Questions about Tools.current

the unity scripting about Tool.none is:

“Set Tools.current to this to implement your own in-inspector toolbar (like the terrain editor does).”

but when i use

Tools.current = Tool.none;

i get an Error :

“error CS0117: Tools' does not contain a definition for current’”

how to use Tools.current?
Thanks.

This is a naming collision. Look for another class in your project named “Tools”