stabilize if_let_rescope

compiler/rustc_feature/src/accepted.rs

@@ -224,6 +224,8 @@ macro_rules! declare_features {
     (accepted, i128_type, "1.26.0", Some(35118)),
     /// Allows the use of `if let` expressions.
     (accepted, if_let, "1.0.0", None),
+    /// Rescoping temporaries in `if let` to align with Rust 2024.
+    (accepted, if_let_rescope, "CURRENT_RUSTC_VERSION", Some(124085)),
     /// Allows top level or-patterns (`p | q`) in `if let` and `while let`.
     (accepted, if_while_or_patterns, "1.33.0", Some(48215)),
     /// Allows lifetime elision in `impl` headers. For example:

compiler/rustc_feature/src/unstable.rs

@@ -482,8 +482,6 @@ pub fn internal(&self, feature: Symbol) -> bool {
     (unstable, half_open_range_patterns_in_slices, "1.66.0", Some(67264)),
     /// Allows `if let` guard in match arms.
     (unstable, if_let_guard, "1.47.0", Some(51114)),
-    /// Rescoping temporaries in `if let` to align with Rust 2024.
-    (unstable, if_let_rescope, "1.83.0", Some(124085)),
     /// Allows `impl Trait` to be used inside associated types (RFC 2515).
     (unstable, impl_trait_in_assoc_type, "1.70.0", Some(63063)),
     /// Allows `impl Trait` as output type in `Fn` traits in return position of functions.

compiler/rustc_hir_analysis/src/check/region.rs

@@ -466,8 +466,7 @@ fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx h
 
         hir::ExprKind::If(cond, then, Some(otherwise)) => {
             let expr_cx = visitor.cx;
-            let data = if expr.span.at_least_rust_2024() && visitor.tcx.features().if_let_rescope()
+            let data = if expr.span.at_least_rust_2024() {
-            {
                 ScopeData::IfThenRescope
             } else {
                 ScopeData::IfThen
@@ -482,8 +481,7 @@ fn resolve_expr<'tcx>(visitor: &mut RegionResolutionVisitor<'tcx>, expr: &'tcx h
 
         hir::ExprKind::If(cond, then, None) => {
             let expr_cx = visitor.cx;
-            let data = if expr.span.at_least_rust_2024() && visitor.tcx.features().if_let_rescope()
+            let data = if expr.span.at_least_rust_2024() {
-            {
                 ScopeData::IfThenRescope
             } else {
                 ScopeData::IfThen

compiler/rustc_lint/src/if_let_rescope.rs

@@ -24,7 +24,6 @@
     /// ### Example
     ///
     /// ```rust,edition2021
-    /// #![feature(if_let_rescope)]
     /// #![warn(if_let_rescope)]
     /// #![allow(unused_variables)]
     ///
@@ -243,7 +242,7 @@ fn probe_if_cascade<'tcx>(&mut self, cx: &LateContext<'tcx>, mut expr: &'tcx hir
 
 impl<'tcx> LateLintPass<'tcx> for IfLetRescope {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
-        if expr.span.edition().at_least_rust_2024() || !cx.tcx.features().if_let_rescope() {
+        if expr.span.edition().at_least_rust_2024() {
             return;
         }
         if let (Level::Allow, _) = cx.tcx.lint_level_at_node(IF_LET_RESCOPE, expr.hir_id) {

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -777,7 +777,7 @@ fn make_mirror_unadjusted(&mut self, expr: &'tcx hir::Expr<'tcx>) -> Expr<'tcx>
                 if_then_scope: region::Scope {
                     id: then.hir_id.local_id,
                     data: {
-                        if expr.span.at_least_rust_2024() && tcx.features().if_let_rescope() {
+                        if expr.span.at_least_rust_2024() {
                             region::ScopeData::IfThenRescope
                         } else {
                             region::ScopeData::IfThen

tests/ui/drop/drop_order.rs

@@ -4,8 +4,8 @@
 //@ [edition2021] edition: 2021
 //@ [edition2024] compile-flags: -Z unstable-options
 //@ [edition2024] edition: 2024
+
 #![feature(let_chains)]
-#![cfg_attr(edition2024, feature(if_let_rescope))]
 
 use std::cell::RefCell;
 use std::convert::TryInto;

tests/ui/drop/drop_order_if_let_rescope.rs

@@ -3,7 +3,6 @@
 //@ compile-flags: -Z validate-mir -Zunstable-options
 
 #![feature(let_chains)]
-#![feature(if_let_rescope)]
 
 use std::cell::RefCell;
 use std::convert::TryInto;

tests/ui/drop/if-let-rescope-borrowck-suggestions.rs

@@ -1,7 +1,6 @@
 //@ edition: 2024
 //@ compile-flags: -Z validate-mir -Zunstable-options
 
