allow local function definitions

src/main/java/com/github/musiKk/Runner.java

@@ -332,6 +332,9 @@ private Value execute(Statement expression, StackFrame frame) {
                 processTraitImplementation(ti, frame.scope);
                 yield null;
             }
+            case FunctionDeclaration functionDeclaration -> {
+                yield registerFunction(functionDeclaration, frame.scope(), "");
+            }
             default -> throw new RuntimeException("not yet implemented " + expression);
         };
     }
@@ -383,13 +386,7 @@ private RuntimeFile initRuntimeFile(String moduleName, Path path, StackFrame fra
             processDataDefinition(dataDefinition, frame.scope);
         });
         processingResult.functionDeclarations().forEach((__, functionDeclaration) -> {
-            var functionName = functionDeclaration.signature().name();
-            var lookupName = switch (functionDeclaration.signature().receiver()) {
-                case FunctionReceiverVariable(String name) -> name + "." + functionName;
-                default -> functionName;
-            };
-            var function = Function.of(moduleName, functionDeclaration, runtimeFile.scope());
-            frame.putVariable(lookupName, new Variable(new FunctionType(functionName), function));
+            registerFunction(functionDeclaration, frame.scope, moduleName);
         });
         processingResult.variableDeclarations().forEach((name, variableDeclaration) -> {
             execute(variableDeclaration, frame);
@@ -427,6 +424,17 @@ CompilationUnitProcessingResult addVariableDeclaration(VariableDeclaration varia
         }
     }
 
+    static Function registerFunction(FunctionDeclaration functionDeclaration, Scope scope, String moduleName) {
+        var functionName = functionDeclaration.signature().name();
+        var lookupName = switch (functionDeclaration.signature().receiver()) {
+            case FunctionReceiverVariable(String name) -> name + "." + functionName;
+            default -> functionName;
+        };
+        var function = Function.of(moduleName, functionDeclaration, scope);
+        scope.putVariable(lookupName, new Variable(new FunctionType(functionName), function));
+        return function;
+    }
+
     static void processDataDefinition(DataDefinition dataDefinition, Scope scope) {
         scope.putVariable(
             dataDefinition.name(),

src/test/resources/runner-tests/dynamic/function-as-retval.test.tst

@@ -0,0 +1,31 @@
+import io
+
+def main() = {
+    var g1 = generator()
+    var g2 = generator()
+    print("g1: " + g1())
+    print("g1: " + g1())
+    print("g2: " + g2())
+    print("g1: " + g1())
+    print("g1: " + g1())
+    print("g2: " + g2())
+    print("g2: " + g2())
+}
+
+def generator() = {
+    var x = 0
+    def next() = {
+        var ret = x
+        x = x + 1
+        ret
+    }
+}
+
+// EXPECTED-OUTPUT
+// g1: 0
+// g1: 1
+// g2: 0
+// g1: 2
+// g1: 3
+// g2: 1
+// g2: 2