[dart2wasm] Don't add dispatch table entries for _WasmBase methods

Some of the `_WasmBase` subtypes are represented as unboxed Wasm values
and cannot be used as virutal method receivers.

Previously we added methods for `_WasmBase` subtypes to the dispatch
table and considered those types as receivers in dynamic invocations.
This causes bad code generation as these types do not represent Dart
objects.

With this CL we don't add `_WasmBase` subtype methods to dispatch
tables, and in dynamic invocations we don't consider `_WasmBase` types
as receivers.

New passing tests:

- language/variable/inference_captured_variable_test
- lib/typed_data/typed_data_list_test

Change-Id: I4f4145db12652133aa55dcce75acad72bb4ec48b
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/268761
Reviewed-by: Aske Simon Christensen <[email protected]>
Commit-Queue: Ömer Ağacan <[email protected]>

Author: osa1

pkg/dart2wasm/lib/dispatch_table.dart

@@ -235,9 +235,14 @@ class DispatchTable {
         ? 1
         : 0;
 
-    bool calledDynamically =
+    // _WasmBase and its subclass methods cannot be called dynamically
+    final cls = member.enclosingClass;
+    final isWasmType = cls != null && translator.isWasmType(cls);
+
+    final calledDynamically = !isWasmType &&
         translator.dynamics.maybeCalledDynamically(member, metadata);
-    var selector = selectorInfo.putIfAbsent(
+
+    final selector = selectorInfo.putIfAbsent(
         selectorId,
         () => SelectorInfo(
             translator,
@@ -277,11 +282,16 @@ class DispatchTable {
 
   void build() {
     // Collect class/selector combinations
+
+    // Maps class IDs to selector IDs of the class
     List<List<int>> selectorsInClass = [];
+
     for (ClassInfo info in translator.classes) {
       List<int> selectorIds = [];
       ClassInfo? superInfo = info.superInfo;
-      if (superInfo != null) {
+
+      // _WasmBase does not inherit from Object
+      if (superInfo != null && info.cls != translator.wasmTypesBaseClass) {
         int superId = superInfo.classId;
         selectorIds = List.of(selectorsInClass[superId]);
         for (int selectorId in selectorIds) {

pkg/dart2wasm/lib/translator.dart

@@ -540,7 +540,8 @@ class Translator {
     return false;
   }
 
-  bool isWasmType(Class cls) => _hasSuperclass(cls, wasmTypesBaseClass);
+  bool isWasmType(Class cls) =>
+      cls == wasmTypesBaseClass || _hasSuperclass(cls, wasmTypesBaseClass);
 
   bool isFfiCompound(Class cls) => _hasSuperclass(cls, ffiCompoundClass);
 

sdk/lib/wasm/wasm_types.dart

@@ -11,6 +11,7 @@ library dart.wasm;
 //   parameter/return of static functions. No other uses of the types are valid.
 // - They are not assignable to or from any ordinary Dart types.
 // - The integer and float types can't be nullable.
+// - Their instance methods cannot be called virtually or dynamically.
 //
 // TODO(askesc): Give an error message if any of these constraints are violated.