This makes them more general than the previous versions which expected
`&wstr`. It comes at the cost of additional eager calls to `chars()`.
To implement `appendln` without having to call `append` twice, implement
`IntoCharIter` for chained iterators whose elements are both the kind of
iterator specified by `IntoCharIter`.
Because `IntoCharIter` is not implemented for owned types to avoid
allocations, some call sites which used to pass `WString` need to be
updated to pass references instead, which constitutes the bulk of the
changes in this commit.
Part of #12396
- Don't use `WString::from_str` for `str`s which are available at
compile-time. Use `L!(input).to_owned()` instead. The reason for this
is that `WString::from_str` can cause problems if the input contains
PUA bytes which we use for our custom encoding scheme. In such cases,
`bytes2wcstring` should be used, to avoid problems when decoding the
`WString`. Removing harmless usages of `WString::from_str` allows us
to focus on the potentially dangerous ones which don't convert
`str`'s that are compiled into the binary.
- Make `cstr2wcstring` actually take `CStr` as its input. The former
version was only used in one place, and the conversion to `CStr`
should happen there, where it can be checked that the conversion makes
sense and is safe. The new version is used in
`src/env/environmant.rs`, to avoid `to_bytes()` calls cluttering the
code there.
- Add `osstr2wcstring` function. This function also works for `Path`.
Now, these types can be converted to widestrings with much less
syntactic clutter.
