explicit generic call sites¶

PEP 695 lets you declare a generic function def f[T](x: T) -> T, but the call site can only ever specialize the type variable through inference from the arguments. basedpython adds an explicit specialization syntax for function calls:

def identity[T](x: T) -> T:
    return x

identity[int](1)
pair[int, str](1, "a")

transpiles to:

def identity[T](x: T) -> T:
    return x

identity(1)
pair(1, "a")

the type arguments are stripped — they exist purely for the type checker. ty sees the explicit specialization through the AST and uses it to constrain inference; the runtime call has no [...] syntax (which would be a parse error in standard Python)

scope¶

the call-site [T] is stripped only when the subscript target is a function defined in the local typing context. constructor calls — Foo[int](...) — are not stripped, because Python supports them natively as __class_getitem__ then __call__:

class Box[T]:
    ...

Box[int](42)   # unchanged — runtime parametrized constructor

limitations¶

only locally-defined function targets are recognized. for cross-module generic calls, prefer the inference path (identity(x))