typethings.notpy

# Simple additional info in type showcase
# Assume normal list
class List<T>:
    ... # List stuff
    
    # Only defining one more type  
    class Index(int):
        # Basically, it's int subtype that on every operation should return int, no overrides
        pass
    
    # This Index class means that for instance list searching may return some additional information, like
    def find<T>(value: T) -> self.length:
        ... # impl
        
    # And now, we get elements by integer as always
    def __getitem__<T>(idx: int) -> T | None:
        ... # impl
    
    # But also use this information to validate access
    def __getitem__<T>(idx: this.Index) -> T:
        ... 
    
    # Now, this works only when addition saveguards are in place or **when List is immutable**