Fix `let_and_return` with temporary variables, and distinguish between Rust editions (#14180)

The first commit fixes #14164 by making sure that temporaries with
non-static references are also looked for in expressions coming from
expansion. The shortcut that was done skipped those parts and reported
an absence of short-lived temporaries, which was incorrect.

The second commit distinguishes between edition 2024 and earlier ones.
Starting from edition 2024, the problematic drop order has been fixed,
and block variables, which might be referenced in a block expression,
are freed after the block expression itself. This allows more
`let_and_return` cases to be reported starting with edition 2024,
whereas in earlier editions an intermediary variable was necessary to
reorder the drops.

Incidentally, since Clippy is compiled in edition 2024 mode, the second
commit has led to a fix in
`clippy_lints/src/matches/significant_drop_in_scrutinee.rs`.

changelog: [`let_and_return`]: lint more cases in edition 2024, and fix
a false positive involving short-lived block temporary variables in
earlier editions.

8 files changed, 944 insertions, 7 deletions

diff --git a/clippy_lints/src/matches/significant_drop_in_scrutinee.rs b/clippy_lints/src/matches/significant_drop_in_scrutinee.rs
index 35f2e780d2e..37bac561a6e 100644
--- a/clippy_lints/src/matches/significant_drop_in_scrutinee.rs
+++ b/clippy_lints/src/matches/significant_drop_in_scrutinee.rs
@@ -199,7 +199,7 @@ impl<'a, 'tcx> SigDropChecker<'a, 'tcx> {
             return false;
         }
 
-        let result = match ty.kind() {
+        match ty.kind() {
             rustc_middle::ty::Adt(adt, args) => {
                 // if some field has significant drop,
                 adt.all_fields()
@@ -223,9 +223,7 @@ impl<'a, 'tcx> SigDropChecker<'a, 'tcx> {
             rustc_middle::ty::Tuple(tys) => tys.iter().any(|ty| self.has_sig_drop_attr_impl(ty)),
             rustc_middle::ty::Array(ty, _) | rustc_middle::ty::Slice(ty) => self.has_sig_drop_attr_impl(*ty),
             _ => false,
-        };
-
-        result
+        }
     }
 }
 
