refactor MirPass to always require a tcx

src/librustc/lib.rs

@@ -126,6 +126,7 @@ pub mod mir {
     pub mod repr;
     pub mod tcx;
     pub mod visit;
+    pub mod transform;
     pub mod mir_map;
 }
 

src/librustc/mir/transform.rs

@@ -0,0 +1,16 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use mir::repr::Mir;
+use middle::ty::ctxt;
+
+pub trait MirPass {
+    fn run_on_mir<'tcx>(&mut self, mir: &mut Mir<'tcx>, tcx: &ctxt<'tcx>);
+}