From 56be9c3ad544e8a0c2ade99a6b0060230f8b43ad Mon Sep 17 00:00:00 2001
From: Erin van der Veen <erin@erinvanderveen.nl>
Date: Wed, 26 Nov 2025 16:19:54 +0100
Subject: [PATCH] fix: `let-and-return` suggests invalid cast

---
 clippy_lints/src/returns/let_and_return.rs |  5 ++++-
 tests/ui/let_and_return.edition2021.fixed  |  8 ++++++++
 tests/ui/let_and_return.edition2021.stderr | 16 +++++++++++++++-
 tests/ui/let_and_return.edition2024.fixed  |  8 ++++++++
 tests/ui/let_and_return.edition2024.stderr | 16 +++++++++++++++-
 tests/ui/let_and_return.rs                 |  8 ++++++++
 6 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/clippy_lints/src/returns/let_and_return.rs b/clippy_lints/src/returns/let_and_return.rs
index 0a00981e15be..7029c22b7e57 100644
--- a/clippy_lints/src/returns/let_and_return.rs
+++ b/clippy_lints/src/returns/let_and_return.rs
@@ -45,7 +45,10 @@ pub(super) fn check_block<'tcx>(cx: &LateContext<'tcx>, block: &'tcx Block<'_>)
                         } else {
                             format!("({src})")
                         }
-                    } else if !cx.typeck_results().expr_adjustments(retexpr).is_empty() {
+                    } else if !cx.typeck_results().expr_adjustments(retexpr).is_empty()
+                        // Do not suggest 'as _' for raw pointers; it's an invalid cast
+                        && !cx.typeck_results().expr_ty_adjusted(retexpr).is_raw_ptr()
+                    {
                         if has_enclosing_paren(&src) {
                             format!("{src} as _")
                         } else {
diff --git a/tests/ui/let_and_return.edition2021.fixed b/tests/ui/let_and_return.edition2021.fixed
index e89e4476bf82..00effc5015ff 100644
--- a/tests/ui/let_and_return.edition2021.fixed
+++ b/tests/ui/let_and_return.edition2021.fixed
@@ -271,4 +271,12 @@ fn issue15987() -> i32 {
     r
 }
 
+// https://github.com/rust-lang/rust-clippy/issues/16135
+fn issue16135() -> *const u8 {
+    let boxed_value = Box::new(42u8);
+    
+    Box::into_raw(boxed_value)
+    //~^ let_and_return
+}
+
 fn main() {}
diff --git a/tests/ui/let_and_return.edition2021.stderr b/tests/ui/let_and_return.edition2021.stderr
index f9536d1b5477..6253a5f8b12f 100644
--- a/tests/ui/let_and_return.edition2021.stderr
+++ b/tests/ui/let_and_return.edition2021.stderr
@@ -148,5 +148,19 @@ LL ~
 LL ~             ({ true } || { false } && { 2 <= 3 })
    |
 
-error: aborting due to 10 previous errors
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:278:5
+   |
+LL |     let ptr = Box::into_raw(boxed_value);
+   |     ------------------------------------- unnecessary `let` binding
+LL |     ptr
+   |     ^^^
+   |
+help: return the expression directly
+   |
+LL ~     
+LL ~     Box::into_raw(boxed_value)
+   |
+
+error: aborting due to 11 previous errors
 
diff --git a/tests/ui/let_and_return.edition2024.fixed b/tests/ui/let_and_return.edition2024.fixed
index d2c76673ca03..e50ba0f1ba16 100644
--- a/tests/ui/let_and_return.edition2024.fixed
+++ b/tests/ui/let_and_return.edition2024.fixed
@@ -271,4 +271,12 @@ fn issue15987() -> i32 {
     r
 }
 
+// https://github.com/rust-lang/rust-clippy/issues/16135
+fn issue16135() -> *const u8 {
+    let boxed_value = Box::new(42u8);
+    
+    Box::into_raw(boxed_value)
+    //~^ let_and_return
+}
+
 fn main() {}
diff --git a/tests/ui/let_and_return.edition2024.stderr b/tests/ui/let_and_return.edition2024.stderr
index ca378fa43232..c669a17bc689 100644
--- a/tests/ui/let_and_return.edition2024.stderr
+++ b/tests/ui/let_and_return.edition2024.stderr
@@ -224,5 +224,19 @@ LL +         None => Ok(Ok(0)),
 LL +     }?
    |
 
-error: aborting due to 15 previous errors
+error: returning the result of a `let` binding from a block
+  --> tests/ui/let_and_return.rs:278:5
+   |
+LL |     let ptr = Box::into_raw(boxed_value);
+   |     ------------------------------------- unnecessary `let` binding
+LL |     ptr
+   |     ^^^
+   |
+help: return the expression directly
+   |
+LL ~     
+LL ~     Box::into_raw(boxed_value)
+   |
+
+error: aborting due to 16 previous errors
 
diff --git a/tests/ui/let_and_return.rs b/tests/ui/let_and_return.rs
index 1af5f8ba5c16..be07b7d3b0e7 100644
--- a/tests/ui/let_and_return.rs
+++ b/tests/ui/let_and_return.rs
@@ -271,4 +271,12 @@ fn issue15987() -> i32 {
     r
 }
 
+// https://github.com/rust-lang/rust-clippy/issues/16135
+fn issue16135() -> *const u8 {
+    let boxed_value = Box::new(42u8);
+    let ptr = Box::into_raw(boxed_value);
+    ptr
+    //~^ let_and_return
+}
+
 fn main() {}