Support specialized function types in element segments (#4109)

Before this, the element segments would be printed as having type
funcref, and then if their table had a specialized type, the element
type would not be a subtype of the table and validation would fail.

1 files changed, 5 insertions, 8 deletions

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index ab229f111..ee3c1a6fa 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -584,11 +584,8 @@ void WasmBinaryWriter::writeElementSegments() {
     Index tableIdx = 0;
 
     bool isPassive = segment->table.isNull();
-    // if all items are ref.func, we can use the shorter form.
-    bool usesExpressions =
-      std::any_of(segment->data.begin(),
-                  segment->data.end(),
-                  [](Expression* curr) { return !curr->is<RefFunc>(); });
+    // If the segment is MVP, we can use the shorter form.
+    bool usesExpressions = TableUtils::usesExpressions(segment.get(), wasm);
 
     bool hasTableIndex = false;
     if (!isPassive) {
@@ -620,7 +617,7 @@ void WasmBinaryWriter::writeElementSegments() {
         // elemType
         writeType(segment->type);
       } else {
-        // elemKind funcref
+        // MVP elemKind of funcref
         o << U32LEB(0);
       }
     }
@@ -2864,12 +2861,12 @@ void WasmBinaryBuilder::readElementSegments() {
       if (usesExpressions) {
         segment->type = getType();
         if (!segment->type.isFunction()) {
-          throwError("Invalid type for an element segment");
+          throwError("Invalid type for a usesExpressions element segment");
         }
       } else {
         auto elemKind = getU32LEB();
         if (elemKind != 0x0) {
-          throwError("Only funcref elem kinds are valid.");
+          throwError("Invalid kind (!= funcref(0)) since !usesExpressions.");
         }
       }
     }