Support custom 'equals' for inline classes

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

@@ -24,6 +24,8 @@ import org.jetbrains.kotlin.backend.common.lower.irNot
 import org.jetbrains.kotlin.backend.konan.*
 import org.jetbrains.kotlin.backend.konan.irasdescriptors.containsNull
 import org.jetbrains.kotlin.backend.konan.irasdescriptors.isSubtypeOf
+import org.jetbrains.kotlin.backend.konan.irasdescriptors.overrides
+import org.jetbrains.kotlin.descriptors.CallableMemberDescriptor
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.ir.builders.*
 import org.jetbrains.kotlin.ir.declarations.IrFile
@@ -37,11 +39,13 @@ import org.jetbrains.kotlin.ir.symbols.IrSimpleFunctionSymbol
 import org.jetbrains.kotlin.ir.types.makeNullable
 import org.jetbrains.kotlin.ir.util.irCall
 import org.jetbrains.kotlin.ir.builders.irGet
+import org.jetbrains.kotlin.ir.declarations.IrClass
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.isNothing
 import org.jetbrains.kotlin.ir.types.toKotlinType
 import org.jetbrains.kotlin.ir.util.defaultOrNullableType
 import org.jetbrains.kotlin.ir.util.isNullConst
+import org.jetbrains.kotlin.ir.util.simpleFunctions
 import org.jetbrains.kotlin.ir.visitors.transformChildrenVoid
 
 /**
@@ -116,6 +120,8 @@ internal class BuiltinOperatorLowering(val context: Context) : FileLoweringPass,
                 extensionReceiver = expression
             }
 
+    private val anyEquals = irBuiltins.anyClass.owner.simpleFunctions().single { it.name.asString() == "equals" }
+
     private fun lowerEqeq(expression: IrCall): IrExpression {
         // TODO: optimize boxing?
 
@@ -133,7 +139,7 @@ internal class BuiltinOperatorLowering(val context: Context) : FileLoweringPass,
 
             if (expression.symbol == irBuiltins.eqeqSymbol) {
                 lhs.type.getInlinedClass()?.let {
-                    if (it == rhs.type.getInlinedClass()) {
+                    if (it == rhs.type.getInlinedClass() && inlinedClassHasDefaultEquals(it)) {
                         return genInlineClassEquals(expression.descriptor, rhs, lhs)
                     }
                 }
@@ -143,6 +149,22 @@ internal class BuiltinOperatorLowering(val context: Context) : FileLoweringPass,
         }
     }
 
+    private fun inlinedClassHasDefaultEquals(irClass: IrClass): Boolean {
+        if (!irClass.descriptor.isInline) {
+            // Implicitly-inlined class, e.g. primitive one.
+            return true
+        }
+
+        val equals = irClass.simpleFunctions()
+                .single { it.name.asString() == "equals" && it.valueParameters.size == 1 && it.overrides(anyEquals) }
+
+        // Note: this is not absolutely correct for inline class from other module
+        // since custom equals implementation can be added after compilation but before linking.
+        // TODO: reimplement after inline classes get properly designed `equals` operator.
+        // see https://youtrack.jetbrains.com/issue/KT-26354.
+        return equals.descriptor.kind == CallableMemberDescriptor.Kind.SYNTHESIZED
+    }
+
     fun IrBuilderWithScope.genInlineClassEquals(
             descriptor: FunctionDescriptor,
             rhs: IrExpression,