Better user experience when attempting to call associated functions with dot notation

[dsciarra]

Closes #22692

[rust-highfive]

r? @zackmdavis

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[csmoe]

cc @estebank

[zackmdavis]

Thanks for your contribution! Some revisions will be needed for tests to pass.

In addition to having the issue number in the commit message and PR description, a brief summary of the change (not more than 72 characters) is also useful for future readers of the repository history; you can edit the commit message with git commit --amend.

[Centril]

Note: we don't call these "static method"s but rather "associated function"s. Methods are only those which you may call with dot notation. Therefore it may be confusing to call them "static method" in error messages.

[dsciarra]

The build is still failing locally, it would be nice if you can have a second look ;)

[zackmdavis]

@dsciarra The third argument to the span_suggestion_ methods should be a code snippet to replace the span passed as the first argument. We're going to need something more like

err.span_suggestion_with_applicability(
    parent.span,
    "use `::` to access an associated function",
    format!("{}::{}", path_str, path_assignment.ident),
    Applicability::MaybeIncorrect
);

(But this probably isn't literally correct as written. In the UI test output, it looks like our span includes the call args (here, just ()), which we don't want to replace.)

[estebank]

If you need to get part of the literal code, you can use Codemap::span_to_snippet to get it, like done here:

rust/src/librustc_typeck/check/demand.rs

Line 270 in f1694ea

if let Ok(src) = cm.span_to_snippet(sp) {

[dsciarra]

Is there a better way to write this?

[estebank]

Is there a better way to write this?

Other than the inline comment, it seems reasonable to me.

[estebank]

@bors r+ rollup

🎉🎉🎉

[bors]

📌 Commit 0390736 has been approved by estebank