feat: Add an assist for inlining all type alias uses

[sancho20021]

Description

inline_type_alias_uses assist tries to inline all selected type alias occurrences.

Currently

Type alias used in PathType position are inlined.

Not supported

• Removing type alias declaration if all uses are inlined.
• Removing redundant imports after inlining all uses in the file.
• Type alias not in PathType position, such as:
  • A::new()
  • let x = A {}
  • let bits = A::BITS
  • etc.

Demonstration

Related Issues

Partially fixes #10881

[sancho20021]

One test (inline_uses_across_files_fails) does not pass, and I don't understand why:
Source:

//- /lib.rs
mod foo;
type $0I = i32;

//- /foo.rs
use super::I;
fn foo() {
    let _: I = 0;
}

Expected output:

//- /lib.rs
mod foo;
type I = i32;

//- /foo.rs
use super::I;
fn foo() {
    let _: i32 = 0;
}

Actual:

use super::I;
fn foo() {
    let _: i32 = 0;
}

I'm not familiar with the way it is being tested, @Veykril, maybe you can help.

[Veykril]

The output will only render files that have changed content, so lib.rs is not being re-rendered since it doesn't contain changes/

[Veykril]

This might hit some paths that it shouldn't right now, like T::Assoc where T is what we inline. In this case we should just go with path_type.syntax().ancestors().nth(3).and_then(ast::Pathtype::cast). We take the third ancestor because of the following hierarchy, NameRef -> PathSegment -> Path -> PathType. As this assist currently only supports single segment path types, so we should make sure to only pick those here as well.

[sancho20021]

Okay, fixed!

[Veykril]

Thanks!
@bors r+

[bors]

📌 Commit 313b004 has been approved by Veykril

It is now in the queue for this repository.

[bors]

⌛ Testing commit 313b004 with merge 02466b2...

[bors]

💔 Test failed - checks-actions

[Veykril]

@bors retry

[bors]

⌛ Testing commit 313b004 with merge 5543dd8...

[bors]

☀️ Test successful - checks-actions
Approved by: Veykril
Pushing 5543dd8 to master...

[ice1000]

The first two "not supported" are now supported in #13091