I just had a look at Fire Code. How do you distinguish -> with ligatures from → (an Unicode arrow)?

Personally, it’s never really come up. I have no Unicode arrows in my actual source code.

On the occasion it’s in a string literal or whatever the it’s pretty obviously different, because it’s a single-width character as opposed to the double-width ligature.

The ligaturized -> is two characters wide and is pretty easy to tell apart.

So it looks like U+27F6 ⟶ rather than U+2192 →?

Sure, but in a monospaced font both of those arrows would have to fit into the same small box, so 27F6 might be the full width while 2192 would be some partial width, while a -> ligature would be two widths.

The Unicode arrow looks smaller and is positioned lower, while the ligature has the same size as -> with the dash extended into the 'arrow'. Not that I use this frequently.

The Unicode arrow is most likely throwing an error in the linter or compiler and is underlined with a red line.