PWSTR → PCWSTR let s: PWSTR=...; let r:PCWSTR = PCWSTR(s.0)
String → PCWSTR let s: String=...; let r:PCWSTR = PCWSTR(HSTRING::from(s).as_ptr())
&str → PCWSTR let r:PCWSTR = w!("example") 
//! Trait for converting &str/String into PWSTR.
//! Thanks <https://github.com/microsoft/windows-rs/issues/973#issue-942298423>

#![cfg(windows)]

use windows::core::PWSTR;

pub trait IntoPWSTR {
    fn into_pwstr(self) -> (PWSTR, Vec<u16>);
}

impl IntoPWSTR for &str {
    fn into_pwstr(self) -> (PWSTR, Vec<u16>) {
        let mut encoded = self.encode_utf16().chain([0u16]).collect::<Vec<u16>>();

        (PWSTR(encoded.as_mut_ptr()), encoded)
    }
}

impl IntoPWSTR for String {
    fn into_pwstr(self) -> (PWSTR, Vec<u16>) {
        let mut encoded = self.encode_utf16().chain([0u16]).collect::<Vec<u16>>();

        (PWSTR(encoded.as_mut_ptr()), encoded)
    }
}

References