A ppx rewriter that rewrites simple match statements with an if then
else expression.

Syntax

ppx_optional rewrites the extension match%optional in expressions.
It requires that a module Optional_syntax is in scope, and that it
has is_none and unsafe_value values.

For instance:

match%optional e with
| None -> none_expression
| Some x -> some_expression

becomes:

if Optional_syntax.is_none e then begin
   none_expression
end else begin
   let x = Optional_syntax.unsafe_value e in
   some_expression
end

Usage

This is normally used to safely access an optional value while
avoiding allocation for immediate values
(e.g. Immediate.{Char,Bool,Int}.Option, Fixed.Option,
Price.Fixed.Option, etc...).