Commits on May 25, 2024

1. Or patterns …

   This commit introduces or-patterns, which allows to express alternatives
   within patterns, including in a deep subpattern.
   
   The compilation of or-patterns is rather simple: we simply try each
   alternative until one matches, and use the corresponding bindings.
   
   Typechecking of or-patterns can be done following the same process as
   for typechecking a whole match expression (which is also a disjunction
   of patterns), although the treatment of bound variables is a bit
   different.
   
   Most of the complexity of this commit comes from the fact that we don't
   want to make `or` a reserved language keyword, which would break
   backward compatibility. This is possible, because `or` in pattern can't
   be confused with an identifier, but it requires some tweaking to make
   our LALR(1) parser accept this.

   

   yannham committed May 25, 2024
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