Take doc(alias) into account when providing typo suggestions

[jyn514]

Given the following code: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=a5d74dbaa80fd7833c2b937fc94f58fa

fn main() {
    let x = [1, 2, 3].length();
}

The current output is:

error[E0599]: no method named `length` found for array `[{integer}; 3]` in the current scope
 --> src/main.rs:2:23
  |
2 |     let x = [1, 2, 3].length();
  |                       ^^^^^^ method not found in `[{integer}; 3]`

Ideally the output should look like:

error[E0599]: no method named `length` found for array `[{integer}; 3]` in the current scope
 --> src/main.rs:2:23
  |
2 |     let x = [1, 2, 3].length();
  |                       ^^^^^^ help: a function with an alias to `length` exists: `len`

Searching for length will already bring up len in the docs: https://doc.rust-lang.org/std/?search=length
It would be nice if the CLI errors had feature parity.

Meta

rustc --version: 1.51.0

[Badel2]

Searching for length will already bring up len in the docs: https://doc.rust-lang.org/std/?search=length

Not anymore?

[amab8901]

I think this issue should be closed. The solution has already been implemented.

fn main() {
    let x = [1, 2, 3].length();
}

in playground (https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=a5d74dbaa80fd7833c2b937fc94f58fa)
yields the following output:

Compiling playground v0.0.1 (/playground)
error[[E0599]](https://doc.rust-lang.org/stable/error-index.html#E0599): no method named `length` found for array `[{integer}; 3]` in the current scope
 --> src/main.rs:2:23
  |
2 |     let x = [1, 2, 3].length();
  |                       ^^^^^^ help: there is a method with a similar name: `len`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground` due to previous error

[jyn514]

@Badel2 @amab8901 this specific issue with len has been fixed, but the underlying problem that doc(alias) is ignored has not been fixed. https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=2aecfff005336e11136e0d063fd93ff8

error[E0425]: cannot find function `memcpy` in this scope
 --> src/main.rs:5:5
  |
5 |     memcpy(&dst, &src[2..]);
  |     ^^^^^^ not found in this scope
  |
help: consider importing one of these items
  |
1 | use libc::memcpy;
  |
1 | use openssl_sys::memcpy;
  |

error[E0599]: no method named `memcpy` found for array `[{integer}; 2]` in the current scope
 --> src/main.rs:6:9
  |
6 |     dst.memcpy(&src[2..]);
  |         ^^^^^^ method not found in `[{integer}; 2]`

[jyn514]

Mentoring instructions: change

rust/compiler/rustc_hir_typeck/src/method/probe.rs

Lines 1923 to 1938 in 9644684

	/// Finds the method with the appropriate name (or return type, as the case may be). If
	/// `allow_similar_names` is set, find methods with close-matching names.
	// The length of the returned iterator is nearly always 0 or 1 and this
	// method is fairly hot.
	fn impl_or_trait_item(&self, def_id: DefId) -> SmallVec<[ty::AssocItem; 1]> {
	if let Some(name) = self.method_name {
	if self.allow_similar_names {
	let max_dist = max(name.as_str().len(), 3) / 3;
	self.tcx
	.associated_items(def_id)
	.in_definition_order()
	.filter(|x| {
	if !self.is_relevant_kind_for_mode(x.kind) {
	return false;
	}
	match lev_distance_with_substrings(name.as_str(), x.name.as_str(), max_dist)

to also consider doc(alias), not just the names themselves.

[sulami]

This looks doable.

@rustbot claim