Annex B.3.3 still doesn't actually allow you to redeclare sloppy functions in block

[syg]

(Thanks to @anba yet again.)

The conclusion to #320 was that we'd allow multiple same-named functions in block in sloppy mode.

Consider the following program:

(function () {
  {
    function g() {1}
    function g() {2}
  }
  print(g);
})();

On all of SpiderMonkey, V8, JSC, and Chakra, this prints function g() {2}. That is, all implementations agree that Annex B.3.3 semantics should apply to the inner, redeclared g.

The actual letter of Annex B.3.3, though, all say something like "If replacing the FunctionDeclaration f with a VariableStatement that has F as a BindingIdentifier would not produce any Early Errors ..."

The thing is, replacing either function g above with an actual var g actually would produce an Early Error, since the allowance we gave to multiple FIB is specifically tied to their FunctionDeclarations. That is,
the following program is an Early Error:

(function () {
  {
    function g() {1}
    var g; /*function g() {2}*/
  }
  print(g);
})();

So according to the current spec text, Annex B.3.3 does not apply to g. This is a spec oversight, since I'm pretty sure we specifically tried to allow this case.

[syg]

@bterlson Feedback on the proposed language in that commit?

[syg]

@bterlson Feedback on the proposed language in that commit?

[bakkot]

@syg that commit seems fine to me insofar as we are willing to continue having hypotheticals in the spec, which is Not Great but works ok (and is after all what we're already doing).

[bakkot]

@syg that commit seems fine to me insofar as we are willing to continue having hypotheticals in the spec, which is Not Great but works ok (and is after all what we're already doing).

[anba]

I don't think the proposed approach works for switch-statements when duplicate function declarations are present across multiple case-clauses:

function f() {
    switch (1) {
        case 1:
          function fb(){} // B.3.3.1 replaces this |var fb|.
        default:
          function fb(){} // The hypothetical block also needs to replace this function.
    }
    print(typeof fb); // Should print "function" per web-reality
}
f();

[anba]

I don't think the proposed approach works for switch-statements when duplicate function declarations are present across multiple case-clauses:

function f() {
    switch (1) {
        case 1:
          function fb(){} // B.3.3.1 replaces this |var fb|.
        default:
          function fb(){} // The hypothetical block also needs to replace this function.
    }
    print(typeof fb); // Should print "function" per web-reality
}
f();