tests: add whitespace tests for vertical tab behavior by Brace1000 · Pull Request #155028 · rust-lang/rust

Brace1000 · 2026-04-09T05:28:53Z

This PR adds two small tests to highlight how vertical tab (\x0B)
is handled differently across Rust's whitespace definitions.

The Rust lexer treats vertical tab as whitespace (Unicode
Pattern_White_Space), while split_ascii_whitespace follows the
WhatWG Infra Standard and does not include vertical tab.

These tests make that difference visible and easier to understand.

See: rust-lang/rust-project-goals#53

Add two small tests to highlight how vertical tab is handled differently. - vertical_tab_lexer.rs checks that the lexer treats vertical tab as whitespace - ascii_whitespace_excludes_vertical_tab.rs shows that split_ascii_whitespace does not split on it This helps document the difference between the Rust parser (which accepts vertical tab) and the standard library’s ASCII whitespace handling. See: rust-lang/rust-project-goals#53

rustbot · 2026-04-09T05:29:01Z

r? @dingxiangfei2009

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make sure tabs and spaces are well checked

Brace1000

fix tidy for whitespace tests spaces, trailing newline

View changes since this review

fix tidy: add whitespace README entry

arrange the tittle in alphabetical order

fix: remove unnecessary output from tests

teor2345

Thanks, just needs a few tweaks

View changes since this review

teor2345 · 2026-04-10T02:28:13Z

tests/ui/whitespace/vertical_tab_lexer.rs

+    let x = 5;
+    let y = 10;
+    let z = x + y;
+


Since vertical tab doesn't show up in GitHub's PR review rendering, please put a comment above each line containing the whitespace.

You might want to add lines with each of the 11 permitted whitespace characters:
https://doc.rust-lang.org/reference/whitespace.html

And then some lines with the other 14 disallowed whitespace characters (the ones from this list marked White_Space, that aren't in the first list):
https://www.unicode.org/Public/UCD/latest/ucd/PropList.txt

teor2345 · 2026-04-10T02:28:39Z

tests/ui/whitespace/ascii_whitespace_excludes_vertical_tab.rs

@@ -0,0 +1,22 @@
+// This test checks that split_ascii_whitespace does NOT split on


I'm not sure if this test is relevant to the compiler?

teor2345 · 2026-04-10T02:29:39Z

tests/ui/README.md


 Tests on `where` clauses. See [Where clauses | Reference](https://doc.rust-lang.org/reference/items/generics.html#where-clauses).

+## `whitespace`


This will need an explanation of why the whitespace tests are needed. It's a good place to mention that is_ascii_whitespace and is_whitespace in the standard library don't match the Rust language's definition of whitespace.

teor2345 · 2026-04-10T23:37:46Z

tests/ui/whitespace/vertical_tab_lexer.rs

+// the standard library's is_ascii_whitespace does NOT include vertical
+// tab, following the WhatWG Infra Standard instead.
+//
+// See: https://github.com/rust-lang/rust-project-goals/issues/53


View changes since the review

Where did you get this link? It's not the Outreachy tracking issue.

…e chars

rustbot · 2026-04-11T07:09:37Z

⚠️ Warning ⚠️

There are issue links (such as #123) in the commit messages of the following commits.
Please move them to the PR description, to avoid spamming the issues with references to the commit, and so this bot can automatically canonicalize them to avoid issues with subtree.
- 5c1a74e
The following commits have merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.
- 0f8f0a6
You can start a rebase with the following commands:
```
$ # rebase
$ git pull --rebase https://github.com/rust-lang/rust.git main
$ git push --force-with-lease
```

rust-log-analyzer · 2026-04-11T07:57:01Z

The job aarch64-gnu-llvm-21-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

