Symbol("a,b") in method signatures should be displayed as var"a,b"

[jishnub]

The issue was pointed out in this discourse discussion. The display appears to be incorrect here:

julia> for TA in [Symbol("a,b")]
       @eval f($TA) = a + b
       end

julia> methods(f)
# 1 method for generic function "f":
[1] f(a,b) in Main at REPL[1]:2

There is no method f(a,b) that is generated, and the method arguments should probably be displayed as var"a,b". For example:

julia> f(1,2)
ERROR: MethodError: no method matching f(::Int64, ::Int64)

[simeonschaub]

It seems like we are using print and string in show(::Method), whereas we probably should be using Base.show_unquoted instead.