Fix abstract method error: implement arity in function references

compiler/backend/src/org/jetbrains/kotlin/codegen/ClosureCodegen.java

@@ -34,7 +34,6 @@ import org.jetbrains.kotlin.load.java.JvmAbi;
 import org.jetbrains.kotlin.psi.JetElement;
 import org.jetbrains.kotlin.resolve.BindingContext;
 import org.jetbrains.kotlin.resolve.DescriptorUtils;
-import org.jetbrains.kotlin.resolve.jvm.AsmTypes;
 import org.jetbrains.kotlin.types.JetType;
 import org.jetbrains.kotlin.types.expressions.OperatorConventions;
 import org.jetbrains.org.objectweb.asm.MethodVisitor;
@@ -337,8 +336,11 @@ public class ClosureCodegen extends MemberCodegen<JetElement> {
 
             iv.load(0, superClassAsmType);
 
-            if (superClassAsmType.equals(AsmTypes.LAMBDA)) {
-                iv.iconst(funDescriptor.getValueParameters().size());
+            if (superClassAsmType.equals(LAMBDA) || superClassAsmType.equals(FUNCTION_REFERENCE)) {
+                int arity = funDescriptor.getValueParameters().size();
+                if (funDescriptor.getExtensionReceiverParameter() != null) arity++;
+                if (funDescriptor.getDispatchReceiverParameter() != null) arity++;
+                iv.iconst(arity);
                 iv.invokespecial(superClassAsmType.getInternalName(), "<init>", "(I)V", false);
             }
             else {

compiler/testData/codegen/boxWithStdlib/callableReference/function/getArityViaFunctionImpl.kt

@@ -0,0 +1,30 @@
+import kotlin.test.assertEquals
+import kotlin.jvm.internal.FunctionImpl
+
+fun test(f: Function<*>, arity: Int) {
+    assertEquals(arity, (f as FunctionImpl).getArity())
+}
+
+fun foo(s: String, i: Int) {}
+class A {
+    fun bar(s: String, i: Int) {}
+}
+fun Double.baz(s: String, i: Int) {}
+
+fun box(): String {
+    test(::foo, 2)
+    test(A::bar, 3)
+    test(Double::baz, 3)
+
+    test(::box, 0)
+
+    fun local(x: Int) {}
+    test(::local, 1)
+
+    test(fun(s: String) = s, 1)
+    test(fun(){}, 0)
+    test({}, 0)
+    test({x: Int -> x}, 1)
+
+    return "OK"
+}

compiler/tests/org/jetbrains/kotlin/codegen/generated/BlackBoxWithStdlibCodegenTestGenerated.java

@@ -483,6 +483,12 @@ public class BlackBoxWithStdlibCodegenTestGenerated extends AbstractBlackBoxCode
                 doTestWithStdlib(fileName);
             }
 
+            @TestMetadata("getArityViaFunctionImpl.kt")
+            public void testGetArityViaFunctionImpl() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/callableReference/function/getArityViaFunctionImpl.kt");
+                doTestWithStdlib(fileName);
+            }
+
             @TestMetadata("innerConstructorFromClass.kt")
             public void testInnerConstructorFromClass() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/callableReference/function/innerConstructorFromClass.kt");

core/runtime.jvm/src/kotlin/jvm/internal/FunctionReference.java

@@ -24,4 +24,14 @@ public abstract class FunctionReference
                    KMemberFunction,
                    KTopLevelExtensionFunction,
                    KLocalFunction {
+    private final int arity;
+
+    public FunctionReference(int arity) {
+        this.arity = arity;
+    }
+
+    @Override
+    public int getArity() {
+        return arity;
+    }
 }