Compare return types when structurally comparing callables

compiler/frontend/src/org/jetbrains/jet/lang/resolve/DescriptorEquivalenceForOverrides.kt

@@ -85,8 +85,8 @@ object DescriptorEquivalenceForOverrides {
             areTypeParametersEquivalent(d1, d2, {x, y -> x == a && y == b})
         }
 
-        return overridingUtil.isOverridableBy(a, b).getResult() == OverrideCompatibilityInfo.Result.OVERRIDABLE
-                && overridingUtil.isOverridableBy(b, a).getResult() == OverrideCompatibilityInfo.Result.OVERRIDABLE
+        return overridingUtil.isOverridableByIncludingReturnType(a, b).getResult() == OverrideCompatibilityInfo.Result.OVERRIDABLE
+                && overridingUtil.isOverridableByIncludingReturnType(b, a).getResult() == OverrideCompatibilityInfo.Result.OVERRIDABLE
 
     }
 

compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInReturnType.kt

@@ -0,0 +1,36 @@
+// !DIAGNOSTICS: -UNNECESSARY_SAFE_CALL
+
+// MODULE: m1
+// FILE: a.kt
+package p
+
+public trait B<T> {
+    public fun foo(): T
+}
+
+// MODULE: m2(m1)
+// FILE: b.kt
+package p
+
+public trait C<X> : B<X> {
+    override fun foo(): X
+
+}
+
+// MODULE: m3
+// FILE: b.kt
+package p
+
+public trait B<T> {
+    public fun foo(): T
+}
+
+// MODULE: m4(m3, m2)
+// FILE: c.kt
+import p.*
+
+fun test(b: B<String>?) {
+    if (b is C) {
+        <!DEBUG_INFO_AUTOCAST!>b<!>?.foo()
+    }
+}

compiler/testData/diagnostics/tests/multimodule/duplicateMethod/covariantReturnTypes.kt

@@ -0,0 +1,36 @@
+// !DIAGNOSTICS: -UNNECESSARY_SAFE_CALL
+
+// MODULE: m1
+// FILE: a.kt
+package p
+
+public trait B {
+    public fun getParent(): B?
+}
+
+// MODULE: m2(m1)
+// FILE: b.kt
+package p
+
+public trait C : B {
+    override fun getParent(): B?
+
+}
+
+// MODULE: m3
+// FILE: b.kt
+package p
+
+public trait B {
+    public fun getParent(): Any?
+}
+
+// MODULE: m4(m3, m2)
+// FILE: c.kt
+import p.*
+
+fun test(b: B?) {
+    if (b is C) {
+        b?.<!OVERLOAD_RESOLUTION_AMBIGUITY!>getParent<!>()
+    }
+}

compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differentReturnTypes.kt

@@ -31,6 +31,6 @@ import p.*
 
 fun test(b: B?) {
     if (b is C) {
-        <!DEBUG_INFO_AUTOCAST!>b<!>?.getParent()
+        b?.<!OVERLOAD_RESOLUTION_AMBIGUITY!>getParent<!>()
     }
 }

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -4797,11 +4797,21 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     doTest("compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInParamsNameMismatch.kt");
                 }
                 
+                @TestMetadata("classGenericsInReturnType.kt")
+                public void testClassGenericsInReturnType() throws Exception {
+                    doTest("compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classGenericsInReturnType.kt");
+                }
+                
                 @TestMetadata("classVsFunctionGenericsInParamsMismatch.kt")
                 public void testClassVsFunctionGenericsInParamsMismatch() throws Exception {
                     doTest("compiler/testData/diagnostics/tests/multimodule/duplicateMethod/classVsFunctionGenericsInParamsMismatch.kt");
                 }
                 
+                @TestMetadata("covariantReturnTypes.kt")
+                public void testCovariantReturnTypes() throws Exception {
+                    doTest("compiler/testData/diagnostics/tests/multimodule/duplicateMethod/covariantReturnTypes.kt");
+                }
+                
                 @TestMetadata("differenceInParamNames.kt")
                 public void testDifferenceInParamNames() throws Exception {
                     doTest("compiler/testData/diagnostics/tests/multimodule/duplicateMethod/differenceInParamNames.kt");