Trait methods with default implementations have their types specialized when performing method resolution, that is, when matching the type of a receiver against the type of the self parameter. This PR does the same when inferring types of calls, for example in

let x : i32 = 0;
let y : usize = 1;
let z = x.max(y);

the target of x.max(y) is https://doc.rust-lang.org/std/cmp/trait.Ord.html#method.max, and before this PR the type of the other parameter would remain Self, which meant that z would have both types i32 and usize. After this PR, the type of other is specialized to i32, which means z will only have type i32.