Add infix flag for class and data declarations
At the moment, data and type declarations using infix formatting produce the same AST as those using prefix.
type a ++ b = c
type (++) a b = c
cannot be distinguished in the parsed source, without looking at the
OccName details of the constructor being defined.
Having access to the
OccName requires an additional constraint which explodes out over the entire AST because of its recursive definitions.
In keeping with moving the parsed source to more directly reflect the source code as parsed, add a specific flag to the declaration to indicate the fixity, as used in a
Match now too.
Note: this flag is to capture the fixity used for the lexical definition of the type, primarily for use by