linear tuple type operators

[jorenham]

an intuitive DRY way of writing repetitive tuple type argument patterns, e.g.

tuple[S, S, T, T, T, T, S, T, S, T, S, T]

could be written as

type Spam[S, T] = 2 * tuple[S] + 4 * tuple[T] + 3 * tuple[S, T]

or

type Spam[S, T] = 2 * (S,) + 4 * (T,) + 3 * (S, T)

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this only involves the + and * binary infix operators