Use assert_unsafe_precondition for char::from_u32_unchecked
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The context for this is #89259 (comment) (in the issue linked above this post). |
joboet
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Co-Authored-By: joboet <[email protected]>
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const_unwrap for char::from_u32_uncheckedassert_unsafe_precondition for char::from_u32_unchecked
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Updated the PR. Also update the OP because it appears in the merge commit. The original can be seen in the edit history. |
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…ieb,dtolnay Use `assert_unsafe_precondition` for `char::from_u32_unchecked` Use `assert_unsafe_precondition` in `char::from_u32_unchecked` so that it can be stabilized as `const`.
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…iaskrgr Rollup of 8 pull requests Successful merges: - rust-lang#117744 (Add -Zuse-sync-unwind) - rust-lang#118649 (Make inductive cycles in coherence ambiguous always) - rust-lang#118979 (Use `assert_unsafe_precondition` for `char::from_u32_unchecked`) - rust-lang#119562 (Rename `pointer` field on `Pin`) - rust-lang#119619 (mir-opt and custom target fixes) - rust-lang#119632 (Fix broken build for ESP IDF due to rust-lang#119026) - rust-lang#119712 (Adding alignment to the cases to test for specific error messages.) - rust-lang#119734 (Miri subtree update) r? `@ghost` `@rustbot` modify labels: rollup
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…iaskrgr Rollup of 7 pull requests Successful merges: - rust-lang#117744 (Add -Zuse-sync-unwind) - rust-lang#118649 (Make inductive cycles in coherence ambiguous always) - rust-lang#118979 (Use `assert_unsafe_precondition` for `char::from_u32_unchecked`) - rust-lang#119619 (mir-opt and custom target fixes) - rust-lang#119632 (Fix broken build for ESP IDF due to rust-lang#119026) - rust-lang#119712 (Adding alignment to the cases to test for specific error messages.) - rust-lang#119734 (Miri subtree update) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#118979 - ChrisDenton:unwrap-const, r=Nilstrieb,dtolnay Use `assert_unsafe_precondition` for `char::from_u32_unchecked` Use `assert_unsafe_precondition` in `char::from_u32_unchecked` so that it can be stabilized as `const`.
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Stabilize const unchecked conversion from u32 to char Closes rust-lang#89259. The functions in this PR were left out of the initial set of `feature(const_char_convert)` stabilizations in rust-lang#102470, but have since been unblocked by rust-lang#118979. If `unsafe { from_u32_unchecked(u) }` is called in const with a value for which `from_u32(u)` returns None, we get the following compile error. ```rust fn main() { let _ = const { unsafe { char::from_u32_unchecked(0xd800) } }; } ``` ```console error[E0080]: it is undefined behavior to use this value --> src/main.rs:2:19 | 2 | let _ = const { unsafe { char::from_u32_unchecked(0xd800) } }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0x0000d800, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`) | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. = note: the raw bytes of the constant (size: 4, align: 4) { 00 d8 00 00 │ .... } note: erroneous constant encountered --> src/main.rs:2:13 | 2 | let _ = const { unsafe { char::from_u32_unchecked(0xd800) } }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ```
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Stabilize const unchecked conversion from u32 to char Closes rust-lang/rust#89259. The functions in this PR were left out of the initial set of `feature(const_char_convert)` stabilizations in rust-lang/rust#102470, but have since been unblocked by rust-lang/rust#118979. If `unsafe { from_u32_unchecked(u) }` is called in const with a value for which `from_u32(u)` returns None, we get the following compile error. ```rust fn main() { let _ = const { unsafe { char::from_u32_unchecked(0xd800) } }; } ``` ```console error[E0080]: it is undefined behavior to use this value --> src/main.rs:2:19 | 2 | let _ = const { unsafe { char::from_u32_unchecked(0xd800) } }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0x0000d800, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`) | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. = note: the raw bytes of the constant (size: 4, align: 4) { 00 d8 00 00 │ .... } note: erroneous constant encountered --> src/main.rs:2:13 | 2 | let _ = const { unsafe { char::from_u32_unchecked(0xd800) } }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ```
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Stabilize const unchecked conversion from u32 to char Closes rust-lang/rust#89259. The functions in this PR were left out of the initial set of `feature(const_char_convert)` stabilizations in rust-lang/rust#102470, but have since been unblocked by rust-lang/rust#118979. If `unsafe { from_u32_unchecked(u) }` is called in const with a value for which `from_u32(u)` returns None, we get the following compile error. ```rust fn main() { let _ = const { unsafe { char::from_u32_unchecked(0xd800) } }; } ``` ```console error[E0080]: it is undefined behavior to use this value --> src/main.rs:2:19 | 2 | let _ = const { unsafe { char::from_u32_unchecked(0xd800) } }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ constructing invalid value: encountered 0x0000d800, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`) | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. = note: the raw bytes of the constant (size: 4, align: 4) { 00 d8 00 00 │ .... } note: erroneous constant encountered --> src/main.rs:2:13 | 2 | let _ = const { unsafe { char::from_u32_unchecked(0xd800) } }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ```
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Use
assert_unsafe_preconditioninchar::from_u32_uncheckedso that it can be stabilized asconst.