One second thought: keep the interface to computeTupleShuffle consistent:

change its implementation to take a list of TupleTypeElt for both the
from/to tuple type, but provider a convenience wrapper that takes the
from/to tuple type as TupleType's.


Swift SVN r31733

lib/Sema/CSSimplify.cpp

@@ -755,8 +755,7 @@ ConstraintSystem::matchTupleTypes(TupleType *tuple1, TupleType *tuple2,
   // Compute the element shuffles for conversions.
   SmallVector<int, 16> sources;
   SmallVector<unsigned, 4> variadicArguments;
-  if (computeTupleShuffle(tuple1->getElements(), tuple2,
-                          sources, variadicArguments))
+  if (computeTupleShuffle(tuple1, tuple2, sources, variadicArguments))
     return SolutionKind::Error;
 
   // Check each of the elements.