hex-literal: enforce const evaluation (#889)

Author: newpavlov

Cargo.lock

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## 0.4.1 (2023-04-05)
+### Changed
+- Enforce const evaluation ([#889])
+
+[#889]: https://github.com/RustCrypto/utils/pull/889
+
 ## 0.4.0 (2023-04-02)
 ### Changed
 - Disallow comments inside hex strings ([#816])

hex-literal/CHANGELOG.md

@@ -1,6 +1,6 @@
 [package]
 name = "hex-literal"
-version = "0.4.0"
+version = "0.4.1"
 authors = ["RustCrypto Developers"]
 license = "MIT OR Apache-2.0"
 description = "Macro for converting hexadecimal string to a byte array at compile time"

hex-literal/Cargo.toml

@@ -31,22 +31,37 @@ let bytes1 = hex!("
     00010203 04050607
     08090a0b 0c0d0e0f
 ");
-assert_eq!(bytes1, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]);
+assert_eq!(
+    bytes1,
+    [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15],
+);
 
-// It's possible to use several literals (results will be concatenated)
+// It's possible to use several literals
+// (results will be concatenated)
 let bytes2 = hex!(
     "00010203 04050607" // first half
-    "08090a0b" /* block comment */ "0c0d0e0f" // second half
+    "08090a0b 0c0d0e0f" // second half
 );
 assert_eq!(bytes1, bytes2);
 ```
 
 Using an unsupported character inside literals will result in a compilation error:
 ```rust,compile_fail
-# use hex_literal::hex;
-hex!("АА"); // Cyrillic "А"
-hex!("11　22"); // Japanese space
-hex!("0123 // Сomments inside literals are not supported");
+hex_literal::hex!("АА"); // Cyrillic "А"
+hex_literal::hex!("11　22"); // Japanese space
+```
+
+Сomments inside literals are not supported:
+```rust,compile_fail
+hex_literal::hex!("0123 // foo");
+```
+
+Each literal must contain an even number of hex characters:
+```rust,compile_fail
+hex_literal::hex!(
+    "01234"
+    "567"
+);
 ```
 
 ## Minimum Supported Rust Version

hex-literal/README.md

@@ -81,6 +81,8 @@ pub const fn decode<const LEN: usize>(strings: &[&[u8]]) -> [u8; LEN] {
 macro_rules! hex {
     ($($s:literal)*) => {{
         const STRINGS: &[&'static [u8]] = &[$($s.as_bytes(),)*];
-        $crate::decode::<{ $crate::len(STRINGS) }>(STRINGS)
+        const LEN: usize = $crate::len(STRINGS);
+        const RES: [u8; LEN] = $crate::decode(STRINGS);
+        RES
     }};
 }