Where is Ruby's string literal juxtaposition feature officially documented?

UPDATE

This is now officially documented in the RDoc that ships with Ruby.

Changes will propagate to RubyDoc the next time they build the documentation.

The added documentation:

Adjacent string literals are automatically concatenated by the interpreter:

  "con" "cat" "en" "at" "ion" #=> "concatenation"
  "This string contains "\
  "no newlines."              #=> "This string contains no newlines."

Any combination of adjacent single-quote, double-quote, percent strings will
be concatenated as long as a percent-string is not last.

  %q{a} 'b' "c" #=> "abc"
  "a" 'b' %q{c} #=> NameError: uninitialized constant q

ORIGINAL

Right now, this isn't anywhere in the official ruby documentation, but I think it should be. As pointed out in a comment, the logical place for the docs to go would be: http://www.ruby-doc.org/core-2.0/doc/syntax/literals_rdoc.html#label-Strings

I've opened a pull request on ruby/ruby with the documentation added.

If this pull request is merged, it will automatically update http://www.ruby-doc.org. I'll update this post if/when that happens. ^_^

The only other mentions of this I've found online are:

• The Ruby Programming Language, page 47 (mentioned in another answer)
• Ruby Forum Post circa 2008
• Programming Ruby

There is a reference in The Ruby Programming Language, page 47.

It looks like it is deliberately in the parser, for situations where you want to split up string literals in code, but don't want to pay the price of concatenating them (and creating 3 or more strings). Long strings with no line breaks, and without requiring line-length busting code, are a good example

text = "This is a long example message without line breaks. " \
    "If it were not for this handy syntax, " \
    "I would need to concatenate many strings, " \
    "or find some other work-around"