reword label as per review

src/librustc_resolve/lib.rs

@@ -204,7 +204,7 @@ fn resolve_struct_error<'sess, 'a>(resolver: &'sess Resolver,
                     }) {
                         err.span_label(
                             reduce_impl_span_to_impl_keyword(cm, impl_span),
-                            "`Self` type implicitly declared here, on the `impl`",
+                            "`Self` type implicitly declared here, by this `impl`",
                         );
                     }
                     match (maybe_trait_defid, maybe_impl_defid) {

src/test/ui/error-codes/E0401.stderr

@@ -24,7 +24,7 @@ error[E0401]: can't use type parameters from outer function
   --> $DIR/E0401.rs:32:25
    |
 LL | impl<T> Iterator for A<T> {
-   | ---- `Self` type implicitly declared here, on the `impl`
+   | ---- `Self` type implicitly declared here, by this `impl`
 ...
 LL |         fn helper(sel: &Self) -> u8 { //~ ERROR E0401
    |                         ^^^^

src/test/ui/use-self-in-inner-fn.rs

@@ -11,7 +11,7 @@
 struct A;
 
 impl A {
-//~^ NOTE `Self` type implicitly declared here, on the `impl`
+//~^ NOTE `Self` type implicitly declared here, by this `impl`
     fn banana(&mut self) {
         fn peach(this: &Self) {
         //~^ ERROR can't use type parameters from outer function

src/test/ui/use-self-in-inner-fn.stderr

@@ -2,7 +2,7 @@ error[E0401]: can't use type parameters from outer function
   --> $DIR/use-self-in-inner-fn.rs:16:25
    |
 LL | impl A {
-   | ---- `Self` type implicitly declared here, on the `impl`
+   | ---- `Self` type implicitly declared here, by this `impl`
 ...
 LL |         fn peach(this: &Self) {
    |                         ^^^^