diff --git a/clippy_lints/src/returns.rs b/clippy_lints/src/returns.rs
index a1cf16e6ce9..0286c9843a9 100644
--- a/clippy_lints/src/returns.rs
+++ b/clippy_lints/src/returns.rs
@@ -1,7 +1,7 @@
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_hir_and_then};
 use clippy_utils::source::{SpanRangeExt, snippet_with_context};
 use clippy_utils::sugg::has_enclosing_paren;
-use clippy_utils::visitors::{Descend, for_each_expr};
+use clippy_utils::visitors::for_each_expr;
 use clippy_utils::{
     binary_expr_needs_parentheses, fn_def_id, is_from_proc_macro, is_inside_let_else, is_res_lang_ctor,
     leaks_droppable_temporary_with_limited_lifetime, path_res, path_to_local_id, span_contains_cfg,
@@ -21,6 +21,7 @@ use rustc_middle::ty::adjustment::Adjust;
 use rustc_middle::ty::{self, GenericArgKind, Ty};
 use rustc_session::declare_lint_pass;
 use rustc_span::def_id::LocalDefId;
+use rustc_span::edition::Edition;
 use rustc_span::{BytePos, Pos, Span, sym};
 use std::borrow::Cow;
 use std::fmt::Display;
@@ -235,7 +236,7 @@ impl<'tcx> LateLintPass<'tcx> for Return {
             && let Some(initexpr) = &local.init
             && let PatKind::Binding(_, local_id, _, _) = local.pat.kind
             && path_to_local_id(retexpr, local_id)
-            && !last_statement_borrows(cx, initexpr)
+            && (cx.sess().edition() >= Edition::Edition2024 || !last_statement_borrows(cx, initexpr))
             && !initexpr.span.in_external_macro(cx.sess().source_map())
             && !retexpr.span.in_external_macro(cx.sess().source_map())
             && !local.span.from_expansion()
@@ -483,7 +484,7 @@ fn last_statement_borrows<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>)
         {
             ControlFlow::Break(())
         } else {
-            ControlFlow::Continue(Descend::from(!e.span.from_expansion()))
+            ControlFlow::Continue(())
         }
     })
     .is_some()
diff --git a/tests/ui/let_and_return.edition2021.fixed b/tests/ui/let_and_return.edition2021.fixed
new file mode 100644
index 00000000000..c160d5df30f
--- /dev/null
+++ b/tests/ui/let_and_return.edition2021.fixed
@@ -0,0 +1,265 @@
+//@revisions: edition2021 edition2024
+//@[edition2021] edition:2021
+//@[edition2024] edition:2024
+
+#![allow(unused)]
+#![warn(clippy::let_and_return)]
+
+use std::cell::RefCell;
+
+fn test() -> i32 {
+    let _y = 0; // no warning
+    
+    5
+    //~^ ERROR: returning the result of a `let` binding from a block
+    //~| NOTE: `-D clippy::let-and-return` implied by `-D warnings`
+}
+
+fn test_inner() -> i32 {
+    if true {
+        
+        5
+        //~^ ERROR: returning the result of a `let` binding from a block
+    } else {
+        0
+    }
+}
+
+fn test_nowarn_1() -> i32 {
+    let mut x = 5;
+    x += 1;
+    x
+}
+
+fn test_nowarn_2() -> i32 {
+    let x = 5;
+    x + 1
+}
+
+fn test_nowarn_3() -> (i32, i32) {
+    // this should technically warn, but we do not compare complex patterns
+    let (x, y) = (5, 9);
+    (x, y)
+}
+
+fn test_nowarn_4() -> i32 {
+    // this should technically warn, but not b/c of clippy::let_and_return, but b/c of useless type
+    let x: i32 = 5;
+    x
+}
+
+fn test_nowarn_5(x: i16) -> u16 {
+    #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
+    let x = x as u16;
+    x
+}
+
+// False positive example
+trait Decode {
+    fn decode<D: std::io::Read>(d: D) -> Result<Self, ()>
+    where
+        Self: Sized;
+}
+
+macro_rules! tuple_encode {
+    ($($x:ident),*) => (
+        impl<$($x: Decode),*> Decode for ($($x),*) {
+            #[inline]
+            #[allow(non_snake_case)]
+            fn decode<D: std::io::Read>(mut d: D) -> Result<Self, ()> {
+                // Shouldn't trigger lint
+                Ok(($({let $x = Decode::decode(&mut d)?; $x }),*))
+            }
+        }
+    );
+}
+
+fn issue_3792() -> String {
+    use std::io::{self, BufRead, Stdin};
+
+    let stdin = io::stdin();
+    // `Stdin::lock` returns `StdinLock<'static>` so `line` doesn't borrow from `stdin`
+    // https://github.com/rust-lang/rust/pull/93965
+    
+    stdin.lock().lines().next().unwrap().unwrap()
+    //~^ ERROR: returning the result of a `let` binding from a block
+}
+
+tuple_encode!(T0, T1, T2, T3, T4, T5, T6, T7);
+
+mod no_lint_if_stmt_borrows {
+    use std::cell::RefCell;
+    use std::rc::{Rc, Weak};
+    struct Bar;
+
+    impl Bar {
+        fn new() -> Self {
+            Bar {}
+        }
+        fn baz(&self) -> u32 {
+            0
+        }
+    }
+
+    fn issue_3324(value: Weak<RefCell<Bar>>) -> u32 {
+        let value = value.upgrade().unwrap();
+        let ret = value.borrow().baz();
+        ret
+        //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    fn borrows_in_closure(value: Weak<RefCell<Bar>>) -> u32 {
+        fn f(mut x: impl FnMut() -> u32) -> impl FnMut() -> u32 {
+            x
+        }
+
+        let value = value.upgrade().unwrap();
