rustc_borrowck: Don't hash types in loan paths

[petrochenkov]

1. Types for equal loan paths are not always equal, they can sometimes differ in lifetimes, making equal loan paths hash differently.

Example:

rust/src/libcollections/linked_list.rs

Lines 835 to 856 in 71bdeea

	pub fn insert_next(&mut self, element: T) {
	match self.head {
	None => self.list.push_back(element),
	Some(head) => unsafe {
	let prev = match (**head).prev {
	None => return self.list.push_front(element),
	Some(prev) => prev,
	};
	let node = Some(Shared::new(Box::into_raw(box Node {
	next: Some(head),
	prev: Some(prev),
	element: element,
	})));
	(**prev).next = node;
	(**head).prev = node;
	self.list.len += 1;
	}
	}
	}

One of self.lists has type

&ReFree(CodeExtent(15013/CallSiteScope { fn_id: 18907, body_id: 18912 }), BrNamed(0:DefIndex(3066), 'a(397), WontChange)) mut linked_list::LinkedList<T>

and other has type

&ReScope(CodeExtent(15018/Remainder(BlockRemainder { block: 18912, first_statement_index: 0 }))) mut linked_list::LinkedList<T>

(... but I'm not sure it's not a bug actually.)

2. Not hashing types is faster than hashing types.

r? @arielb1

[petrochenkov]

cc @nikomatsakis
This is also included into #36016, but I wanted to give this issue some more visibility.

[arielb1]

@bors r+

[bors]

📌 Commit 14b4d72 has been approved by arielb1