Question: Different letter handling behavior compared to Google libphonenumber

[Itsoon]

I'm noticing a different behavior between rust-phonenumber and the official Google libphonenumber library when parsing phone numbers with letters. I'm not sure if this is intentional or a bug.

The difference

When parsing +3367a829916:

• rust-phonenumber: converts to +33672829916 (letter 'a' → digit '2')
• Google libphonenumber (Python): converts to +3367829916 (letter 'a' is removed)

Rust code:

use phonenumber::*;

fn main() {
    let number = parse(None, "+3367a829916").expect("Invalid number");
    let e164 = number.format().mode(Mode::E164).to_string();
    println!("E. 164 number: {}", e164);
    // Output: +33672829916
}

Python code (official libphonenumber):

import phonenumbers

number = phonenumbers.parse("+3367a829916", None)
e164 = phonenumbers.format_number(number, phonenumbers.PhoneNumberFormat. E164)
print(f"E.164 number: {e164}")
# Output: +3367829916

My test expectation

In my tests, I expected this input to return an InvalidPhone error since it contains a letter in an invalid position for a French phone number:

// Test at tests/phone. rs:64: 13
// Expected:  Err(InvalidPhone)
// Got:  Ok("+33672829916")

Question

Is this difference in behavior intentional (a feature), or should rust-phonenumber match the behavior of the official Google library?

I understand that vanity numbers (like "1-800-FLOWERS") should convert letters to digits, but I'm wondering if rust-phonenumber's conversion might be too broad compared to the original implementation.

Thanks for clarifying!