+        let ret = f(|| value.borrow().baz())();
+        ret
+        //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    mod free_function {
+        struct Inner;
+
+        struct Foo<'a> {
+            inner: &'a Inner,
+        }
+
+        impl Drop for Foo<'_> {
+            fn drop(&mut self) {}
+        }
+
+        impl<'a> Foo<'a> {
+            fn new(inner: &'a Inner) -> Self {
+                Self { inner }
+            }
+
+            fn value(&self) -> i32 {
+                42
+            }
+        }
+
+        fn some_foo(inner: &Inner) -> Foo<'_> {
+            Foo { inner }
+        }
+
+        fn test() -> i32 {
+            let x = Inner {};
+            let value = some_foo(&x).value();
+            value
+            //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+        }
+
+        fn test2() -> i32 {
+            let x = Inner {};
+            let value = Foo::new(&x).value();
+            value
+            //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+        }
+    }
+}
+
+mod issue_5729 {
+    use std::sync::Arc;
+
+    trait Foo {}
+
+    trait FooStorage {
+        fn foo_cloned(&self) -> Arc<dyn Foo>;
+    }
+
+    struct FooStorageImpl<T: Foo> {
+        foo: Arc<T>,
+    }
+
+    impl<T: Foo + 'static> FooStorage for FooStorageImpl<T> {
+        fn foo_cloned(&self) -> Arc<dyn Foo> {
+            
+            (Arc::clone(&self.foo)) as _
+            //~^ ERROR: returning the result of a `let` binding from a block
+        }
+    }
+}
+
+mod issue_11335 {
+    pub enum E<T> {
+        A(T),
+        B(T),
+    }
+
+    impl<T> E<T> {
+        pub fn inner(&self) -> &T {
+            
+
+            (match self {
+                E::A(x) => x,
+                E::B(x) => x,
+            }) as _
+            //~^ ERROR: returning the result of a `let` binding from a block
+        }
+    }
+}
+
+// https://github.com/rust-lang/rust-clippy/issues/11167
+macro_rules! fn_in_macro {
+    ($b:block) => {
+        fn f() -> usize $b
+    }
+}
+fn_in_macro!({
+    return 1;
+});
+
+fn issue9150() -> usize {
+    let x = 1;
+    #[cfg(any())]
+    panic!("can't see me");
+    x
+}
+
+fn issue12801() {
+    fn left_is_if() -> String {
+        
+        (if true { "a".to_string() } else { "b".to_string() } + "c")
+        //~^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    fn no_par_needed() -> String {
+        
+        "c".to_string() + if true { "a" } else { "b" }
+        //~^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    fn conjunctive_blocks() -> String {
+        
+        ({ "a".to_string() } + "b" + { "c" } + "d")
+        //~^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    #[allow(clippy::overly_complex_bool_expr)]
+    fn other_ops() {
+        let _ = || {
+            
+            (if true { 2 } else { 3 } << 4)
+            //~^ ERROR: returning the result of a `let` binding from a block
+        };
+        let _ = || {
+            
+            ({ true } || { false } && { 2 <= 3 })
+            //~^ ERROR: returning the result of a `let` binding from a block
+        };
+    }
+}
+
+fn issue14164() -> Result<u32, ()> {
+    let v = std::cell::RefCell::new(Some(vec![1]));
+    let r = match &*v.borrow() {
+        Some(v) => Ok(Ok(v[0])),
+        None => Ok(Ok(0)),
+    }?;
+    r
+    //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+}
+
+fn main() {}
diff --git a/tests/ui/let_and_return.edition2021.stderr b/tests/ui/let_and_return.edition2021.stderr
new file mode 100644
index 00000000000..105fa7a722d
--- /dev/null
+++ b/tests/ui/let_and_return.edition2021.stderr
@@ -0,0 +1,152 @@
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:13:5
+   |
+LL |     let x = 5;
+   |     ---------- unnecessary `let` binding
+LL |     x
+   |     ^
+   |
+   = note: `-D clippy::let-and-return` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::let_and_return)]`
+help: return the expression directly
+   |
+LL ~     
+LL ~     5
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:21:9
+   |
+LL |         let x = 5;
+   |         ---------- unnecessary `let` binding
+LL |         x
+   |         ^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         5
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:84:5
+   |
+LL |     let line = stdin.lock().lines().next().unwrap().unwrap();
+   |     --------------------------------------------------------- unnecessary `let` binding
+LL |     line
+   |     ^^^^
+   |
+help: return the expression directly
+   |
+LL ~     
+LL ~     stdin.lock().lines().next().unwrap().unwrap()
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:179:13
+   |
+LL |             let clone = Arc::clone(&self.foo);
+   |             ---------------------------------- unnecessary `let` binding
+LL |             clone
+   |             ^^^^^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL ~             (Arc::clone(&self.foo)) as _
