From 1c2e689dd476e507fca2e468c1de82e88cfc0808 Mon Sep 17 00:00:00 2001
From: Tim Holy <tim.holy@gmail.com>
Date: Sat, 19 Aug 2017 09:14:24 -0500
Subject: [PATCH] Fix eltype conversion for StepRangeLen{BigFloat} (fixes
 #23300)

---
 base/twiceprecision.jl | 3 ++-
 test/ranges.jl         | 7 +++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/base/twiceprecision.jl b/base/twiceprecision.jl
index 6607c12e1d1ce..8a849dcb9af68 100644
--- a/base/twiceprecision.jl
+++ b/base/twiceprecision.jl
@@ -422,7 +422,7 @@ function rat(x)
     y = x
     a = d = 1
     b = c = 0
-    m = maxintfloat(narrow(typeof(x)))
+    m = maxintfloat(narrow(typeof(x)), Int)
     while abs(y) <= m
         f = trunc(Int,y)
         y -= f
@@ -435,6 +435,7 @@ function rat(x)
     return a, b
 end
 
+narrow(::Type{T}) where {T<:AbstractFloat} = Float64
 narrow(::Type{Float64}) = Float32
 narrow(::Type{Float32}) = Float16
 narrow(::Type{Float16}) = Float16
diff --git a/test/ranges.jl b/test/ranges.jl
index 6ec04c6f89038..1b04b345d8eab 100644
--- a/test/ranges.jl
+++ b/test/ranges.jl
@@ -957,3 +957,10 @@ end
         @test logspace(a, b, n, base=base) == base.^linspace(a, b, n)
     end
 end
+
+# Issue #23300
+x = -5:big(1.0):5
+@test map(Float64, x) === -5.0:1.0:5.0
+@test map(Float32, x) === -5.0f0:1.0f0:5.0f0
+@test map(Float16, x) === Float16(-5.0):Float16(1.0):Float16(5.0)
+@test map(BigFloat, x) === x