Cannot read property 'clone' of undefined.

[laino]

@c: 1 + 1 / 1;

SyntaxError: Cannot read property 'clone' of undefined in /home/lain/test.less on line 1, column 1:

[matthew-dean]

That can't be your only line in the file? Do you have more context?

[laino]

Nope. That's the only line. It takes just that.

[laino]

Here's a video ;)

[laino]

Actually the * 4 isn't even necessary.

Just this is enough:

@c: 1 + 1 / 1;

[RealDolos]

oopsie whoopsie. other is {operand: "/", ... } still when this code is called:
https://github.com/less/less.js/blob/master/packages/less/src/less/tree/dimension.js#L73

[matthew-dean]

This is a bug that just got introduced?

[laino]

It's a bug that has existed at least since the 4.0.0 release and is still present in 4.1.0.

It's probably related to the "Parens-division now the default math setting" change.

[matthew-dean]

So it looks like for the above code, Less should be throwing 'Operation on an invalid type'. See: #3589

[RealDolos]

Less should be throwing 'Operation on an invalid type'

Why?

[matthew-dean]

@RealDolos Because in parens-division mode (the 4.0 Less default), you're trying to add 1 + a CSS expression 1 / 1. The division won't divide; it will be output as is, so you can't add 1 to it.

[matthew-dean]

@RealDolos Now, an argument could be made that just the 1 + 1 should add together in that case, but unfortunately that's not the way it's parsed. As it is, division is parsed as a division operation, even if it's not performed, so when it's not performed, it can't be part of other operations, and should throw an error.

[RealDolos]

Adding 1 + 1 would be surprising behavior I suppose.
Still, "Operation on an invalid type" is a bit of a shit error message