Suggest case insensitive import suggestions by GTimothy · Pull Request #156239 · rust-lang/rust

GTimothy · 2026-05-06T12:04:57Z

This PR proposes case insensitive import suggestions.
Previous discussion of this topic here: #72641 and in this PR: #72988
If that is still of interest, a discussion may be needed to limit or expand the included list.
I initially followed the suggestions in #72988.

The tests are based on the tests by @chrissimpkins in #72988.

I added a is_exact_match field to ImportSuggestion to modify the suggestion text accordingly.

Only when no other suggestion is made, do I check for case insensitive import suggestion.

fn test_layout(_x: LayOut){}
//~^ ERROR: cannot find type `LayOut` in this scope

error[E0425]: cannot find type `LayOut` in this scope
  --> $DIR/libstd.rs:3:20
   |
LL | fn test_layout(_x: LayOut){}
   |                    ^^^^^^ not found in this scope
   |
help: consider importing this similarly named struct
   |
LL + use std::alloc::Layout;
   |

for a more complex case:
SystemTime exists in the stdlib, but I only suggest case insensitive import when nothing else is suggested

fn test_systemtime(_x: Systemtime){}
//~^ ERROR: cannot find type `Systemtime` in this scope

struct SystemTome{}
mod st{
    struct SystemTame{}
}

error[E0425]: cannot find type `Systemtime` in this scope
  --> $DIR/libstd.rs:428:24
   |
LL | fn test_systemtime(_x: Systemtime){}
   |                        ^^^^^^^^^^
...
LL | struct SystemTome{}
   | ----------------- similarly named struct `SystemTome` defined here
   |
help: a struct with a similar name exists
   |
LL - fn test_systemtime(_x: Systemtime){}
LL + fn test_systemtime(_x: SystemTome){}
   |

During this PR, I ended up adding two other things which could arguably be two separate PRs:

GTimothy · 2026-05-06T12:26:45Z

I see from the 247 failed tests that 1-edit difference is too big for small names. 'net' should probably NOT be suggested to replace 'new'...

Edit: i have now switched to case insensitive match only.

rustbot · 2026-06-02T06:57:00Z

r? @TaKO8Ki

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GTimothy · 2026-06-24T12:48:51Z

upstream change #157991 contains commit cd2d10a and 4f6a600 from #157974 which do some weird file swapping instead of renamings that completely confuses and breaks my rebase attempts.
I may have some skill issue here, does anyone know how to fix this? Is there a proper git workflow to resolve this or do I need to copy my changes over to the swapped file and delete the changes in the original file by hand?

If this is not a skill issue on my part, maybe avoiding this kind of file swapping and splitting this in multiple rename commits would help git not getting confused ?

GTimothy · 2026-06-26T09:41:04Z

For anyone having trouble with the file swap, my cleanest solution is:

assuming I have 7 commits on top of my out of date branch.
assuming no existing *.patch files present.

# make patches out of my commits
git format-patch HEAD~7..HEAD

# edit the patch files to change the file path
sed -i 's|a/compiler/rustc_resolve/src/diagnostics.rs|a/compiler/rustc_resolve/src/error_helper.rs|g; s|b/compiler/rustc_resolve/src/diagnostics.rs|b/compiler/rustc
_resolve/src/error_helper.rs|g' *.patch  

# create new 'fix-swapped-files' branch from upstream latest
git checkout -b fix-swapped-files <upstream>/main

# apply updated patches
git am --committer-date-is-author-date *.patch

apiraino · 2026-08-12T14:06:23Z

@rustbot reroll

mu001999

During this PR, I ended up adding two other things which could arguably be two separate PRs

I think it would be good to extract them as separate PRs. Let's keep this PR only related to case-insensitive import suggestions.

