Fix super method call inside let expression

pkl-core/src/main/java/org/pkl/core/ast/builder/SymbolTable.java

@@ -327,6 +327,8 @@ public final boolean isClassScope() {
     }
 
     public final boolean isClassMemberScope() {
+      var effectiveScope = skipLambdaScopes();
+      var parent = effectiveScope.parent;
       if (parent == null) return false;
 
       return parent.isClassScope()

pkl-core/src/main/java/org/pkl/core/ast/expression/member/InvokeSuperMethodNode.java

@@ -66,6 +66,9 @@ protected Object eval(
 
   protected ClassMethod findSupermethod(VirtualFrame frame) {
     var owner = VmUtils.getOwner(frame);
+    while (owner instanceof org.pkl.core.runtime.VmFunction) {
+      owner = owner.getEnclosingOwner();
+    }
     assert owner.isPrototype();
 
     var superclass = owner.getVmClass().getSuperclass();

pkl-core/src/test/files/LanguageSnippetTests/input/classes/supercallsInLet.pkl

@@ -0,0 +1,44 @@
+open class A {
+  function foo() = "a"
+}
+
+class B extends A {
+  function foo() =
+    let (bar = "b")
+      super.foo() + bar
+}
+
+local b = new B {}
+
+res1 = b.foo()
+
+// Also test with property access
+open class C {
+  value = "c"
+}
+
+class D extends C {
+  result =
+    let (x = "d")
+      super.value + x
+}
+
+local d = new D {}
+
+res2 = d.result
+
+// Test with nested let expressions
+open class E {
+  function getValue() = "e"
+}
+
+class F extends E {
+  function getValue() =
+    let (x = "f")
+      let (y = " and " + x)
+        super.getValue() + y
+}
+
+local f = new F {}
+
+res3 = f.getValue()

pkl-core/src/test/files/LanguageSnippetTests/output/classes/supercallsInLet.pcf

@@ -0,0 +1,3 @@
+res1 = "ab"
+res2 = "cd"
+res3 = "e and f"