Raise NoMatchingPatternError when `expr in pat` doesn't match
Currently, single line pattern matching(
expr in pat) returns true or false.
[1, 2, 3] in [x, y, z] #=> true (with assigning 1 to x, 2 to y, and 3 to z) [1, 2, 3] in [1, 2, 4] #=> false
expr in pat should raise an exception when it doesn't match.
Because if a user doesn't check the return value of
expr in pat, matching failure occurs implicitly and it may cause problems in subsequent processes.
expr in [0, x] # A user expects it always matches, but if it doesn't match... ... (snip) ... x.foo #=> NoMethodError (undefined method `foo' for nil:NilClass)
I also propose that
expr in pat returns the result of
expr if it matches.
It is similar to assignment.
x, y, z = 1, 2, 3 #=> [1, 2, 3] [1, 2, 3] in [x, y, z] #=> [1, 2, 3]