As documented, string.gub( 'foo', '%a', '%1' ) should raise an invalid
capture index error because there is no capture with index 1 in the
pattern. But in fact it treats %1 as %0 in this situation. The ustring
library should match this behavior.
This patch also adds some tests for the behavior of gsub with table and
function replacements when the pattern does have captures.
Bug: T207623
Change-Id: Ie3e6c2eafa4a05989815c62c7037167642581751
If the replacement table or function results in a value that isn't a
string or number (or nil), string.gsub raises an error. Have ustring
raise the same error.
Bug: T195326
Change-Id: Ic36f9f5d7adc0c14e7a4a94d3747335107acd8b6