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:198:13
+   |
+LL | /             let result = match self {
+LL | |                 E::A(x) => x,
+LL | |                 E::B(x) => x,
+LL | |             };
+   | |______________- unnecessary `let` binding
+LL |
+LL |               result
+   |               ^^^^^^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL |
+LL ~             (match self {
+LL +                 E::A(x) => x,
+LL +                 E::B(x) => x,
+LL +             }) as _
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:224:9
+   |
+LL |         let s = if true { "a".to_string() } else { "b".to_string() } + "c";
+   |         ------------------------------------------------------------------- unnecessary `let` binding
+LL |         s
+   |         ^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         (if true { "a".to_string() } else { "b".to_string() } + "c")
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:230:9
+   |
+LL |         let s = "c".to_string() + if true { "a" } else { "b" };
+   |         ------------------------------------------------------- unnecessary `let` binding
+LL |         s
+   |         ^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         "c".to_string() + if true { "a" } else { "b" }
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:236:9
+   |
+LL |         let s = { "a".to_string() } + "b" + { "c" } + "d";
+   |         -------------------------------------------------- unnecessary `let` binding
+LL |         s
+   |         ^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         ({ "a".to_string() } + "b" + { "c" } + "d")
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:244:13
+   |
+LL |             let s = if true { 2 } else { 3 } << 4;
+   |             -------------------------------------- unnecessary `let` binding
+LL |             s
+   |             ^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL ~             (if true { 2 } else { 3 } << 4)
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:249:13
+   |
+LL |             let s = { true } || { false } && { 2 <= 3 };
+   |             -------------------------------------------- unnecessary `let` binding
+LL |             s
+   |             ^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL ~             ({ true } || { false } && { 2 <= 3 })
+   |
+
+error: aborting due to 10 previous errors
+
diff --git a/tests/ui/let_and_return.edition2024.fixed b/tests/ui/let_and_return.edition2024.fixed
new file mode 100644
index 00000000000..f958f70e1dc
--- /dev/null
+++ b/tests/ui/let_and_return.edition2024.fixed
@@ -0,0 +1,265 @@
+//@revisions: edition2021 edition2024
+//@[edition2021] edition:2021
+//@[edition2024] edition:2024
+
+#![allow(unused)]
+#![warn(clippy::let_and_return)]
+
+use std::cell::RefCell;
+
+fn test() -> i32 {
+    let _y = 0; // no warning
+    
+    5
+    //~^ ERROR: returning the result of a `let` binding from a block
+    //~| NOTE: `-D clippy::let-and-return` implied by `-D warnings`
+}
+
+fn test_inner() -> i32 {
+    if true {
+        
+        5
+        //~^ ERROR: returning the result of a `let` binding from a block
+    } else {
+        0
+    }
+}
+
+fn test_nowarn_1() -> i32 {
+    let mut x = 5;
+    x += 1;
+    x
+}
+
+fn test_nowarn_2() -> i32 {
+    let x = 5;
+    x + 1
+}
+
+fn test_nowarn_3() -> (i32, i32) {
+    // this should technically warn, but we do not compare complex patterns
+    let (x, y) = (5, 9);
+    (x, y)
+}
+
+fn test_nowarn_4() -> i32 {
+    // this should technically warn, but not b/c of clippy::let_and_return, but b/c of useless type
+    let x: i32 = 5;
+    x
+}
+
+fn test_nowarn_5(x: i16) -> u16 {
+    #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
+    let x = x as u16;
+    x
+}
+
+// False positive example
+trait Decode {
+    fn decode<D: std::io::Read>(d: D) -> Result<Self, ()>
+    where
+        Self: Sized;
+}
+
+macro_rules! tuple_encode {
+    ($($x:ident),*) => (
+        impl<$($x: Decode),*> Decode for ($($x),*) {
+            #[inline]
+            #[allow(non_snake_case)]
+            fn decode<D: std::io::Read>(mut d: D) -> Result<Self, ()> {
+                // Shouldn't trigger lint
+                Ok(($({let $x = Decode::decode(&mut d)?; $x }),*))
+            }
+        }
+    );
+}
+
+fn issue_3792() -> String {
+    use std::io::{self, BufRead, Stdin};
+
+    let stdin = io::stdin();
+    // `Stdin::lock` returns `StdinLock<'static>` so `line` doesn't borrow from `stdin`
+    // https://github.com/rust-lang/rust/pull/93965
+    
+    stdin.lock().lines().next().unwrap().unwrap()
+    //~^ ERROR: returning the result of a `let` binding from a block
+}
+
+tuple_encode!(T0, T1, T2, T3, T4, T5, T6, T7);
+
+mod no_lint_if_stmt_borrows {
+    use std::cell::RefCell;
+    use std::rc::{Rc, Weak};
+    struct Bar;
+
+    impl Bar {
+        fn new() -> Self {
