Make rule name available inside action blocks

[frostburn]

It would be nice if Rule.name and maybe even Rule.displayName were available inside action blocks.

Use case:

FooLiteral
  = "foo" {
    return {
       type: ruleName, // type: "FooLiteral"
       location: location(),
    };
  }

Here ruleName is a block scope constant, but it could also be a callable i.e. ruleName() if that's easier to implement.

[hildjj]

If we weren't in strict mode, we could do:

function ruleName() {
  return arguments.callee.caller.name;
}

Since we're not, we could generate a parameter to each action method containing the name:

function peg$f0() {
  const ruleName = "FooLiteral";
  return {
    type: ruleName, // type: "FooLiteral"
    location: location(),
  };
}

or:

// Slight preference for this, since it doesn't modify the text of the action code.
function peg$f0(ruleName = "FooLiteral") {
  return {
    type: ruleName, // type: "FooLiteral"
    location: location(),
  };
}

which isn't too bad, except for increasing the size of all generated parsers and causing a backwards-compatibility issue with a grammar like this:

Rule = ruleName:$[a-z]i+ { return {ruleName} }

which currently generates this JS:

function peg$f0(ruleName) { return {ruleName} }

I guess we could make this an option for generate. Does anyone else want this?