improve concrete-foldability of intfuncs

Author: aviatesk

base/intfuncs.jl

@@ -183,7 +183,7 @@ julia> gcdx(240, 46)
     their `typemax`, and the identity then holds only via the unsigned
     integers' modulo arithmetic.
 """
-function gcdx(a::Integer, b::Integer)
+Base.@assume_effects :terminates_locally function gcdx(a::Integer, b::Integer)
     T = promote_type(typeof(a), typeof(b))
     # a0, b0 = a, b
     s0, s1 = oneunit(T), zero(T)
@@ -233,7 +233,7 @@ function invmod(n::Integer, m::Integer)
         n == typeof(n)(-1) && m == typemin(typeof(n)) && return T(-1)
     end
     g, x, y = gcdx(n, m)
-    g != 1 && throw(DomainError((n, m), "Greatest common divisor is $g."))
+    g != 1 && throw(DomainError((n, m), LazyString("Greatest common divisor is ", g, ".")))
     # Note that m might be negative here.
     if n isa Unsigned && hastypemax(typeof(n)) && x > typemax(n)>>1
         # x might have wrapped if it would have been negative
@@ -1057,7 +1057,7 @@ julia> binomial(-5, 3)
 # External links
 * [Binomial coefficient](https://en.wikipedia.org/wiki/Binomial_coefficient) on Wikipedia.
 """
-function binomial(n::T, k::T) where T<:Integer
+Base.@assume_effects :terminates_locally function binomial(n::T, k::T) where T<:Integer
     n0, k0 = n, k
     k < 0 && return zero(T)
     sgn = one(T)
@@ -1079,7 +1079,7 @@ function binomial(n::T, k::T) where T<:Integer
     while rr <= k
         xt = div(widemul(x, nn), rr)
         x = xt % T
-        x == xt || throw(OverflowError("binomial($n0, $k0) overflows"))
+        x == xt || throw(OverflowError(LazyString("binomial(", n0, ", ", k0, " overflows")))
         rr += one(T)
         nn += one(T)
     end

test/intfuncs.jl

@@ -519,3 +519,9 @@ end
         @test binomial(x...) == (x != (false,true))
     end
 end
+
+# concrete-foldability
+@test Base.infer_effects(gcd, (Int,Int)) |> Core.Compiler.is_foldable
+@test Base.infer_effects(gcdx, (Int,Int)) |> Core.Compiler.is_foldable
+@test Base.infer_effects(invmod, (Int,Int)) |> Core.Compiler.is_foldable
+@test Base.infer_effects(binomial, (Int,Int)) |> Core.Compiler.is_foldable