Address review comments

src/librustc/middle/liveness.rs

@@ -104,6 +104,8 @@
  *   fallthrough node.  It is only live if the function could converge
  *   via means other than an explicit `return` expression. That is, it is
  *   only dead if the end of the function's block can never be reached.
+ *   It is the responsibility of typeck to ensure that there are no
+ *   `return` expressions in a function declared as diverging.
  */
 
 use middle::def::*;

src/librustc/middle/trans/callee.rs

@@ -876,11 +876,8 @@ pub fn trans_call_inner<'blk, 'tcx>(bcx: Block<'blk, 'tcx>,
         _ => {}
     }
 
-    match ret_ty {
-        ty::FnConverging(_) => {},
-        ty::FnDiverging => {
-            Unreachable(bcx);
-        }
+    if ret_ty == ty::FnDiverging {
+        Unreachable(bcx);
     }
 
     Result::new(bcx, llresult)

src/librustc/middle/trans/intrinsic.rs

@@ -204,7 +204,7 @@ pub fn trans_intrinsic_call<'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>, node: ast::N
 
     fcx.pop_custom_cleanup_scope(cleanup_scope);
 
-    // The only intrinsic function that diverges.
+    // These are the only intrinsic functions that diverge.
     if name.get() == "abort" {
         let llfn = ccx.get_intrinsic(&("llvm.trap"));
         Call(bcx, llfn, [], None);

src/librustc/util/ppaux.rs

@@ -957,12 +957,10 @@ impl Repr for ty::FnSig {
 impl Repr for ty::FnOutput {
     fn repr(&self, tcx: &ctxt) -> String {
         match *self {
-          ty::FnConverging(ty) => {
-            format!("FnConverging({0})", ty.repr(tcx))
-          }
-          ty::FnDiverging => {
-            "FnDiverging".to_string()
-          }
+            ty::FnConverging(ty) =>
+                format!("FnConverging({0})", ty.repr(tcx)),
+            ty::FnDiverging =>
+                "FnDiverging".to_string()
         }
     }
 }