Improves migrations lint for RFC2229

src/test/ui/closures/2229_closure_analysis/migrations/auto_traits.fixed

@@ -1,5 +1,6 @@
 // run-rustfix
 #![deny(rust_2021_incompatible_closure_captures)]
+//~^ NOTE: the lint level is defined here
 
 use std::thread;
 
@@ -11,9 +12,12 @@ fn test_send_trait() {
     let mut f = 10;
     let fptr = SendPointer(&mut f as *mut i32);
     thread::spawn(move || { let _ = &fptr; unsafe {
-        //~^ ERROR: `Send` trait implementation
+        //~^ ERROR: `Send` trait implementation for closure
+        //~| NOTE: in Rust 2018, this closure would implement `Send` as `fptr` implements `Send`, but in Rust 2021, this closure would no longer implement `Send` as `fptr.0` does not implement `Send`
+        //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `fptr` to be fully captured
         *fptr.0 = 20;
+        //~^ NOTE: in Rust 2018, closure captures all of `fptr`, but in Rust 2021, it only captures `fptr.0`
     } });
 }
 
@@ -28,9 +32,12 @@ fn test_sync_trait() {
     let f = CustomInt(&mut f as *mut i32);
     let fptr = SyncPointer(f);
     thread::spawn(move || { let _ = &fptr; unsafe {
-        //~^ ERROR: `Sync`, `Send` trait implementation
+        //~^ ERROR: `Sync`, `Send` trait implementation for closure
+        //~| NOTE: in Rust 2018, this closure would implement `Sync`, `Send` as `fptr` implements `Sync`, `Send`, but in Rust 2021, this closure would no longer implement `Sync`, `Send` as `fptr.0.0` does not implement `Sync`, `Send`
+        //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `fptr` to be fully captured
         *fptr.0.0 = 20;
+        //~^ NOTE: in Rust 2018, closure captures all of `fptr`, but in Rust 2021, it only captures `fptr.0.0`
     } });
 }
 
@@ -49,16 +56,20 @@ impl Clone for U {
 fn test_clone_trait() {
     let f = U(S(String::from("Hello World")), T(0));
     let c = || { let _ = &f; 
-        //~^ ERROR: `Clone` trait implementation, and drop order
+        //~^ ERROR: `Clone` trait implementation for closure and drop order
+        //~| NOTE: in Rust 2018, this closure would implement `Clone` as `f` implements `Clone`, but in Rust 2021, this closure would no longer implement `Clone` as `f.1` does not implement `Clone`
+        //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `f` to be fully captured
         let f_1 = f.1;
+        //~^ NOTE: in Rust 2018, closure captures all of `f`, but in Rust 2021, it only captures `f.1`
         println!("{:?}", f_1.0);
     };
 
     let c_clone = c.clone();
 
     c_clone();
 }
+//~^ NOTE: in Rust 2018, `f` would be dropped here, but in Rust 2021, only `f.1` would be dropped here alongside the closure
 
 fn main() {
     test_send_trait();

src/test/ui/closures/2229_closure_analysis/migrations/auto_traits.rs

@@ -1,5 +1,6 @@
 // run-rustfix
 #![deny(rust_2021_incompatible_closure_captures)]
+//~^ NOTE: the lint level is defined here
 
 use std::thread;
 
@@ -11,9 +12,12 @@ fn test_send_trait() {
     let mut f = 10;
     let fptr = SendPointer(&mut f as *mut i32);
     thread::spawn(move || unsafe {
-        //~^ ERROR: `Send` trait implementation
+        //~^ ERROR: `Send` trait implementation for closure
+        //~| NOTE: in Rust 2018, this closure would implement `Send` as `fptr` implements `Send`, but in Rust 2021, this closure would no longer implement `Send` as `fptr.0` does not implement `Send`
+        //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `fptr` to be fully captured
         *fptr.0 = 20;
+        //~^ NOTE: in Rust 2018, closure captures all of `fptr`, but in Rust 2021, it only captures `fptr.0`
     });
 }
 
@@ -28,9 +32,12 @@ fn test_sync_trait() {
     let f = CustomInt(&mut f as *mut i32);
     let fptr = SyncPointer(f);
     thread::spawn(move || unsafe {
-        //~^ ERROR: `Sync`, `Send` trait implementation
+        //~^ ERROR: `Sync`, `Send` trait implementation for closure
+        //~| NOTE: in Rust 2018, this closure would implement `Sync`, `Send` as `fptr` implements `Sync`, `Send`, but in Rust 2021, this closure would no longer implement `Sync`, `Send` as `fptr.0.0` does not implement `Sync`, `Send`
+        //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `fptr` to be fully captured
         *fptr.0.0 = 20;
+        //~^ NOTE: in Rust 2018, closure captures all of `fptr`, but in Rust 2021, it only captures `fptr.0.0`
     });
 }
 
