Merge pull request #1739 from SciML/myb/check

Check states and parameters are actually states and parameters

Author: YingboMa

src/utils.jl

@@ -126,6 +126,8 @@ function check_parameters(ps, iv)
     for p in ps
         isequal(iv, p) &&
             throw(ArgumentError("Independent variable $iv not allowed in parameters."))
+        isparameter(p) ||
+            throw(ArgumentError("$p is not a parameter."))
     end
 end
 
@@ -150,6 +152,8 @@ function check_variables(dvs, iv)
             throw(ArgumentError("Independent variable $iv not allowed in dependent variables."))
         (is_delay_var(iv, dv) || occursin(iv, dv)) ||
             throw(ArgumentError("Variable $dv is not a function of independent variable $iv."))
+        isparameter(dv) &&
+            throw(ArgumentError("$dv is not a state. It is a parameter."))
     end
 end
 

test/odesystem.jl

@@ -867,3 +867,13 @@ let
     prob = ODAEProblem(sys4s, [x => 1.0, D(x) => 1.0], (0, 1.0))
     @test string.(prob.f.syms) == ["x(t)", "xˍt(t)"]
 end
+
+let
+    @variables t
+    @parameters P(t) Q(t)
+    ∂t = Differential(t)
+
+    eqs = [∂t(Q) ~ 0.2P
+           ∂t(P) ~ -80.0sin(Q)]
+    @test_throws ArgumentError @named sys = ODESystem(eqs)
+end