GDScript: Allow void functions to return calls to other void functions

modules/gdscript/tests/scripts/analyzer/features/allow_void_function_to_return_void.gd

@@ -0,0 +1,20 @@
+func test():
+	return_call()
+	return_nothing()
+	return_side_effect()
+	var r = return_side_effect.call() # Untyped call to check return value.
+	prints(r, typeof(r) == TYPE_NIL)
+	print("end")
+
+func side_effect(v):
+	print("effect")
+	return v
+
+func return_call() -> void:
+	return print("hello")
+
+func return_nothing() -> void:
+	return
+
+func return_side_effect() -> void:
+	return side_effect("x")

modules/gdscript/tests/scripts/analyzer/features/allow_void_function_to_return_void.out

@@ -0,0 +1,10 @@
+GDTEST_OK
+>> WARNING
+>> Line: 20
+>> UNSAFE_VOID_RETURN
+>> The method 'return_side_effect()' returns 'void' but it's trying to return a call to 'side_effect()' that can't be ensured to also be 'void'.
+hello
+effect
+effect
+<null> true
+end