Ruby: ensure pruning works with startInContent

Author: asgerf

ruby/ql/lib/codeql/ruby/typetracking/TypeTracker.qll

@@ -220,7 +220,15 @@ module StepSummary {
 
 private newtype TTypeTracker =
   MkTypeTracker(Boolean hasCall, OptionalTypeTrackerContent content) {
-    content = noContent() or basicStoreStep(_, _, content)
+    content = noContent()
+    or
+    // Restrict `content` to those that might eventually match a load.
+    // We can't rely on `basicStoreStep` since `startInContent` might be used with
+    // a content that has no corresponding store.
+    exists(TypeTrackerContent loadContents |
+      basicLoadStep(_, _, loadContents) and
+      compatibleContents(content, loadContents)
+    )
   }
 
 /**
@@ -376,7 +384,13 @@ module TypeTracker {
 
 private newtype TTypeBackTracker =
   MkTypeBackTracker(Boolean hasReturn, OptionalTypeTrackerContent content) {
-    content = noContent() or basicLoadStep(_, _, content)
+    content = noContent()
+    or
+    // As in MkTypeTracker, restrict `content` to those that might eventually match a store.
+    exists(TypeTrackerContent storeContent |
+      basicStoreStep(_, _, storeContent) and
+      compatibleContents(storeContent, content)
+    )
   }
 
 /**

ruby/ql/test/library-tests/dataflow/type-tracker/TypeTracker.expected

@@ -156,10 +156,6 @@ track
 | type_tracker.rb:34:18:34:20 | obj | type tracker with call steps | type_tracker.rb:40:5:40:12 | ...[...] |
 | type_tracker.rb:34:18:34:20 | obj | type tracker with call steps | type_tracker.rb:44:5:44:13 | ...[...] |
 | type_tracker.rb:34:18:34:20 | obj | type tracker with call steps | type_tracker.rb:52:5:52:13 | ...[...] |
-| type_tracker.rb:34:18:34:20 | obj | type tracker with call steps with content attribute [] | type_tracker.rb:39:5:39:9 | [post] array |
-| type_tracker.rb:34:18:34:20 | obj | type tracker with call steps with content attribute [] | type_tracker.rb:43:5:43:10 | [post] array2 |
-| type_tracker.rb:34:18:34:20 | obj | type tracker with call steps with content attribute [] | type_tracker.rb:47:5:47:10 | [post] array3 |
-| type_tracker.rb:34:18:34:20 | obj | type tracker with call steps with content attribute [] | type_tracker.rb:51:5:51:10 | [post] array4 |
 | type_tracker.rb:34:18:34:20 | obj | type tracker with call steps with content element | type_tracker.rb:38:13:38:25 | call to [] |
 | type_tracker.rb:34:18:34:20 | obj | type tracker with call steps with content element | type_tracker.rb:50:14:50:26 | call to [] |
 | type_tracker.rb:34:18:34:20 | obj | type tracker with call steps with content element 0 or unknown | type_tracker.rb:35:11:35:15 | call to [] |
@@ -173,10 +169,6 @@ track
 | type_tracker.rb:34:18:34:20 | obj | type tracker without call steps | type_tracker.rb:40:5:40:12 | ...[...] |
 | type_tracker.rb:34:18:34:20 | obj | type tracker without call steps | type_tracker.rb:44:5:44:13 | ...[...] |
 | type_tracker.rb:34:18:34:20 | obj | type tracker without call steps | type_tracker.rb:52:5:52:13 | ...[...] |
-| type_tracker.rb:34:18:34:20 | obj | type tracker without call steps with content attribute [] | type_tracker.rb:39:5:39:9 | [post] array |
-| type_tracker.rb:34:18:34:20 | obj | type tracker without call steps with content attribute [] | type_tracker.rb:43:5:43:10 | [post] array2 |
-| type_tracker.rb:34:18:34:20 | obj | type tracker without call steps with content attribute [] | type_tracker.rb:47:5:47:10 | [post] array3 |
-| type_tracker.rb:34:18:34:20 | obj | type tracker without call steps with content attribute [] | type_tracker.rb:51:5:51:10 | [post] array4 |
 | type_tracker.rb:34:18:34:20 | obj | type tracker without call steps with content element | type_tracker.rb:38:13:38:25 | call to [] |
 | type_tracker.rb:34:18:34:20 | obj | type tracker without call steps with content element | type_tracker.rb:50:14:50:26 | call to [] |
 | type_tracker.rb:34:18:34:20 | obj | type tracker without call steps with content element 0 or unknown | type_tracker.rb:35:11:35:15 | call to [] |