handle round(x; base=...) (JuliaLang#28199)

Fixes JuliaLang#28160.

base/floatfuncs.jl

@@ -123,19 +123,35 @@ round(::Type{T}, x::AbstractFloat, r::RoundingMode) where {T<:Integer} = trunc(T
 
 # NOTE: this relies on the current keyword dispatch behaviour (#9498).
 function round(x::Real, r::RoundingMode=RoundNearest;
- digits::Union{Nothing,Integer}=nothing, sigdigits::Union{Nothing,Integer}=nothing, base=10)
+  digits::Union{Nothing,Integer}=nothing, sigdigits::Union{Nothing,Integer}=nothing, base::Union{Nothing,Integer}=nothing)
  isfinite(x) || return x
- _round(x,r,digits,sigdigits,base)
+ if digits === nothing
+ if sigdigits === nothing
+ if base === nothing
+ # avoid recursive calls
+ throw(MethodError(round, (x,r)))
+ else
+ round(x,r)
+ # or throw(ArgumentError("`round` cannot use `base` argument without `digits` or `sigdigits` arguments."))
+ end
+ else
+ _round_sigdigits(x, r, sigdigits, base === nothing ? 10 : base)
+ end
+ else
+ if sigdigits === nothing
+ _round_digits(x, r, digits, base === nothing ? 10 : base)
+ else
+ throw(ArgumentError("`round` cannot use both `digits` and `sigdigits` arguments."))
+ end
+ end
 end
+
 trunc(x::Real; kwargs...) = round(x, RoundToZero; kwargs...)
 floor(x::Real; kwargs...) = round(x, RoundDown; kwargs...)
 ceil(x::Real; kwargs...) = round(x, RoundUp; kwargs...)
 
 round(x::Integer, r::RoundingMode) = x
 
-# if we hit this method, it means that no `round(x, r)` method is defined
-_round(x::Real, r::RoundingMode, digits::Nothing, sigdigits::Nothing, base) = throw(MethodError(round, (x,r)))
-
 # round x to multiples of 1/invstep
 function _round_invstep(x, invstep, r::RoundingMode)
  y = round(x * invstep, r) / invstep
@@ -161,7 +177,7 @@ function _round_step(x, step, r::RoundingMode)
  return y
 end
 
-function _round(x, r::RoundingMode, digits::Integer, sigdigits::Nothing, base)
+function _round_digits(x, r::RoundingMode, digits::Integer, base)
  fx = float(x)
  if digits >= 0
  invstep = oftype(fx, base)^digits
@@ -185,14 +201,11 @@ function hidigit(x::AbstractFloat, base)
 end
 hidigit(x::Real, base) = hidigit(float(x), base)
 
-function _round(x, r::RoundingMode, digits::Nothing, sigdigits::Integer, base)
+function _round_sigdigits(x, r::RoundingMode, sigdigits::Integer, base)
  h = hidigit(x, base)
- _round(x, r, sigdigits-h, nothing, base)
+ _round_digits(x, r, sigdigits-h, base)
 end
 
-_round(x, r::RoundingMode, digits::Integer, sigdigits::Integer, base) =
- throw(ArgumentError("`round` cannot use both `digits` and `sigdigits` arguments."))
-
 # C-style round
 function round(x::AbstractFloat, ::RoundingMode{:NearestTiesAway})
  y = trunc(x)

test/rounding.jl

@@ -211,6 +211,7 @@ end
 # custom rounding and significant-digit ops
 @testset "rounding to digits relative to the decimal point" begin
  @test round(pi) ≈ 3.
+ @test round(pi, base=10) ≈ 3.
  @test round(pi, digits=0) ≈ 3.
  @test round(pi, digits=1) ≈ 3.1
  @test round(pi, digits=3, base=2) ≈ 3.125