Move StateKind trait to BifurcationsBase

src/Bifurcations.jl

@@ -15,6 +15,9 @@ include("base/base.jl")
 # TimeKind trait:
 using .BifurcationsBase: timekind, Continuous, Discrete
 import .BifurcationsBase: TimeKind
+# StateKind trait:
+using .BifurcationsBase: statekind, MutableState, ImmutableState
+import .BifurcationsBase: StateKind
 
 include("codim1/codim1.jl")
 

src/base/base.jl

@@ -1,3 +1,4 @@
 module BifurcationsBase
 include("timekind.jl")
+include("statekind.jl")
 end  # module

src/base/statekind.jl

@@ -0,0 +1,6 @@
+abstract type StateKind end
+struct MutableState <: StateKind end
+struct ImmutableState <: StateKind end
+
+statekind(::T) where T = StateKind(T)
+# TODO: Use StateKind everywhere instead of boolean iip type parameter.

src/diffeq.jl

@@ -4,15 +4,6 @@ using Setfield: Lens, set, get
 const DEP{iip} = AbstractODEProblem{uType, tType, iip} where {uType, tType}
 
 
-abstract type StateKind end
-struct MutableState <: StateKind end
-struct ImmutableState <: StateKind end
-
-statekind(::T) where T = StateKind(T)
-# TODO: Move StateKind to continuations/base.jl and use it everywhere.
-# It's only used in here at the moment.
-
-
 TimeKind(::Type{<: DiscreteProblem}) = Discrete()
 TimeKind(::Type{<: AbstractODEProblem}) = Continuous()
 StateKind(::Type{<: DEP{true}}) = MutableState()