correct migration's generator (incorrect code is generated for "matching" expression)
Revert "correct migration's generator (incorrect code is generated for "matching" expression)"

This reverts commit 75ef9834caf2123a21026af7f8c9c797633f95a2.
Revert "Revert "correct migration's generator (incorrect code is generated for "matching" expression)""

This reverts commit 8d0d661b2b75962c3927e18dfd00b65443184fc2.