-#![feature(if_let_rescope)]
 #![deny(if_let_rescope)]
 
 struct Droppy;

tests/ui/drop/if-let-rescope-borrowck-suggestions.stderr

@@ -1,5 +1,5 @@
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/if-let-rescope-borrowck-suggestions.rs:22:39
+  --> $DIR/if-let-rescope-borrowck-suggestions.rs:21:39
    |
 LL |     do_something(if let Some(value) = Droppy.get_ref() { value } else { &0 });
    |                                       ^^^^^^                   - temporary value is freed at the end of this statement
@@ -7,7 +7,7 @@ LL |     do_something(if let Some(value) = Droppy.get_ref() { value } else { &0
    |                                       creates a temporary value which is freed while still in use
    |
 note: lifetimes for temporaries generated in `if let`s have been shortened in Edition 2024 so that they are dropped here instead
-  --> $DIR/if-let-rescope-borrowck-suggestions.rs:22:64
+  --> $DIR/if-let-rescope-borrowck-suggestions.rs:21:64
    |
 LL |     do_something(if let Some(value) = Droppy.get_ref() { value } else { &0 });
    |                                                                ^
@@ -22,7 +22,7 @@ LL |     do_something({ match Droppy.get_ref()  { Some(value) => { value } _ =>
    |                  ~~~~~~~                   ++++++++++++++++           ~~~~       ++
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/if-let-rescope-borrowck-suggestions.rs:24:39
+  --> $DIR/if-let-rescope-borrowck-suggestions.rs:23:39
    |
 LL |     do_something(if let Some(value) = Droppy.get_ref() {
    |                                       ^^^^^^ creates a temporary value which is freed while still in use
@@ -31,7 +31,7 @@ LL |     } else if let Some(value) = Droppy.get_ref() {
    |     - temporary value is freed at the end of this statement
    |
 note: lifetimes for temporaries generated in `if let`s have been shortened in Edition 2024 so that they are dropped here instead
-  --> $DIR/if-let-rescope-borrowck-suggestions.rs:27:5
+  --> $DIR/if-let-rescope-borrowck-suggestions.rs:26:5
    |
 LL |     } else if let Some(value) = Droppy.get_ref() {
    |     ^
@@ -53,7 +53,7 @@ LL ~     }}});
    |
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/if-let-rescope-borrowck-suggestions.rs:27:33
+  --> $DIR/if-let-rescope-borrowck-suggestions.rs:26:33
    |
 LL |     } else if let Some(value) = Droppy.get_ref() {
    |                                 ^^^^^^ creates a temporary value which is freed while still in use
@@ -62,7 +62,7 @@ LL |     } else {
    |     - temporary value is freed at the end of this statement
    |
 note: lifetimes for temporaries generated in `if let`s have been shortened in Edition 2024 so that they are dropped here instead
-  --> $DIR/if-let-rescope-borrowck-suggestions.rs:30:5
+  --> $DIR/if-let-rescope-borrowck-suggestions.rs:29:5
    |
 LL |     } else {
    |     ^

tests/ui/drop/lint-if-let-rescope-gated.rs

@@ -1,13 +1,13 @@
 // This test checks that the lint `if_let_rescope` only actions
-// when the feature gate is enabled.
+// when Edition 2021 or prior is targeted here because the lint should work especially
-// Edition 2021 is used here because the lint should work especially
+// when edition migration towards 2024 is executed.
-// when edition migration towards 2024 is run.
 
-//@ revisions: with_feature_gate without_feature_gate
+//@ revisions: edition2021 edition2024
-//@ [without_feature_gate] check-pass
+//@ [edition2021] edition: 2021
-//@ edition: 2021
+//@ [edition2024] edition: 2024
+//@ [edition2024] compile-flags: -Zunstable-options
+//@ [edition2024] check-pass
 
-#![cfg_attr(with_feature_gate, feature(if_let_rescope))]
 #![deny(if_let_rescope)]
 #![allow(irrefutable_let_patterns)]
 
@@ -25,10 +25,10 @@ fn get(&self) -> Option<u8> {
 
 fn main() {
     if let Some(_value) = Droppy.get() {
-        //[with_feature_gate]~^ ERROR: `if let` assigns a shorter lifetime since Edition 2024
+        //[edition2021]~^ ERROR: `if let` assigns a shorter lifetime since Edition 2024
-        //[with_feature_gate]~| HELP: a `match` with a single arm can preserve the drop order up to Edition 2021
+        //[edition2021]~| HELP: a `match` with a single arm can preserve the drop order up to Edition 2021
-        //[with_feature_gate]~| WARN: this changes meaning in Rust 2024
+        //[edition2021]~| WARN: this changes meaning in Rust 2024
     } else {
-        //[with_feature_gate]~^ HELP: the value is now dropped here in Edition 2024
+        //[edition2021]~^ HELP: the value is now dropped here in Edition 2024
     }
 }

tests/ui/drop/lint-if-let-rescope-with-macro.rs

@@ -4,7 +4,6 @@
 //@ edition:2021
 //@ compile-flags: -Z unstable-options
 
-#![feature(if_let_rescope)]
 #![deny(if_let_rescope)]
 #![allow(irrefutable_let_patterns)]
 

