Treat deducible generic parameter types as unresolved types, because

they need to be substituted away for any type containing them to be
useful. A nice side-effect of this is that we'll actually properly
walk into the source type when a generic function returns, e.g., a
tuple type that involves type parameters not resolved by the input
arguments.


Swift SVN r2302

include/swift/AST/Types.h

@@ -1235,7 +1235,7 @@ class DeducibleGenericParamType : public SubstitutableType {
   DeducibleGenericParamType(ASTContext &Ctx, Identifier Name, unsigned Index,
                             ArrayRef<ProtocolDecl *> ConformsTo)
     : SubstitutableType(TypeKind::DeducibleGenericParam, &Ctx,
-                        /*Unresolved=*/false, ConformsTo),
+                        /*Unresolved=*/true, ConformsTo),
       Name(Name), Index(Index) { }
 
 public: