Julia: Cannot juxtapose string literal error for QuotedNode with str macro

[tomyun]

While :(A.a"xx") is parsed as expected like below,

julia> dump(:(A.a"xx"))
Expr
  head: Symbol macrocall
  args: Array{Any}((3,))
    1: Expr
      head: Symbol .
      args: Array{Any}((2,))
        1: Symbol A
        2: QuoteNode
          value: Symbol @a_str
    2: LineNumberNode
      line: Int64 1
      file: Symbol REPL[25]
    3: String "xx"

:(:A.a"xx") with QuotedNode resulted into a bit cryptic error.

julia> :(:A.a"xx")
ERROR: syntax: cannot juxtapose string literal

It's something not expected as some similar uses of QuotedNode seem to work fine. Is this an intended behavior? Tested on Julia 1.4.2.

julia> dump(:(:A.a))
Expr
  head: Symbol .
  args: Array{Any}((2,))
    1: QuoteNode
      value: Symbol A
    2: QuoteNode
      value: Symbol a

julia> dump(:(:A.a(x, y)))
Expr
  head: Symbol call
  args: Array{Any}((3,))
    1: Expr
      head: Symbol .
      args: Array{Any}((2,))
        1: QuoteNode
          value: Symbol A
        2: QuoteNode
          value: Symbol a
    2: Symbol x
    3: Symbol y

[Keno]

Just to be clear, the issue is about the precedence of quoting-: vs string literals? In general, for these kinds of odd cases, it's always better to use parentheses to indicate what you mean, but @JeffBezanson can chime in if he'd like to adjust the precedence relation here.

[tomyun]

Not sure if this issue is only about precedence, since I tried some parentheses, still with no luck.

julia> dump(:((:A).a"xx"))
ERROR: syntax: cannot juxtapose string literal

julia> dump(:(:(A).a"xx"))
ERROR: syntax: cannot juxtapose string literal

[Keno]

Ok, I see what you're saying. The issue is this parse difference:

julia> dump(:((A).a"xx"))
Expr
  head: Symbol macrocall
  args: Array{Any}((3,))
    1: Expr
      head: Symbol .
      args: Array{Any}((2,))
        1: Symbol A
        2: QuoteNode
          value: Symbol @a_str
    2: LineNumberNode
      line: Int64 1
      file: Symbol REPL[10]
    3: String "xx"

julia> dump(:((:A).a"xx"))
ERROR: syntax: cannot juxtapose string literal
Stacktrace:
 [1] top-level scope
   @ none:1

I agree that looks a bit odd to me.

[JeffBezanson]

The idea is that the syntax A.b"..." is for using a string macro with a qualified name. What is (:A).a"XX" supposed to do?

[tomyun]

Well, I wanted to have :A or something similar as a placeholder that could be later replaced by other symbols during macro processing.

[Keno]

The idea is that the syntax A.b"..." is for using a string macro with a qualified name. What is (:A).a"XX" supposed to do?

I think the thing bothered me is that it just looks like a bit of "Spooky action at a distance", since it changes the interpretation of whether or not the thing is a string literal. Perhaps the only thing to do is to give a better parse error.

[JeffBezanson]

We could certainly change this to allow any dot expression juxtaposed before a string, and interpret it as a string macro call. Probably just one of those cases where we're giving an error to be conservative.