removed factorial (#297)

Co-authored-by: PaulXiCao <>

Author: PaulXiCao

Diff for: src/gamma.jl

@@ -818,13 +818,6 @@ logabsbeta(a::Number, b::Number) = loggamma(a) + loggamma(b) - loggamma(a + b),
 
 ## from base/numbers.jl
 
-# this trickery is needed while the deprecated method in Base exists
-@static if !hasmethod(Base.factorial, Tuple{Number})
-    import Base: factorial
-end
-factorial(x) = Base.factorial(x) # to make SpecialFunctions.factorial work unconditionally
-factorial(x::Number) = gamma(x + 1) # fallback for x not Integer
-
 """
     logabsbinomial(n, k)
 

Diff for: test/gamma.jl

@@ -68,10 +68,6 @@
         @test loggamma(1.4+3.7im) ≈ -3.7094025330996841898 + 2.4568090502768651184im
         @test loggamma(1.4+3.7im) ≈ log(gamma(1.4+3.7im))
         @test loggamma(-4.2+0im) ≈ logabsgamma(-4.2)[1] - 5pi*im
-        @test SpecialFunctions.factorial(3.0) == gamma(4.0) == factorial(3)
-        for x in (3.2, 2+1im, 3//2, 3.2+0.1im)
-            @test SpecialFunctions.factorial(x) == gamma(1+x)
-        end
         @test logfactorial(0) == logfactorial(1) == 0
         @test logfactorial(2) == loggamma(3)
         # Ensure that the domain of logfactorial matches that of factorial (issue #21318)