[IR] Erase non-trivial type projections off of super types

This fixes https://youtrack.jetbrains.com/issue/KT-44826

kotlin-native/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/FunctionReferenceLowering.kt

@@ -32,10 +32,13 @@ import org.jetbrains.kotlin.ir.symbols.impl.IrClassSymbolImpl
 import org.jetbrains.kotlin.ir.symbols.impl.IrConstructorSymbolImpl
 import org.jetbrains.kotlin.ir.symbols.impl.IrSimpleFunctionSymbolImpl
 import org.jetbrains.kotlin.ir.types.*
+import org.jetbrains.kotlin.ir.types.impl.buildSimpleType
+import org.jetbrains.kotlin.ir.types.impl.makeTypeProjection
 import org.jetbrains.kotlin.ir.util.*
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.types.Variance
 
 internal class FunctionReferenceLowering(val context: Context): FileLoweringPass {
 
@@ -89,6 +92,21 @@ internal class FunctionReferenceLowering(val context: Context): FileLoweringPass
                 return result
             }
 
+            // TODO: Move to common IR utils.
+            fun IrType.eraseProjections(): IrType {
+                if (this !is IrSimpleType) return this
+                return buildSimpleType {
+                    this.classifier = this@eraseProjections.classifier
+                    this.hasQuestionMark = this@eraseProjections.hasQuestionMark
+                    this.annotations = this@eraseProjections.annotations
+                    this.arguments = this@eraseProjections.arguments.map {
+                        if (it !is IrTypeProjection)
+                            it
+                        else makeTypeProjection(it.type.eraseProjections(), Variance.INVARIANT)
+                    }
+                }
+            }
+
             // Handle SAM conversions which wrap a function reference:
             //     class sam$n(private val receiver: R) : Interface { override fun method(...) = receiver.target(...) }
             //
@@ -111,7 +129,7 @@ internal class FunctionReferenceLowering(val context: Context): FileLoweringPass
                         return super.visitTypeOperator(expression)
                     }
                     reference.transformChildrenVoid()
-                    return transformFunctionReference(reference, expression.typeOperand)
+                    return transformFunctionReference(reference, expression.typeOperand.eraseProjections())
                 }
                 return super.visitTypeOperator(expression)
             }

kotlin-native/backend.native/tests/build.gradle

@@ -2881,6 +2881,10 @@ task funInterface_implIsNotFunction(type: KonanLocalTest) {
     source = "codegen/funInterface/implIsNotFunction.kt"
 }
 
+task funInterface_nonTrivialProjectionInSuperType(type: KonanLocalTest) {
+    source = "codegen/funInterface/nonTrivialProjectionInSuperType.kt"
+}
+
 task objectExpression1(type: KonanLocalTest) {
     goldValue = "aabb\n"
     source = "codegen/objectExpression/expr1.kt"

kotlin-native/backend.native/tests/codegen/funInterface/nonTrivialProjectionInSuperType.kt

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2010-2021 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.funInterface.nonTrivialProjectionInSuperType
+
+import kotlin.test.*
+
+fun <T> foo(comparator: kotlin.Comparator<in T>, a: T, b: T) = comparator.compare(a, b)
+
+fun bar(x: Int, y: Int) = foo<Int> ({ a, b -> a - b}, x, y)
+
+@Test
+fun test() {
+    assertTrue(bar(42, 117) < 0)
+}