Utf16String::truncate panics if new_len > self.len()

[bryal]

The documentation for Utf16String::truncate says that

If new_len is greater than the string’s current length, this has no effect.

But because of the assertion in that method, this is not true. If new_len is greater than the string's current length, truncate will always panic.

widestring-rs/src/utfstring.rs

Line 1527 in c731486

assert!(self.is_char_boundary(new_len));

As a user of the library, I would expect the implementation to conform to the documentation, which also matches the behavior of std::string::String::truncate. No effect would be least surprising, a panic is not. Though, as an alternative, adjusting the documentation to match the current behavior would at least be less surprising than there being a mismatch.