Fix build error.

src/main/jastadd/Backend.jadd

@@ -222,6 +222,9 @@ aspect BackendDirectedAPI {
   public void RightDirection.generateAPI(StringBuilder sb) {
     relation().getLeft().generateDirectedAPI(sb);
   }
+  public void LeftDirection.generateAPI(StringBuilder sb) {
+    relation().getRight().generateDirectedAPI(sb);
+  }
 
   public abstract void RelationComponent.generateDirectedAPI(StringBuilder sb);
   public void OneRelationComponent.generateDirectedAPI(StringBuilder sb) {
@@ -910,6 +913,9 @@ aspect NameResolutionHelper {
   public void RightDirection.generateContextDependentNameResolution(StringBuilder sb) {
     relation().getLeft().generateContextDependentNameResolution(sb);
   }
+  public void LeftDirection.generateContextDependentNameResolution(StringBuilder sb) {
+    relation().getRight().generateContextDependentNameResolution(sb);
+  }
   public void Bidirectional.generateContextDependentNameResolution(StringBuilder sb) {
     relation().getLeft().generateContextDependentNameResolution(sb);
     relation().getRight().generateContextDependentNameResolution(sb);
@@ -1473,6 +1479,9 @@ aspect PrettyPrint {
   public String RightDirection.prettyPrint() {
     return "->";
   }
+  public String LeftDirection.prettyPrint() {
+    return "<-";
+  }
   public String Bidirectional.prettyPrint() {
     return "<->";
   }