Rollup merge of #158034 - kevin-valerio:fix/issue-158033-reborrow-source-unsafety, r=dingxiangfei2009

Fix reborrow source expression visits

Fixes #158033

Author: JonathanBrouwer

compiler/rustc_middle/src/thir/visit.rs

@@ -187,7 +187,9 @@ pub fn walk_expr<'thir, 'tcx: 'thir, V: Visitor<'thir, 'tcx>>(
         }
         ThreadLocalRef(_) => {}
         Yield { value } => visitor.visit_expr(&visitor.thir()[value]),
-        Reborrow { .. } => {}
+        Reborrow { source, mutability: _, target: _ } => {
+            visitor.visit_expr(&visitor.thir()[source])
+        }
     }
 }
 

tests/ui/reborrow/reborrow-source-unsafety.rs

@@ -0,0 +1,28 @@
+// Regression test for rust-lang/rust#158033.
+
+#![feature(reborrow)]
+#![allow(dead_code)]
+#![deny(unsafe_code)]
+
+use std::marker::Reborrow;
+
+struct Thing<'a> {
+    field: &'a mut usize,
+}
+
+impl<'a> Reborrow for Thing<'a> {}
+
+fn takes(_: Thing<'_>) {}
+
+fn main() {
+    let mut x = 0;
+    let thing = Thing { field: &mut x };
+    let y = 123usize;
+
+    takes({
+        let p: *const usize = &y;
+        std::hint::black_box(std::ptr::read(p));
+        //~^ ERROR call to unsafe function `std::ptr::read` is unsafe
+        thing
+    });
+}

tests/ui/reborrow/reborrow-source-unsafety.stderr

@@ -0,0 +1,11 @@
+error[E0133]: call to unsafe function `std::ptr::read` is unsafe and requires unsafe function or block
+  --> $DIR/reborrow-source-unsafety.rs:24:30
+   |
+LL |         std::hint::black_box(std::ptr::read(p));
+   |                              ^^^^^^^^^^^^^^^^^ call to unsafe function
+   |
+   = note: consult the function's documentation for information on how to avoid undefined behavior
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0133`.