Adding Guard Clauses to the Match Operator in Elixir

Brett aims to enrich Elixir's pattern matching by allowing guard clauses with the match operator. His approach involves using metaprogramming to transform guard-enhanced match expressions into equivalent `case` constructs that respect the semantics of guards. The transformations are made using a custom `when/2` macro. This macro carefully emulates the existing match operator while adding the ability to specify guards. Brett anticipates potential conflicts with macros expecting unguarded matches, such as `ExUnit.Assertions.assert/1`, and suggests cautious use to maintain compatibility. To avoid compiler warnings about unused variables within the macro-converted match, he uses metadata tagging. Brett acknowledges some limitations with this approach, such as the need to manually separate guard assertions in certain scenarios, but feels the macro fits naturally into the language.