Specify that range patterns must be nonempty. #2093
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src/patterns.md
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| That is, in `a..=b`, a ≤ b must be the case. | ||
| For example, it is an error to have a range pattern `10..=0`. | ||
| r[patterns.range.constraint-nonempty] | ||
| A range pattern must match at least one possible value. In other words: |
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The wording here seemed little strange to me. Does this make sense? Obviously range patterns that are outside the range of the scrutinee won't match the value at all.
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| A range pattern must match at least one possible value. In other words: | |
| A range pattern must be able to match at least one possible value. In other words: |
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I wrote it this way to be consistent with the other lines in this section, for example:
The exclusive range pattern matches all values from the lower bound up to, but not including the upper bound.
This changes the reference to match the behavior of the compiler, based on my empirical testing. See also rust-lang/rust#149165
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This PR was rebased onto a different master 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. |
Let's revise the wording to avoid a possible ambiguity about what we're matching against.
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This updates to mdbook 0.5.2 from mdbook 0.4.52. A primary aspect of this change is that it splits the `mdbook` crate into multiple crates, and various API changes and cleanup. There's full release notes and a migration guide at https://github.com/rust-lang/mdBook/blob/master/CHANGELOG.md#mdbook-050. This also includes submodule updates: ## book 8 commits in f660f341887c8bbcd6c24fbfdf5d2a262f523965..9c9104e8a82430f97f42e738051bda718919211c 2025-10-27 21:41:51 -0400 to 2025-12-10 11:33:49 -0500 - Update to mdbook 0.5 - Update ch07-02-defining-modules-to-control-scope-and-privacy.md - use AND for search terms - Consistently use let...else - Merge branch 'main' into fix-typo-17-02 - Fix typo in section 17.2 - Revert "Fix typo in section 17.2" - Fix typo in section 17.2 ## edition-guide 2 commits in 5c621253d8f2a5a4adb64a6365905db67dffe3a2..c3c0f0b3da26610138b7ba7663f60cd2c68cf184 2025-10-23 14:13:01 +0000 to 2025-11-28 18:54:18 +0000 - Update to mdbook 0.5 (rust-lang/edition-guide#381) - Link to 1.56.0 and 1.85.0 blog posts (rust-lang/edition-guide#380) ## nomicon 6 commits in 60f0b30d8ec1c9eb5c2582f2ec55f1094b0f8c42..9fe8fa599ad228dda74f240cc32b54bc5c1aa3e6 2025-10-20 13:05:39 +0000 to 2025-12-03 11:54:04 +0000 - Remove references to outdated unsafe code guidelines (rust-lang/nomicon#512) - Update to mdbook 0.5 (rust-lang/nomicon#511) - Fix grammar in ffi.md (rust-lang/nomicon#510) - Add CITATION.cff (rust-lang/nomicon#507) - Use the newest Layout::array size checks for vec-alloc (rust-lang/nomicon#508) - review comment: dropck analysis is *not* trivial (rust-lang/nomicon#498) ## reference 17 commits in e122eefff3fef362eb7e0c08fb7ffbf5f9461905..50c5de90487b68d429a30cc9466dc8f5b410128f 2025-10-28 20:52:27 +0000 to 2025-12-09 22:19:05 +0000 - UB: update the extra clause for provenance UB during const evaluation (rust-lang/reference#2091) - Remove `[no-mentions]` handler in our triagebot config (rust-lang/reference#2102) - Clarify that omitting `nostack` is a promise from the compiler to the programmer (rust-lang/reference#1999) - Specify that range patterns must be nonempty. (rust-lang/reference#2093) - Update to mdbook 0.5 (rust-lang/reference#2096) - get rid of const.no-mut-refs (rust-lang/reference#2080) - use oxford comma (rust-lang/reference#2099) - document `cfg` conditions on inline assembly templates and operands (rust-lang/reference#2063) - remove unused "link reference definitions" (rust-lang/reference#2092) - Add review process overview to review-policy.md (rust-lang/reference#2088) - Remove restriction on dereferencing pointers in const (rust-lang/reference#2090) - add 'system' to variadic ABIs (rust-lang/reference#2069) - Guarantee the binary representation of `isize` explicitly (rust-lang/reference#2064) - Update `no_implicit_prelude` to use the attribute template (rust-lang/reference#1914) - Update `no_std` to use the attribute template (rust-lang/reference#1913) - const_eval.md: be more clear where link leads to (rust-lang/reference#2083) - specify s390x target features (rust-lang/reference#1972) ## rust-by-example 7 commits in 160e6bbca70b0c01aa4de88d19db7fc5ff8447c3..7d21279e40e8f0e91c2a22c5148dd2d745aef8b6 2025-11-03 09:26:45 -0300 to 2025-12-01 15:02:09 -0300 - Update to mdbook 0.5 (rust-lang/rust-by-example#1977) - Use `From::from` fn pointer to convert to boxed errors (rust-lang/rust-by-example#1906) - link the _tuple_ page instead "TupleStruct" (rust-lang/rust-by-example#1909) - enum_use.md: avoid an uncommon term (rust-lang/rust-by-example#1976) - make search less surprising (rust-lang/rust-by-example#1975) - Update documentation for `any` function in iter_any.md (rust-lang/rust-by-example#1973) - Revise `Path` type documentation for clarity (rust-lang/rust-by-example#1972)
ehuss
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Dec 11, 2025
This updates to mdbook 0.5.2 from mdbook 0.4.52. A primary aspect of this change is that it splits the `mdbook` crate into multiple crates, and various API changes and cleanup. There's full release notes and a migration guide at https://github.com/rust-lang/mdBook/blob/master/CHANGELOG.md#mdbook-050. This also includes submodule updates: ## book 1 commits in 8c0eacd5c4acbb650497454f3a58c9e8083202a4..9c9104e8a82430f97f42e738051bda718919211c 2025-11-18 10:36:41 -0500 to 2025-12-10 11:33:49 -0500 - Update to mdbook 0.5 ## edition-guide 1 commits in 9cf5443d632673c4d41edad5e8ed8be86eeb3b8f..c3c0f0b3da26610138b7ba7663f60cd2c68cf184 2025-11-15 21:51:11 +0000 to 2025-11-28 18:54:18 +0000 - Update to mdbook 0.5 (rust-lang/edition-guide#381) ## nomicon 2 commits in 0fe83ab28985b99aba36a1f0dbde3e08286fefda..9fe8fa599ad228dda74f240cc32b54bc5c1aa3e6 2025-11-15 00:03:14 +0000 to 2025-12-03 11:54:04 +0000 - Remove references to outdated unsafe code guidelines (rust-lang/nomicon#512) - Update to mdbook 0.5 (rust-lang/nomicon#511) ## reference 5 commits in b14b4e40f53ca468beaf2f5d0dfb4f4c4ba6bc7b..50c5de90487b68d429a30cc9466dc8f5b410128f 2025-12-02 21:17:44 +0000 to 2025-12-09 22:19:05 +0000 - UB: update the extra clause for provenance UB during const evaluation (rust-lang/reference#2091) - Remove `[no-mentions]` handler in our triagebot config (rust-lang/reference#2102) - Clarify that omitting `nostack` is a promise from the compiler to the programmer (rust-lang/reference#1999) - Specify that range patterns must be nonempty. (rust-lang/reference#2093) - Update to mdbook 0.5 (rust-lang/reference#2096) ## rust-by-example 1 commits in 111cfae2f9c3a43f7b0ff8fa68c51cc8f930637c..7d21279e40e8f0e91c2a22c5148dd2d745aef8b6 2025-11-27 17:16:42 -0300 to 2025-12-01 15:02:09 -0300 - Update to mdbook 0.5 (rust-lang/rust-by-example#1977)
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This changes the reference to match the behavior of the compiler, based on my empirical testing.
See also rust-lang/rust#149165