Rollup merge of #87403 - LeSeulArtichaut:assign-dropping-union, r=oli-obk

Implement `AssignToDroppingUnionField` in THIR unsafeck

r? ``@oli-obk`` cc rust-lang/project-thir-unsafeck#7

2 files changed, 19 insertions, 3 deletions

diff --git a/src/test/ui/union/union-unsafe.rs b/src/test/ui/union/union-unsafe.rs
index e8414903d54..3cb3a18cb75 100644
--- a/src/test/ui/union/union-unsafe.rs
+++ b/src/test/ui/union/union-unsafe.rs
@@ -36,8 +36,8 @@ fn deref_union_field(mut u: URef) {
 
 fn assign_noncopy_union_field(mut u: URefCell) {
     // FIXME(thir-unsafeck)
-    u.a = (RefCell::new(0), 1); //[mir]~ ERROR assignment to union field that might need dropping
-    u.a.0 = RefCell::new(0); //[mir]~ ERROR assignment to union field that might need dropping
+    u.a = (RefCell::new(0), 1); //~ ERROR assignment to union field that might need dropping
+    u.a.0 = RefCell::new(0); //~ ERROR assignment to union field that might need dropping
     u.a.1 = 1; // OK
 }
 
diff --git a/src/test/ui/union/union-unsafe.thir.stderr b/src/test/ui/union/union-unsafe.thir.stderr
index 51f19879c81..e88642b0ff7 100644
--- a/src/test/ui/union/union-unsafe.thir.stderr
+++ b/src/test/ui/union/union-unsafe.thir.stderr
@@ -6,6 +6,22 @@ LL |     *(u.p) = 13;
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
+error[E0133]: assignment to union field that might need dropping is unsafe and requires unsafe function or block
+  --> $DIR/union-unsafe.rs:39:5
+   |
+LL |     u.a = (RefCell::new(0), 1);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to union field that might need dropping
+   |
+   = note: the previous content of the field will be dropped, which causes undefined behavior if the field was not properly initialized
+
+error[E0133]: assignment to union field that might need dropping is unsafe and requires unsafe function or block
+  --> $DIR/union-unsafe.rs:40:5
+   |
+LL |     u.a.0 = RefCell::new(0);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ assignment to union field that might need dropping
+   |
+   = note: the previous content of the field will be dropped, which causes undefined behavior if the field was not properly initialized
+
 error[E0133]: access to union field is unsafe and requires unsafe function or block
   --> $DIR/union-unsafe.rs:47:6
    |
@@ -70,6 +86,6 @@ LL |     *u3.a = String::from("new");
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
-error: aborting due to 9 previous errors
+error: aborting due to 11 previous errors
 
 For more information about this error, try `rustc --explain E0133`.