Use Base.remove_linenums! to obtain cleaner macro output

[devmotion]

This PR replaces strip_linenos (the function, not the macro) with Base.remove_linenums!. This leads to cleaner output of the macros, e.g., on master one gets

julia> @macroexpand @scalar_rule identity(x) 1.0
quote                   
    #= /home/david/.julia/packages/ChainRulesCore/JWrYo/src/rule_definition_tools.jl:94 =#
    if !(identity isa ChainRulesCore.Type) && ChainRulesCore.fieldcount(ChainRulesCore.typeof(identity)) > 0
        #= /home/david/.julia/packages/ChainRulesCore/JWrYo/src/rule_definition_tools.jl:95 =#
        ChainRulesCore.throw(ChainRulesCore.ArgumentError("@scalar_rule cannot be used on closures/functors (such as $(identity))"))
    end
    #= /home/david/.julia/packages/ChainRulesCore/JWrYo/src/rule_definition_tools.jl:100 =#
    begin
        nothing
        function (ChainRulesCore.ChainRulesCore).frule((ChainRulesCore._, var"##Δ1#253"), ::ChainRulesCore.typeof(identity), x::Number)
            nothing
            nothing
            #= REPL[4]:1 =#
            nothing
            Ω = identity(x)
            nothing
            nothing
            nothing
            return (Ω, 1.0var"##Δ1#253")
        end
    end
    #= /home/david/.julia/packages/ChainRulesCore/JWrYo/src/rule_definition_tools.jl:101 =#
    begin
        nothing
        function (ChainRulesCore.ChainRulesCore).rrule(::ChainRulesCore.typeof(identity), x::Number)
            nothing
            nothing
            #= REPL[4]:1 =#
            nothing
            Ω = identity(x)
            nothing
            nothing
            nothing
            return (Ω, begin
                        nothing
                        function identity_pullback(var"##Δ1#254")
                            $(Expr(:meta, :inline))
                            nothing
                            nothing
                            #= REPL[4]:1 =#
                            nothing
                            return (ChainRulesCore.NO_FIELDS, ChainRulesCore.conj(1.0) * var"##Δ1#254")
                        end
                    end)
        end
    end
end

whereas this PR yields

julia> @macroexpand @scalar_rule identity(x) 1.0
quote
    #= /home/david/.julia/dev/ChainRulesCore/src/rule_definition_tools.jl:91 =#
    if !(identity isa ChainRulesCore.Type) && ChainRulesCore.fieldcount(ChainRulesCore.typeof(identity)) > 0
        #= /home/david/.julia/dev/ChainRulesCore/src/rule_definition_tools.jl:92 =#
        ChainRulesCore.throw(ChainRulesCore.ArgumentError("@scalar_rule cannot be used on closures/functors (such as $(identity))"))
    end
    #= /home/david/.julia/dev/ChainRulesCore/src/rule_definition_tools.jl:97 =#
    begin
        function (ChainRulesCore.ChainRulesCore).frule((ChainRulesCore._, var"##Δ1#259"), ::ChainRulesCore.typeof(identity), x::Number)
            #= REPL[14]:1 =#
            Ω = identity(x)
            nothing
            return (Ω, 1.0var"##Δ1#259")
        end
    end
    #= /home/david/.julia/dev/ChainRulesCore/src/rule_definition_tools.jl:98 =#
    begin
        function (ChainRulesCore.ChainRulesCore).rrule(::ChainRulesCore.typeof(identity), x::Number)
            #= REPL[14]:1 =#
            Ω = identity(x)
            nothing
            return (Ω, begin
                        function identity_pullback(var"##Δ1#260")
                            $(Expr(:meta, :inline))
                            #= REPL[14]:1 =#
                            return (ChainRulesCore.NO_FIELDS, ChainRulesCore.conj(1.0) * var"##Δ1#260")                        end
                    end)
        end
    end
end

Additionally, Base.remove_linenums! removes not only LineNumberNodes but also Expr(:line, ...): https://github.com/JuliaLang/julia/blob/5d4eaca0c9fa3d555c79dbacdccb9169fdf64b65/base/expr.jl#L349

[oxinabox]

Thanks.
I did think there was something in base for this.
Can you bump the version also so we can tag a release?

[devmotion]

Sure, I updated the version number.

[codecov-io]

Codecov Report

Merging #323 (643e140) into master (6c2d1fb) will decrease coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #323      +/-   ##
==========================================
- Coverage   89.83%   89.76%   -0.07%     
==========================================
  Files          13       13              
  Lines         472      469       -3     
==========================================
- Hits          424      421       -3     
  Misses         48       48              

Impacted Files	Coverage Δ
src/rule_definition_tools.jl	96.03% <100.00%> (-0.10%)	⬇️

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