Only allow labels on composite statements.

[lrhn]

The grammar allows you to put labels on simple single statements (e.g., "foo:break foo;") where they don't make any sense.
There is really no reason for allowing them, except to make the grammar slightly smaller *but, IMO, the language less clear (Why can you write it? What does it do?).

I suggest introducing a syntactic category of composite statements which includes block-statements, loops, switches, trys and ifs (i.e., anything that may contain other statements), and then only allow labels on these (and on switch cases, ofcourse).

I.e.:

 statement:
  label* compositeStatement |
  initializedVariableDeclaration ';' |
  breakStatement |
  continueStatement |
  returnStatement |
  throwStatement |
  expressionStatement |
  assertStatement |
  functionSignature functionBody
  ;

 compositeStatement:
  block |
  forStatement |
  whileStatement |
  doStatement |
  switchStatement |
  ifStatement |
  tryStatement
  ;

[gbracha]

AFIK, this was intentional. It may make life easier for code generators that target Dart.

---

Set owner to @gbracha.
Added Accepted label.

[gbracha]

Added AsDesigned label.