upcall fail: print_type shouldn't see a ty_infer

[grahame]

Calling vec::each incorrectly causes a compiler internal error. Compiling this code

fn main(s: [str]) {
    let a = [];
    vec::each(a) { |x| 

    }
}

with rust 851fde8 gives this error:

bug.rs:4:17: 6:5 error: in function anon, not all control paths return a value
bug.rs:4     vec::each(a) { |x| 
bug.rs:5 
bug.rs:6     }
rust: upcall fail 'print_type shouldn't see a ty_infer', ../src/librustsyntax/print/pprust.rs:384
error: internal compiler error unexpected failure
note: The compiler hit an unexpected failure path. This is a bug. Try running with RUST_LOG=rustc=0,::rt::backtrace to get further details and report the results to github.com/mozilla/rust/issues
rust: upcall fail 'explicit failure', ../src/rustc/driver/rustc.rs:182
rust: domain main @0x7f8203018810 root task failed
[1]    79399 exit 101   RUST_LOG=rustc=0,::rt::backtrace rustc bug.rs