Invalid non-exhaustive pattern error on scalar values

[lifthrasiir]

fn foo(c: char) {
    match c {
        '\u0000'..'\ud7ff' | '\ue000'..'\uffff' => println!("BMP"),
        '\U00010000'..'\U0010ffff' => println!("non-BMP"),
    }
}

...results in:

<anon>:2:5: 5:6 error: non-exhaustive patterns: `_` not covered [E0004]
<anon>:2     match c {
<anon>:3         '\u0000'..'\ud7ff' | '\ue000'..'\uffff' => println!("BMP"),
<anon>:4         '\U00010000'..'\U0010ffff' => println!("non-BMP"),
<anon>:5     }

These patterns clearly encompass the entire domain of char but the exhaustiveness checker doesn't know that. In fact, this occurs for every scalar value:

fn foo(v: u8) {
    match v {
        -128 .. 7 => println!("<= 7"),
        8 .. 127 => println!("> 7"),
    }
}

...but char is the prominent example of this issue.

Dup of #12483.

[alexcrichton]

Looks to be so!