bug#16567: 24.3.50; pcase should signal an error if no case matches

[Stefan Monnier]

> What could happen if you would change it?

Obviously: errors signaled instead of returning the expected nil.
Returning nil by default is "the norm" in Elisp (think of missing `else'
branches in `if', or missing default case in `cond' or even missing
default case in `cl-case'), so it's to be expected that pcase users
would rely on this default behavior as well, even if it strikes you as
utter nonsense.

> The "nil default" would make more sense in a pcase-if or pif macro.

Changing the default of `pcase' is not an option at this point.


        Stefan