Add type-asserts to the results of parse_brackets()#617

KristofferC merged 1 commit intoJuliaLang:backports-julialang-1.13JuliaLang/JuliaSyntax.jl:backports-julialang-1.13from

JamesWrigley:parse-brackets-typeassertJamesWrigley/JuliaSyntax.jl:parse-brackets-typeassertCopy head branch name to clipboard