needs -> might need

compiler/rustc_middle/src/mir/query.rs

@@ -95,7 +95,7 @@ impl UnsafetyViolationDetails {
                  and cause data races: all of these are undefined behavior",
             ),
             AssignToDroppingUnionField => (
-                "assignment to union field that needs dropping",
+                "assignment to union field that might need dropping",
                 "the previous content of the field will be dropped, which causes undefined \
                  behavior if the field was not properly initialized",
             ),

src/test/ui/union/union-unsafe.rs

@@ -32,8 +32,8 @@ fn deref_union_field(mut u: URef) {
 }
 
 fn assign_noncopy_union_field(mut u: URefCell) {
-    u.a = (RefCell::new(0), 1); //~ ERROR assignment to union field that needs dropping
-    u.a.0 = RefCell::new(0); //~ ERROR assignment to union field that needs 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
 }
 

src/test/ui/union/union-unsafe.stderr

@@ -6,19 +6,19 @@ 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 needs dropping is unsafe and requires unsafe function or block
+error[E0133]: assignment to union field that might need dropping is unsafe and requires unsafe function or block
   --> $DIR/union-unsafe.rs:35:5
    |
 LL |     u.a = (RefCell::new(0), 1);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ assignment to union field that needs dropping
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ 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 needs dropping is unsafe and requires unsafe function or block
+error[E0133]: assignment to union field that might need dropping is unsafe and requires unsafe function or block
   --> $DIR/union-unsafe.rs:36:5
    |
 LL |     u.a.0 = RefCell::new(0);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^ assignment to union field that needs dropping
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ 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