Fix leading qualifiers in use-import prefixes by PLeVasseur · Pull Request #717 · rust-lang/fls

PLeVasseur · 2026-08-07T21:37:17Z

Summary

Preserve leading :: in import path prefixes, distinguishing an empty prefix from bare :: and qualified paths such as ::std.

Replace the stateful construction with a declarative definition and reject misplaced root qualifiers, including in empty nested groups.

Clarify the construction cases, separator, nesting, and self-specific legality wording in response to review.

Reconcile the shadowing rules with explicit global lookup: local names do not prevent ::std from selecting the external crate. The broader nonglobal ambiguity model and trait-parent rules are unchanged.

Closes #711

Reference alignment

Rust Reference: use declarations

Global paths and prelude shadowing, for Rust 2021.

Testing

CI passes.

PLeVasseur · 2026-08-13T20:34:22Z

Me, realizing I did not request @tshepang and @kirtchev-adacore to review 🙃

PLeVasseur

Following up! I think this is probably worth another review now.

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rustbot · 2026-09-22T15:34:27Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

tshepang

Have left some comments, but maybe before handling those, I do wonder why we need the concept of an "import path prefix" when we have "common path prefix". To support that, I don't think we should treat "global paths" (paths starting with ::) in such a special way... they should only add additional tooling-related behavior, and the distinction defined in just one place.

With examples, I think in...

use a::{b, c};, a should be a "common path prefix"
use ::a::{b, c};, a (or ::a, not sure) should similarly be considered a "common path prefix"
- additional semantics of this being a "global path" can be explained elsewhere

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tshepang · 2026-09-24T10:21:09Z

+   For each :t:`nesting import` in which the :t:`glob import` or :t:`simple import` is nested, from outermost to innermost:

-   * :dp:`fls_MOXId37fcNPY`
-     If the :t:`use import` is a :t:`simple import` then start with the
-     :t:`[path segment]s` of the :t:`simple import`'s :t:`simple path`
-     :t:`path prefix`.
+   * :dp:`fls_irdKqoYzBM0M`
+     A sequence determined as follows:


looks like the extra paragraph is not needed here

this also fix grammar

Suggested change

For each :t:`nesting import` in which the :t:`glob import` or :t:`simple import` is nested, from outermost to innermost:

* :dp:`fls_MOXId37fcNPY`

If the :t:`use import` is a :t:`simple import` then start with the

:t:`[path segment]s` of the :t:`simple import`'s :t:`simple path`

:t:`path prefix`.

* :dp:`fls_irdKqoYzBM0M`

A sequence determined as follows:

For each :t:`nesting import` in which the :t:`glob import` or :t:`simple import` is nested, from outermost to innermost, the sequence is determined as follows:

tshepang · 2026-09-24T10:51:31Z

+     * :dp:`fls_9dRQ4YGKstSN`
+       Otherwise the sequence is empty.
+


this seems invalid, since a nesting import has a common path prefix or not
but maybe am failing to follow reasoning

Suggested change

* :dp:`fls_9dRQ4YGKstSN`

Otherwise the sequence is empty.

tshepang · 2026-09-24T10:52:04Z

+     * :dp:`fls_GO9rlHrbXAZn`
+       Otherwise the sequence is empty.
+


similar to https://github.com/rust-lang/fls/pull/717/changes#r4092739338

Suggested change

* :dp:`fls_GO9rlHrbXAZn`

Otherwise the sequence is empty.

tshepang · 2026-09-24T11:01:14Z

+       Otherwise the sequence is empty.
+
+   * :dp:`fls_MOXId37fcNPY`
+     For a :t:`simple import`, the :t:`simple import`'s :t:`simple path` after removing the last :t:`path segment` and any :t:`namespace qualifier` ``::`` that separates the last :t:`path segment` from a preceding :t:`path segment`.


avoids making it seem like the namespace qualifier is optional here

Suggested change

For a :t:`simple import`, the :t:`simple import`'s :t:`simple path` after removing the last :t:`path segment` and any :t:`namespace qualifier` ``::`` that separates the last :t:`path segment` from a preceding :t:`path segment`.

For a :t:`simple import`, the :t:`simple import`'s :t:`simple path` after removing the last :t:`path segment` and the :t:`namespace qualifier` ``::`` preceding the :t:`path segment`.

tshepang · 2026-09-24T11:08:51Z

 into :t:`scope`.

+:dp:`fls_BMtRtjJ7gBKT`
+A :t:`glob import`, :t:`nesting import`, or :t:`simple import` expressed with a leading :t:`namespace qualifier` ``::`` shall not be nested within any :t:`nesting import` that has a :t:`common path prefix` or is expressed with a leading :t:`namespace qualifier` ``::``.


using a shortcut since this is all of them

Suggested change

A :t:`glob import`, :t:`nesting import`, or :t:`simple import` expressed with a leading :t:`namespace qualifier` ``::`` shall not be nested within any :t:`nesting import` that has a :t:`common path prefix` or is expressed with a leading :t:`namespace qualifier` ``::``.

