Add post-update nodes for implicit field read nodes

Author: owen-mc

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

@@ -838,7 +838,11 @@ module Public {
       exists(IR::MethodReadInstruction mri |
         ce.getTarget() instanceof Method and
         mri = IR::evalExprInstruction(ce.getCalleeExpr()) and
-        insn = mri.getReceiver()
+        // If a.x is reading a promoted field, and it's equivalent to a.b.c.x,
+        // then mri.getReceiver() will give us the implicit field read a.b.c
+        // and we want to have post-update nodes for a, the implicit field
+        // read a.b and the implicit field read a.b.c.
+        insn = IR::lookThroughImplicitFieldRead*(mri.getReceiver())
       )
     ) and
     mutableType(insn.getResultType())

go/ql/test/library-tests/semmle/go/Types/CONSISTENCY/DataFlowConsistency.expected

@@ -1,11 +1,5 @@
 reverseRead
-| pkg1/embedding.go:56:29:56:39 | implicit dereference | Origin of readStep is missing a PostUpdateNode. |
-| pkg1/embedding.go:57:33:57:46 | implicit dereference | Origin of readStep is missing a PostUpdateNode. |
-| pkg1/embedding.go:58:14:58:22 | implicit read of field embedder | Origin of readStep is missing a PostUpdateNode. |
-| pkg1/embedding.go:58:31:58:42 | implicit read of field embedder | Origin of readStep is missing a PostUpdateNode. |
 | pkg1/tst.go:43:6:43:6 | t | Origin of readStep is missing a PostUpdateNode. |
 | pkg1/tst.go:46:6:46:6 | t | Origin of readStep is missing a PostUpdateNode. |
-| pkg1/tst.go:50:2:50:2 | t | Origin of readStep is missing a PostUpdateNode. |
 | pkg1/tst.go:53:6:53:7 | t2 | Origin of readStep is missing a PostUpdateNode. |
 | pkg1/tst.go:55:6:55:7 | t2 | Origin of readStep is missing a PostUpdateNode. |
-| promoted.go:18:6:18:6 | t | Origin of readStep is missing a PostUpdateNode. |