From 77fcc0d010444ae2ec18bb98b1e18e028367092c Mon Sep 17 00:00:00 2001
From: SvyatoslavScherbina <Svyatoslav.Scherbina@jetbrains.com>
Date: Mon, 2 Nov 2020 20:52:45 +0300
Subject: [PATCH] Fix type safe barrier bridges for generics with non-trivial
 upper bound

---
 .../kotlin/backend/konan/llvm/IrToBitcode.kt  |  2 +-
 .../backend/konan/lower/BridgesBuilding.kt    |  7 ++-
 .../konan/lower/TypeOperatorLowering.kt       | 41 +++++++++--------
 .../backend.native/tests/build.gradle         |  4 ++
 .../tests/codegen/bridges/specialGeneric.kt   | 44 +++++++++++++++++++
 5 files changed, 77 insertions(+), 21 deletions(-)
 create mode 100644 kotlin-native/backend.native/tests/codegen/bridges/specialGeneric.kt

diff --git a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt
index 3f102561879..0832299a239 100644
--- a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt
+++ b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/llvm/IrToBitcode.kt
@@ -1459,7 +1459,7 @@ internal class CodeGeneratorVisitor(val context: Context, val lifetimes: Map<IrE
         } else {
             // E.g. when generating type operation with reified type parameter in the original body of inline function.
             kTrue
-            // TODO: this code should be unreachable, however [BridgesBuilding] generates IR with such type checks.
+            // TODO: this code should be unreachable, recheck.
         }
         functionGenerationContext.br(bbExit)
         val bbInstanceOfResult = functionGenerationContext.currentBlock
diff --git a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/BridgesBuilding.kt b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/BridgesBuilding.kt
index e5caa09c3e7..be643ec4c34 100644
--- a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/BridgesBuilding.kt
+++ b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/BridgesBuilding.kt
@@ -207,7 +207,12 @@ private fun IrBlockBodyBuilder.buildTypeSafeBarrier(function: IrFunction,
     for (i in valueParameters.indices) {
         if (!typeSafeBarrierDescription.checkParameter(i))
             continue
-        val type = originalValueParameters[i].type
+
+        val type = originalValueParameters[i].type.erasureForTypeOperation()
+        // Note: erasing to single type is not entirely correct if type parameter has multiple upper bounds.
+        // In this case the compiler could generate multiple type checks, one for each upper bound.
+        // But let's keep it simple here for now; JVM backend doesn't do this anyway.
+
         if (!type.isNullableAny()) {
             +returnIfBadType(irGet(valueParameters[i]), type,
                     if (typeSafeBarrierDescription == SpecialGenericSignatures.TypeSafeBarrierDescription.MAP_GET_OR_DEFAULT)
diff --git a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/TypeOperatorLowering.kt b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/TypeOperatorLowering.kt
index f33aad224d5..3aea32306ae 100644
--- a/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/TypeOperatorLowering.kt
+++ b/kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/TypeOperatorLowering.kt
@@ -25,30 +25,33 @@ import org.jetbrains.kotlin.ir.util.irCall
 import org.jetbrains.kotlin.ir.util.isSimpleTypeWithQuestionMark
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 
+internal fun IrType.erasureForTypeOperation(): IrType {
+    if (this !is IrSimpleType) return this
+
+    return when (val classifier = classifier) {
+        is IrClassSymbol -> this
+        is IrTypeParameterSymbol -> {
+            val upperBound = classifier.owner.superTypes.firstOrNull()
+                    ?: TODO("${classifier.descriptor} : ${classifier.descriptor.upperBounds}")
+
+            if (this.hasQuestionMark) {
+                // `T?`
+                upperBound.erasureForTypeOperation().makeNullable()
+            } else {
+                upperBound.erasureForTypeOperation()
+            }
+        }
+        else -> TODO(classifier.toString())
+    }
+}
+
 internal class TypeOperatorLowering(val context: CommonBackendContext) : FileLoweringPass, IrBuildingTransformer(context) {
+
     override fun lower(irFile: IrFile) {
         irFile.transformChildren(this, null)
     }
 
-    private fun IrType.erasure(): IrType {
-        if (this !is IrSimpleType) return this
-
-        return when (val classifier = classifier) {
-            is IrClassSymbol -> this
-            is IrTypeParameterSymbol -> {
-                val upperBound = classifier.owner.superTypes.firstOrNull() ?:
-                        TODO("${classifier.descriptor} : ${classifier.descriptor.upperBounds}")
-
-                if (this.hasQuestionMark) {
-                    // `T?`
-                    upperBound.erasure().makeNullable()
-                } else {
-                    upperBound.erasure()
-                }
-            }
-            else -> TODO(classifier.toString())
-        }
-    }
+    private fun IrType.erasure(): IrType = this.erasureForTypeOperation()
 
     private fun lowerCast(expression: IrTypeOperatorCall): IrExpression {
         builder.at(expression)
diff --git a/kotlin-native/backend.native/tests/build.gradle b/kotlin-native/backend.native/tests/build.gradle
index 072a924b0ea..2557e1a3a88 100644
--- a/kotlin-native/backend.native/tests/build.gradle
+++ b/kotlin-native/backend.native/tests/build.gradle
@@ -1540,6 +1540,10 @@ task bridges_special(type: KonanLocalTest) {
     source = "codegen/bridges/special.kt"
 }
 
+task bridges_specialGeneric(type: KonanLocalTest) {
+    source = "codegen/bridges/specialGeneric.kt"
+}
+
 task bridges_nativePointed(type: KonanLocalTest) {
     source = "codegen/bridges/nativePointed.kt"
 }
diff --git a/kotlin-native/backend.native/tests/codegen/bridges/specialGeneric.kt b/kotlin-native/backend.native/tests/codegen/bridges/specialGeneric.kt
new file mode 100644
index 00000000000..5749dc36dba
--- /dev/null
+++ b/kotlin-native/backend.native/tests/codegen/bridges/specialGeneric.kt
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
+package codegen.bridges.specialGeneric
+
+import kotlin.test.*
+
+interface Element {
+    val isContained: Boolean
+}
+
+object ContainedElement : Element {
+    override val isContained: Boolean = true
+}
+
+object NotContainedElement : Element {
+    override val isContained: Boolean = false
+}
+
+internal class MySet<E : Element> : Set<E> {
+    override fun contains(element: E): Boolean = element.isContained
+
+    override fun equals(other: Any?): Boolean = TODO()
+    override fun hashCode(): Int = TODO()
+    override fun toString(): String = TODO()
+
+    override val size: Int get() = TODO()
+    override fun isEmpty(): Boolean = TODO()
+    override fun containsAll(elements: Collection<E>): Boolean = TODO()
+
+    override fun iterator(): Iterator<E> = TODO()
+}
+
+fun set(): Set<Any> = MySet<Element>()
+
+@Test
+fun testMySet() {
+    val set = set()
+    assertFalse(set.contains(Any()))
+    assertFalse(set.contains(NotContainedElement))
+    assertTrue(set.contains(ContainedElement))
+}