Elide object safety errors on non-existent trait function

Fix #58734.

src/test/ui/issues/issue-58734.rs

@@ -0,0 +1,22 @@
+trait Trait {
+    fn exists(self) -> ();
+
+    fn not_object_safe() -> Self;
+}
+
+impl Trait for () {
+    fn exists(self) -> () {
+    }
+
+    fn not_object_safe() -> Self {
+        ()
+    }
+}
+
+fn main() {
+    // object-safe or not, this call is OK
+    Trait::exists(());
+    // no object safety error
+    Trait::nonexistent(());
+    //~^ ERROR no function or associated item named `nonexistent` found for type `dyn Trait`
+}

src/test/ui/issues/issue-58734.stderr

@@ -0,0 +1,11 @@
+error[E0599]: no function or associated item named `nonexistent` found for type `dyn Trait` in the current scope
+  --> $DIR/issue-58734.rs:20:12
+   |
+LL |     Trait::nonexistent(());
+   |     -------^^^^^^^^^^^
+   |     |
+   |     function or associated item not found in `dyn Trait`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0599`.