Make store step to send stmt's channel use post-update node

Author: owen-mc

go/ql/lib/semmle/go/dataflow/internal/ContainerFlow.qll

@@ -36,8 +36,10 @@ predicate containerStoreStep(Node node1, Node node2, Content c) {
     )
     or
     c instanceof CollectionContent and
-    exists(SendStmt send |
-      send.getChannel() = node2.(ExprNode).asExpr() and send.getValue() = node1.(ExprNode).asExpr()
+    exists(SendStmt send, Node channelExprNode |
+      send.getChannel() = channelExprNode.(ExprNode).asExpr() and
+      node2.(PostUpdateNode).getPreUpdateNode() = channelExprNode and
+      send.getValue() = node1.(ExprNode).asExpr()
     )
     or
     c instanceof MapKeyContent and

go/ql/test/library-tests/semmle/go/dataflow/ChannelField/test.expected

@@ -1,22 +1,14 @@
 invalidModelRow
 edges
 | test.go:9:9:9:11 | selection of c [collection] | test.go:9:7:9:11 | <-... | provenance |  |
-| test.go:13:16:13:16 | definition of s [pointer, c, collection] | test.go:16:2:16:2 | s [pointer, c, collection] | provenance |  |
 | test.go:15:10:15:17 | call to source | test.go:16:9:16:12 | data | provenance |  |
-| test.go:16:2:16:2 | implicit dereference [c, collection] | test.go:13:16:13:16 | definition of s [pointer, c, collection] | provenance |  |
-| test.go:16:2:16:2 | implicit dereference [c, collection] | test.go:16:2:16:4 | selection of c [collection] | provenance |  |
-| test.go:16:2:16:2 | s [pointer, c, collection] | test.go:16:2:16:2 | implicit dereference [c, collection] | provenance |  |
-| test.go:16:2:16:4 | selection of c [collection] | test.go:9:9:9:11 | selection of c [collection] | provenance |  |
-| test.go:16:2:16:4 | selection of c [collection] | test.go:16:2:16:2 | implicit dereference [c, collection] | provenance |  |
-| test.go:16:9:16:12 | data | test.go:16:2:16:4 | selection of c [collection] | provenance |  |
+| test.go:16:2:16:4 | selection of c [postupdate] [collection] | test.go:9:9:9:11 | selection of c [collection] | provenance |  |
+| test.go:16:9:16:12 | data | test.go:16:2:16:4 | selection of c [postupdate] [collection] | provenance |  |
 nodes
 | test.go:9:7:9:11 | <-... | semmle.label | <-... |
 | test.go:9:9:9:11 | selection of c [collection] | semmle.label | selection of c [collection] |
-| test.go:13:16:13:16 | definition of s [pointer, c, collection] | semmle.label | definition of s [pointer, c, collection] |
 | test.go:15:10:15:17 | call to source | semmle.label | call to source |
-| test.go:16:2:16:2 | implicit dereference [c, collection] | semmle.label | implicit dereference [c, collection] |
-| test.go:16:2:16:2 | s [pointer, c, collection] | semmle.label | s [pointer, c, collection] |
-| test.go:16:2:16:4 | selection of c [collection] | semmle.label | selection of c [collection] |
+| test.go:16:2:16:4 | selection of c [postupdate] [collection] | semmle.label | selection of c [postupdate] [collection] |
 | test.go:16:9:16:12 | data | semmle.label | data |
 subpaths
 #select