Arbitrary self types v2: no deshadow pre feature.

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1337,6 +1337,15 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         mutbl: hir::Mutability,
         track_unstable_candidates: bool,
     ) -> Result<(), MethodError<'tcx>> {
+        // The errors emitted by this function are part of
+        // the arbitrary self types work, and should not impact
+        // other users.
+        if !self.tcx.features().arbitrary_self_types()
+            && !self.tcx.features().arbitrary_self_types_pointers()
+        {
+            return Ok(());
+        }
+
         // We don't want to remember any of the diagnostic hints from this
         // shadow search, but we do need to provide Some/None for the
         // unstable_candidates in order to reflect the behavior of the

tests/ui/self/arbitrary_self_types_pin_getref.feature.stderr

@@ -0,0 +1,16 @@
+error[E0034]: multiple applicable items in scope
+  --> $DIR/arbitrary_self_types_pin_getref.rs:23:22
+   |
+LL |     let _ = pinned_a.get_ref();
+   |                      ^^^^^^^ multiple `get_ref` found
+   |
+note: candidate #1 is defined in an impl for the type `A`
+  --> $DIR/arbitrary_self_types_pin_getref.rs:17:5
+   |
+LL |     fn get_ref(self: &Pin<&A>) {}  // note &Pin
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: candidate #2 is defined in an impl for the type `Pin<&'a T>`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0034`.

tests/ui/self/arbitrary_self_types_pin_getref.rs

@@ -0,0 +1,25 @@
+// Confirms that Pin::get_ref can no longer shadow methods in pointees
+// once arbitrary_self_types is enabled.
+//
+//@ revisions: default feature
+#![cfg_attr(feature, feature(arbitrary_self_types))]
+
+//@[default] check-pass
+
+#![allow(dead_code)]
+
+use std::pin::Pin;
+use std::pin::pin;
+
+struct A;
+
+impl A {
+    fn get_ref(self: &Pin<&A>) {}  // note &Pin
+}
+
+fn main() {
+    let pinned_a: Pin<&mut A> = pin!(A);
+    let pinned_a: Pin<&A> = pinned_a.as_ref();
+    let _ = pinned_a.get_ref();
+    //[feature]~^ ERROR: multiple applicable items
+}