steiner tree: eliminate identity loops

src/morphism.rs

@@ -98,7 +98,12 @@ impl<M: Morphism + Clone> MorphismBase<M> {
                 &src_type.clone().param_normalize(),
                 &m.get_type().src_type.param_normalize(),
             ) {
-                dst_types.push(MorphismInstance{ halo, m: m.clone(), σ });
+                let dst_type =
+                    m.get_type().dst_type.clone()
+                    .apply_substitution( &|x| σ.get(x).cloned() )
+                    .clone();
+
+                dst_types.push( (σ, dst_type) );
             }
         }
         dst_types

src/steiner_tree.rs

@@ -107,8 +107,13 @@ impl PathApproxSteinerTreeSolver {
                 let mut new_path_iter = new_path.into_iter().peekable();
 
                 // check all existing nodes..
+
+                if new_path_iter.peek().unwrap() == &src_type {
+                    new_path_iter.next();
+                }
+
                 for mt in tree.iter() {
-//                    assert!( mt.src_type == &src_type );
+                    //assert!( mt.src_type == &src_type );
                     if let Some(t) = new_path_iter.peek() {
                         if &mt.dst_type == t {
                             // eliminate this node from new path

src/term.rs

@@ -14,8 +14,6 @@ pub enum TypeTerm {
     Num(i64),
     Char(char),
 
-    
-
     /* Complex Terms */
 
     // Type Parameters
@@ -47,10 +45,9 @@ impl TypeTerm {
                 *self = TypeTerm::App(vec![
                     self.clone(),
                     t.into()
-                ])                
+                ])
             }
         }
-
         self
     }