[project @ 2003-01-24 14:04:41 by simonmar]
- Generalise seq to allow an unlifted type in its second argument. This
works because seq is *always* inlined and replaced by a case.
- Remove getTag, a wired-in Id with an unfolding, with a definition
in GHC.Base:
getTag x = x `seq` dataToTag# x
this is why we required the above generalisation to seq (dataToTag#
returns an Int#). See the comments in GHC.Base for more details.
- As a side-effect, this fixes a bug in the interpreter, where the
compiler optimised away the evaluation of the argument to dataToTag#,
but the interpreter ended up passing it an unevaluated thunk (nullary
constructors aren't always evaluated in GHCi, but the simplifier
assumes they are). Now, in the interpreter, getTag won't be inlined
so the compiler can't optimise away the evaluation, and we're saved.
The real bug here is either (a) dataToTag# requires an evaluated
argument or (b) the interpreter doesn't supply it with one, take your
pick.