"Non-breaking space (U+00A0) used instead of regular space" warning in Xcode

Question

When typing a space character in Xcode, a warning appears sometimes:

Non-breaking space (U+00A0) used instead of regular space

Earlier Xcode versions display these messages:

Treating Unicode character as whitespace

or

Invalid character in source file

If I re-write the character, the warning disappears. What causes this?

Answer 1

That happens to me when I type too fast and accidentally hold down Alt while pressing down Space. This creates a non-breaking space (0xA0) which is not recognized as a valid space character by Xcode.

For a (hacky) solution, I've remapped this combination to Insert Tab inside Xcode's Preferences/Key Bindings, so it enters a tabulator character instead.