A :t:`use import` expressed with a leading :t:`namespace qualifier` ``::`` shall not be nested within any :t:`nesting import` that has a :t:`common path prefix` or is expressed with a leading :t:`namespace qualifier` ``::``.

I understand the part "A use import expressed with a leading namespace qualifier shall not be nested within any nesting import" to mean that use a::{::b, c}; is not allowed, but I don't understand the rest of the sentence.

tshepang · 2026-09-24T11:15:26Z

+:dp:`fls_UZHHtqJ0ekju`
+An empty :t:`import path prefix` of a :t:`simple import` whose :t:`simple path` is expressed as :t:`keyword` ``self`` resolves to the current :t:`module`.
+


I don't we should have such a thing as empty path prefix

Suggested change

:dp:`fls_UZHHtqJ0ekju`

An empty :t:`import path prefix` of a :t:`simple import` whose :t:`simple path` is expressed as :t:`keyword` ``self`` resolves to the current :t:`module`.

tshepang · 2026-09-24T11:15:51Z

+
 :dp:`fls_JHU0ersYB6eL`
-An :t:`import path prefix` shall resolve to a :t:`module` or :t:`enum`.
+An :t:`import path prefix` that contains a :t:`path segment` shall resolve to an :t:`enum` or :t:`module`.


related to https://github.com/rust-lang/fls/pull/717/changes#r4092947510

PLeVasseur added 3 commits July 31, 2026 19:36

docs(resolve): preserve leading qualifiers in use imports

0ab3bab

docs(resolve): reject empty glob import prefixes

a341052

docs(resolve): centralize glob import restrictions

8e9c110

PLeVasseur requested review from kirtchev-adacore and tshepang August 13, 2026 20:33

tshepang requested changes Aug 15, 2026

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PLeVasseur mentioned this pull request Aug 18, 2026

updates for Rust 1.97 release #713

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PLeVasseur added 3 commits September 5, 2026 00:29

chore: merge upstream main into import-prefix fix

be13734

docs(resolve): address import-prefix review

d7239cb

docs(resolve): reject nested root qualifiers

b3ba110

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PLeVasseur added 3 commits September 5, 2026 09:10

docs(resolve): alphabetize import enumerations

75af3c8

docs(resolve): unwrap import paragraphs

847ff2e

docs(resolve): preserve global lookup under shadowing

60e7f26

PLeVasseur commented Sep 6, 2026

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PLeVasseur requested review from kirtchev-adacore and tshepang September 6, 2026 21:12

kirtchev-adacore reviewed Sep 7, 2026

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docs(resolve): clarify import-prefix wording

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PLeVasseur requested a review from kirtchev-adacore September 17, 2026 12:34

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PLeVasseur added 3 commits September 20, 2026 01:52

docs(resolve): use term-based import-prefix cases

4b53dc4

docs(resolve): express nesting restriction with terms

9d73a0d

chore: merge upstream main into import-prefix fix

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PLeVasseur requested a review from kirtchev-adacore September 22, 2026 15:42

kirtchev-adacore approved these changes Sep 23, 2026

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tshepang requested changes Sep 24, 2026

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	For a :t:`simple import`, the :t:`simple import`'s :t:`simple path` after removing the last :t:`path segment` and any :t:`namespace qualifier` ``::`` that separates the last :t:`path segment` from a preceding :t:`path segment`.
	For a :t:`simple import`, the :t:`simple import`'s :t:`simple path` after removing the last :t:`path segment` and the :t:`namespace qualifier` ``::`` preceding the :t:`path segment`.

	A :t:`glob import`, :t:`nesting import`, or :t:`simple import` expressed with a leading :t:`namespace qualifier` ``::`` shall not be nested within any :t:`nesting import` that has a :t:`common path prefix` or is expressed with a leading :t:`namespace qualifier` ``::``.
	A :t:`use import` expressed with a leading :t:`namespace qualifier` ``::`` shall not be nested within any :t:`nesting import` that has a :t:`common path prefix` or is expressed with a leading :t:`namespace qualifier` ``::``.

		:dp:`fls_UZHHtqJ0ekju`
		An empty :t:`import path prefix` of a :t:`simple import` whose :t:`simple path` is expressed as :t:`keyword` ``self`` resolves to the current :t:`module`.

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PLeVasseur commented Aug 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Reference alignment

Testing

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PLeVasseur commented Aug 13, 2026

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PLeVasseur commented Aug 7, 2026 •

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