From ca15457b358d7b57cf14f3a1215ce609645c942b Mon Sep 17 00:00:00 2001
From: Frotty <Frotty@users.noreply.github.com>
Date: Sat, 18 Oct 2025 19:21:19 +0200
Subject: [PATCH] Correctly set type args binding for derived classes, fixes
 #871

---
 .../validation/WurstValidator.java            | 25 ++++++++-----
 .../tests/wurstscript/tests/BugTests.java     | 36 +++++++++++++++++++
 2 files changed, 53 insertions(+), 8 deletions(-)

diff --git a/de.peeeq.wurstscript/src/main/java/de/peeeq/wurstscript/validation/WurstValidator.java b/de.peeeq.wurstscript/src/main/java/de/peeeq/wurstscript/validation/WurstValidator.java
index 28ad77798..126f624bc 100644
--- a/de.peeeq.wurstscript/src/main/java/de/peeeq/wurstscript/validation/WurstValidator.java
+++ b/de.peeeq.wurstscript/src/main/java/de/peeeq/wurstscript/validation/WurstValidator.java
@@ -1742,7 +1742,7 @@ private void checkParams(Element where, String preMsg, List<Expr> args, List<Wur
                 // if (expected instanceof AstElementWithTypeArgs)
                 if (!actual.isSubtypeOf(expected, where)) {
                     args.get(i).addError(
-                            preMsg + "Expected " + expected + " as parameter " + (i + 1) + " but  found " + actual);
+                            preMsg + "Expected " + expected + " as parameter " + (i + 1) + " but found " + actual);
                 }
             }
         }
@@ -2356,22 +2356,30 @@ private void checkConstructor(ConstructorDef d) {
             WurstTypeClass ct = c.attrTypC();
             WurstTypeClass extendedClass = ct.extendedClass();
             if (extendedClass != null) {
-                // check if super constructor is called correctly...
-                // TODO check constr: get it from ct so that it has the correct type binding
+                // Use the *bound* super-constructor signature
                 ConstructorDef sc = d.attrSuperConstructor();
                 if (sc == null) {
                     d.addError("No super constructor found.");
                 } else {
-                    List<WurstType> paramTypes = Lists.newArrayList();
+                    // Build expected param types in the subclass binding context
+                    List<WurstType> expected = Lists.newArrayList();
+
+                    // The binding that maps the superclass type params to the subclass type args
+                    VariableBinding binding = extendedClass.getTypeArgBinding();
+
                     for (WParameter p : sc.getParameters()) {
-                        paramTypes.add(p.attrTyp());
+                        WurstType t = p.attrTyp();
+                        t = t.setTypeArgs(binding);
+
+                        expected.add(t);
                     }
+
                     if (d.getSuperConstructorCall() instanceof NoSuperConstructorCall
-                            && paramTypes.size() > 0) {
+                        && !expected.isEmpty()) {
                         c.addError("The extended class <" + extendedClass.getName() + "> does not expose a no-arg constructor. " +
-                                "You must define a constructor that calls super(..) appropriately, in this class.");
+                            "You must define a constructor that calls super(..) appropriately, in this class.");
                     } else {
-                        checkParams(d, "Incorrect call to super constructor: ", superArgs(d), paramTypes);
+                        checkParams(d, "Incorrect call to super constructor: ", superArgs(d), expected);
                     }
                 }
             }
@@ -2383,6 +2391,7 @@ private void checkConstructor(ConstructorDef d) {
     }
 
 
+
     private void checkArrayAccess(ExprVarArrayAccess ea) {
         checkNameRefDeprecated(ea, ea.tryGetNameDef());
         for (Expr index : ea.getIndexes()) {
diff --git a/de.peeeq.wurstscript/src/test/java/tests/wurstscript/tests/BugTests.java b/de.peeeq.wurstscript/src/test/java/tests/wurstscript/tests/BugTests.java
index 864fedda7..6163af115 100644
--- a/de.peeeq.wurstscript/src/test/java/tests/wurstscript/tests/BugTests.java
+++ b/de.peeeq.wurstscript/src/test/java/tests/wurstscript/tests/BugTests.java
@@ -1459,5 +1459,41 @@ public void duplicateNameInClassHierachy() {
             "endpackage");
     }
 
+    @Test
+    public void derivedGenericClassConstructor() {
+        testAssertOkLinesWithStdLib(true,
+            "package test",
+            "import LinkedList",
+            "public class ListIterator<T> extends LLIterator<T>",
+            "    construct(LinkedList<T> parent)",
+            "        super(parent)",
+            "init",
+            "	let b = new ListIterator<int>(new LinkedList<int>())",
+            "	if b != null",
+            "		testSuccess()",
+            "endpackage");
+    }
+
+    @Test
+    public void derivedGenericClassConstructorNewGenerics() {
+        testAssertOkLines(true,
+            "package test",
+            "native testSuccess()",
+            "class A<T:>",
+            "    T value",
+            "class B<X:>",
+            "    A<X> a",
+            "    construct(A<X> a)",
+            "        this.a = a",
+            "public class C<T:> extends B<T>",
+            "    construct(A<T> parent)",
+            "        super(parent)",
+            "init",
+            "	let b = new C<int>(new A<int>())",
+            "	if b != null",
+            "		testSuccess()",
+            "endpackage");
+    }
+
 
 }