Warn about trailing whitespace followed by a newline in a string

What it does

Detect trailing whitespace followed by a newline in a string.

Categories (optional)

• Kind: style or correctness, not sure

What is the advantage of the recommended code over the original code

Text editors tend to remove whitespace at the end of line which would modify what the code does. Using \x20 instead of a space in such situations will prevent text editor from doing so. Also, whitespace at the end of line is invisible to humans making for very confusing code.

Drawbacks

None.

Example

fn main() {
    println!("    
        Hello, world!
    ");
}

Could be written as:

fn main() {
    println!("   \x20
        Hello, world!
    ");
}

Start by searching the rust-clippy repository for existing string or style lints and their test fixtures. The work is complete when a lint detects trailing whitespace immediately before a newline in a string and the behavior is covered by tests for the examples described in this issue.