[dart2wasm] Make is/as-checker helpers be used even if operand type is not InterfaceType

Right now the optimized is/as-checkers are only used when the operand
type is an [InterfaceType]. That means they don't get used for e.g.

   dynamic obj;
   T obj2;
   obj is String
   obj2 is List<dynamic>;

But we can use the is/as-checkers on any operand type as long as the
type we test against is an [InterfaceType] without arguments or where
the type arguments are equivalent to defaults-to-bounds (i.e. require
no checking).

Issue #55516

Change-Id: I1adff52b3d880c37c344edb0c42ffd454d7b1164
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/371124
Reviewed-by: Ömer Ağacan <[email protected]>
Commit-Queue: Martin Kustermann <[email protected]>

Author: mkustermann

pkg/dart2wasm/lib/types.dart

@@ -484,15 +484,14 @@ class Types {
   InterfaceType? _canUseTypeCheckHelper(
       DartType testedAgainstType, DartType operandType) {
     // The is/as check helpers are for cid-range checks of interface types.
-    if (testedAgainstType is! InterfaceType || operandType is! InterfaceType) {
-      return null;
-    }
+    if (testedAgainstType is! InterfaceType) return null;
 
     if (_hasOnlyDefaultTypeArguments(testedAgainstType)) {
       return testedAgainstType;
     }
 
-    if (_staticTypesEnsureTypeArgumentsMatch(testedAgainstType, operandType)) {
+    if (operandType is InterfaceType &&
+        _staticTypesEnsureTypeArgumentsMatch(testedAgainstType, operandType)) {
       // We only need to check whether the nullability and the class itself fits
       // (the [testedAgainstType] arguments are guaranteed to fit statically)
       final parameters = testedAgainstType.classNode.typeParameters;