+            Bar {}
+        }
+        fn baz(&self) -> u32 {
+            0
+        }
+    }
+
+    fn issue_3324(value: Weak<RefCell<Bar>>) -> u32 {
+        let value = value.upgrade().unwrap();
+        
+        value.borrow().baz()
+        //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    fn borrows_in_closure(value: Weak<RefCell<Bar>>) -> u32 {
+        fn f(mut x: impl FnMut() -> u32) -> impl FnMut() -> u32 {
+            x
+        }
+
+        let value = value.upgrade().unwrap();
+        
+        f(|| value.borrow().baz())()
+        //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    mod free_function {
+        struct Inner;
+
+        struct Foo<'a> {
+            inner: &'a Inner,
+        }
+
+        impl Drop for Foo<'_> {
+            fn drop(&mut self) {}
+        }
+
+        impl<'a> Foo<'a> {
+            fn new(inner: &'a Inner) -> Self {
+                Self { inner }
+            }
+
+            fn value(&self) -> i32 {
+                42
+            }
+        }
+
+        fn some_foo(inner: &Inner) -> Foo<'_> {
+            Foo { inner }
+        }
+
+        fn test() -> i32 {
+            let x = Inner {};
+            
+            some_foo(&x).value()
+            //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+        }
+
+        fn test2() -> i32 {
+            let x = Inner {};
+            
+            Foo::new(&x).value()
+            //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+        }
+    }
+}
+
+mod issue_5729 {
+    use std::sync::Arc;
+
+    trait Foo {}
+
+    trait FooStorage {
+        fn foo_cloned(&self) -> Arc<dyn Foo>;
+    }
+
+    struct FooStorageImpl<T: Foo> {
+        foo: Arc<T>,
+    }
+
+    impl<T: Foo + 'static> FooStorage for FooStorageImpl<T> {
+        fn foo_cloned(&self) -> Arc<dyn Foo> {
+            
+            (Arc::clone(&self.foo)) as _
+            //~^ ERROR: returning the result of a `let` binding from a block
+        }
+    }
+}
+
+mod issue_11335 {
+    pub enum E<T> {
+        A(T),
+        B(T),
+    }
+
+    impl<T> E<T> {
+        pub fn inner(&self) -> &T {
+            
+
+            (match self {
+                E::A(x) => x,
+                E::B(x) => x,
+            }) as _
+            //~^ ERROR: returning the result of a `let` binding from a block
+        }
+    }
+}
+
+// https://github.com/rust-lang/rust-clippy/issues/11167
+macro_rules! fn_in_macro {
+    ($b:block) => {
+        fn f() -> usize $b
+    }
+}
+fn_in_macro!({
+    return 1;
+});
+
+fn issue9150() -> usize {
+    let x = 1;
+    #[cfg(any())]
+    panic!("can't see me");
+    x
+}
+
+fn issue12801() {
+    fn left_is_if() -> String {
+        
+        (if true { "a".to_string() } else { "b".to_string() } + "c")
+        //~^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    fn no_par_needed() -> String {
+        
+        "c".to_string() + if true { "a" } else { "b" }
+        //~^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    fn conjunctive_blocks() -> String {
+        
+        ({ "a".to_string() } + "b" + { "c" } + "d")
+        //~^ ERROR: returning the result of a `let` binding from a block
+    }
+
+    #[allow(clippy::overly_complex_bool_expr)]
+    fn other_ops() {
+        let _ = || {
+            
+            (if true { 2 } else { 3 } << 4)
+            //~^ ERROR: returning the result of a `let` binding from a block
+        };
+        let _ = || {
+            
+            ({ true } || { false } && { 2 <= 3 })
+            //~^ ERROR: returning the result of a `let` binding from a block
+        };
+    }
+}
+
+fn issue14164() -> Result<u32, ()> {
+    let v = std::cell::RefCell::new(Some(vec![1]));
+    
+    match &*v.borrow() {
+        Some(v) => Ok(Ok(v[0])),
+        None => Ok(Ok(0)),
+    }?
+    //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+}
+
+fn main() {}
diff --git a/tests/ui/let_and_return.edition2024.stderr b/tests/ui/let_and_return.edition2024.stderr
new file mode 100644
index 00000000000..ec87e32b582
--- /dev/null
+++ b/tests/ui/let_and_return.edition2024.stderr
@@ -0,0 +1,228 @@
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:13:5
+   |
+LL |     let x = 5;
+   |     ---------- unnecessary `let` binding
+LL |     x
+   |     ^
+   |
+   = note: `-D clippy::let-and-return` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::let_and_return)]`
+help: return the expression directly
+   |
+LL ~     
+LL ~     5
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:21:9
+   |
+LL |         let x = 5;
+   |         ---------- unnecessary `let` binding
+LL |         x
+   |         ^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         5
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:84:5
+   |
+LL |     let line = stdin.lock().lines().next().unwrap().unwrap();
+   |     --------------------------------------------------------- unnecessary `let` binding