##[endgroup]
Executing "/scripts/stage_2_test_set1.sh"
+ /scripts/stage_2_test_set1.sh
+ '[' 1 == 1 ']'
+ echo 'PR_CI_JOB set; skipping tidy'
+ SKIP_TIDY='--skip tidy'
+ ../x.py --stage 2 test --skip tidy --skip compiler --skip src
PR_CI_JOB set; skipping tidy
##[group]Building bootstrap
    Finished `dev` profile [unoptimized] target(s) in 0.04s
##[endgroup]
---
error: ui test did not emit an error
note: by default, ui tests are expected not to compile.
hint: use check-pass, build-pass, or run-pass directive to change this behavior.
status: exit status: 0
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/whitespace/ascii_whitespace_excludes_vertical_tab.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/whitespace/ascii_whitespace_excludes_vertical_tab" "-A" "unused" "-W" "unused_attributes" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
stderr: none

---- [ui] tests/ui/whitespace/ascii_whitespace_excludes_vertical_tab.rs stdout end ----
---- [ui] tests/ui/whitespace/vertical_tab_lexer.rs stdout ----
Saved the actual stderr to `/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/whitespace/vertical_tab_lexer/vertical_tab_lexer.stderr`
normalized stderr:
error[E0425]: cannot find value `let_ws2` in this scope
##[error]  --> $DIR/vertical_tab_lexer.rs:23:5
   |
LL |     let_ws2 = 2_i32;
   |     ^^^^^^^
   |
help: you might have meant to introduce a new binding
   |
LL -     let_ws2 = 2_i32;
LL +     let ws2 = 2_i32;
   |

error[E0425]: cannot find value `let_ws3` in this scope
##[error]  --> $DIR/vertical_tab_lexer.rs:26:5
   |
LL |     let_ws3 = 3_i32;
   |     ^^^^^^^
   |
help: you might have meant to introduce a new binding
   |
LL -     let_ws3 = 3_i32;
LL +     let ws3 = 3_i32;
   |

error[E0425]: cannot find value `let_ws5` in this scope
##[error]  --> $DIR/vertical_tab_lexer.rs:32:5
   |
LL |     let_ws5 = 5_i32;
   |     ^^^^^^^
   |
help: you might have meant to introduce a new binding
   |
LL -     let_ws5 = 5_i32;
LL +     let ws5 = 5_i32;
   |

error[E0425]: cannot find value `_ws2` in this scope
##[error]  --> $DIR/vertical_tab_lexer.rs:56:23
   |
LL |     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
   |                       ^^^^
   |
help: a local variable with a similar name exists
   |
LL -     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
LL +     let _sum = _ws1 + _ws1 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
   |

error[E0425]: cannot find value `_ws3` in this scope
##[error]  --> $DIR/vertical_tab_lexer.rs:56:30
   |
LL |     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
   |                              ^^^^
   |
help: a local variable with a similar name exists
   |
LL -     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
LL +     let _sum = _ws1 + _ws2 + _ws1 + _ws4 + _ws5 + _ws6 + _ws7;
   |

error[E0425]: cannot find value `_ws5` in this scope
##[error]  --> $DIR/vertical_tab_lexer.rs:56:44
   |
LL |     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
   |                                            ^^^^
   |
help: a local variable with a similar name exists
   |
LL -     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
LL +     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws1 + _ws6 + _ws7;
   |

error: aborting due to 6 previous errors

For more information about this error, try `rustc --explain E0425`.
---
To only update this specific test, also pass `--test-args whitespace/vertical_tab_lexer.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/whitespace/vertical_tab_lexer.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/whitespace/vertical_tab_lexer" "-A" "unused" "-W" "unused_attributes" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers"
stdout: none
--- stderr -------------------------------
error[E0425]: cannot find value `let_ws2` in this scope
##[error]  --> /checkout/tests/ui/whitespace/vertical_tab_lexer.rs:23:5
   |
LL |     let_ws2 = 2_i32;
   |     ^^^^^^^
   |
help: you might have meant to introduce a new binding
   |
LL -     let_ws2 = 2_i32;
LL +     let ws2 = 2_i32;
   |

error[E0425]: cannot find value `let_ws3` in this scope
##[error]  --> /checkout/tests/ui/whitespace/vertical_tab_lexer.rs:26:5
   |
LL |     let_ws3 = 3_i32;
   |     ^^^^^^^
   |
help: you might have meant to introduce a new binding
   |
LL -     let_ws3 = 3_i32;
LL +     let ws3 = 3_i32;
   |

error[E0425]: cannot find value `let_ws5` in this scope
##[error]  --> /checkout/tests/ui/whitespace/vertical_tab_lexer.rs:32:5
   |
LL |     let_ws5 = 5_i32;
   |     ^^^^^^^
   |
help: you might have meant to introduce a new binding
   |
LL -     let_ws5 = 5_i32;
LL +     let ws5 = 5_i32;
   |

error[E0425]: cannot find value `_ws2` in this scope
##[error]  --> /checkout/tests/ui/whitespace/vertical_tab_lexer.rs:56:23
   |
LL |     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
   |                       ^^^^
   |
help: a local variable with a similar name exists
   |
LL -     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
LL +     let _sum = _ws1 + _ws1 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
   |

error[E0425]: cannot find value `_ws3` in this scope
##[error]  --> /checkout/tests/ui/whitespace/vertical_tab_lexer.rs:56:30
   |
LL |     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
   |                              ^^^^
   |
help: a local variable with a similar name exists
   |
LL -     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
LL +     let _sum = _ws1 + _ws2 + _ws1 + _ws4 + _ws5 + _ws6 + _ws7;
   |

error[E0425]: cannot find value `_ws5` in this scope
##[error]  --> /checkout/tests/ui/whitespace/vertical_tab_lexer.rs:56:44
   |
LL |     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
   |                                            ^^^^
   |
help: a local variable with a similar name exists
   |
LL -     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws5 + _ws6 + _ws7;
LL +     let _sum = _ws1 + _ws2 + _ws3 + _ws4 + _ws1 + _ws6 + _ws7;
   |

error: aborting due to 6 previous errors

For more information about this error, try `rustc --explain E0425`.

rustbot assigned dingxiangfei2009 Apr 9, 2026

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Apr 9, 2026

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This was referenced Apr 9, 2026

Goal for resolving cargo-semver-checks blockers for merging into cargo. rust-lang/rust-project-goals#53

Merged

Outreachy tracking issue for Rust whitespace check bugs rustfoundation/interop-initiative#53

Open

tests: add ignore-tidy-tab directive to whitespace tests

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Brace1000 added 5 commits April 9, 2026 10:41

Update ascii_whitespace_excludes_vertical_tab.rs

c6403d9

Update ascii_whitespace_excludes_vertical_tab.rs

6c8b0bf

make sure tabs and spaces are well checked

Update vertical_tab_lexer.rs

f8e9276

Update ascii_whitespace_excludes_vertical_tab.rs

027201d

Update vertical_tab_lexer.rs

f2f460a

Brace1000 commented Apr 9, 2026

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a5c0c3c

fix tidy: add whitespace README entry

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Update README.md

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arrange the tittle in alphabetical order

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Brace1000 added 2 commits April 9, 2026 15:48

Update README.md with missing full stop

44df8f9

Update README.md with all spaces checked

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Brace1000 added 2 commits April 9, 2026 16:09

Update ascii_whitespace_excludes_vertical_tab.rs

fde6f69

Update vertical_tab_lexer.rs

1bd1021

fix: remove unnecessary output from tests

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teor2345 reviewed Apr 10, 2026

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Brace1000 added 3 commits April 11, 2026 03:02

tests: expand vertical tab lexer test to cover all Pattern_White_Spac…

6a48814

…e chars

tests: add whitespace/ README entry explaining lexer vs stdlib mismatch

215b21e

resolve merge conflicts, keep local reviewer fixes

0f8f0a6

rustbot added has-merge-commits PR has merge commits, merge with caution. S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Apr 11, 2026

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Brace1000 added 2 commits April 11, 2026 03:23

fix tidy: use full path format for whitespace README entry

3974132

fix tidy: README order, trailing newlines in whitespace tests

f7a598b

		@@ -0,0 +1,22 @@
		// This test checks that split_ascii_whitespace does NOT split on


		Tests on `where` clauses. See [Where clauses \| Reference](https://doc.rust-lang.org/reference/items/generics.html#where-clauses).

		## `whitespace`

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