Overridden functions using default arguments in recursive call are no more considered tail recursive #KT-4285 Fixed

compiler/frontend/src/org/jetbrains/kotlin/cfg/ControlFlowInformationProvider.java

@@ -957,6 +957,9 @@ public class ControlFlowInformationProvider {
                         // is this a recursive call?
                         CallableDescriptor functionDescriptor = resolvedCall.getResultingDescriptor();
                         if (!functionDescriptor.getOriginal().equals(subroutineDescriptor)) return;
+                        // Overridden functions using default arguments at tail call are not included: KT-4285
+                        if (resolvedCall.getCall().getValueArguments().size() != functionDescriptor.getValueParameters().size() &&
+                            !functionDescriptor.getOverriddenDescriptors().isEmpty()) return;
 
                         KtElement element = callInstruction.getElement();
                         //noinspection unchecked

compiler/testData/codegen/box/diagnostics/functions/tailRecursion/defaultArgsOverridden.kt

@@ -0,0 +1,11 @@
+open class A {
+    open fun foo(s: String = "OK") = s
+}
+
+class B : A() {
+    <!NO_TAIL_CALLS_FOUND!>override tailrec fun foo(s: String): String<!> {
+        return if (s == "OK") s else foo()
+    }
+}
+
+fun box() = B().foo("FAIL")

compiler/testData/codegen/box/diagnostics/functions/tailRecursion/defaultArgsOverridden.txt

@@ -0,0 +1,19 @@
+package
+
+public fun box(): kotlin.String
+
+public open class A {
+    public constructor A()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun foo(/*0*/ s: kotlin.String = ...): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class B : A {
+    public constructor B()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open tailrec override /*1*/ fun foo(/*0*/ s: kotlin.String = ...): kotlin.String
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/tailRecOverridden.kt

@@ -0,0 +1,32 @@
+// See also KT-4285
+open class A {
+    open fun foo(x: Int = 0) {}
+
+    open fun gav(y: Int = 1, z: Int = 2) {}
+}
+
+class B: A() {
+    <!NO_TAIL_CALLS_FOUND!>tailrec override fun foo(x: Int)<!> {
+        foo()
+    }
+
+    <!NO_TAIL_CALLS_FOUND!>tailrec override fun gav(y: Int, z: Int)<!> {
+        gav(y)
+    }
+
+    tailrec fun bar(y: Double): Double = bar(y * 2.0)
+}
+
+class C: A() {
+    tailrec override fun foo(x: Int) {
+        foo(0)
+    }
+
+    tailrec override fun gav(y: Int, z: Int) {
+        gav(y - 1, z - 1)
+    }
+
+    tailrec fun bar(<!UNUSED_PARAMETER!>y<!>: Int = 1, z: Int = 2) {
+        bar(z)
+    }
+}

compiler/testData/diagnostics/tests/tailRecOverridden.txt

@@ -0,0 +1,30 @@
+package
+
+public open class A {
+    public constructor A()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun foo(/*0*/ x: kotlin.Int = ...): kotlin.Unit
+    public open fun gav(/*0*/ y: kotlin.Int = ..., /*1*/ z: kotlin.Int = ...): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class B : A {
+    public constructor B()
+    public final tailrec fun bar(/*0*/ y: kotlin.Double): kotlin.Double
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open tailrec override /*1*/ fun foo(/*0*/ x: kotlin.Int = ...): kotlin.Unit
+    public open tailrec override /*1*/ fun gav(/*0*/ y: kotlin.Int = ..., /*1*/ z: kotlin.Int = ...): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class C : A {
+    public constructor C()
+    public final tailrec fun bar(/*0*/ y: kotlin.Int = ..., /*1*/ z: kotlin.Int = ...): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open tailrec override /*1*/ fun foo(/*0*/ x: kotlin.Int = ...): kotlin.Unit
+    public open tailrec override /*1*/ fun gav(/*0*/ y: kotlin.Int = ..., /*1*/ z: kotlin.Int = ...): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -679,6 +679,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
             doTest(fileName);
         }
 
+        @TestMetadata("tailRecOverridden.kt")
+        public void testTailRecOverridden() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/tailRecOverridden.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("TraitOverrideObjectMethods.kt")
         public void testTraitOverrideObjectMethods() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/TraitOverrideObjectMethods.kt");
@@ -19772,6 +19778,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("defaultArgsOverridden.kt")
+                public void testDefaultArgsOverridden() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/diagnostics/functions/tailRecursion/defaultArgsOverridden.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("extensionTailCall.kt")
                 public void testExtensionTailCall() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/diagnostics/functions/tailRecursion/extensionTailCall.kt");

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -5135,6 +5135,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
                     doTest(fileName);
                 }
 
+                @TestMetadata("defaultArgsOverridden.kt")
+                public void testDefaultArgsOverridden() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/diagnostics/functions/tailRecursion/defaultArgsOverridden.kt");
+                    doTest(fileName);
+                }
+
                 @TestMetadata("extensionTailCall.kt")
                 public void testExtensionTailCall() throws Exception {
                     String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/diagnostics/functions/tailRecursion/extensionTailCall.kt");