Fix JuliaLang#8257

This version of `rand(r::Range)` and `rand!(r::Range,a::AbstractArray)`
uses getindex instead of trying to calculate the exact value of the
range. This is good because we avoid duplicating the getindex logic in
`FloatRange`

Also added tests, and fixed a small issue in `in(v, r::Range)` where two
calls to step() is not needed

base/random.jl

@@ -207,7 +207,7 @@ function rand{T<:Integer, U<:Unsigned}(g::RandIntGen{T,U})
 end
 
 rand{T<:Union(Signed,Unsigned,Bool,Char)}(r::UnitRange{T}) = rand(RandIntGen(r))
-rand{T}(r::Range{T}) = convert(T, first(r) + rand(0:(length(r)-1)) * step(r))
+rand{T}(r::Range{T}) = r[rand(1:(length(r)))]
 
 function rand!(g::RandIntGen, A::AbstractArray)
     for i = 1 : length(A)
@@ -218,18 +218,10 @@ end
 
 rand!{T<:Union(Signed,Unsigned,Bool,Char)}(r::UnitRange{T}, A::AbstractArray) = rand!(RandIntGen(r), A)
 
-function rand!{T}(r::Range{T}, A::AbstractArray)
-    g = RandIntGen(0:(length(r)-1))
-    f = first(r)
-    s = step(r)
-    if s == 1
-        for i = 1 : length(A)
-            @inbounds A[i] = convert(T, f + rand(g))
-        end
-    else
-        for i = 1 : length(A)
-            @inbounds A[i] = convert(T, f + rand(g) * s)
-        end
+function rand!(r::Range, A::AbstractArray)
+    g = RandIntGen(1:(length(r)))
+    for i = 1 : length(A)
+        @inbounds A[i] = r[rand(g)]
     end
     return A
 end

base/range.jl

@@ -567,7 +567,7 @@ function map!(f::Callable, dest, r::Range)
 end
 
 function in(x, r::Range)
-    n = step(r) == zero(step(r)) ? 1 : iround((x-first(r))/step(r))+1
+    n = step(r) == 0 ? 1 : iround((x-first(r))/step(r))+1
     n >= 1 && n <= length(r) && r[n] == x
 end
 

test/random.jl

@@ -165,3 +165,9 @@ a = uuid4()
 @test_throws ArgumentError UUID("550e8400e29b-41d4-a716-446655440000")
 @test_throws ArgumentError UUID("550e8400e29b-41d4-a716-44665544000098")
 @test_throws ArgumentError UUID("z50e8400-e29b-41d4-a716-446655440000")
+
+#issue 8257
+i8257 = 1:1/3:100
+for i = 1:100
+    @test rand(i8257) in i8257
+end