And, please squash the commits to three commits, which would be helpful to review:

Adding tests and make a snapshot of current compiler behavior
The new implementation
Bless tests

@rustbot author

View changes since this review

rustbot · 2026-08-12T15:08:15Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

rustbot · 2026-08-15T15:15:43Z

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.

stdlib case insensitive tests Co-authored-by: Chris Simpkins <git.simpkins@gmail.com> additional insensitive import test

adds a is_exact_match field to ImportSuggestion use is_exact_match field to customize help message suggest imports with different casing only suggest modules if the following segment matches something in scope of the suggestion rebase: fix compilation error after rebase fix: use error code const directly

GTimothy · 2026-08-16T16:53:16Z

During this PR, I ended up adding two other things which could arguably be two separate PRs

I think it would be good to extract them as separate PRs. Let's keep this PR only related to case-insensitive import suggestions.

Done, I extracted them as #161180 and #161182

And, please squash the commits to three commits, which would be helpful to review:
1. Adding tests and make a snapshot of current compiler behavior

2. The new implementation

3. Bless tests

Done :)

@rustbot ready

mu001999 · 2026-08-20T08:31:17Z

+    fn shutdown_not_in_scope()->Shutdown{ //~ ERROR
+        unimplemented!()
+    }
+    fn both_not_in_scope_and_capitalization()->both{ //~ ERROR
+        unimplemented!()
+    }
+    fn shutdown_both_not_in_scope_and_capitalization()->shutdown{ //~ ERROR
+        both //~ ERROR
+    }
+    fn both_missing_std()->std::net::Shutdown{
+        net::shutdown::Both //~ ERROR
+    }
+    fn shutdown_capitalization()->std::net::Shutdown{
+        std::net::shutdown::Both //~ ERROR
+    }
+    fn shutdown_and_both_missing_capitalization()->std::net::Shutdown{
+        std::net::shutdown::both //~ ERROR
+    }


I think these could be moved into the part of std::net in file tests/ui/imports/case-insensitive/libstd.rs.

View changes since the review

mu001999 · 2026-08-22T08:28:44Z

+help: consider importing this module
+   |
+LL +     use crate::bar;
+   |
+


And this suggestion

View changes since the review

mu001999 · 2026-08-22T08:28:58Z

+help: consider importing this module
+   |
+LL +     use foo;
+   |


Also this suggestion

View changes since the review

mu001999 · 2026-08-22T08:29:04Z

+help: consider importing this module
+   |
+LL +     use crate::foo;
+   |


Are this suggestion expected?

View changes since the review

mu001999 · 2026-08-22T09:05:58Z

 }

-type PathString<'a> = (String, &'a str, Option<Span>, &'a Option<String>, bool);
+type PathString<'a> = (String, &'a str, Option<Span>, &'a Option<String>, bool, bool);


Could you convert this tuple to a struct with named fields? Because it has six fields for now.

View changes since the review

mu001999 · 2026-08-22T15:38:11Z

Could you add tests like let _ = Hashmap::new();?

We have suggested the following:

error[E0433]: cannot find type `HashMap` in this scope --> src/main.rs:2:13 | 2 | let x = HashMap::new(); | ^^^^^^^ use of undeclared type `HashMap` | help: consider importing this struct | 1 + use std::collections::HashMap; |

Although I think it is not easy to support this.

View changes since the review

mu001999 · 2026-08-22T17:54:30Z

+        if let Some(E0425) = err.code
+            && candidates.is_empty()
+            && no_suggestion
+        {


I'm afraid this is not enough. Because the code of err may be changed to the parent err's code. And other suggestions may also be added later. And this is why we emit some (unexpected) suggestions in tests/ui/resolve/export-fully-qualified.rs and tests/ui/suggestions/crate-or-module-typo.rs.

So I think a better way is to share most logic between the two branches in try_lookup_name_relaxed, like what I commented. And we could return an additional candidates_case_insensitive in this function.

And finnaly, we could use candidates_case_insensitive only if candidates is empty and the final err.code is Some(E0425) when constructing UseError in fn smart_resolve_path_fragment.

