FIR2IR: Unwrap intersection overrides for intersection types

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt

@@ -232,7 +232,19 @@ internal tailrec fun FirCallableSymbol<*>.unwrapCallRepresentative(root: FirCall
         val originalForTypeAlias = fir.originalConstructorIfTypeAlias
         if (originalForTypeAlias != null) return originalForTypeAlias.symbol.unwrapCallRepresentative(this)
     }
-    if (fir.isIntersectionOverride) return this
+
+    if (fir.isIntersectionOverride) {
+        // We've got IR declarations (fake overrides) for intersection overrides in classes, but not for intersection types
+        // interface A { fun foo() }
+        // interface B { fun foo() }
+        // interface C : A, B // for C.foo we've got an IR fake override
+        // for {A & B} we don't have such an IR declaration, so we're unwrapping it
+        if (fir is FirCallableMemberDeclaration && fir.dispatchReceiverType is ConeIntersectionType) {
+            return fir.baseForIntersectionOverride!!.symbol.unwrapCallRepresentative(this)
+        }
+
+        return this
+    }
 
     val overriddenSymbol = fir.originalForSubstitutionOverride?.takeIf {
         it.containingClass() == root.containingClass()

compiler/fir/fir2ir/tests-gen/org/jetbrains/kotlin/codegen/FirCompileKotlinAgainstKotlinTestGenerated.java

@@ -150,6 +150,11 @@ public class FirCompileKotlinAgainstKotlinTestGenerated extends AbstractFirCompi
         runTest("compiler/testData/compileKotlinAgainstKotlin/expectClassActualTypeAlias.kt");
     }
 
+    @TestMetadata("fakeOverridesForIntersectionTypes.kt")
+    public void testFakeOverridesForIntersectionTypes() throws Exception {
+        runTest("compiler/testData/compileKotlinAgainstKotlin/fakeOverridesForIntersectionTypes.kt");
+    }
+
     @TestMetadata("importCompanion.kt")
     public void testImportCompanion() throws Exception {
         runTest("compiler/testData/compileKotlinAgainstKotlin/importCompanion.kt");

compiler/testData/compileKotlinAgainstKotlin/fakeOverridesForIntersectionTypes.kt

@@ -0,0 +1,40 @@
+// TARGET_BACKEND: JVM
+// FILE: A.kt
+package a
+
+interface T {
+    var x: String
+}
+
+interface A : T {
+    override var x: String
+}
+
+interface B : T {
+    override var x: String
+}
+
+class C : A, B {
+    override var x: String = ""
+}
+
+class D : A, B {
+    override var x: String = ""
+}
+
+// FILE: B.kt
+import a.*
+
+fun foo(condition: Boolean): String {
+    val aAndB = if (condition) C() else D()
+    aAndB.x = "OK"
+
+    return aAndB.x
+}
+
+fun box(): String {
+    if (foo(true) != "OK") return "fail 1"
+    if (foo(false) != "OK") return "fail 2"
+
+    return "OK"
+}

compiler/tests-gen/org/jetbrains/kotlin/codegen/CompileKotlinAgainstKotlinTestGenerated.java

@@ -149,6 +149,11 @@ public class CompileKotlinAgainstKotlinTestGenerated extends AbstractCompileKotl
         runTest("compiler/testData/compileKotlinAgainstKotlin/expectClassActualTypeAlias.kt");
     }
 
+    @TestMetadata("fakeOverridesForIntersectionTypes.kt")
+    public void testFakeOverridesForIntersectionTypes() throws Exception {
+        runTest("compiler/testData/compileKotlinAgainstKotlin/fakeOverridesForIntersectionTypes.kt");
+    }
+
     @TestMetadata("importCompanion.kt")
     public void testImportCompanion() throws Exception {
         runTest("compiler/testData/compileKotlinAgainstKotlin/importCompanion.kt");

compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/IrCompileKotlinAgainstKotlinTestGenerated.java

@@ -150,6 +150,11 @@ public class IrCompileKotlinAgainstKotlinTestGenerated extends AbstractIrCompile
         runTest("compiler/testData/compileKotlinAgainstKotlin/expectClassActualTypeAlias.kt");
     }
 
+    @TestMetadata("fakeOverridesForIntersectionTypes.kt")
+    public void testFakeOverridesForIntersectionTypes() throws Exception {
+        runTest("compiler/testData/compileKotlinAgainstKotlin/fakeOverridesForIntersectionTypes.kt");
+    }
+
     @TestMetadata("importCompanion.kt")
     public void testImportCompanion() throws Exception {
         runTest("compiler/testData/compileKotlinAgainstKotlin/importCompanion.kt");

compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/JvmIrAgainstOldBoxTestGenerated.java

@@ -150,6 +150,11 @@ public class JvmIrAgainstOldBoxTestGenerated extends AbstractJvmIrAgainstOldBoxT
         runTest("compiler/testData/compileKotlinAgainstKotlin/expectClassActualTypeAlias.kt");
     }
 
+    @TestMetadata("fakeOverridesForIntersectionTypes.kt")
+    public void testFakeOverridesForIntersectionTypes() throws Exception {
+        runTest("compiler/testData/compileKotlinAgainstKotlin/fakeOverridesForIntersectionTypes.kt");
+    }
+
     @TestMetadata("importCompanion.kt")
     public void testImportCompanion() throws Exception {
         runTest("compiler/testData/compileKotlinAgainstKotlin/importCompanion.kt");

compiler/tests-gen/org/jetbrains/kotlin/codegen/ir/JvmOldAgainstIrBoxTestGenerated.java

@@ -150,6 +150,11 @@ public class JvmOldAgainstIrBoxTestGenerated extends AbstractJvmOldAgainstIrBoxT
         runTest("compiler/testData/compileKotlinAgainstKotlin/expectClassActualTypeAlias.kt");
     }
 
+    @TestMetadata("fakeOverridesForIntersectionTypes.kt")
+    public void testFakeOverridesForIntersectionTypes() throws Exception {
+        runTest("compiler/testData/compileKotlinAgainstKotlin/fakeOverridesForIntersectionTypes.kt");
+    }
+
     @TestMetadata("importCompanion.kt")
     public void testImportCompanion() throws Exception {
         runTest("compiler/testData/compileKotlinAgainstKotlin/importCompanion.kt");