@
-error[E0277]: the trait bound `bool: Try` is not satisfied
+error[E0277]: a `try` block must return `Result` or `Option` (or another type that implements `Try`)
   --> $DIR/try-block-in-while.rs:6:17
    |
 LL |     while try { false } {}
-   |                 ^^^^^ the trait `Try` is not implemented for `bool`
+   |                 ^^^^^ could not wrap the final value of the block as `bool` doesn't implement `Try`
    |
-   = note: required by `from_ok`
+   = help: the trait `Try` is not implemented for `bool`
+   = note: required by `from_output`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/try-block/try-block-type-error.stderr b/src/test/ui/try-block/try-block-type-error.stderr
index df1441c83d4..3e9a584a551 100644
--- a/src/test/ui/try-block/try-block-type-error.stderr
+++ b/src/test/ui/try-block/try-block-type-error.stderr
@@ -1,4 +1,4 @@
-error[E0271]: type mismatch resolving `<Option<f32> as Try>::Ok == {integer}`
+error[E0271]: type mismatch resolving `<Option<f32> as Try>::Output == {integer}`
   --> $DIR/try-block-type-error.rs:10:9
    |
 LL |         42
@@ -7,7 +7,7 @@ LL |         42
    |         expected `f32`, found integer
    |         help: use a float literal: `42.0`
 
-error[E0271]: type mismatch resolving `<Option<i32> as Try>::Ok == ()`
+error[E0271]: type mismatch resolving `<Option<i32> as Try>::Output == ()`
   --> $DIR/try-block-type-error.rs:16:5
    |
 LL |     };