+LL |     line
+   |     ^^^^
+   |
+help: return the expression directly
+   |
+LL ~     
+LL ~     stdin.lock().lines().next().unwrap().unwrap()
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:107:9
+   |
+LL |         let ret = value.borrow().baz();
+   |         ------------------------------- unnecessary `let` binding
+LL |         ret
+   |         ^^^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         value.borrow().baz()
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:118:9
+   |
+LL |         let ret = f(|| value.borrow().baz())();
+   |         --------------------------------------- unnecessary `let` binding
+LL |         ret
+   |         ^^^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         f(|| value.borrow().baz())()
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:150:13
+   |
+LL |             let value = some_foo(&x).value();
+   |             --------------------------------- unnecessary `let` binding
+LL |             value
+   |             ^^^^^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL ~             some_foo(&x).value()
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:157:13
+   |
+LL |             let value = Foo::new(&x).value();
+   |             --------------------------------- unnecessary `let` binding
+LL |             value
+   |             ^^^^^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL ~             Foo::new(&x).value()
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:179:13
+   |
+LL |             let clone = Arc::clone(&self.foo);
+   |             ---------------------------------- unnecessary `let` binding
+LL |             clone
+   |             ^^^^^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL ~             (Arc::clone(&self.foo)) as _
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:198:13
+   |
+LL | /             let result = match self {
+LL | |                 E::A(x) => x,
+LL | |                 E::B(x) => x,
+LL | |             };
+   | |______________- unnecessary `let` binding
+LL |
+LL |               result
+   |               ^^^^^^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL |
+LL ~             (match self {
+LL +                 E::A(x) => x,
+LL +                 E::B(x) => x,
+LL +             }) as _
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:224:9
+   |
+LL |         let s = if true { "a".to_string() } else { "b".to_string() } + "c";
+   |         ------------------------------------------------------------------- unnecessary `let` binding
+LL |         s
+   |         ^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         (if true { "a".to_string() } else { "b".to_string() } + "c")
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:230:9
+   |
+LL |         let s = "c".to_string() + if true { "a" } else { "b" };
+   |         ------------------------------------------------------- unnecessary `let` binding
+LL |         s
+   |         ^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         "c".to_string() + if true { "a" } else { "b" }
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:236:9
+   |
+LL |         let s = { "a".to_string() } + "b" + { "c" } + "d";
+   |         -------------------------------------------------- unnecessary `let` binding
+LL |         s
+   |         ^
+   |
+help: return the expression directly
+   |
+LL ~         
+LL ~         ({ "a".to_string() } + "b" + { "c" } + "d")
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:244:13
+   |
+LL |             let s = if true { 2 } else { 3 } << 4;
+   |             -------------------------------------- unnecessary `let` binding
+LL |             s
+   |             ^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL ~             (if true { 2 } else { 3 } << 4)
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:249:13
+   |
+LL |             let s = { true } || { false } && { 2 <= 3 };
+   |             -------------------------------------------- unnecessary `let` binding
+LL |             s
+   |             ^
+   |
+help: return the expression directly
+   |
+LL ~             
+LL ~             ({ true } || { false } && { 2 <= 3 })
+   |
+
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:261:5
+   |
+LL | /     let r = match &*v.borrow() {
+LL | |         Some(v) => Ok(Ok(v[0])),
+LL | |         None => Ok(Ok(0)),
+LL | |     }?;
+   | |_______- unnecessary `let` binding
+LL |       r
+   |       ^
+   |
+help: return the expression directly
+   |
+LL ~     
+LL ~     match &*v.borrow() {
+LL +         Some(v) => Ok(Ok(v[0])),
+LL +         None => Ok(Ok(0)),
+LL +     }?
+   |
+
+error: aborting due to 15 previous errors
+
diff --git a/tests/ui/let_and_return.fixed b/tests/ui/let_and_return.fixed
index b68b41cdca2..e22e66eb522 100644
--- a/tests/ui/let_and_return.fixed
+++ b/tests/ui/let_and_return.fixed
@@ -244,4 +244,14 @@ fn issue12801() {
     }
 }
 
