`unreachable-pub` lint (as authorized by RFC 2126) #45569

zackmdavis · 2017-10-27T05:57:18Z

To whom it may concern:

RFC 2126 commissions the creation of a lint for pub items that are not visible from crate root (#45521). We understand (but seek confirmation from more knowledgable compiler elders) that this can be implemented by linting HIR items that are not ~~cx.access_levels.is_exported~~ cx.access_levels.is_reachable but have a vis (-ibility) field of hir::Visibility::Public.

The lint, tentatively called ~~unexported-pub~~ unreachable-pub (with the understanding that much could be written on the merits of various names, as it is said of the colors of bicycle-sheds), suggests crate as a replacement for pub if the crate_visibility_modifier feature is enabled (see #45388), and pub(crate) otherwise. We also use help messaging to suggest the other potential fix of exporting the item; feedback is desired as to whether this may be confusing or could be worded better.

As a preview of what respecting the proposed lint would look like (and to generate confirmatory evidence that this implementation doesn't issue false positives), ~~we take its suggestions for libcore~~ (save one, which is deferred to another pull request because it brings up an unrelated technical matter). I remain your obedient servant.

r? @petrochenkov

petrochenkov · 2017-10-27T23:52:30Z

src/libcore/fmt/builders.rs

-pub fn debug_struct_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>,
-                                name: &str)
-                                -> DebugStruct<'a, 'b> {
+pub(crate) fn debug_struct_new<'a, 'b>(fmt: &'a mut fmt::Formatter<'b>,


I'd avoid changing libcore until the crate sugar for pub(crate) is available in bootstrap compiler.

petrochenkov · 2017-10-27T23:57:34Z

src/librustc_lint/builtin.rs

+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnexportedPub {
+    fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
+        if !cx.access_levels.is_exported(item.id) && item.vis == hir::Visibility::Public {


As I mentioned on gitter, this should use is_reachable instead of is_exported.
With is_exported this lint will give false positives on anything that is leaked through any other means than use (type aliases, return types, field types). All these things still need to be pub to be usable from other crates.

Test to add:

mod m { pub struct S; // The lint should not fire on this struct } pub fn f() -> m::S { m::S }

petrochenkov · 2017-10-28T00:00:30Z

src/librustc_lint/builtin.rs

+pub struct UnexportedPub;
+
+declare_lint! {
+    UNEXPORTED_PUB,


I'd actually rename the lint into unreachable_pub (+ update all the comments, etc).

petrochenkov · 2017-10-28T00:02:24Z

src/librustc_lint/builtin.rs

+        if !cx.access_levels.is_exported(item.id) && item.vis == hir::Visibility::Public {
+            let mut err = cx.struct_span_lint(UNEXPORTED_PUB, item.span, "unexported `pub` item");
+            err.help("consider exporting it for use by other crates");
+            // `pub` is three chars at start of declaration


This is a bold claim!
pub can be passed to an item through a $vis matcher, for example.

Could you add a test for this case? Something like

mod m { macro_rules! m { ($visibility: vis) => { $visibility struct S; } } m!(pub); }

petrochenkov · 2017-10-28T00:07:33Z

src/librustc_lint/builtin.rs

+    fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
+        if !cx.access_levels.is_exported(item.id) && item.vis == hir::Visibility::Public {
+            let mut err = cx.struct_span_lint(UNEXPORTED_PUB, item.span, "unexported `pub` item");
+            err.help("consider exporting it for use by other crates");


Looking at the tests, "or consider exporting it for use by other crates" would look better.

petrochenkov · 2017-10-28T00:12:44Z

src/librustc_lint/builtin.rs

+}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnexportedPub {
+    fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {


check_item doesn't cover pub on impl items, foreign items and struct fields.

petrochenkov · 2017-10-28T00:13:46Z

src/librustc_lint/builtin.rs

+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnexportedPub {
+    fn check_item(&mut self, cx: &LateContext, item: &hir::Item) {
+        if !cx.access_levels.is_exported(item.id) && item.vis == hir::Visibility::Public {
+            let mut err = cx.struct_span_lint(UNEXPORTED_PUB, item.span, "unexported `pub` item");


def_span will probably look better here (see an example of use in #44847)

zackmdavis · 2017-10-30T23:42:00Z

updated (force-push)

estebank

Could you do a squash of your commits while you're at it?

estebank · 2017-10-31T22:46:58Z

src/test/ui/lint/unreachable_pub.rs

+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(crate_visibility_modifier)]


Could you add a test without this feature enabled to make sure there're no regressions going forward with the pub(crate) suggestion?

