ICE: ^-char in match using regex crashes compiler

[tx46]

Code

• Target: js (maybe irrelevant)

pub fn Env::is_valid_var_name(var_name : String) -> Bool {
  match var_name.to_bytes() using regex {
    ["^[A-Z_][A-Z0-9_]*"] => true
    _ => false
  }
}

The initial hat (^) in the regex causes the ICE.

Environment

• OS: Linux
• OS distribution and/or version: Void
• CPU Architecture: x86_6

moon 0.1.20250724 (2797252 2025-07-24) ~/.moon/bin/moon
moonc v0.6.22 ~/.moon/bin/moonc
moonrun 0.1.20250724 (2797252 2025-07-24) ~/.moon/bin/moonrun

Error output

Oops, the compiler has encountered an unexpected situation.
This is a bug in the compiler.

A bug report containing the error description and relevant code would be
greatly appreciated. You can submit the bug report here:

  https://github.com/moonbitlang/moonbit-docs/issues/new?template=ice.md

Error: File "moonc.ml", line 241426, characters 28-34: Assertion failed

[hackwaly]

@tx46 Thank you for trying our experimental match using regex feature. This feature is unstable and plan to change the syntax in near future. So it's parser is not as solid as expected.

"^" anchor is not supported in our regex. You don't need it to make regex match at beginning. Just remove the "^" from your regex.

[tx46]

@tx46 Thank you for trying our experimental match using regex feature. This feature is unstable and plan to change the syntax in near future. So it's parser is not as solid as expected.

"^" anchor is not supported in our regex. You don't need it to make regex match at beginning. Just remove the "^" from your regex.

thanks, i reverted to using moonbitlang/regexp, however i still feel that it should not cause an ice or crash, hence the report. you may close this if you feel it's unhelpful. :)