Using the "alt" key on the Mac keyboard interferes with the usage of "alt" (with and without "shift") to produce other characters. This is especially difficult because the keymap is not restricted to coding in CoffeeScript, but also seems to be active in other modes.
In general, the only way to avoid this problem is to avoid "alt" as a modifier unless accompanied by "ctrl" or "super", as almost all keys produce some special character when modified by "alt".
Using the "alt" key on the Mac keyboard interferes with the usage of "alt" (with and without "shift") to produce other characters. This is especially difficult because the keymap is not restricted to coding in CoffeeScript, but also seems to be active in other modes.
In general, the only way to avoid this problem is to avoid "alt" as a modifier unless accompanied by "ctrl" or "super", as almost all keys produce some special character when modified by "alt".