Ignore unsized types when trying to determine the size of a type

Urgau · Urgau · commit ddec8c5edc48 · 2024-02-14T19:23:20.000+01:00
diff --git a/compiler/rustc_lint/src/reference_casting.rs b/compiler/rustc_lint/src/reference_casting.rs
@@ -207,6 +207,13 @@ fn is_cast_to_bigger_memory_layout<'tcx>(
     }
 
     let from_layout = cx.layout_of(*inner_start_ty).ok()?;
+
+    // if the type isn't sized, we bail out, instead of potentially giving
+    // the user a meaningless warning.
+    if from_layout.is_unsized() {
+        return None;
+    }
+
     let alloc_layout = cx.layout_of(alloc_ty).ok()?;
     let to_layout = cx.layout_of(*inner_end_ty).ok()?;
 
diff --git a/tests/ui/lint/reference_casting.rs b/tests/ui/lint/reference_casting.rs
@@ -239,6 +239,11 @@ unsafe fn bigger_layout() {
         //~^ ERROR casting references to a bigger memory layout
     }
 
+    {
+        let x: Box<dyn Send> = Box::new(0i32);
+        let _z = unsafe { &*(&*x as *const dyn Send as *const i32) };
+    }
+
     unsafe fn from_ref(this: &i32) -> &i64 {
         &*(this as *const i32 as *const i64)
     }

Original file line number	Diff line number	Diff line change
`@@ -239,6 +239,11 @@ unsafe fn bigger_layout() {`
`239`	`239`	`//~^ ERROR casting references to a bigger memory layout`
`240`	`240`	`}`
`241`	`241`
	`242`	`+ {`
	`243`	`+ let x: Box<dyn Send> = Box::new(0i32);`
	`244`	`+ let _z = unsafe { &(&x as const dyn Send as const i32) };`
	`245`	`+ }`
	`246`	`+`
`242`	`247`	`unsafe fn from_ref(this: &i32) -> &i64 {`
`243`	`248`	`&(this as const i32 as *const i64)`
`244`	`249`	`}`