Cycles console message

Hi guys! I have this console message:

Cycles shader graph connect: can oly connect closure to closure (shadernode:add_closure, shaderoutput:closure, type:6 -> to shader: bsdf, shaderinput roughness, type:0).

What does mean?
How I correct this?

It mean that closures (BSDF’s) nodes are different from other nodes. You can only connect them using Mix / Add nodes.