How to use `@capture` with variable expression

capture.md

How to use @capture with variable expression

The @capture macro from MacroTools expects one to pass the pattern directly when the macro is called. From Slack, someone asked if the pattern can be stored in a variable and then passed to the macro. I could make it work with the following "hack":

julia> code
:(foo(bar + xyz))

julia> pattern
:(phi1_(x_ + y_))

julia> x = :(@capture(code,pattern))
:(#= REPL[177]:1 =# @capture code pattern)

julia> x.args[3] = Expr(:quote, code)
:($(Expr(:quote, :(foo(bar + xyz)))))

julia> x.args[4] = pattern
:(phi1_(x_ + y_))

julia> eval(x)
true

julia> phi1, x, y
(:foo, :bar, :xyz)