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.

1 files changed, 44 insertions, 49 deletions

diff --git a/src/test/mir-opt/simplify_try.try_identity.DestinationPropagation.diff b/src/test/mir-opt/simplify_try.try_identity.DestinationPropagation.diff
index b1bae447f9c..e09b8cb39bd 100644
--- a/src/test/mir-opt/simplify_try.try_identity.DestinationPropagation.diff
+++ b/src/test/mir-opt/simplify_try.try_identity.DestinationPropagation.diff
@@ -2,67 +2,62 @@
 + // MIR for `try_identity` after DestinationPropagation
   
   fn try_identity(_1: Result<u32, i32>) -> Result<u32, i32> {
-      debug x => _1;                       // in scope 0 at $DIR/simplify_try.rs:7:17: 7:18
-      let mut _0: std::result::Result<u32, i32>; // return place in scope 0 at $DIR/simplify_try.rs:7:41: 7:57
-      let _2: u32;                         // in scope 0 at $DIR/simplify_try.rs:8:9: 8:10
-      let mut _3: std::result::Result<u32, i32>; // in scope 0 at $DIR/simplify_try.rs:8:13: 8:15
-      let mut _4: std::result::Result<u32, i32>; // in scope 0 at $DIR/simplify_try.rs:8:13: 8:14
-      let mut _5: isize;                   // in scope 0 at $DIR/simplify_try.rs:8:14: 8:15
-      let _6: i32;                         // in scope 0 at $DIR/simplify_try.rs:8:14: 8:15
-      let mut _7: !;                       // in scope 0 at $DIR/simplify_try.rs:8:14: 8:15
-      let mut _8: i32;                     // in scope 0 at $DIR/simplify_try.rs:8:14: 8:15
-      let mut _9: i32;                     // in scope 0 at $DIR/simplify_try.rs:8:14: 8:15
-      let _10: u32;                        // in scope 0 at $DIR/simplify_try.rs:8:13: 8:15
-      let mut _11: u32;                    // in scope 0 at $DIR/simplify_try.rs:9:8: 9:9
+      debug x => _1;                       // in scope 0 at $DIR/simplify_try.rs:20:17: 20:18
+      let mut _0: std::result::Result<u32, i32>; // return place in scope 0 at $DIR/simplify_try.rs:20:41: 20:57
+      let _2: u32;                         // in scope 0 at $DIR/simplify_try.rs:21:9: 21:10
+      let mut _3: std::result::Result<u32, i32>; // in scope 0 at $DIR/simplify_try.rs:21:19: 21:33
+      let mut _4: std::result::Result<u32, i32>; // in scope 0 at $DIR/simplify_try.rs:21:31: 21:32
+      let mut _5: isize;                   // in scope 0 at $DIR/simplify_try.rs:22:9: 22:15
+      let _6: i32;                         // in scope 0 at $DIR/simplify_try.rs:22:13: 22:14
+      let mut _7: !;                       // in scope 0 at $DIR/simplify_try.rs:22:19: 22:51
+      let mut _8: i32;                     // in scope 0 at $DIR/simplify_try.rs:22:37: 22:50
+      let mut _9: i32;                     // in scope 0 at $DIR/simplify_try.rs:22:48: 22:49
+      let _10: u32;                        // in scope 0 at $DIR/simplify_try.rs:23:12: 23:13
+      let mut _11: u32;                    // in scope 0 at $DIR/simplify_try.rs:25:8: 25:9
       scope 1 {
-          debug y => ((_0 as Ok).0: u32);  // in scope 1 at $DIR/simplify_try.rs:8:9: 8:10
+          debug y => ((_0 as Ok).0: u32);  // in scope 1 at $DIR/simplify_try.rs:21:9: 21:10
       }
       scope 2 {
-          debug err => ((_0 as Err).0: i32); // in scope 2 at $DIR/simplify_try.rs:8:14: 8:15
-          scope 3 {
-              scope 7 (inlined <i32 as From<i32>>::from) { // at $DIR/simplify_try.rs:8:14: 8:15
-                  debug t => ((_0 as Err).0: i32); // in scope 7 at $DIR/simplify_try.rs:8:14: 8:15
-              }
-              scope 8 (inlined <Result<u32, i32> as Try>::from_error) { // at $DIR/simplify_try.rs:8:13: 8:15
-                  debug v => ((_0 as Err).0: i32); // in scope 8 at $DIR/simplify_try.rs:8:13: 8:15
-                  let mut _12: i32;        // in scope 8 at $DIR/simplify_try.rs:8:13: 8:15
-              }
+          debug e => ((_0 as Err).0: i32); // in scope 2 at $DIR/simplify_try.rs:22:13: 22:14
+          scope 5 (inlined <i32 as From<i32>>::from) { // at $DIR/simplify_try.rs:22:37: 22:50
+              debug t => ((_0 as Err).0: i32); // in scope 5 at $DIR/simplify_try.rs:22:37: 22:50
           }
-      }
-      scope 4 {
-          debug val => ((_0 as Ok).0: u32); // in scope 4 at $DIR/simplify_try.rs:8:13: 8:15
-          scope 5 {
+          scope 6 (inlined from_error::<u32, i32>) { // at $DIR/simplify_try.rs:22:26: 22:51
+              debug e => ((_0 as Err).0: i32); // in scope 6 at $DIR/simplify_try.rs:22:26: 22:51
           }
       }
-      scope 6 (inlined <Result<u32, i32> as Try>::into_result) { // at $DIR/simplify_try.rs:8:13: 8:15
--         debug self => _4;                // in scope 6 at $DIR/simplify_try.rs:8:13: 8:15
-+         debug self => _0;                // in scope 6 at $DIR/simplify_try.rs:8:13: 8:15
+      scope 3 {
+          debug v => ((_0 as Ok).0: u32);  // in scope 3 at $DIR/simplify_try.rs:23:12: 23:13
+      }
+      scope 4 (inlined into_result::<u32, i32>) { // at $DIR/simplify_try.rs:21:19: 21:33
+-         debug r => _4;                   // in scope 4 at $DIR/simplify_try.rs:21:19: 21:33
++         debug r => _0;                   // in scope 4 at $DIR/simplify_try.rs:21:19: 21:33
       }
   
