4 files changed, 32 insertions, 19 deletions

diff --git a/source/slang/slang-check-modifier.cpp b/source/slang/slang-check-modifier.cpp
index 473b5e5da..97da31f39 100644
--- a/source/slang/slang-check-modifier.cpp
+++ b/source/slang/slang-check-modifier.cpp
@@ -189,8 +189,7 @@ namespace Slang
         //
         attrDecl->ParentDecl = parentDecl;
         parentDecl->Members.add(attrDecl);
-        parentDecl->memberDictionaryIsValid = false;
-
+        
         // Finally, we perform any required semantic checks on
         // the newly constructed attribute decl.
         //
diff --git a/source/slang/slang-decl-defs.h b/source/slang/slang-decl-defs.h
index b4c3bcfd4..7dc58539c 100644
--- a/source/slang/slang-decl-defs.h
+++ b/source/slang/slang-decl-defs.h
@@ -18,15 +18,20 @@ ABSTRACT_SYNTAX_CLASS(ContainerDecl, Decl)
         return FilteredMemberList<T>(Members);
     }
 
+    bool isMemberDictionaryValid() const { return dictionaryLastCount == Members.getCount(); }
+
+    void invalidateMemberDictionary() { dictionaryLastCount = -1; }
+
+    // Denotes how much of Members has been placed into the dictionary/transparentMembers.
+    // If this value equals the Members.getCount(), the dictionary is completely full and valid.
+    // If it's >= 0, then the Members after dictionaryLastCount are all that need to be added.
+    // If it < 0 it means that the dictionary/transparentMembers is invalid and needs to be recreated.
+    Index dictionaryLastCount = 0;
 
     // Dictionary for looking up members by name.
     // This is built on demand before performing lookup.
     Dictionary<Name*, Decl*> memberDictionary;
-
-    // Whether the `memberDictionary` is valid.
-    // Should be set to `false` if any members get added/remoed.
-    bool memberDictionaryIsValid = false;
-
+    
     // A list of transparent members, to be used in lookup
     // Note: this is only valid if `memberDictionaryIsValid` is true
     List<TransparentMemberInfo> transparentMembers;
diff --git a/source/slang/slang-lookup.cpp b/source/slang/slang-lookup.cpp
index 6a2d31c32..5f2927ccb 100644
--- a/source/slang/slang-lookup.cpp
+++ b/source/slang/slang-lookup.cpp
@@ -30,24 +30,35 @@ struct BreadcrumbInfo
 void buildMemberDictionary(ContainerDecl* decl)
 {
     // Don't rebuild if already built
-    if (decl->memberDictionaryIsValid)
+    if (decl->isMemberDictionaryValid())
         return;
 
-    decl->memberDictionary.Clear();
-    decl->transparentMembers.clear();
+    // If it's < 0 it means that the dictionaries are entirely invalid
+    if (decl->dictionaryLastCount < 0)
+    {
+        decl->dictionaryLastCount = 0;
+        decl->memberDictionary.Clear();
+        decl->transparentMembers.clear();
+    }
 
     // are we a generic?
     GenericDecl* genericDecl = as<GenericDecl>(decl);
 
-    for (auto m : decl->Members)
+    const Index membersCount = decl->Members.getCount();
+
+    SLANG_ASSERT(decl->dictionaryLastCount >= 0 && decl->dictionaryLastCount <= membersCount);
+
+    for (Index i = decl->dictionaryLastCount; i < membersCount; ++i)
     {
+        Decl* m = decl->Members[i];
+
         auto name = m->getName();
 
         // Add any transparent members to a separate list for lookup
         if (m->HasModifier<TransparentModifier>())
         {
             TransparentMemberInfo info;
-            info.decl = m.Ptr();
+            info.decl = m;
             decl->transparentMembers.add(info);
         }
 
@@ -59,17 +70,17 @@ void buildMemberDictionary(ContainerDecl* decl)
         if (genericDecl && m == genericDecl->inner)
             continue;
 
-
         m->nextInContainerWithSameName = nullptr;
 
         Decl* next = nullptr;
         if (decl->memberDictionary.TryGetValue(name, next))
             m->nextInContainerWithSameName = next;
 
-        decl->memberDictionary[name] = m.Ptr();
-
+        decl->memberDictionary[name] = m;
     }
-    decl->memberDictionaryIsValid = true;
+
+    decl->dictionaryLastCount = membersCount;
+    SLANG_ASSERT(decl->isMemberDictionaryValid());
 }
 
 
@@ -186,7 +197,7 @@ static void _lookUpDirectAndTransparentMembers(
     ContainerDecl* containerDecl = containerDeclRef.getDecl();
 
     // Ensure that the lookup dictionary in the container is up to date
-    if (!containerDecl->memberDictionaryIsValid)
+    if (!containerDecl->isMemberDictionaryValid())
     {
         buildMemberDictionary(containerDecl);
     }
diff --git a/source/slang/slang-parser.cpp b/source/slang/slang-parser.cpp
index 03f53634d..4ce4c49b5 100644
--- a/source/slang/slang-parser.cpp
+++ b/source/slang/slang-parser.cpp
@@ -1080,8 +1080,6 @@ namespace Slang
         {
             member->ParentDecl = container.Ptr();
             container->Members.add(member);
-
-            container->memberDictionaryIsValid = false;
         }
     }