[Haskell-cafe] Is a type synonym declaration really a synonym ?

alpheccar misc at alpheccar.org
Sat Dec 22 16:22:46 EST 2007

Can someone confirm me that:

type TA = A :+: B
type TB = C :+: D
type T = TA :+: TB

is not equivalent to

type T = A :+: B :+: C :+: D

where I have defined

infixr 6 :+:
data (f :+: g)
data A
data B
data C
data D

I have a computation at type level which is working with the later  
definition of T but not with the former (ghc 6.8.1)


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