only downgrade Error -> Ambiguous if type error is in predicate

src/test/ui/functions-closures/fn-help-with-err-generic-is-not-function.rs

@@ -8,15 +8,7 @@ where
     //~^ ERROR cannot find type `T` in this scope
     //~| NOTE not found in this scope
 {
-    // The part where it claims that there is no method named `len` is a bug. Feel free to fix it.
-    // This test is intended to ensure that a different bug, where it claimed
-    // that `v` was a function, does not regress.
     fn method(v: Vec<u8>) { v.len(); }
-    //~^ ERROR type annotations needed
-    //~| NOTE cannot infer type
-    //~| NOTE type must be known at this point
-    //~| ERROR no method named `len`
-    //~| NOTE private field, not a method
 }
 
 fn main() {}