diff --git a/pkg/_js_interop_checks/lib/src/transformations/js_util_optimizer.dart b/pkg/_js_interop_checks/lib/src/transformations/js_util_optimizer.dart
index c8cd9e8ea7c..cad1e2525df 100644
--- a/pkg/_js_interop_checks/lib/src/transformations/js_util_optimizer.dart
+++ b/pkg/_js_interop_checks/lib/src/transformations/js_util_optimizer.dart
@@ -671,6 +671,7 @@ class JsUtilOptimizer extends Transformer {
   /// Returns whether the given DartType is guaranteed to be not a function
   /// and therefore allowed to interop with JS.
   bool _allowedInteropType(DartType type) {
+    type = type.extensionTypeErasure;
     if (type is InterfaceType) {
       return type.classNode != _coreTypes.functionClass &&
           type.classNode != _coreTypes.objectClass;
diff --git a/pkg/front_end/test/spell_checking_list_tests.txt b/pkg/front_end/test/spell_checking_list_tests.txt
index 32567bde15e..6c0af482383 100644
--- a/pkg/front_end/test/spell_checking_list_tests.txt
+++ b/pkg/front_end/test/spell_checking_list_tests.txt
@@ -113,6 +113,7 @@ builddir
 bulkcompile
 busy
 busywait
+bx
 bye
 c's
 ca
diff --git a/pkg/front_end/testcases/dart2js/extension_types/external.dart.strong.transformed.expect b/pkg/front_end/testcases/dart2js/extension_types/external.dart.strong.transformed.expect
index fa5a49dcc1f..6439e61aa93 100644
--- a/pkg/front_end/testcases/dart2js/extension_types/external.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/dart2js/extension_types/external.dart.strong.transformed.expect
@@ -84,14 +84,14 @@ static method method(self::A a) → void {
   a = js_2::getProperty<self::A>(b1, "field");
   js_2::setProperty<self::A>(b1, "field", a);
   a = js_2::_callMethodUnchecked0<self::A>(b1, "method");
-  b2 = js_2::callMethod<self::B% /* = self::A */>(b2, "genericMethod", <dynamic>[b2]);
+  b2 = js_2::_callMethodUnchecked1<self::B% /* = self::A */>(b2, "genericMethod", b2);
   b1 = js_2::getProperty<self::B /* = self::A */>(b2, "getter");
   js_2::setProperty<self::B /* = self::A */>(b1, "setter", b2);
   js_2::setProperty<self::B /* = self::A */>(b1, "property", js_2::getProperty<self::B /* = self::A */>(b2, "property"));
   a = js_2::getProperty<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticField");
   js_2::setProperty<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticField", a);
   a = js_2::_callMethodUnchecked0<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticMethod");
-  b2 = js_2::callMethod<self::B% /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGenericMethod", <dynamic>[b2]);
+  b2 = js_2::_callMethodUnchecked1<self::B% /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGenericMethod", b2);
   b1 = js_2::getProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGetter");
   js_2::setProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticSetter", b2);
   js_2::setProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticProperty", js_2::getProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticProperty"));
diff --git a/pkg/front_end/testcases/dart2js/extension_types/external.dart.weak.transformed.expect b/pkg/front_end/testcases/dart2js/extension_types/external.dart.weak.transformed.expect
index fa5a49dcc1f..6439e61aa93 100644
--- a/pkg/front_end/testcases/dart2js/extension_types/external.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/dart2js/extension_types/external.dart.weak.transformed.expect
@@ -84,14 +84,14 @@ static method method(self::A a) → void {
   a = js_2::getProperty<self::A>(b1, "field");
   js_2::setProperty<self::A>(b1, "field", a);
   a = js_2::_callMethodUnchecked0<self::A>(b1, "method");
-  b2 = js_2::callMethod<self::B% /* = self::A */>(b2, "genericMethod", <dynamic>[b2]);
+  b2 = js_2::_callMethodUnchecked1<self::B% /* = self::A */>(b2, "genericMethod", b2);
   b1 = js_2::getProperty<self::B /* = self::A */>(b2, "getter");
   js_2::setProperty<self::B /* = self::A */>(b1, "setter", b2);
   js_2::setProperty<self::B /* = self::A */>(b1, "property", js_2::getProperty<self::B /* = self::A */>(b2, "property"));
   a = js_2::getProperty<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticField");
   js_2::setProperty<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticField", a);
   a = js_2::_callMethodUnchecked0<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticMethod");
-  b2 = js_2::callMethod<self::B% /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGenericMethod", <dynamic>[b2]);
