possibly fix SymbolicIndexingInterface.observed(fn::AbstractSciMLFunc…

…tion, sym)

This feels deeply wrong to me.

src/scimlfunctions.jl

@@ -2324,7 +2324,7 @@ function ODEFunction{iip, specialize}(f;
             typeof(_colorvec),
             typeof(sys)}(_f, mass_matrix, analytic, tgrad, jac,
             jvp, vjp, jac_prototype, sparsity, Wfact,
-            Wfact_t, W_prototype, paramjac, 
+            Wfact_t, W_prototype, paramjac,
             observed, _colorvec, sys)
     else
         ODEFunction{iip, specialize,
@@ -2336,7 +2336,7 @@ function ODEFunction{iip, specialize}(f;
             typeof(_colorvec),
             typeof(sys)}(_f, mass_matrix, analytic, tgrad, jac,
             jvp, vjp, jac_prototype, sparsity, Wfact,
-            Wfact_t, W_prototype, paramjac, 
+            Wfact_t, W_prototype, paramjac,
             observed, _colorvec, sys)
     end
 end
@@ -2848,7 +2848,7 @@ function unwrapped_f(f::SDEFunction, newf = unwrapped_f(f.f),
             typeof(f.mass_matrix), typeof(f.analytic), typeof(f.tgrad),
             typeof(f.jac), typeof(f.jvp), typeof(f.vjp), typeof(f.jac_prototype),
             typeof(f.sparsity), typeof(f.Wfact), typeof(f.Wfact_t),
-            typeof(f.paramjac), typeof(f.ggprime), 
+            typeof(f.paramjac), typeof(f.ggprime),
             typeof(f.observed), typeof(f.colorvec), typeof(f.sys)}(newf, newg,
             f.mass_matrix,
             f.analytic,
@@ -2943,7 +2943,7 @@ function SplitSDEFunction{iip, specialize}(f1, f2, g;
             typeof(colorvec),
             typeof(sys)}(f1, f2, g, mass_matrix, _func_cache, analytic,
             tgrad, jac, jvp, vjp, jac_prototype, sparsity,
-            Wfact, Wfact_t, paramjac, 
+            Wfact, Wfact_t, paramjac,
             observed, colorvec, sys)
     end
 end
@@ -3120,7 +3120,7 @@ function RODEFunction{iip, specialize}(f;
             typeof(analytic), typeof(tgrad),
             typeof(jac), typeof(jvp), typeof(vjp), typeof(jac_prototype),
             typeof(sparsity), typeof(Wfact), typeof(Wfact_t),
-            typeof(paramjac), 
+            typeof(paramjac),
             typeof(observed), typeof(_colorvec),
             typeof(sys)}(_f, mass_matrix, analytic, tgrad,
             jac, jvp, vjp, jac_prototype, sparsity,
@@ -3473,7 +3473,7 @@ function SDDEFunction{iip, specialize}(f, g;
             jvp, vjp, jac_prototype,
             sparsity, Wfact,
             Wfact_t,
-            paramjac, ggprime, 
+            paramjac, ggprime,
             observed, _colorvec, sys)
     end
 end
@@ -3566,7 +3566,7 @@ function NonlinearFunction{iip, specialize}(f;
             typeof(_f), typeof(mass_matrix), typeof(analytic), typeof(tgrad),
             typeof(jac), typeof(jvp), typeof(vjp), typeof(jac_prototype),
             typeof(sparsity), typeof(Wfact),
-            typeof(Wfact_t), typeof(paramjac), 
+            typeof(Wfact_t), typeof(paramjac),
             typeof(observed),
             typeof(_colorvec), typeof(sys), typeof(resid_prototype)}(_f, mass_matrix,
             analytic, tgrad, jac,
@@ -3935,7 +3935,7 @@ has_Wfact(f::AbstractSciMLFunction) = __has_Wfact(f) && f.Wfact !== nothing
 has_Wfact_t(f::AbstractSciMLFunction) = __has_Wfact_t(f) && f.Wfact_t !== nothing
 has_paramjac(f::AbstractSciMLFunction) = __has_paramjac(f) && f.paramjac !== nothing
 has_sys(f::AbstractSciMLFunction) = __has_sys(f) && f.sys !== nothing
-function has_syms(f::AbstractSciMLFunction) 
+function has_syms(f::AbstractSciMLFunction)
   if __has_syms(f)
     f.syms !== nothing
   else
@@ -4051,9 +4051,21 @@ SymbolicIndexingInterface.is_observed(fn::AbstractSciMLFunction, sym) = has_obse
 function SymbolicIndexingInterface.observed(fn::AbstractSciMLFunction, sym)
   if has_observed(fn)
     if is_time_dependent(fn)
-      return (u, p, t) -> fn.observed(sym, u, p, t)
+      return if hasmethod(fn.observed, Tuple{typeof(sym)})
+        fn.observed(sym)
+      else
+        let obs = fn.observed, sym = sym
+          (u, p, t) -> obs(sym, u, p, t)
+        end
+      end
     else
-      return (u, p) -> fn.observed(sym, u, p)
+      return if hasmethod(fn.observed, Tuple{typeof(sym)})
+        fn.observed(sym)
+      else
+        let obs = fn.observed, sym = sym
+          (u, p) -> obs(sym, u, p)
+        end
+      end
     end
   end
   error("SciMLFunction does not have observed")