wiki:Instances

Type-class and type-function instances

This page collects pointers to stuff about type-class, and type function, instances. Especially things to do with overlap.

But not 'deriving'; there's a separate page for that

Tickets

Use Keyword = Instances to ensure that a ticket ends up on these lists.

Open Tickets:

#2986
:info printing instances often isn't wanted
#7102
Type family instance overlap accepted in ghci
#9918
GHC chooses an instance between two overlapping, but cannot resolve a clause within the similar closed type family
#10089
feature: warn about unused data definitions (with typeclass instances)
#13061
Incorrect constraints given single flexible undecidable instance.
#15177
Faulty instance termination check, with PolyKinds and/or TypeInType
#15191
Deriving via DeriveAnyClass not behaving the same as an emply instance declaration
#15632
Undependable Dependencies
#15895
Unable to match instance signatures

Closed Tickets:

#2118
deriving for GRose
#3383
Confluent type family instances confuse the solver
#3877
Require XOverlappingInstances for the most specific instance only
#7777
ghc panic: varargs + sets
#9582
Associated Type Synonyms do not unfold in InstanceSigs
#11674
GHC accepts overly general instance sigs
#12201
Wrong instance selection with overlapping instance in a superclass
#12787
Weird type constraint with undecidable instances
#13320
Unfortunate compiler loop when creating type loop (with UndecidableInstances)
#13950
IncoherentInstances
#14442
InstanceSigs fails
#14846
Renamer hangs (because of -XInstanceSigs?)

Last modified 15 months ago Last modified on May 23, 2018 2:23:58 PM