From 45db87d61debb13e252056d3ee68936dc1e72ff8 Mon Sep 17 00:00:00 2001
From: Ellie Kornstaedt <ellieko@meta.com>
Date: Fri, 4 Aug 2023 17:00:30 -0700
Subject: [PATCH] Properly maintain type index when field is found in base type

---
 AbstractMemorySnapshot/SegmentedHeap.cs |  2 +-
 AbstractMemorySnapshot/TypeSystem.cs    | 18 +++++++++++-------
 ReferenceClassifiers/BoundRuleset.cs    |  3 ++-
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/AbstractMemorySnapshot/SegmentedHeap.cs b/AbstractMemorySnapshot/SegmentedHeap.cs
index 4b3e305..64c5ef9 100644
--- a/AbstractMemorySnapshot/SegmentedHeap.cs
+++ b/AbstractMemorySnapshot/SegmentedHeap.cs
@@ -168,7 +168,7 @@ public NativeWord ReadValue(MemoryView objectView, PointerInfo<int> pointerInfo)
                     }
                     else
                     {
-                        fieldNumber = m_typeSystem.GetFieldNumber(typeIndex, fieldName);
+                        (typeIndex, fieldNumber) = m_typeSystem.GetFieldNumber(typeIndex, fieldName);
                         if (fieldNumber == -1)
                         {
                             // TODO: emit warning
diff --git a/AbstractMemorySnapshot/TypeSystem.cs b/AbstractMemorySnapshot/TypeSystem.cs
index 2744b31..c6b4390 100644
--- a/AbstractMemorySnapshot/TypeSystem.cs
+++ b/AbstractMemorySnapshot/TypeSystem.cs
@@ -188,26 +188,30 @@ public IEnumerable<PointerInfo<int>> GetArrayElementPointerOffsets(int typeIndex
             }
         }
 
-        public int GetFieldNumber(int typeIndex, string fieldName)
+        public (int typeIndex, int fieldNumber) GetFieldNumber(int typeIndex, string fieldName)
         {
             if (IsArray(typeIndex))
             {
-                return -1;
+                return (-1, -1);
             }
             else if (IsValueType(typeIndex))
             {
-                return GetOwnFieldNumber(typeIndex, fieldName);
+                return (typeIndex, GetOwnFieldNumber(typeIndex, fieldName));
             }
 
             int currentTypeIndex = typeIndex;
-            int fieldNumber = -1;
-            while (currentTypeIndex != -1 && fieldNumber == -1)
+            do
             {
-                fieldNumber = GetOwnFieldNumber(currentTypeIndex, fieldName);
+                int fieldNumber = GetOwnFieldNumber(currentTypeIndex, fieldName);
+                if (fieldNumber != -1)
+                {
+                    return (currentTypeIndex, fieldNumber);
+                }
                 currentTypeIndex = BaseOrElementTypeIndex(currentTypeIndex);
             }
+            while (currentTypeIndex != -1);
 
-            return fieldNumber;
+            return (-1, -1);
         }
 
         int GetOwnFieldNumber(int typeIndex, string fieldName)
diff --git a/ReferenceClassifiers/BoundRuleset.cs b/ReferenceClassifiers/BoundRuleset.cs
index cc8992d..cd0a6a9 100644
--- a/ReferenceClassifiers/BoundRuleset.cs
+++ b/ReferenceClassifiers/BoundRuleset.cs
@@ -151,7 +151,7 @@ Selector BindSelector(int typeIndex, string[] fieldNames)
                 }
                 else
                 {
-                    fieldNumber = m_typeSystem.GetFieldNumber(currentTypeIndex, fieldNames[i]);
+                    (int baseTypeIndex, fieldNumber) = m_typeSystem.GetFieldNumber(currentTypeIndex, fieldNames[i]);
                     if (fieldNumber == -1)
                     {
                         // TODO: better warning management
@@ -164,6 +164,7 @@ Selector BindSelector(int typeIndex, string[] fieldNames)
                         return new Selector { StaticPrefix = fieldPath, DynamicTail = dynamicFieldNames };
                     }
 
+                    currentTypeIndex = baseTypeIndex;
                     fieldTypeIndex = m_typeSystem.FieldType(currentTypeIndex, fieldNumber);
                 }