From 699155e21a4041bafd3d469f681c6160b3f78b78 Mon Sep 17 00:00:00 2001
From: Victorious3 <vic@nightfall.moe>
Date: Sun, 3 Jul 2022 19:24:54 +0200
Subject: [PATCH] Equalize type variables in covariant and contravariant
 position

---
 .../target/generate/ASTToTargetAST.java       | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/main/java/de/dhbwstuttgart/target/generate/ASTToTargetAST.java b/src/main/java/de/dhbwstuttgart/target/generate/ASTToTargetAST.java
index 6a8e2612..a118339b 100644
--- a/src/main/java/de/dhbwstuttgart/target/generate/ASTToTargetAST.java
+++ b/src/main/java/de/dhbwstuttgart/target/generate/ASTToTargetAST.java
@@ -270,10 +270,29 @@ public class ASTToTargetAST {
             computedGenericsOfClasses.put(classOrInterface, result);
             eliminateCyclesAndInfima(result);
             eliminateInnerTypeVariables(classOrInterface, result);
+            equalizeTypeVariables(result);
+
             System.out.println("Class " + classOrInterface.getClassName().getClassName() + ": " + result);
             return result;
         }
 
+        void equalizeTypeVariables(Set<ResultPair<?, ?>> input) {
+            for (var pair : new HashSet<>(input)) {
+                if (pair instanceof PairTPHsmallerTPH ptph) {
+                    if (ptph.left.getVariance() == 1 && ptph.right.getVariance() == -1) {
+                        equality.put(ptph.left, ptph.right);
+                        input.remove(ptph);
+                        for (var pair2 : new HashSet<>(input)) {
+                            if (pair2 instanceof PairTPHsmallerTPH ptph2 && ptph2.right.equals(ptph.left)) {
+                                input.remove(pair2);
+                                input.add(new PairTPHsmallerTPH(ptph2.left, ptph.right));
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
         void findTphs(RefTypeOrTPHOrWildcardOrGeneric type, Set<TypePlaceholder> tphs) {
             if (type instanceof RefType refType) {
                 refType.getParaList().forEach(t -> findTphs(t, tphs));