JS/RTTI: use typeof f === 'function' to check function instance

js/js.tests/test/org/jetbrains/kotlin/js/test/semantics/CastTestGenerated.java

@@ -41,6 +41,12 @@ public class CastTestGenerated extends AbstractCastTest {
         doTest(fileName);
     }
 
+    @TestMetadata("castToFunction.kt")
+    public void testCastToFunction() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("js/js.translator/testData/expression/cast/cases/castToFunction.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("castToGenericType.kt")
     public void testCastToGenericType() throws Exception {
         String fileName = JetTestUtils.navigationMetadata("js/js.translator/testData/expression/cast/cases/castToGenericType.kt");

js/js.translator/src/org/jetbrains/kotlin/js/translate/expression/PatternTranslator.java

@@ -22,6 +22,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.KtNodeTypes;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
+import org.jetbrains.kotlin.JetNodeTypes;
 import org.jetbrains.kotlin.descriptors.CallableDescriptor;
 import org.jetbrains.kotlin.descriptors.ClassDescriptor;
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptor;
@@ -43,6 +44,9 @@ import org.jetbrains.kotlin.psi.KtTypeReference;
 import org.jetbrains.kotlin.resolve.DescriptorUtils;
 import org.jetbrains.kotlin.types.KotlinType;
 
+import static org.jetbrains.kotlin.builtins.KotlinBuiltIns.isAnyOrNullableAny;
+import static org.jetbrains.kotlin.builtins.KotlinBuiltIns.isFunctionOrExtensionFunctionType;
+import static org.jetbrains.kotlin.js.descriptorUtils.DescriptorUtilsPackage.getNameIfStandardType;
 import static org.jetbrains.kotlin.js.translate.utils.JsAstUtils.equality;
 import static org.jetbrains.kotlin.js.translate.utils.JsAstUtils.negated;
 import static org.jetbrains.kotlin.psi.KtPsiUtil.findChildByType;
@@ -125,7 +129,9 @@ public final class PatternTranslator extends AbstractTranslator {
 
     @NotNull
     private JsExpression doGetIsTypeCheckCallable(@NotNull KotlinType type) {
-        if (KotlinBuiltIns.isAnyOrNullableAny(type)) return namer().isAny();
+        if (isAnyOrNullableAny(type)) return namer().isAny();
+
+        if (isFunctionOrExtensionFunctionType(type)) return namer().isTypeOf(program().getStringLiteral("function"));
 
         JsExpression builtinCheck = getIsTypeCheckCallableForBuiltin(type);
         if (builtinCheck != null) return builtinCheck;

js/js.translator/testData/expression/cast/cases/castToFunction.kt

@@ -0,0 +1,13 @@
+package foo
+
+fun test(fn: Any?): Function0<Int> =
+        fn as Function0<Int>
+
+fun box(): String {
+    val get11: Any? = { 11 }
+    assertEquals(11, test(get11)(), "get11")
+    failsClassCast("null") { test(null)() }
+    failsClassCast("object {}") { test(object {})() }
+
+    return "OK"
+}