TP0219

Error: generic instantiation too deep (polymorphic recursion)

Messages

• instantiating '<f>' needs '<f>[<T>]', which is too deep, at the call that starts the chain

Example

From the golden case tests/cases/m8/tp0219_polymorphic.tpn:

tp0219_polymorphic.tpn

def grow[T](x: T, n: int) -> int:
    if n == 0:
        return 0
    return grow([x], n - 1)

print(grow(1, 3))

The compiler reports:

tp0219_polymorphic.tpn:6:1: error TP0219: instantiating 'grow' needs 'grow[list[list[list[...]]]]', which is too deep

The specification lists every code.