id summary reporter owner description type status priority milestone component version resolution keywords cc
84 Fix postgeneralisation check. benl "Testcase is Error/Closure/LateExport
{{{
main ()
= do ref = Ref id
f = \x -> ref.x
ref#x #= succ
f () ""oh noes""
}}}
Adding the type scheme for f back to the graph overwrites the original fn
constructor there, so we can't sensibly extract the type and re-generalise.
Need to store complete type schemes in a separate table, or in the graph in
a way that doesn't prevent us from extracting and generalising types again.
The error in above program would have been detected before we started
trimming type constructors out of closures. After inference, the type of f
would have been
{{{
f :: forall a. () -(e1 c1)> a -> a
:- e1 = Read r1
, c1 = ref : forall b. Ref r1 (b -> b)
, Mutable r1
}}}
As r1 is mutable, the fact that b is quantified in the constraint for c1
tells us that the scheme is bad. However, trimming constructors like Ref
out of types gives:
{{{
f :: forall a. () -(e1 c1)> a -> a
:- e1 = Read r1
, c1 = ref : r1
}}}
This is valid if r1 is really constant. But if it's not then we've lost the
forall b. (b -> b) part, can't do the simpler check, and have to do a
complete re-extract and re-generalise instead.
" defect closed blocker 0.1.3 Source Type Inferencer 0.1.2 fixed