       bb0: {
-          StorageLive(_2);                 // scope 0 at $DIR/simplify_try.rs:8:9: 8:10
--         StorageLive(_3);                 // scope 0 at $DIR/simplify_try.rs:8:13: 8:15
--         StorageLive(_4);                 // scope 0 at $DIR/simplify_try.rs:8:13: 8:14
--         _4 = _1;                         // scope 0 at $DIR/simplify_try.rs:8:13: 8:14
--         _3 = move _4;                    // scope 6 at $DIR/simplify_try.rs:8:13: 8:15
--         StorageDead(_4);                 // scope 0 at $DIR/simplify_try.rs:8:14: 8:15
--         _5 = discriminant(_3);           // scope 0 at $DIR/simplify_try.rs:8:14: 8:15
-+         nop;                             // scope 0 at $DIR/simplify_try.rs:8:13: 8:15
-+         nop;                             // scope 0 at $DIR/simplify_try.rs:8:13: 8:14
-+         _0 = _1;                         // scope 0 at $DIR/simplify_try.rs:8:13: 8:14
-+         nop;                             // scope 6 at $DIR/simplify_try.rs:8:13: 8:15
-+         nop;                             // scope 0 at $DIR/simplify_try.rs:8:14: 8:15
-+         _5 = discriminant(_0);           // scope 0 at $DIR/simplify_try.rs:8:14: 8:15
-          goto -> bb1;                     // scope 0 at $DIR/simplify_try.rs:8:14: 8:15
+          StorageLive(_2);                 // scope 0 at $DIR/simplify_try.rs:21:9: 21:10
+-         StorageLive(_3);                 // scope 0 at $DIR/simplify_try.rs:21:19: 21:33
+-         StorageLive(_4);                 // scope 0 at $DIR/simplify_try.rs:21:31: 21:32
+-         _4 = _1;                         // scope 0 at $DIR/simplify_try.rs:21:31: 21:32
+-         _3 = move _4;                    // scope 4 at $DIR/simplify_try.rs:21:19: 21:33
+-         StorageDead(_4);                 // scope 0 at $DIR/simplify_try.rs:21:32: 21:33
+-         _5 = discriminant(_3);           // scope 0 at $DIR/simplify_try.rs:22:9: 22:15
++         nop;                             // scope 0 at $DIR/simplify_try.rs:21:19: 21:33
++         nop;                             // scope 0 at $DIR/simplify_try.rs:21:31: 21:32
++         _0 = _1;                         // scope 0 at $DIR/simplify_try.rs:21:31: 21:32
++         nop;                             // scope 4 at $DIR/simplify_try.rs:21:19: 21:33
++         nop;                             // scope 0 at $DIR/simplify_try.rs:21:32: 21:33
++         _5 = discriminant(_0);           // scope 0 at $DIR/simplify_try.rs:22:9: 22:15
+          goto -> bb1;                     // scope 0 at $DIR/simplify_try.rs:22:9: 22:15
       }
   
       bb1: {
--         _0 = move _3;                    // scope 1 at $DIR/simplify_try.rs:9:5: 9:10
--         StorageDead(_3);                 // scope 0 at $DIR/simplify_try.rs:8:15: 8:16
-+         nop;                             // scope 1 at $DIR/simplify_try.rs:9:5: 9:10
-+         nop;                             // scope 0 at $DIR/simplify_try.rs:8:15: 8:16
-          StorageDead(_2);                 // scope 0 at $DIR/simplify_try.rs:10:1: 10:2
-          return;                          // scope 0 at $DIR/simplify_try.rs:10:2: 10:2
+-         _0 = move _3;                    // scope 1 at $DIR/simplify_try.rs:25:5: 25:10
+-         StorageDead(_3);                 // scope 0 at $DIR/simplify_try.rs:24:6: 24:7
++         nop;                             // scope 1 at $DIR/simplify_try.rs:25:5: 25:10
++         nop;                             // scope 0 at $DIR/simplify_try.rs:24:6: 24:7
+          StorageDead(_2);                 // scope 0 at $DIR/simplify_try.rs:26:1: 26:2
+          return;                          // scope 0 at $DIR/simplify_try.rs:26:2: 26:2
       }
   }