Triple-quoted strings treated an expressions in macros

[dcjones]

macro foo(arg)
    println(typeof(arg))
end

@foo("hello")
@foo("""hello""")

The first call to foo is ASCIIString the second is Expr. This prevents triple-quoted strings from being used as format strings in printf, among other things.

[JeffBezanson]

Yes, I'd say the indentation processing should be moved to the parser like interpolation was.

[ivarne]

Marking this as "up for grabs", because it is a pretty annoying issue, and if we are going to fix it, we don't want people to write workaround solutions.

As far as I understand the reason for the whole mstr stuff for triple quoted strings is because we want some special de-indentation behaviour that we have implemented in triplequoted() base/string.jl:1039. It was easier to just emit @mstr("triple quoted string") than to implement triplequoted in C or scheme, so the current behaviour should be considered a temporary workaround.

Is this a correct work description?