tests/ui/drop/lint-if-let-rescope-with-macro.stderr

@@ -1,5 +1,5 @@
 error: `if let` assigns a shorter lifetime since Edition 2024
-  --> $DIR/lint-if-let-rescope-with-macro.rs:13:12
+  --> $DIR/lint-if-let-rescope-with-macro.rs:12:12
    |
 LL |           if let $p = $e { $($conseq)* } else { $($alt)* }
    |              ^^^
@@ -16,7 +16,7 @@ LL | |     };
    = warning: this changes meaning in Rust 2024
    = note: for more information, see issue #124085 <https://github.com/rust-lang/rust/issues/124085>
 help: the value is now dropped here in Edition 2024
-  --> $DIR/lint-if-let-rescope-with-macro.rs:13:38
+  --> $DIR/lint-if-let-rescope-with-macro.rs:12:38
    |
 LL |           if let $p = $e { $($conseq)* } else { $($alt)* }
    |                                        ^
@@ -29,7 +29,7 @@ LL | |         {}
 LL | |     };
    | |_____- in this macro invocation
 note: the lint level is defined here
-  --> $DIR/lint-if-let-rescope-with-macro.rs:8:9
+  --> $DIR/lint-if-let-rescope-with-macro.rs:7:9
    |
 LL | #![deny(if_let_rescope)]
    |         ^^^^^^^^^^^^^^

tests/ui/drop/lint-if-let-rescope.fixed

@@ -1,7 +1,7 @@
 //@ run-rustfix
 
 #![deny(if_let_rescope)]
-#![feature(if_let_rescope, stmt_expr_attributes)]
+#![feature(stmt_expr_attributes)]
 #![allow(irrefutable_let_patterns, unused_parens)]
 
 fn droppy() -> Droppy {

tests/ui/drop/lint-if-let-rescope.rs

@@ -1,7 +1,7 @@
 //@ run-rustfix
 
 #![deny(if_let_rescope)]
-#![feature(if_let_rescope, stmt_expr_attributes)]
+#![feature(stmt_expr_attributes)]
 #![allow(irrefutable_let_patterns, unused_parens)]
 
 fn droppy() -> Droppy {

tests/ui/feature-gates/feature-gate-if-let-rescope.rs

@@ -1,27 +0,0 @@
-// This test shows the code that could have been accepted by enabling #![feature(if_let_rescope)]
-
-struct A;
-struct B<'a, T>(&'a mut T);
-
-impl A {
-    fn f(&mut self) -> Option<B<'_, Self>> {
-        Some(B(self))
-    }
-}
-
-impl<'a, T> Drop for B<'a, T> {
-    fn drop(&mut self) {
-        // this is needed to keep NLL's hands off and to ensure
-        // the inner mutable borrow stays alive
-    }
-}
-
-fn main() {
-    let mut a = A;
-    if let None = a.f().as_ref() {
-        unreachable!()
-    } else {
-        a.f().unwrap();
-        //~^ ERROR cannot borrow `a` as mutable more than once at a time
-    };
-}

tests/ui/feature-gates/feature-gate-if-let-rescope.stderr

@@ -1,18 +0,0 @@
-error[E0499]: cannot borrow `a` as mutable more than once at a time
-  --> $DIR/feature-gate-if-let-rescope.rs:24:9
-   |
-LL |     if let None = a.f().as_ref() {
-   |                   -----
-   |                   |
-   |                   first mutable borrow occurs here
-   |                   a temporary with access to the first borrow is created here ...
-...
-LL |         a.f().unwrap();
-   |         ^ second mutable borrow occurs here
-LL |
-LL |     };
-   |      - ... and the first borrow might be used here, when that temporary is dropped and runs the destructor for type `Option<B<'_, A>>`
-
-error: aborting due to 1 previous error
-
-For more information about this error, try `rustc --explain E0499`.

tests/ui/mir/mir_let_chains_drop_order.rs

@@ -8,7 +8,6 @@
 // See `mir_drop_order.rs` for more information
 
 #![feature(let_chains)]
-#![cfg_attr(edition2024, feature(if_let_rescope))]
 #![allow(irrefutable_let_patterns)]
 
 use std::cell::RefCell;

tests/ui/nll/issue-54556-niconii.edition2021.stderr

@@ -1,5 +1,5 @@
 error[E0597]: `counter` does not live long enough
-  --> $DIR/issue-54556-niconii.rs:30:20
+  --> $DIR/issue-54556-niconii.rs:28:20
    |
 LL |     let counter = Mutex;
    |         ------- binding `counter` declared here

tests/ui/nll/issue-54556-niconii.rs

@@ -12,8 +12,6 @@
 //@ [edition2024] compile-flags: -Z unstable-options
 //@ [edition2024] check-pass
 
-#![cfg_attr(edition2024, feature(if_let_rescope))]
-
 struct Mutex;
 struct MutexGuard<'a>(&'a Mutex);