Rename alias changes original import

[glmdgrielson]

Given

// blah.rs
pub struct Parser<P>(pub P);
// lib.rs
use blah::Parser as ParserTrait;

Renaming ParserTrait to say Combo gives

// blah.rs
pub struct Combo<P>(pub P);
// lib.rs
use blah::Combo as Combo;

Compare that to

// blah.ts
export const blah = () => true;
export const what = () => false;
// index.ts
import { what as why } from "./blah.ts";

which turns into

export const blah = () => true;
export const what = () => false;
// index.ts
import { what as how } from "./blah.ts";

This is kind of annoying. What gives? (Also, feel free to make the title more descriptive)

EDIT: Checklist!:

• rls-data 0.16.0 released
• rustc - save-analysis: handle aliasing imports a bit more nicely rust#50399
• rls-analysis - handle import changes, blocked on rustc change, needs a test
• RLS - update rls-analysis version
• push updated RLS to Rust repo

[nrc]

The Rust compiler loses knowledge of aliasing very early in compilation so by the later stages (and in the RLS) we only know that uses of ParserTrait refer to the definition Parser. A rename therefore ends up renaming both 'sides' of the alias.

We should not do this, we'll need to detect it in the RLS, but I'm not sure how to do that.

[glmdgrielson]

You know, I don't think relying on the compiler is such a good idea and this is a reason why. And what if I did this with an external crate? What actually requires the compiler and what could be done with just static analysis?

[nrc]

OK, so this is a bit trickier than expected. Tracking the bits of work:

• rls-data 0.16.0 released
• rustc - save-analysis: handle aliasing imports a bit more nicely rust#50399
• rls-analysis - handle import changes, blocked on rustc change, needs a test
• RLS - update rls-analysis version
• push updated RLS to Rust repo

[nrc]

Most of this is done now (with rust-lang/rust#50795 merging).

Outstanding work:

• add a test to rls-analysis
• check that this works in the RLS (waiting on a nightly Rust release before I can test)

[nrc]

This sort of works in the RLS: we block renaming the aliased import, but we seem to block renaming all functions too.

[nrc]

Tested and working and added a test to rls-analysis.