Closes egraphs-good#316; Added test for existance + fix bad connectio…

…n choice and bad drop of `rest_if_proof`

src/explain.rs

@@ -1,19 +1,18 @@
-use crate::Symbol;
-use crate::{
-    util::pretty_print, Analysis, EClass, ENodeOrVar, FromOp, HashMap, HashSet, Id, Language,
-    PatternAst, RecExpr, Rewrite, UnionFind, Var,
-};
-
 use std::cmp::Ordering;
 use std::collections::{BinaryHeap, VecDeque};
 use std::fmt::{self, Debug, Display, Formatter};
 use std::ops::{Deref, DerefMut};
 use std::rc::Rc;
 
-use symbolic_expressions::Sexp;
-
 use num_bigint::BigUint;
 use num_traits::identities::{One, Zero};
+use symbolic_expressions::Sexp;
+
+use crate::{
+    Analysis, EClass, ENodeOrVar, FromOp, HashMap, HashSet, Id, Language, PatternAst,
+    RecExpr, Rewrite, UnionFind, util::pretty_print, Var,
+};
+use crate::Symbol;
 
 type ProofCost = BigUint;
 
@@ -1276,18 +1275,26 @@ impl<'x, L: Language> ExplainNodes<'x, L> {
         if graphnode.parent_connection.next == existance
             || existance_node.parent_connection.next == node
         {
-            let mut connection = graphnode.parent_connection.clone();
+            let mut connection = if graphnode.parent_connection.next == existance {
+                graphnode.parent_connection.clone()
+            } else {
+                existance_node.parent_connection.clone()
+            };
 
             if graphnode.parent_connection.next == existance {
                 connection.is_rewrite_forward = !connection.is_rewrite_forward;
                 std::mem::swap(&mut connection.next, &mut connection.current);
             }
-            return self.explain_enode_existance(
+
+            let adj = self.explain_adjacent(connection, cache, enode_cache, false);
+            let mut exp = self.explain_enode_existance(
                 existance,
-                self.explain_adjacent(connection, cache, enode_cache, false),
+                adj,
                 cache,
                 enode_cache,
             );
+            exp.push(rest_of_proof);
+            return exp;
         }
 
         // case 3)
@@ -1944,7 +1951,6 @@ impl<'x, L: Language> ExplainNodes<'x, L> {
 
 #[cfg(test)]
 mod tests {
-
     use super::super::*;
 
     #[test]
@@ -2049,6 +2055,27 @@ mod tests {
 
         egraph.dot().to_dot("target/foo.dot").unwrap();
     }
+
+    #[test]
+    fn simple_explain_exists() {
+        //! Same as previous test, but now I want to make a rewrite add some term and see it exists in
+        //! more then one step
+        use crate::SymbolLang;
+        init_logger();
+
+        let rws: Vec<Rewrite<SymbolLang, ()>> = [rewrite!("makeb"; "a" => "b"), rewrite!("makec"; "b" => "c")].iter().cloned().collect();
+        let mut egraph = Runner::default().with_explanations_enabled()
+            .without_explanation_length_optimization()
+            .with_expr(&"a".parse().unwrap())
+            .run(&rws).egraph;
+        egraph.rebuild();
+        let a: Symbol = "a".parse().unwrap();
+        let b: Symbol = "b".parse().unwrap();
+        let c: Symbol = "c".parse().unwrap();
+        let mut exp = egraph.explain_existance(&"c".parse().unwrap());
+        println!("{:?}", exp.make_flat_explanation());
+        assert_eq!(exp.make_flat_explanation().len(), 3, "Expected 3 steps, got {:?}", exp.make_flat_explanation());
+    }
 }
 
 #[test]