@@ -49,16 +56,20 @@ impl Clone for U {
 fn test_clone_trait() {
     let f = U(S(String::from("Hello World")), T(0));
     let c = || {
-        //~^ ERROR: `Clone` trait implementation, and drop order
+        //~^ ERROR: `Clone` trait implementation for closure and drop order
+        //~| NOTE: in Rust 2018, this closure would implement `Clone` as `f` implements `Clone`, but in Rust 2021, this closure would no longer implement `Clone` as `f.1` does not implement `Clone`
+        //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `f` to be fully captured
         let f_1 = f.1;
+        //~^ NOTE: in Rust 2018, closure captures all of `f`, but in Rust 2021, it only captures `f.1`
         println!("{:?}", f_1.0);
     };
 
     let c_clone = c.clone();
 
     c_clone();
 }
+//~^ NOTE: in Rust 2018, `f` would be dropped here, but in Rust 2021, only `f.1` would be dropped here alongside the closure
 
 fn main() {
     test_send_trait();

src/test/ui/closures/2229_closure_analysis/migrations/auto_traits.stderr

@@ -1,13 +1,11 @@
-error: `Send` trait implementation will change in Rust 2021
-  --> $DIR/auto_traits.rs:13:19
+error: changes to closure capture in Rust 2021 will affect `Send` trait implementation for closure
+  --> $DIR/auto_traits.rs:14:19
    |
-LL |       thread::spawn(move || unsafe {
-   |  ___________________^
-LL | |
-LL | |
-LL | |         *fptr.0 = 20;
-LL | |     });
-   | |_____^
+LL |     thread::spawn(move || unsafe {
+   |                   ^^^^^^^^^^^^^^ in Rust 2018, this closure would implement `Send` as `fptr` implements `Send`, but in Rust 2021, this closure would no longer implement `Send` as `fptr.0` does not implement `Send`
+...
+LL |         *fptr.0 = 20;
+   |         ------- in Rust 2018, closure captures all of `fptr`, but in Rust 2021, it only captures `fptr.0`
    |
 note: the lint level is defined here
   --> $DIR/auto_traits.rs:2:9
@@ -20,53 +18,53 @@ help: add a dummy let to cause `fptr` to be fully captured
 LL |     thread::spawn(move || { let _ = &fptr; unsafe {
 LL |
 LL |
+LL |
+LL |
 LL |         *fptr.0 = 20;
-LL |     } });
-   |
+ ...
 
-error: `Sync`, `Send` trait implementation will change in Rust 2021
-  --> $DIR/auto_traits.rs:30:19
+error: changes to closure capture in Rust 2021 will affect `Sync`, `Send` trait implementation for closure
+  --> $DIR/auto_traits.rs:34:19
    |
-LL |       thread::spawn(move || unsafe {
-   |  ___________________^
-LL | |
-LL | |
-LL | |         *fptr.0.0 = 20;
-LL | |     });
-   | |_____^
+LL |     thread::spawn(move || unsafe {
+   |                   ^^^^^^^^^^^^^^ in Rust 2018, this closure would implement `Sync`, `Send` as `fptr` implements `Sync`, `Send`, but in Rust 2021, this closure would no longer implement `Sync`, `Send` as `fptr.0.0` does not implement `Sync`, `Send`
+...
+LL |         *fptr.0.0 = 20;
+   |         --------- in Rust 2018, closure captures all of `fptr`, but in Rust 2021, it only captures `fptr.0.0`
    |
    = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/disjoint-capture-in-closures.html>
 help: add a dummy let to cause `fptr` to be fully captured
    |
 LL |     thread::spawn(move || { let _ = &fptr; unsafe {
 LL |
 LL |
+LL |
+LL |
 LL |         *fptr.0.0 = 20;
-LL |     } });
-   |
+ ...
 
-error: `Clone` trait implementation, and drop order will change in Rust 2021
-  --> $DIR/auto_traits.rs:51:13
+error: changes to closure capture in Rust 2021 will affect `Clone` trait implementation for closure and drop order
+  --> $DIR/auto_traits.rs:58:13
    |
-LL |       let c = || {
-   |  _____________^
-LL | |
-LL | |
-LL | |         let f_1 = f.1;
-LL | |         println!("{:?}", f_1.0);
-LL | |     };
-   | |_____^
+LL |     let c = || {
+   |             ^^ in Rust 2018, this closure would implement `Clone` as `f` implements `Clone`, but in Rust 2021, this closure would no longer implement `Clone` as `f.1` does not implement `Clone`
+...
+LL |         let f_1 = f.1;
+   |                   --- in Rust 2018, closure captures all of `f`, but in Rust 2021, it only captures `f.1`
+...
+LL | }
+   | - in Rust 2018, `f` would be dropped here, but in Rust 2021, only `f.1` would be dropped here alongside the closure
    |
    = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/disjoint-capture-in-closures.html>
 help: add a dummy let to cause `f` to be fully captured
    |
 LL |     let c = || { let _ = &f; 
 LL |
 LL |
+LL |
+LL |
 LL |         let f_1 = f.1;
-LL |         println!("{:?}", f_1.0);
-LL |     };
-   |
+ ...
 
