handle method ambiguity ss/tf

Author: baggepinnen

lib/ControlSystemsBase/src/connections.jl

@@ -215,6 +215,10 @@ function /(sys1::Union{StateSpace,AbstractStateSpace}, sys2::LTISystem)
     sys1new, sys2new = promote(sys1, 1/sys2)
     return sys1new*sys2new
 end
+function /(sys1::Union{StateSpace,AbstractStateSpace}, sys2::TransferFunction) # This method is handling ambiguity between method above and one with explicit TF as second argument, hit by ss(1)/tf(1)
+    sys1new, sys2new = promote(sys1, 1/sys2)
+    return sys1new*sys2new
+end
 
 @static if VERSION >= v"1.8.0-beta1"
     blockdiag(anything...) = cat(anything..., dims=Val((1,2)))

lib/ControlSystemsBase/test/test_connections.jl

@@ -438,4 +438,6 @@ Pr = input_resolvent(P)
 @test Pr.C == I
 @test iszero(Pr.D)
 
+@test ss(1) / tf(1) == ss(1) # Test no method ambiguity
+
 end