review comments

src/librustc/hir/mod.rs

@@ -1054,7 +1054,7 @@ impl Mutability {
         }
     }
 
-    pub fn not(self) -> Self {
+    pub fn invert(self) -> Self {
         match self {
             MutMutable => MutImmutable,
             MutImmutable => MutMutable,

src/librustc_typeck/check/method/mod.rs

@@ -217,7 +217,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if let ty::Ref(region, t_type, mutability) = self_ty.kind {
             let trait_type = self.tcx.mk_ref(region, ty::TypeAndMut {
                 ty: t_type,
-                mutbl: mutability.not(),
+                mutbl: mutability.invert(),
             });
             match self.lookup_probe(
                 span,

src/librustc_typeck/check/method/suggest.rs

@@ -582,7 +582,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     if needs_mut {
                         let trait_type = self.tcx.mk_ref(region, ty::TypeAndMut {
                             ty: t_type,
-                            mutbl: mutability.not(),
+                            mutbl: mutability.invert(),
                         });
                         err.note(&format!("you need `{}` instead of `{}`", trait_type, rcvr_ty));
                     }