View changes since the review

mu001999 · 2026-08-22T18:21:16Z

+        let is_expected = &|res| {
+            if case_sensitive {
+                source.is_expected(res)
+            } else {
+                if following_seg.is_none() {
+                    source.is_expected(res)
+                } else {
+                    matches!(res, Res::Def(DefKind::Mod, _)) //fixme(GTimothy):check that this is
+                    // necessary/correct
+                }
+            }
+        };


Keep let is_expected = &|res| source.is_expected(res); here.

View changes since the review

mu001999 · 2026-08-22T18:21:33Z

+                if !case_sensitive {
+                    // If there's a following segment, only keep modules that contain it
+                    if let Some(following) = following_seg {
+                        let Some(did) = did else { return false };
+                        let Some(module) = self.r.get_module(*did) else { return false };
+                        let mut found = false;
+                        module.for_each_child(self.r, |_, ident, _, _, _| {
+                            if ident.name == following.ident.name {
+                                found = true;
+                            }
+                        });
+                        if !found {
+                            return false;
+                        }
+                    }
+
+                    // Filter out items that are in the prelude
+                    if let Some(prelude) = self.r.prelude {
+                        if let Some(suggestion_did) = did {
+                            let mut is_in_prelude = false;
+                            prelude.for_each_child(self.r, |_, _, _, _, decl| {
+                                if decl.res().opt_def_id() == Some(*suggestion_did) {
+                                    is_in_prelude = true;
+                                }
+                            });
+                            if is_in_prelude {
+                                return false;
+                            }
+                        }
+                    }
+                }


This is also unnecessary.

View changes since the review

mu001999 · 2026-08-22T18:22:02Z

+        if !case_sensitive {
+            return (false, suggested_candidates, candidates);
+        }


This is also unneeded.

View changes since the review

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels May 6, 2026

GTimothy force-pushed the issue-suggest-similar-imports branch from 36cee45 to a23f444 Compare May 6, 2026 12:06

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GTimothy force-pushed the issue-suggest-similar-imports branch 3 times, most recently from fdc8fcc to 2893b67 Compare June 1, 2026 20:18

GTimothy marked this pull request as ready for review June 2, 2026 06:56

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 2, 2026

rustbot assigned TaKO8Ki Jun 2, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jun 2, 2026

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GTimothy force-pushed the issue-suggest-similar-imports branch from 1bcb37c to 981c290 Compare June 24, 2026 14:02

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GTimothy changed the title ~~Suggest importable type that differs slightly~~ Suggest case insensitive import suggestions Jun 26, 2026

GTimothy force-pushed the issue-suggest-similar-imports branch from 65853f4 to 1fdd975 Compare June 26, 2026 09:40

GTimothy force-pushed the issue-suggest-similar-imports branch from 1fdd975 to 9f894a0 Compare June 26, 2026 09:50

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rustbot assigned mu001999 and unassigned TaKO8Ki Aug 12, 2026

mu001999 reviewed Aug 12, 2026

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Comment thread tests/ui/cast/cast-errors-issue-43825.stderr

Comment thread tests/ui/imports/case-insensitive/libstd.stderr

Comment thread compiler/rustc_resolve/src/late/diagnostics.rs Outdated

Comment thread compiler/rustc_resolve/src/late/diagnostics.rs Outdated

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 12, 2026

rustbot added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Aug 12, 2026

GTimothy force-pushed the issue-suggest-similar-imports branch from 9f894a0 to 6122965 Compare August 15, 2026 15:15

GTimothy added 3 commits August 16, 2026 16:21

add case insensitive suggestion tests

5c7056c

stdlib case insensitive tests Co-authored-by: Chris Simpkins <git.simpkins@gmail.com> additional insensitive import test

bless tests

c051a58

This was referenced Aug 16, 2026

Detect missing binding available: add a MaybeIncorrect suggestion #161180

Open

Import suggestion noise: add a generic parameter filter #161182

Draft

GTimothy force-pushed the issue-suggest-similar-imports branch from 6122965 to c051a58 Compare August 16, 2026 15:58

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 16, 2026

mu001999 requested changes Aug 22, 2026

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rustbot 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 Aug 22, 2026

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