__precompile__()
module PrecompileTester
module M
    using SpecialFunctions
    const A = digamma(1) # precompile hint
    const B = digamma(1.0) # precompile hint
end
end # module

...

WARNING: Method definition digamma(Union{Float16, Main.Base.Complex{Float16}, Float32, Main.Base.Complex{Float32}}) in module SpecialFunctions at /Users/user/.julia/v0.6/SpecialFunctions/src/gamma.jl:497 overwritten in module SpecialFunctions at /Users/user/.julia/v0.6/SpecialFunctions/src/gamma.jl:497.
WARNING: Method definition digamma(Number) in module SpecialFunctions at /Users/user/.julia/v0.6/SpecialFunctions/src/gamma.jl:501 overwritten in module SpecialFunctions at /Users/user/.julia/v0.6/SpecialFunctions/src/gamma.jl:501.