Ensure switch branches reordering happens only for constant branch expressions

[elad-yosifon]

#1084 @jridgewell

[fabiosantoscode]

Hey, this looks good to me!

Is this just for @jridgewell to merge in his PR, or is this the correct fix?

[elad-yosifon]

@fabiosantoscode this is a “counter commit” to @jridgewell revert attempt. The existing code is buggy, this is a fix.

[jridgewell]

Nit: I'm not sure this properly catches the bug (but the output isn't optimized, so it's not a hard blocker). We need to test that non-mutually-exclusive branches are correct:

Suggested change

	case 3 == i:
	console.log(i);
	break;
	case 5 == i:
	console.log(5);
	break;
	case 1 == i:
	console.log(i);
	break;
	case 3 == i:
	console.log('equals');
	break;
	case 5 > i:
	console.log('greater than');
	break;
	case 1 == i:
	console.log('equals');
	break;

This case should log 'greater than', but if we did the optimization, it would log equals (because the 1 == i would have been moved up).

[jridgewell]

Let's merge this, and I'll work it into my PR.