 error: aborting due to 3 previous errors
 

src/test/ui/closures/2229_closure_analysis/migrations/insignificant_drop.fixed

@@ -18,12 +18,18 @@ fn test1_all_need_migration() {
         //~| HELP: add a dummy let to cause `t`, `t1`, `t2` to be fully captured
 
         let _t = t.0;
+        //~^ NOTE: in Rust 2018, closure captures all of `t`, but in Rust 2021, it only captures `t.0`
         let _t1 = t1.0;
+        //~^ NOTE: in Rust 2018, closure captures all of `t1`, but in Rust 2021, it only captures `t1.0`
         let _t2 = t2.0;
+        //~^ NOTE: in Rust 2018, closure captures all of `t2`, but in Rust 2021, it only captures `t2.0`
     };
 
     c();
 }
+//~^ in Rust 2018, `t` would be dropped here, but in Rust 2021, only `t.0` would be dropped here alongside the closure
+//~| in Rust 2018, `t1` would be dropped here, but in Rust 2021, only `t1.0` would be dropped here alongside the closure
+//~| in Rust 2018, `t2` would be dropped here, but in Rust 2021, only `t2.0` would be dropped here alongside the closure
 
 // String implements drop and therefore should be migrated.
 // But in this test cases, `t2` is completely captured and when it is dropped won't be affected
@@ -37,12 +43,16 @@ fn test2_only_precise_paths_need_migration() {
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t`, `t1` to be fully captured
         let _t = t.0;
+        //~^ NOTE: in Rust 2018, closure captures all of `t`, but in Rust 2021, it only captures `t.0`
         let _t1 = t1.0;
+        //~^ NOTE: in Rust 2018, closure captures all of `t1`, but in Rust 2021, it only captures `t1.0`
         let _t2 = t2;
     };
 
     c();
 }
+//~^ in Rust 2018, `t` would be dropped here, but in Rust 2021, only `t.0` would be dropped here alongside the closure
+//~| in Rust 2018, `t1` would be dropped here, but in Rust 2021, only `t1.0` would be dropped here alongside the closure
 
 // If a variable would've not been captured by value then it would've not been
 // dropped with the closure and therefore doesn't need migration.
@@ -54,11 +64,13 @@ fn test3_only_by_value_need_migration() {
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
+        //~^ NOTE: in Rust 2018, closure captures all of `t`, but in Rust 2021, it only captures `t.0`
         println!("{}", t1.1);
     };
 
     c();
 }
+//~^ in Rust 2018, `t` would be dropped here, but in Rust 2021, only `t.0` would be dropped here alongside the closure
 
 // Copy types get copied into the closure instead of move. Therefore we don't need to
 // migrate then as their drop order isn't tied to the closure.
@@ -73,11 +85,13 @@ fn test4_only_non_copy_types_need_migration() {
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
+        //~^ NOTE: in Rust 2018, closure captures all of `t`, but in Rust 2021, it only captures `t.0`
         let _t1 = t1.0;
     };
 
     c();
 }
+//~^ in Rust 2018, `t` would be dropped here, but in Rust 2021, only `t.0` would be dropped here alongside the closure
 
 fn test5_only_drop_types_need_migration() {
     struct S(i32, i32);
@@ -92,11 +106,13 @@ fn test5_only_drop_types_need_migration() {
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
+        //~^ NOTE: in Rust 2018, closure captures all of `t`, but in Rust 2021, it only captures `t.0`
         let _s = s.0;
     };
 
     c();
 }
+//~^ in Rust 2018, `t` would be dropped here, but in Rust 2021, only `t.0` would be dropped here alongside the closure
 
 // Since we are using a move closure here, both `t` and `t1` get moved
 // even though they are being used by ref inside the closure.
@@ -108,10 +124,14 @@ fn test6_move_closures_non_copy_types_might_need_migration() {
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t1`, `t` to be fully captured
         println!("{} {}", t1.1, t.1);
+        //~^ NOTE: in Rust 2018, closure captures all of `t`, but in Rust 2021, it only captures `t.1`
+        //~| NOTE: in Rust 2018, closure captures all of `t1`, but in Rust 2021, it only captures `t1.1`
     };
 
     c();
 }
+//~^ in Rust 2018, `t` would be dropped here, but in Rust 2021, only `t.1` would be dropped here alongside the closure
+//~| in Rust 2018, `t1` would be dropped here, but in Rust 2021, only `t1.1` would be dropped here alongside the closure
 
 // Test migration analysis in case of Drop + Non Drop aggregates.
 // Note we need migration here only because the non-copy (because Drop type) is captured,
@@ -124,10 +144,12 @@ fn test7_drop_non_drop_aggregate_need_migration() {
         //~| NOTE: for more information, see
         //~| HELP: add a dummy let to cause `t` to be fully captured
         let _t = t.0;
+        //~^ NOTE: in Rust 2018, closure captures all of `t`, but in Rust 2021, it only captures `t.0`
     };
 
     c();
 }
+//~^ in Rust 2018, `t` would be dropped here, but in Rust 2021, only `t.0` would be dropped here alongside the closure
 
 fn main() {
     test1_all_need_migration();