[project @ 2005-05-20 11:32:03 by simonpj]
Liberalise the defaulting rules for GHCi
Merge to STABLE?
The H98 defaulting rules are these. Group constraints of the form (C v),
for some particular type variable v. Then default v if
a) v appears only in this group (no implicit params or D [v])
b) at least one of the C's is numeric
c) all the C's are standard
GHCi changed rules (b) to
(b') at least one of the C's is numeric, or Eq,Ord,Show
This commit further liberalises GHCi to change (c):
(c') any of the C's are standard
Otherwise the existence of a non-standard class (e.g. Random) is enough
to kill defaulting altogether.