Autocomplete popup highlighting fails when string is over 32 chars long

[pthurlow]

The highlighting implementation for ace autocomplete popup menu relies on a bit mask to determine the location of characters in the string to highlight. Since this bit mask is stored as an integer it can only store characters up to the maximum bits of an integer - 1, 31.

When shifting more than 31 characters the bitwise shift clips the first 31 bits off and converts the remaining bits as shown here:

// shift 1 bit 3 places left to get 8
1 << 3  = 8

// shift 1 bit 31 places left to get almost the max signed integer
1 << 31 = -2147483648

// shift 1 bit 32 places to roll over back to 1
1 << 32 = 1

// shift 1 bit 35 places to get back to 8
1 << 35 = 8

This manifests itself in the autocomplete popover by causing text to get highlighted incorrectly. In this contrived example you can see the character at index 2 is incorrectly highlighted because the masked position of the A to be highlighted is 2 passed the 32nd character in the string.

[Cwallice]

+1
Long names are necessary sometimes.