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Simon Peyton Jones authored
See Note [Unbound template type variables] in Rules.hs This fixes Trac #10689. The problem was a rule LHS that mentioned a type variable in a phantom argument to a type synonym. Then matching the LHS didn't bind the type variable, and the rule matcher complained. This patch fixes the problem, as described by the Note. I also went back to not-cloning the template varaibles during rule matching. I'm convinced that it's not necessary now (if it ever was), and cloning makes the fix for #10689 much more fiddly.
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