+  b2 = js_2::_callMethodUnchecked1<self::B% /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGenericMethod", b2);
   b1 = js_2::getProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGetter");
   js_2::setProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticSetter", b2);
   js_2::setProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticProperty", js_2::getProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticProperty"));
diff --git a/pkg/front_end/testcases/dartdevc/extension_types/external.dart.strong.transformed.expect b/pkg/front_end/testcases/dartdevc/extension_types/external.dart.strong.transformed.expect
index fa5a49dcc1f..6439e61aa93 100644
--- a/pkg/front_end/testcases/dartdevc/extension_types/external.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/dartdevc/extension_types/external.dart.strong.transformed.expect
@@ -84,14 +84,14 @@ static method method(self::A a) → void {
   a = js_2::getProperty<self::A>(b1, "field");
   js_2::setProperty<self::A>(b1, "field", a);
   a = js_2::_callMethodUnchecked0<self::A>(b1, "method");
-  b2 = js_2::callMethod<self::B% /* = self::A */>(b2, "genericMethod", <dynamic>[b2]);
+  b2 = js_2::_callMethodUnchecked1<self::B% /* = self::A */>(b2, "genericMethod", b2);
   b1 = js_2::getProperty<self::B /* = self::A */>(b2, "getter");
   js_2::setProperty<self::B /* = self::A */>(b1, "setter", b2);
   js_2::setProperty<self::B /* = self::A */>(b1, "property", js_2::getProperty<self::B /* = self::A */>(b2, "property"));
   a = js_2::getProperty<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticField");
   js_2::setProperty<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticField", a);
   a = js_2::_callMethodUnchecked0<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticMethod");
-  b2 = js_2::callMethod<self::B% /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGenericMethod", <dynamic>[b2]);
+  b2 = js_2::_callMethodUnchecked1<self::B% /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGenericMethod", b2);
   b1 = js_2::getProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGetter");
   js_2::setProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticSetter", b2);
   js_2::setProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticProperty", js_2::getProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticProperty"));
diff --git a/pkg/front_end/testcases/dartdevc/extension_types/external.dart.weak.transformed.expect b/pkg/front_end/testcases/dartdevc/extension_types/external.dart.weak.transformed.expect
index fa5a49dcc1f..6439e61aa93 100644
--- a/pkg/front_end/testcases/dartdevc/extension_types/external.dart.weak.transformed.expect
+++ b/pkg/front_end/testcases/dartdevc/extension_types/external.dart.weak.transformed.expect
@@ -84,14 +84,14 @@ static method method(self::A a) → void {
   a = js_2::getProperty<self::A>(b1, "field");
   js_2::setProperty<self::A>(b1, "field", a);
   a = js_2::_callMethodUnchecked0<self::A>(b1, "method");
-  b2 = js_2::callMethod<self::B% /* = self::A */>(b2, "genericMethod", <dynamic>[b2]);
+  b2 = js_2::_callMethodUnchecked1<self::B% /* = self::A */>(b2, "genericMethod", b2);
   b1 = js_2::getProperty<self::B /* = self::A */>(b2, "getter");
   js_2::setProperty<self::B /* = self::A */>(b1, "setter", b2);
   js_2::setProperty<self::B /* = self::A */>(b1, "property", js_2::getProperty<self::B /* = self::A */>(b2, "property"));
   a = js_2::getProperty<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticField");
   js_2::setProperty<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticField", a);
   a = js_2::_callMethodUnchecked0<self::A>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticMethod");
-  b2 = js_2::callMethod<self::B% /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGenericMethod", <dynamic>[b2]);
+  b2 = js_2::_callMethodUnchecked1<self::B% /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGenericMethod", b2);
   b1 = js_2::getProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticGetter");
   js_2::setProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticSetter", b2);
   js_2::setProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticProperty", js_2::getProperty<self::B /* = self::A */>(js_2::_getPropertyTrustType<core::Object>(_js2::staticInteropGlobalContext, "B"), "staticProperty"));