Empty statements unexpectedly removed.

[mbostock]

I expected the following code to be unchanged by Rollup:

var result = 0;
(function(test) {
  if (test === 0);
  else ++result;
})(0);
console.log(result);

However, the resulting output drops the semicolon from the if block, resulting in invalid JavaScript:

var result = 0;
(function(test) {
  if (test === 0)
  else ++result;
})(0);
console.log(result);

  else ++result;
  ^^^^
SyntaxError: Unexpected token else

You can workaround this issue by using an empty block instead of an empty statement:

var result = 0;
(function(test) {
  if (test === 0) {}
  else ++result;
})(0);
console.log(result);

Naturally, the problem also applies to else-if and else:

var result = 0;
(function(test) {
  if (test === 0) {}
  else if (test === 1);
  else;
})(0);
console.log(result);

Which results in:

var result = 0;
(function(test) {
  if (test === 0) {}
  else if (test === 1)
  else
})(0);
console.log(result);

  else
  ^^^^
SyntaxError: Unexpected token else

This example is slightly more complicated than it should be (using the IIFE) because #930 was causing the simpler test case to be removed entirely.

[kzc]

@Rich-Harris I don't know if rollup shares any code with buble other than acorn and magic-string but this Issue is somewhat related to the block-less if/else/loop body problem in buble:

https://gitlab.com/Rich-Harris/buble/merge_requests/80

https://gitlab.com/Rich-Harris/buble/issues/110

[eventualbuddha]

Fixed in v0.35.10.