digits!: check for typemax only when applicable (JuliaLang#16844)

Author: rfourquet

base/gmp.jl

@@ -9,7 +9,7 @@ import Base: *, +, -, /, <, <<, >>, >>>, <=, ==, >, >=, ^, (~), (&), (|), xor,
              ndigits, promote_rule, rem, show, isqrt, string, powermod,
              sum, trailing_zeros, trailing_ones, count_ones, base, tryparse_internal,
              bin, oct, dec, hex, isequal, invmod, prevpow2, nextpow2, ndigits0zpb,
-             widen, signed, unsafe_trunc, trunc, iszero, big, flipsign, signbit
+             widen, signed, unsafe_trunc, trunc, iszero, big, flipsign, signbit, hastypemax
 
 if Clong == Int32
     const ClongMax = Union{Int8, Int16, Int32}
@@ -228,6 +228,8 @@ signed(x::BigInt) = x
 
 convert(::Type{BigInt}, x::BigInt) = x
 
+hastypemax(::Type{BigInt}) = false
+
 function tryparse_internal(::Type{BigInt}, s::AbstractString, startpos::Int, endpos::Int, base_::Integer, raise::Bool)
     _n = Nullable{BigInt}()
 

base/int.jl

@@ -29,6 +29,8 @@ const BitIntegerSmall  = Union{BitIntegerSmall_types...}
 const BitSigned64T     = Union{Type{Int8}, Type{Int16}, Type{Int32}, Type{Int64}}
 const BitUnsigned64T   = Union{Type{UInt8}, Type{UInt16}, Type{UInt32}, Type{UInt64}}
 
+const BitIntegerType = Union{map(T->Type{T}, BitInteger_types)...}
+
 throw_inexacterror(f::Symbol, ::Type{T}, val) where T =
     (@_noinline_meta; throw(InexactError(f, T, val)))
 

base/intfuncs.jl

@@ -743,6 +743,14 @@ function digits(T::Type{<:Integer}, n::Integer, base::Integer=10, pad::Integer=1
     digits!(zeros(T, ndigits(n, base, pad)), n, base)
 end
 
+"""
+    hastypemax(T::Type) -> Bool
+
+Return `true` if and only if `typemax(T)` is defined.
+"""
+hastypemax(::Base.BitIntegerType) = true
+hastypemax(::Type{T}) where {T} = applicable(typemax, T)
+
 """
     digits!(array, n::Integer, base::Integer=10)
 
@@ -772,7 +780,8 @@ julia> digits!([2,2,2,2,2,2], 10, 2)
 function digits!(a::AbstractVector{T}, n::Integer, base::Integer=10) where T<:Integer
     base < 0 && isa(n, Unsigned) && return digits!(a, convert(Signed, n), base)
     2 <= abs(base) || throw(ArgumentError("base must be ≥ 2 or ≤ -2, got $base"))
-    abs(base) - 1 <= typemax(T) || throw(ArgumentError("type $T too small for base $base"))
+    hastypemax(T) && abs(base) - 1 > typemax(T) &&
+        throw(ArgumentError("type $T too small for base $base"))
     for i in eachindex(a)
         if base > 0
             a[i] = rem(n, base)

base/random.jl

@@ -28,8 +28,7 @@ mutable struct Close1Open2 <: FloatInterval end
 
 ## RandomDevice
 
-const BitIntegerType = Union{map(T->Type{T}, Base.BitInteger_types)...}
-const BoolBitIntegerType = Union{Type{Bool},BitIntegerType}
+const BoolBitIntegerType = Union{Type{Bool},Base.BitIntegerType}
 const BoolBitIntegerArray = Union{Array{Bool},Base.BitIntegerArray}
 
 if Sys.iswindows()

test/bigint.jl

@@ -289,6 +289,9 @@ end
 
 @test Base.ndigits0zpb(big(0), big(rand(2:100))) == 0
 
+# digits with BigInt bases (#16844)
+@test digits(big(2)^256, big(2)^128) == [0, 0, 1]
+
 # conversion from float
 @test BigInt(2.0) == BigInt(2.0f0) == BigInt(big(2.0)) == 2
 @test_throws InexactError convert(BigInt, 2.1)