Merge branch 'fixiserror'

Author: jakobnissen

docs/src/usage.md

@@ -124,11 +124,11 @@ function harmonic_mean(v::AbstractArray{<:Integer})::Option{Float64}
     sm = 0.0
     for i in v
         invi = safe_div(1, i)
-        is_none(invi) && return none
+        is_error(invi) && return none
         sm += unwrap(invi)
     end
     res = safe_div(length(v), sm)
-    is_none(res) && return none
+    is_error(res) && return none
     return some(unwrap(res))
 end
 ```

src/ErrorTypes.jl

@@ -79,6 +79,18 @@ Alias for `Result{T, Nothing}`
 """
 const Option{T} = Result{T, Nothing}
 
+"""
+	is_error(x::Result)
+
+Check if `x` contains an error value.
+
+# Example
+
+```jldoctest
+julia> is_error(none(Int)), is_error(some(5))
+(true, false)
+```
+"""
 is_error(x::Result) = x.x isa Err
 
 Option(x::Result{T, E}) where {T, E} = is_error(x) ? none(T) : Option{T}(x.x)