[MIR] Mir generation for match statements seems to miss arms with guard clauses

[michaelwoerister]

Example:

#![feature(rustc_attrs)]
#[rustc_mir(graphviz="match.dot")]
fn main() {
    let _abc = match Some(101i8) {
        Some(xyz) if xyz > 100 => xyz,
        Some(_) => -1,
        None => -2
    };
}

The resulting MIR does not contain the Some(xyz) arm: http://i.imgur.com/EF489mM.png

[nikomatsakis]

cc me