Fix overridability rules for suspend functions

Treat suspend and non-suspend functions as conflicting

 #KT-15413 Fixed

compiler/testData/diagnostics/tests/coroutines/mixingSuspendability.kt

@@ -0,0 +1,6 @@
+interface AsyncVal { suspend fun getVal(): Int = 1}
+interface SyncVal { fun getVal(): Int = 1 }
+
+<!CONFLICTING_INHERITED_MEMBERS!>class MixSuspend<!> : AsyncVal, SyncVal {
+
+}

compiler/testData/diagnostics/tests/coroutines/mixingSuspendability.txt

@@ -0,0 +1,23 @@
+package
+
+public interface AsyncVal {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open suspend fun getVal(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class MixSuspend : AsyncVal, SyncVal {
+    public constructor MixSuspend()
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open suspend override /*1*/ /*fake_override*/ fun getVal(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface SyncVal {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun getVal(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/coroutines/suspendConflictsWithNoSuspend.kt

@@ -0,0 +1,15 @@
+// FILE: main.kt
+interface A {
+    <!CONFLICTING_OVERLOADS!>suspend fun foo()<!>
+    <!CONFLICTING_OVERLOADS!>fun foo()<!>
+}
+
+interface B : A {
+    <!CONFLICTING_OVERLOADS, CONFLICTING_OVERLOADS!>suspend override fun foo()<!> {
+
+    }
+
+    <!CONFLICTING_OVERLOADS, CONFLICTING_OVERLOADS!>override fun foo()<!> {
+
+    }
+}

compiler/testData/diagnostics/tests/coroutines/suspendConflictsWithNoSuspend.txt

@@ -0,0 +1,17 @@
+package
+
+public interface A {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Unit
+    public abstract suspend fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface B : A {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ fun foo(): kotlin.Unit
+    public open suspend override /*1*/ fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/coroutines/suspendOverridability.kt

@@ -0,0 +1,37 @@
+// FILE: main.kt
+interface A {
+    suspend fun foo()
+    fun bar()
+}
+
+interface B : A {
+    <!CONFLICTING_OVERLOADS!><!NOTHING_TO_OVERRIDE!>override<!> fun foo()<!> {
+
+    }
+
+    <!CONFLICTING_OVERLOADS!><!NOTHING_TO_OVERRIDE!>override<!> suspend fun bar()<!> {
+
+    }
+}
+
+interface C : A {
+    suspend override fun foo() {
+
+    }
+
+    override fun bar() {
+
+    }
+}
+
+<!ABSTRACT_MEMBER_NOT_IMPLEMENTED!>class D<!> : J {
+    suspend override fun foo() {
+
+    }
+}
+
+// FILE: J.java
+
+public interface J extends A {
+    Object foo(kotlin.coroutines.Continuation<kotlin.Unit> y);
+}

compiler/testData/diagnostics/tests/coroutines/suspendOverridability.txt

@@ -0,0 +1,44 @@
+package
+
+public interface A {
+    public abstract fun bar(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract suspend fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface B : A {
+    public open suspend fun bar(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface C : A {
+    public open override /*1*/ fun bar(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open suspend override /*1*/ fun foo(): 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 D : J {
+    public constructor D()
+    public abstract override /*1*/ /*fake_override*/ fun bar(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open suspend override /*1*/ fun foo(): kotlin.Unit
+    public abstract override /*1*/ /*fake_override*/ fun foo(/*0*/ y: kotlin.coroutines.Continuation!): kotlin.Any!
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface J : A {
+    public abstract override /*1*/ /*fake_override*/ fun bar(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract suspend override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public abstract fun foo(/*0*/ y: kotlin.coroutines.Continuation!): kotlin.Any!
+    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

@@ -4318,6 +4318,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("mixingSuspendability.kt")
+            public void testMixingSuspendability() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/coroutines/mixingSuspendability.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("noDefaultCoroutineImports.kt")
             public void testNoDefaultCoroutineImports() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/coroutines/noDefaultCoroutineImports.kt");
@@ -4336,6 +4342,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("suspendConflictsWithNoSuspend.kt")
+            public void testSuspendConflictsWithNoSuspend() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/coroutines/suspendConflictsWithNoSuspend.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("suspendCoroutineOrReturn.kt")
             public void testSuspendCoroutineOrReturn() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/coroutines/suspendCoroutineOrReturn.kt");
@@ -4354,6 +4366,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("suspendOverridability.kt")
+            public void testSuspendOverridability() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/coroutines/suspendOverridability.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("tryCatchLambda.kt")
             public void testTryCatchLambda() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/coroutines/tryCatchLambda.kt");

core/descriptors/src/org/jetbrains/kotlin/resolve/OverridingUtil.java

@@ -260,6 +260,11 @@ public class OverridingUtil {
             }
         }
 
+        if (superDescriptor instanceof FunctionDescriptor && subDescriptor instanceof FunctionDescriptor &&
+            ((FunctionDescriptor) superDescriptor).isSuspend() != ((FunctionDescriptor) subDescriptor).isSuspend()) {
+            return OverrideCompatibilityInfo.conflict("Incompatible suspendability");
+        }
+
         if (checkReturnType) {
             KotlinType superReturnType = superDescriptor.getReturnType();
             KotlinType subReturnType = subDescriptor.getReturnType();