Add an Init mode to MutateMode.

This isn't necessary right now, but check_loans needs to be able to
distinguish between initialization and writes in the ExprUseVisitor
mutate callback.

src/librustc/middle/borrowck/move_data.rs

@@ -356,7 +356,7 @@ pub fn add_assignment(&self,
         let path_index = self.move_path(tcx, lp.clone());
 
         match mode {
-            euv::JustWrite => {
+            euv::Init | euv::JustWrite => {
                 self.assignee_ids.borrow_mut().insert(assignee_id);
             }
             euv::WriteAndRead => { }

src/librustc/middle/expr_use_visitor.rs

@@ -86,6 +86,7 @@ pub enum ConsumeMode {
 
 #[deriving(PartialEq,Show)]
 pub enum MutateMode {
+    Init,
     JustWrite,    // x = y
     WriteAndRead, // x += y
 }
@@ -712,7 +713,7 @@ fn walk_pat(&mut self, cmt_discr: mc::cmt, pat: @ast::Pat) {
                 let def = def_map.borrow().get_copy(&pat.id);
                 match mc.cat_def(pat.id, pat.span, pat_ty, def) {
                     Ok(binding_cmt) => {
-                        delegate.mutate(pat.id, pat.span, binding_cmt, JustWrite);
+                        delegate.mutate(pat.id, pat.span, binding_cmt, Init);
                     }
                     Err(_) => { }
                 }