fix donach error

Author: Frotty

de.peeeq.wurstscript/src/main/java/de/peeeq/wurstscript/types/FunctionSignature.java

@@ -234,7 +234,6 @@ public WurstType getVarargType() {
         for (int i = 0; i < argTypes.size(); i++) {
             WurstType pt = getParamType(i);
             WurstType at = argTypes.get(i);
-            mapping = at.matchAgainstSupertype(pt, location, mapping, VariablePosition.RIGHT);
             VariableBinding before = mapping;
             VariableBinding after = at.matchAgainstSupertype(pt, location, mapping, VariablePosition.RIGHT);
             WLogger.trace(() -> "[IMPLCONV]   vb " + System.identityHashCode(before)

de.peeeq.wurstscript/src/test/java/tests/wurstscript/tests/GenericsTests.java

@@ -1212,4 +1212,21 @@ public void nestedList2() {
         );
     }
 
+    @Test
+    public void conflictingTypeArgsMemberMethod() {
+        // Regression test: calling a generic method via dot notation with conflicting type arguments
+        // used to cause a NullPointerException instead of a proper type error.
+        // The two arguments infer conflicting types for T (int vs string), which should produce
+        // a "Wrong parameter type" compile error, not a compiler crash.
+        testAssertErrorsLines(false, "Wrong parameter type",
+            "package test",
+            "class C",
+            "    function combine<T>(T x, T y) returns T",
+            "        return x",
+            "init",
+            "    let c = new C()",
+            "    c.combine(1, \"hello\")"
+        );
+    }
+
 }