failed to compile definition

Stream: lean4

[gengenshin]

I use Complex.cpow to defined an function
Complex.cpow (P1.x^2-P1.y^2 : ℂ ) ( half_one : ℂ )

but lean return me an error

failed to compile definition, consider marking it as 'noncomputable' because it depends on 'Complex.instRatCastComplex', and it does not have executable code

How should I do?

[Jireh Loreaux]

noncomputable def ....

[gengenshin]

Jireh Loreaux said:

noncomputable def ....

thanks so much!