6 files changed, 27 insertions, 6 deletions
diff --git a/src/ir/module-utils.cpp b/src/ir/module-utils.cpp
index 8e6ac0d1a..f7ba7d776 100644
--- a/src/ir/module-utils.cpp
+++ b/src/ir/module-utils.cpp
@@ -317,11 +317,10 @@ std::vector<HeapType> getPublicHeapTypes(Module& wasm) {
 }
 
 std::vector<HeapType> getPrivateHeapTypes(Module& wasm) {
-  auto allTypes = getHeapTypeCounts(wasm, true);
+  auto usedTypes = getHeapTypeCounts(wasm, true);
   auto publicTypes = getPublicTypeSet(wasm);
   std::vector<HeapType> types;
-  types.reserve(allTypes.size() - publicTypes.size());
-  for (auto& [type, _] : allTypes) {
+  for (auto& [type, _] : usedTypes) {
     if (!publicTypes.count(type)) {
       types.push_back(type);
     }
diff --git a/src/passes/GlobalTypeOptimization.cpp b/src/passes/GlobalTypeOptimization.cpp
index 9015f3ab5..8ef6a3b89 100644
--- a/src/passes/GlobalTypeOptimization.cpp
+++ b/src/passes/GlobalTypeOptimization.cpp
@@ -118,6 +118,10 @@ struct GlobalTypeOptimization : public Pass {
       return;
     }
 
+    if (!getPassOptions().closedWorld) {
+      Fatal() << "GTO requires --closed-world";
+    }
+
     // Find and analyze struct operations inside each function.
     StructUtils::FunctionStructValuesMap<FieldInfo> functionNewInfos(*module),
       functionSetGetInfos(*module);
diff --git a/src/passes/RemoveUnusedTypes.cpp b/src/passes/RemoveUnusedTypes.cpp
index d346bc585..1ea65fb0f 100644
--- a/src/passes/RemoveUnusedTypes.cpp
+++ b/src/passes/RemoveUnusedTypes.cpp
@@ -34,6 +34,16 @@ struct RemoveUnusedTypes : Pass {
       // This pass only does anything with GC types.
       return;
     }
+
+    // Consider (rec $A $unused), where anyrefs received from the outside are
+    // cast to `$A`. In an open world we cannot remove $unused because that
+    // would change the identity of $A. Currently we would incorrectly remove
+    // $unused. To fix that, we need to fix our collection of public types to
+    // consider $A (and $unused) public in an open world.
+    if (!getPassOptions().closedWorld) {
+      Fatal() << "RemoveUnusedTypes requires --closed-world";
+    }
+
     // We're not changing the contents of any of the types, so we just round
     // trip them throgh GlobalTypeRewriter, which will put all the private types
     // in a single new rec group and leave out all the unused types.
diff --git a/src/passes/SignaturePruning.cpp b/src/passes/SignaturePruning.cpp
index 3244ee103..168ef8454 100644
--- a/src/passes/SignaturePruning.cpp
+++ b/src/passes/SignaturePruning.cpp
@@ -53,6 +53,10 @@ struct SignaturePruning : public Pass {
       return;
     }
 
+    if (!getPassOptions().closedWorld) {
+      Fatal() << "SignaturePruning requires --closed-world";
+    }
+
     if (!module->tables.empty()) {
       // When there are tables we must also take their types into account, which
       // would require us to take call_indirect, element segments, etc. into
diff --git a/src/passes/TypeMerging.cpp b/src/passes/TypeMerging.cpp
index d873152f2..c5028ee20 100644
--- a/src/passes/TypeMerging.cpp
+++ b/src/passes/TypeMerging.cpp
@@ -109,6 +109,10 @@ struct TypeMerging : public Pass {
       return;
     }
 
+    if (!getPassOptions().closedWorld) {
+      Fatal() << "TypeMerging requires --closed-world";
+    }
+
     // First, find all the cast types.
 
     ModuleUtils::ParallelFunctionAnalysis<ReferredTypes> analysis(
diff --git a/src/passes/TypeRefining.cpp b/src/passes/TypeRefining.cpp
index 6e2c96fce..0938f6d8e 100644
--- a/src/passes/TypeRefining.cpp
+++ b/src/passes/TypeRefining.cpp
@@ -103,9 +103,9 @@ struct TypeRefining : public Pass {
     if (!module->features.hasGC()) {
       return;
     }
-    if (getTypeSystem() != TypeSystem::Nominal &&
-        getTypeSystem() != TypeSystem::Isorecursive) {
-      Fatal() << "TypeRefining requires nominal/hybrid typing";
+
+    if (!getPassOptions().closedWorld) {
+      Fatal() << "TypeRefining requires --closed-world";
     }
 
     // Find and analyze struct operations inside each function.