Go: fix models through redefined types

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

@@ -377,7 +377,8 @@ module SourceSinkInterpretationInput implements
       or
       n2.asExpr() = n.asInstruction().(IR::EvalImplicitDerefInstruction).getOperand()
     |
-      result = lookThroughPointerType(skipImplicitFieldReads(n2).getType())
+      result =
+        maybeLookThroughNamedType(lookThroughPointerType(skipImplicitFieldReads(n2).getType()))
     )
   }
 
@@ -395,6 +396,12 @@ module SourceSinkInterpretationInput implements
           .getBaseInstruction()
   }
 
+  private DefinedType maybeLookThroughNamedType(DefinedType t) {
+    // We do not have information on what a defined type is defined to be, only
+    // the underlying type, so we have to be a bit imprecise.
+    result.getBaseType() = t.getBaseType()
+  }
+
   /** Provides additional sink specification logic. */
   bindingset[c]
   predicate interpretOutput(string c, InterpretNode mid, InterpretNode node) {

go/ql/test/library-tests/semmle/go/dataflow/ExternalFlowInheritance/test_fields.go

@@ -83,3 +83,13 @@ func TestFieldsSEmbedS1AndSEmbedS1(t test.SEmbedS1AndSEmbedS1) {
 	a := t.SourceField
 	t.SinkField = a // $ S1[t] ql_S1
 }
+
+func TestFieldsRedefinedP1(t test.RedefinedP1) {
+	a := t.SourceField
+	t.SinkField = a // $ P1[f] P1[t] ql_P1
+}
+
+func TestFieldsRedefinedS1(t test.RedefinedS1) {
+	a := t.SourceField
+	t.SinkField = a // $ S1[f] S1[t] ql_S1
+}

go/ql/test/library-tests/semmle/go/dataflow/ExternalFlowInheritance/test_methods.go

@@ -171,3 +171,9 @@ func TestMethodsSEmbedS1AndSEmbedS1(t test.SEmbedS1AndSEmbedS1) {
 	y := t.Step(x)
 	t.Sink(y) // $ I1[t] S1[t] ql_S1
 }
+
+func TestMethodsRedefinedI1(t test.RedefinedI1) {
+	x := t.Source()
+	y := t.Step(x)
+	t.Sink(y) // $ I1[f] I1[t] ql_I1 SPURIOUS: ql_P1 ql_S1
+}