rename fn param to clarify its adjustments on a

Author: BoxyUwU

compiler/rustc_hir_typeck/src/coercion.rs

@@ -825,25 +825,25 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         &self,
         a: ty::PolyFnSig<'tcx>,
         b: ty::PolyFnSig<'tcx>,
-        adjustment: Option<Adjust>,
+        a_adjustment: Option<Adjust>,
     ) -> CoerceResult<'tcx> {
         let a_ty = Ty::new_fn_ptr(self.tcx, a);
         let b_ty = Ty::new_fn_ptr(self.tcx, b);
 
         // Handle coercing `fn(..)` to `unsafe fn(..)`
         if a.safety().is_safe() && b.safety().is_unsafe() {
             let unsafe_a_ty = self.tcx.safe_to_unsafe_fn_ty(a);
-            let adjustment = adjustment.map(|kind| Adjustment { kind, target: a_ty });
+            let a_adjustment = a_adjustment.map(|kind| Adjustment { kind, target: a_ty });
 
             self.unify_and(
                 unsafe_a_ty,
                 b_ty,
-                adjustment,
+                a_adjustment,
                 Adjust::Pointer(PointerCoercion::UnsafeFnPointer),
             )
         } else {
-            match adjustment {
-                Some(adjust) => self.unify_and(a_ty, b_ty, [], adjust),
+            match a_adjustment {
+                Some(a_adjust) => self.unify_and(a_ty, b_ty, [], a_adjust),
                 None => self.unify(a_ty, b_ty),
             }
         }