8 files changed, 26 insertions, 10 deletions
diff --git a/src/ir/literal-utils.h b/src/ir/literal-utils.h
index 498085796..ce7da69cd 100644
--- a/src/ir/literal-utils.h
+++ b/src/ir/literal-utils.h
@@ -32,7 +32,7 @@ inline Expression* makeFromInt32(int32_t x, Type type, Module& wasm) {
 }
 
 inline bool canMakeZero(Type type) {
-  if (type.isRef() && !type.isNullable()) {
+  if (type.isNonNullable()) {
     return false;
   }
   if (type.isTuple()) {
diff --git a/src/ir/type-updating.cpp b/src/ir/type-updating.cpp
index 2dc60d2df..d91c5f385 100644
--- a/src/ir/type-updating.cpp
+++ b/src/ir/type-updating.cpp
@@ -34,7 +34,7 @@ void handleNonDefaultableLocals(Function* func, Module& wasm) {
   }
   bool hasNonNullable = false;
   for (auto type : func->vars) {
-    if (type.isRef() && !type.isNullable()) {
+    if (type.isNonNullable()) {
       hasNonNullable = true;
       break;
     }
@@ -52,7 +52,7 @@ void handleNonDefaultableLocals(Function* func, Module& wasm) {
       continue;
     }
     auto type = func->getLocalType(get->index);
-    if (type.isRef() && !type.isNullable()) {
+    if (type.isNonNullable()) {
       // The get should now return a nullable value, and a ref.as_non_null
       // fixes that up.
       get->type = Type(type.getHeapType(), Nullable);
@@ -74,7 +74,7 @@ void handleNonDefaultableLocals(Function* func, Module& wasm) {
       continue;
     }
     auto type = func->getLocalType(set->index);
-    if (type.isRef() && !type.isNullable()) {
+    if (type.isNonNullable()) {
       set->type = Type(type.getHeapType(), Nullable);
       *setp = builder.makeRefAs(RefAsNonNull, set);
     }
@@ -83,7 +83,7 @@ void handleNonDefaultableLocals(Function* func, Module& wasm) {
   // Rewrite the types of the function's vars (which we can do now, after we
   // are done using them to know which local.gets etc to fix).
   for (auto& type : func->vars) {
-    if (type.isRef() && !type.isNullable()) {
+    if (type.isNonNullable()) {
       type = Type(type.getHeapType(), Nullable);
     }
   }
diff --git a/src/passes/Inlining.cpp b/src/passes/Inlining.cpp
index 7c51e78cb..f4baf706d 100644
--- a/src/passes/Inlining.cpp
+++ b/src/passes/Inlining.cpp
@@ -293,7 +293,7 @@ doInlining(Module* module, Function* into, const InliningAction& action) {
   // zero-init value
   for (Index i = 0; i < from->vars.size(); i++) {
     auto type = from->vars[i];
-    if (type.isRef() && !type.isNullable()) {
+    if (type.isNonNullable()) {
       // Non-nullable locals do not need to be zeroed out. They have no zero
       // value, and by definition should not be used before being written to, so
       // any value we set here would not be observed anyhow.
diff --git a/src/passes/RedundantSetElimination.cpp b/src/passes/RedundantSetElimination.cpp
index ccf6e6ac2..f42119a92 100644
--- a/src/passes/RedundantSetElimination.cpp
+++ b/src/passes/RedundantSetElimination.cpp
@@ -190,7 +190,7 @@ struct RedundantSetElimination
             std::cout << "new param value for " << i << '\n';
 #endif
             start[i] = getUniqueValue();
-          } else if (type.isRef() && !type.isNullable()) {
+          } else if (type.isNonNullable()) {
 #ifdef RSE_DEBUG
             std::cout << "new unique value for non-nullable " << i << '\n';
 #endif
diff --git a/src/wasm-type.h b/src/wasm-type.h
index 12b4f3df7..ff1019e55 100644
--- a/src/wasm-type.h
+++ b/src/wasm-type.h
@@ -146,7 +146,15 @@ public:
   bool isRef() const;
   bool isFunction() const;
   bool isData() const;
+  // Checks whether a type is a reference and is nullable. This returns false
+  // for a value that is not a reference, that is, for which nullability is
+  // irrelevant.
   bool isNullable() const;
+  // Checks whether a type is a reference and is non-nullable. This returns
+  // false for a value that is not a reference, that is, for which nullability
+  // is irrelevant. (For that reason, this is only the negation of isNullable()
+  // on references, but both return false on non-references.)
+  bool isNonNullable() const;
   bool isRtt() const;
   bool isStruct() const;
   bool isArray() const;
diff --git a/src/wasm/literal.cpp b/src/wasm/literal.cpp
index 4ff354e56..151ea83e5 100644
--- a/src/wasm/literal.cpp
+++ b/src/wasm/literal.cpp
@@ -34,7 +34,7 @@ Literal::Literal(Type type) : type(type) {
     // i31ref is special in that it is non-nullable, so we construct with zero
     i32 = 0;
   } else {
-    assert(type != Type::unreachable && (!type.isRef() || type.isNullable()));
+    assert(type != Type::unreachable && !type.isNonNullable());
     if (isData()) {
       new (&gcData) std::shared_ptr<GCData>();
     } else if (type.isRtt()) {
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 43ab509a8..f58c4f783 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -2572,7 +2572,7 @@ void WasmBinaryBuilder::pushExpression(Expression* curr) {
     std::vector<Type> finalTypes;
     if (!wasm.features.hasGCNNLocals()) {
       for (auto t : type) {
-        if (t.isRef() && !t.isNullable()) {
+        if (t.isNonNullable()) {
           t = Type(t.getHeapType(), Nullable);
         }
         finalTypes.push_back(t);
diff --git a/src/wasm/wasm-type.cpp b/src/wasm/wasm-type.cpp
index eb1bd14b1..d4f38cc2c 100644
--- a/src/wasm/wasm-type.cpp
+++ b/src/wasm/wasm-type.cpp
@@ -845,6 +845,14 @@ bool Type::isNullable() const {
   }
 }
 
+bool Type::isNonNullable() const {
+  if (isRef()) {
+    return !isNullable();
+  } else {
+    return false;
+  }
+}
+
 bool Type::isRtt() const {
   if (isBasic()) {
     return false;
@@ -869,7 +877,7 @@ bool Type::isDefaultable() const {
     }
     return true;
   }
-  return isConcrete() && (!isRef() || isNullable()) && !isRtt();
+  return isConcrete() && !isNonNullable() && !isRtt();
 }
 
 Nullability Type::getNullability() const {