+// Do not lint
+fn issue14164() -> Result<u32, ()> {
+    let v = std::cell::RefCell::new(Some(vec![1]));
+    let r = match &*v.borrow() {
+        Some(v) => Ok(Ok(v[0])),
+        None => Ok(Ok(0)),
+    }?;
+    r
+}
+
 fn main() {}
diff --git a/tests/ui/let_and_return.rs b/tests/ui/let_and_return.rs
index 6b9035f9428..0b7a1e26890 100644
--- a/tests/ui/let_and_return.rs
+++ b/tests/ui/let_and_return.rs
@@ -1,3 +1,7 @@
+//@revisions: edition2021 edition2024
+//@[edition2021] edition:2021
+//@[edition2024] edition:2024
+
 #![allow(unused)]
 #![warn(clippy::let_and_return)]
 
@@ -101,6 +105,7 @@ mod no_lint_if_stmt_borrows {
         let value = value.upgrade().unwrap();
         let ret = value.borrow().baz();
         ret
+        //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
     }
 
     fn borrows_in_closure(value: Weak<RefCell<Bar>>) -> u32 {
@@ -111,6 +116,7 @@ mod no_lint_if_stmt_borrows {
         let value = value.upgrade().unwrap();
         let ret = f(|| value.borrow().baz())();
         ret
+        //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
     }
 
     mod free_function {
@@ -142,12 +148,14 @@ mod no_lint_if_stmt_borrows {
             let x = Inner {};
             let value = some_foo(&x).value();
             value
+            //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
         }
 
         fn test2() -> i32 {
             let x = Inner {};
             let value = Foo::new(&x).value();
             value
+            //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
         }
     }
 }
@@ -244,4 +252,14 @@ fn issue12801() {
     }
 }
 
+fn issue14164() -> Result<u32, ()> {
+    let v = std::cell::RefCell::new(Some(vec![1]));
+    let r = match &*v.borrow() {
+        Some(v) => Ok(Ok(v[0])),
+        None => Ok(Ok(0)),
+    }?;
+    r
+    //~[edition2024]^ ERROR: returning the result of a `let` binding from a block
+}
+
 fn main() {}