Note [Data Constructors]

see also: Note [Data Constructor Naming] in GHC.Core.DataCon

$real_vs_source_data_constructors
There are two forms of data constructor:

     [Source data constructors] The data constructors mentioned in Haskell source code

     [Real data constructors] The data constructors of the representation type, which may not be the same as the source type

For example:

> data T = T !(Int, Int)

The source datacon has type @(Int, Int) -> T@
The real   datacon has type @Int -> Int -> T@

GHC chooses a representation based on the strictness etc.