Respect parameter types

Fix #2296

src/parameters.jl

@@ -103,6 +103,18 @@ function split_parameters_by_type(ps)
         if length(split_ps) == 1  #Tuple not needed, only 1 type
             return split_ps[1], split_idxs
         else
+            T = Float16
+            idx = 0
+            for (i, p) in enumerate(split_ps)
+                E = eltype(p)
+                if E == promote_type(T, E)
+                    T = E
+                    idx = i
+                end
+            end
+            if idx != 0 && idx != 1
+                split_ps[idx], split_ps[1] = split_ps[1], split_ps[idx]
+            end
             return (split_ps...,), split_idxs
         end
     end

src/systems/diffeqs/abstractodesystem.jl

@@ -769,7 +769,7 @@ function get_u0_p(sys,
     u0map,
     parammap = nothing;
     use_union = true,
-    tofloat = true,
+    tofloat = false,
     symbolic_u0 = false)
     dvs = states(sys)
     ps = parameters(sys)
@@ -799,7 +799,7 @@ function process_DEProblem(constructor, sys::AbstractODESystem, u0map, parammap;
     linenumbers = true, parallel = SerialForm(),
     eval_expression = true,
     use_union = true,
-    tofloat = true,
+    tofloat = false,
     symbolic_u0 = false,
     u0_constructor = identity,
     kwargs...)

test/split_parameters.jl

@@ -102,7 +102,7 @@ sys = structural_simplify(model)
 tspan = (0.0, t_end)
 prob = ODEProblem(sys, [], tspan, [])
 
-@test prob.p isa Vector{Float64}
+@test prob.p isa Tuple{Vector{Float64}, Vector{Int}}
 sol = solve(prob, ImplicitEuler());
 @test sol.retcode == ReturnCode.Success
 
@@ -184,3 +184,9 @@ connections = [[state_feedback.input.u[i] ~ model_outputs[i] for i in 1:4]
     connect(add.output, :u, model.torque.tau)]
 @named closed_loop = ODESystem(connections, t, systems = [model, state_feedback, add, d])
 S = get_sensitivity(closed_loop, :u)
+
+@variables t
+@parameters a b c
+@named s = ODESystem(Equation[], t, [], [a, b, c])
+prob = ODEProblem(s, nothing, (0.0, 1.0), Pair[a => 1, b => 1, c => 1.0])
+@test prob.p == ([1.0], [1, 1])