fine-tune the drop span and messages

Author: dingxiangfei2009

compiler/rustc_mir_transform/messages.ftl

@@ -26,14 +26,14 @@ mir_transform_must_not_suspend = {$pre}`{$def_path}`{$post} held across a suspen
 mir_transform_operation_will_panic = this operation will panic at runtime
 
 mir_transform_tail_expr_drop_order = relative drop order changing in Rust 2024
-    .temporaries = in Rust 2024, this temporary will be dropped first
+    .temporaries = in Rust 2024, this temporary value will be dropped first
     .observers = in Rust 2024, this local variable or temporary value will be dropped second
     .note_dtors =
-        dropping the temporary runs this custom `Drop` impl, which will run first in Rust 2024
+        dropping the temporary value runs this custom `Drop` impl, which will run first in Rust 2024
     .note_observer_dtors =
         dropping the local runs this custom `Drop` impl, which will run second in Rust 2024
     .drop_location =
-        temporary will be dropped on exiting the block, before the block's local variables
+        now the temporary value is dropped here, before the local variables in the block or statement
     .note_epilogue = most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
     .label_local_epilogue = {$is_dropped_first_edition_2024 ->
         [true] up until Edition 2021 `{$name}` is dropped last but will be dropped earlier in Edition 2024

compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs

@@ -129,8 +129,7 @@ impl<'a, 'mir, 'tcx> DropsReachable<'a, 'mir, 'tcx> {
                 if self.drop_span.is_none() {
                     // FIXME(@dingxiangfei2009): it turns out that `self.body.source_scopes` are still a bit wonky.
                     // There is a high chance that this span still points to a block rather than a statement semicolon.
-                    *self.drop_span =
-                        Some(self.body.source_scopes[terminator.source_info.scope].span);
+                    *self.drop_span = Some(terminator.source_info.span);
                 }
                 // Now we have discovered a simple control flow path from a future drop point
                 // to the current drop point.

tests/ui/drop/lint-tail-expr-drop-order.rs

@@ -35,7 +35,6 @@ impl LoudDropper {
 }
 
 fn should_lint() -> i32 {
-    //~^ NOTE: temporary will be dropped on exiting the block, before the block's local variables
     let x = LoudDropper;
     //~^ NOTE: `x` calls a custom destructor
     //~| NOTE: `x` will be dropped later since Edition 2024
@@ -48,6 +47,7 @@ fn should_lint() -> i32 {
     //~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
     //~| NOTE: for more information, see issue #123739
 }
+//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
 
 fn should_not_lint_closure() -> impl FnOnce() -> i32 {
     let x = LoudDropper;
@@ -60,7 +60,6 @@ fn should_not_lint_closure() -> impl FnOnce() -> i32 {
 
 fn should_lint_in_nested_items() {
     fn should_lint_me() -> i32 {
-        //~^ NOTE: temporary will be dropped on exiting the block, before the block's local variables
         let x = LoudDropper;
         //~^ NOTE: `x` calls a custom destructor
         //~| NOTE: `x` will be dropped later since Edition 2024
@@ -73,6 +72,7 @@ fn should_lint_in_nested_items() {
         //~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
         //~| NOTE: for more information, see issue #123739
     }
+    //~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
 }
 
 fn should_not_lint_params(x: LoudDropper) -> i32 {
@@ -88,7 +88,6 @@ fn should_not_lint() -> i32 {
 }
 
 fn should_lint_in_nested_block() -> i32 {
-    //~^ NOTE: temporary will be dropped on exiting the block, before the block's local variables
     let x = LoudDropper;
     //~^ NOTE: `x` calls a custom destructor
     //~| NOTE: `x` will be dropped later since Edition 2024
@@ -100,6 +99,7 @@ fn should_lint_in_nested_block() -> i32 {
     //~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
     //~| NOTE: for more information, see issue #123739
 }
+//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
 
 fn should_not_lint_in_match_arm() -> i32 {
     let x = LoudDropper;
@@ -134,7 +134,6 @@ fn should_not_lint_when_moved() -> i32 {
 }
 
 fn should_lint_into_async_body() -> i32 {
-    //~^ NOTE: temporary will be dropped on exiting the block, before the block's local variables
     async fn f() {
         async fn f() {}
         let x = LoudDropper;
@@ -153,9 +152,9 @@ fn should_lint_into_async_body() -> i32 {
     //~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
     //~| NOTE: for more information, see issue #123739
 }
+//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
 
 fn should_lint_generics<T: Default>() -> &'static str {
-    //~^ NOTE: temporary will be dropped on exiting the block, before the block's local variables
     fn extract<T>(_: &T) -> &'static str {
         todo!()
     }
@@ -170,9 +169,9 @@ fn should_lint_generics<T: Default>() -> &'static str {
     //~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
     //~| NOTE: for more information, see issue #123739
 }
+//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
 
 fn should_lint_adt() -> i32 {
-    //~^ NOTE: temporary will be dropped on exiting the block, before the block's local variables
     let x: Result<LoudDropper, ()> = Ok(LoudDropper);
     //~^ NOTE: `x` calls a custom destructor
     //~| NOTE: `x` will be dropped later since Edition 2024
@@ -184,14 +183,14 @@ fn should_lint_adt() -> i32 {
     //~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
     //~| NOTE: for more information, see issue #123739
 }
+//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
 
 fn should_not_lint_insign_dtor() -> i32 {
     let x = String::new();
     LoudDropper.get()
 }
 
 fn should_lint_with_dtor_span() -> i32 {
-    //~^ NOTE: temporary will be dropped on exiting the block, before the block's local variables
     struct LoudDropper3;
     impl Drop for LoudDropper3 {
         //~^ NOTE: `#1` invokes this custom destructor
@@ -228,9 +227,9 @@ fn should_lint_with_dtor_span() -> i32 {
     //~| NOTE: most of the time, changing drop order is harmless; inspect the `impl Drop`s for side effects
     //~| NOTE: for more information, see issue #123739
 }
+//~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
 
 fn should_lint_with_transient_drops() {
-    //~^ NOTE: temporary will be dropped on exiting the block, before the block's local variables
     drop((
         {
             LoudDropper.get()
@@ -247,6 +246,7 @@ fn should_lint_with_transient_drops() {
             //~| NOTE: `_x` will be dropped later since Edition 2024
         },
     ));
+    //~^ NOTE: now the temporary value is dropped here, before the local variables in the block or statement
 }
 
 fn main() {}