petrochenkov · 2017-11-01T23:16:41Z

r=me with @estebank's comment (#45569 (comment)) addressed

This is with deepest thanks to Vadim Petrochenkov for thorough review, and resolves rust-lang#45521.

zackmdavis · 2017-11-03T03:56:25Z

(added non-crate_visibility_modifier UI test and squashed) 🏁 💖

petrochenkov · 2017-11-03T09:09:40Z

@bors r+

bors · 2017-11-03T09:09:41Z

📌 Commit 085ec6d has been approved by petrochenkov

bors · 2017-11-03T09:09:51Z

⌛ Testing commit 085ec6d with merge 9140b5dc5dc016024470e9ab1139c8a86cfec4b8...

bors · 2017-11-03T09:14:08Z

💔 Test failed - status-travis

kennytm · 2017-11-03T14:17:56Z

@bors retry

bors · 2017-11-03T16:28:32Z

⌛ Testing commit 085ec6d with merge 59d4845...

@petrochenkov

`unreachable-pub` lint (as authorized by RFC 2126) To whom it may concern: RFC 2126 commissions the creation of a lint for `pub` items that are not visible from crate root (#45521). We understand (but seek confirmation from more knowledgable compiler elders) that this can be implemented by linting HIR items that are _not_ ~~`cx.access_levels.is_exported`~~ `cx.access_levels.is_reachable` but have a `vis` (-ibility) field of `hir::Visibility::Public`. The lint, tentatively called ~~`unexported-pub`~~ `unreachable-pub` (with the understanding that much could be written on the merits of various names, as it is said of the colors of bicycle-sheds), suggests `crate` as a replacement for `pub` if the `crate_visibility_modifier` feature is enabled (see #45388), and `pub(crate)` otherwise. We also use help messaging to suggest the other potential fix of exporting the item; feedback is desired as to whether this may be confusing or could be worded better. As a preview of what respecting the proposed lint would look like (and to generate confirmatory evidence that this implementation doesn't issue false positives), ~~we take its suggestions for `libcore`~~ (save one, which is deferred to another pull request because it brings up an unrelated technical matter). I remain your obedient servant. ![unexported_pub](https://user-images.githubusercontent.com/1076988/32089794-fbd02420-baa0-11e7-87e5-3ec01f18924a.png) r? @petrochenkov

bors · 2017-11-03T19:07:39Z

☀️ Test successful - status-appveyor, status-travis
Approved by: petrochenkov
Pushing 59d4845 to master...

…hton regenerate libcore/char_private.rs (filed separately from the work in #45569, because of this matter of the updated Unicode data; see also #45567) char_private.rs is generated programmatically by char_private.py, using data retrieved from the Unicode Consortium's website. The motivation here was to make `is_printable` crate-visible (with `pub(crate)`), but it would seem that the Unicode data has changed slightly since char_private.rs was last generated.

rust-highfive assigned petrochenkov Oct 27, 2017

zackmdavis mentioned this pull request Oct 27, 2017

regenerate libcore/char_private.rs #45571

Merged

kennytm added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 27, 2017

petrochenkov reviewed Oct 27, 2017

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petrochenkov reviewed Oct 28, 2017

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zackmdavis force-pushed the unexported_pub_lint branch from 2e7a731 to 7edd04d Compare October 30, 2017 23:40

zackmdavis changed the title ~~unexported-pub lint (as authorized by RFC 2126)~~ unreachable-pub lint (as authorized by RFC 2126) Oct 30, 2017

estebank reviewed Oct 31, 2017

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kennytm added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 1, 2017

unreachable-pub lint for pub items not reachable from crate root

085ec6d

This is with deepest thanks to Vadim Petrochenkov for thorough review, and resolves rust-lang#45521.

zackmdavis force-pushed the unexported_pub_lint branch from 7edd04d to 085ec6d Compare November 3, 2017 03:55

bors merged commit 085ec6d into rust-lang:master Nov 3, 2017

zackmdavis deleted the unexported_pub_lint branch January 13, 2018 07:40

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`unreachable-pub` lint (as authorized by RFC 2126) #45569

`unreachable-pub` lint (as authorized by RFC 2126) #45569

zackmdavis commented Oct 27, 2017 •

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unreachable-pub lint (as authorized by RFC 2126) #45569

unreachable-pub lint (as authorized by RFC 2126) #45569

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`unreachable-pub` lint (as authorized by RFC 2126) #45569

`unreachable-pub` lint (as authorized by RFC 2126) #45569

zackmdavis commented Oct 27, 2017 •

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