努力填坑 Julia Cheat Sheet 时发现的疑似 bug
可复现版本：v0.64/v0.7/v1.0/v1.02
# 下面那个符号是 Set Difference: \setminus
# 理论上应该和 setdiff() 等价
?∖
help?> ∖
ERROR: LoadError: Invalid @var syntax `invalid character "∖"`.
Stacktrace:
[1] error(::String) at .\error.jl:33
[2] splitexpr(::Any) at .\docs\bindings.jl:28
[3] bindingexpr(::Any) at .\docs\bindings.jl:17
[4] lookup_doc(::Expr) at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\REPL\src\docview.jl:137
[5] docm(::LineNumberNode, ::Module, ::Any) at .\docs\Docs.jl:501
[6] @doc(::LineNumberNode, ::Module, ::Expr, ::Vararg{Expr,N} where N) at .\boot.jl:451
in expression starting at C:\cygwin\home\Administrator\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.0\REPL\src\docview.jl:301
julia> Char('∖')
'∖': Unicode U+2216 (category Sm: Symbol, math)
找不到符号定义很正常，不显示 can be typed by 也行，报错就有问题了。