That's known as a ligature and they're pretty common in many programming-oriented fonts, which usually have stylistic sets with different ligatures for different programming languages that you can optionally enable in your editor's configuration. For example, here's the stylistic sets the Monaspace font offers:

Personally I'm not too fond of ligatures so I never enable any, but many folks do like them.

Edit: and just as a side note, ligatures are super common in many fonts, you just might not notice them. Here's some classic examples from the DejaVu Serif font, with and without a ligature: