fix #105788, Remove unreasonable help message for auto trait

Author: chenyukang

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -943,6 +943,9 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             });
         } else {
             debug_assert!(self.tcx.is_trait(trait_def_id));
+            if self.tcx.trait_is_auto(trait_def_id) {
+                return;
+            }
             for item in self.impl_or_trait_item(trait_def_id) {
                 // Check whether `trait_def_id` defines a method with suitable name.
                 if !self.has_applicable_self(&item) {

compiler/rustc_hir_typeck/src/method/suggest.rs

@@ -2306,6 +2306,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         _ => false,
                     }
                 }) && (type_is_local || info.def_id.is_local())
+                    && !self.tcx.trait_is_auto(info.def_id)
                     && self
                         .associated_value(info.def_id, item_name)
                         .filter(|item| {

src/test/ui/methods/issues/issue-105732.rs

@@ -6,7 +6,8 @@ auto trait Foo {
 
 trait Bar {
     fn f(&self) {
-        self.g(); //~ ERROR the method `g` exists for reference `&Self`, but its trait bounds were not satisfied
+        // issue #105788
+        self.g(); //~ ERROR no method named `g` found for reference `&Self` in the current scope
     }
 }
 

src/test/ui/methods/issues/issue-105732.stderr

@@ -6,21 +6,11 @@ LL | auto trait Foo {
 LL |     fn g(&self);
    |     ---^-------- help: remove these associated items
 
-error[E0599]: the method `g` exists for reference `&Self`, but its trait bounds were not satisfied
-  --> $DIR/issue-105732.rs:9:14
+error[E0599]: no method named `g` found for reference `&Self` in the current scope
+  --> $DIR/issue-105732.rs:10:14
    |
 LL |         self.g();
-   |              ^
-   |
-   = note: the following trait bounds were not satisfied:
-           `Self: Foo`
-           which is required by `&Self: Foo`
-           `&Self: Foo`
-   = help: items from traits can only be used if the type parameter is bounded by the trait
-help: the following trait defines an item `g`, perhaps you need to add a supertrait for it:
-   |
-LL | trait Bar: Foo {
-   |          +++++
+   |              ^ help: there is a method with a similar name: `f`
 
 error: aborting due to 2 previous errors