Summary

missing-trailing-comma (COM812) and prohibited-trailing-comma (COM819) have false negatives for type parameter lists, wherein trailing commas make no difference. The comma rules for type parameter lists should be the same as for normal parameter lists.

COM812 should fix this:

type X[
    T
] = T
def f[
    T
](): pass
class C[
    T
]: pass

to this:

type X[
    T,
] = T
def f[
    T,
](): pass
class C[
    T,
]: pass

COM819 should fix this:

type X[T,] = T
def f[T,](): pass
class C[T,]: pass

to this:

type X[T] = T
def f[T](): pass
class C[T]: pass

Version

ruff 0.12.0 (87f0feb 2025-06-17)