JVM_IR: support @JvmDefaults in compatibility mode.

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/ir/IrUtils.kt

@@ -6,13 +6,14 @@
 package org.jetbrains.kotlin.backend.jvm.ir
 
 import org.jetbrains.kotlin.backend.jvm.codegen.isJvmInterface
-import org.jetbrains.kotlin.ir.declarations.IrClass
-import org.jetbrains.kotlin.ir.declarations.IrTypeParameter
+import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.symbols.IrClassSymbol
 import org.jetbrains.kotlin.ir.symbols.IrTypeParameterSymbol
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.types.classOrNull
 import org.jetbrains.kotlin.ir.types.classifierOrNull
+import org.jetbrains.kotlin.ir.util.hasAnnotation
+import org.jetbrains.kotlin.resolve.jvm.annotations.JVM_DEFAULT_FQ_NAME
 
 /**
  * Computes the erased class for this type parameter according to the java erasure rules.
@@ -37,3 +38,8 @@ val IrType.erasedUpperBound: IrClass
         is IrTypeParameterSymbol -> classifier.owner.erasedUpperBound
         else -> throw IllegalStateException()
     }
+
+val IrFunction.propertyIfAccessor: IrDeclaration
+    get() = (this as? IrSimpleFunction)?.correspondingPropertySymbol?.owner ?: this
+
+fun IrFunction.hasJvmDefault(): Boolean = propertyIfAccessor.hasAnnotation(JVM_DEFAULT_FQ_NAME)

compiler/ir/backend.jvm/src/org/jetbrains/kotlin/backend/jvm/lower/InterfaceLowering.kt

@@ -9,16 +9,22 @@ import org.jetbrains.kotlin.backend.common.ClassLoweringPass
 import org.jetbrains.kotlin.backend.common.descriptors.WrappedSimpleFunctionDescriptor
 import org.jetbrains.kotlin.backend.common.ir.copyTo
 import org.jetbrains.kotlin.backend.common.ir.copyTypeParametersFrom
+import org.jetbrains.kotlin.backend.common.ir.passTypeArgumentsFrom
 import org.jetbrains.kotlin.backend.common.lower.InitializersLowering.Companion.clinitName
 import org.jetbrains.kotlin.backend.common.lower.VariableRemapper
 import org.jetbrains.kotlin.backend.common.phaser.makeIrFilePhase
 import org.jetbrains.kotlin.backend.jvm.JvmBackendContext
 import org.jetbrains.kotlin.backend.jvm.JvmLoweredDeclarationOrigin
+import org.jetbrains.kotlin.backend.jvm.ir.hasJvmDefault
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.descriptors.Visibilities
 import org.jetbrains.kotlin.descriptors.annotations.Annotations
 import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.declarations.impl.IrFunctionImpl
+import org.jetbrains.kotlin.ir.expressions.IrCall
+import org.jetbrains.kotlin.ir.expressions.impl.IrCallImpl
+import org.jetbrains.kotlin.ir.expressions.impl.IrExpressionBodyImpl
+import org.jetbrains.kotlin.ir.expressions.impl.IrGetValueImpl
 import org.jetbrains.kotlin.ir.symbols.impl.IrSimpleFunctionSymbolImpl
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.util.isInterface
@@ -51,8 +57,15 @@ private class InterfaceLowering(val context: JvmBackendContext) : IrElementTrans
                 val element = context.declarationFactory.getDefaultImplsFunction(function)
                 members.add(element)
                 element.body = function.body?.patchDeclarationParents(element)
-                function.body = null
-                //TODO reset modality to abstract
+                if (function.hasJvmDefault() &&
+                    function.origin != JvmLoweredDeclarationOrigin.SYNTHETIC_METHOD_FOR_PROPERTY_ANNOTATIONS
+                ) {
+                    // TODO: don't touch function and only generate element / DefaultImpls when needed.
+                    function.body = IrExpressionBodyImpl(callDefaultImpls(element, function))
+                } else {
+                    function.body = null
+                    //TODO reset modality to abstract
+                }
             }
         }
 
@@ -67,6 +80,26 @@ private class InterfaceLowering(val context: JvmBackendContext) : IrElementTrans
         Visibilities.isPrivate(function.visibility) && function.name != clinitName ||
                 function.origin == IrDeclarationOrigin.FUNCTION_FOR_DEFAULT_PARAMETER ||
                 function.origin == JvmLoweredDeclarationOrigin.SYNTHETIC_METHOD_FOR_PROPERTY_ANNOTATIONS
+
+    private fun callDefaultImpls(defaultImpls: IrFunction, interfaceMethod: IrFunction): IrCall {
+        val startOffset = interfaceMethod.startOffset
+        val endOffset = interfaceMethod.endOffset
+
+        return IrCallImpl(interfaceMethod.startOffset, interfaceMethod.endOffset, interfaceMethod.returnType, defaultImpls.symbol).apply {
+            passTypeArgumentsFrom(interfaceMethod)
+
+            var offset = 0
+            interfaceMethod.dispatchReceiverParameter?.let {
+                putValueArgument(offset++, IrGetValueImpl(startOffset, endOffset, it.symbol))
+            }
+            interfaceMethod.extensionReceiverParameter?.let {
+                putValueArgument(offset++, IrGetValueImpl(startOffset, endOffset, it.symbol))
+            }
+            interfaceMethod.valueParameters.forEachIndexed { i, it ->
+                putValueArgument(i + offset, IrGetValueImpl(startOffset, endOffset, it.symbol))
+            }
+        }
+    }
 }
 
 

compiler/testData/codegen/box/jvm8/defaults/compatibility/bridge.kt

@@ -1,5 +1,4 @@
 // !JVM_DEFAULT_MODE: compatibility
-// IGNORE_BACKEND: JVM_IR
 // TARGET_BACKEND: JVM
 // FILE: Simple.java
 

compiler/testData/codegen/box/jvm8/defaults/compatibility/inheritedJvmDefault.kt

@@ -1,5 +1,4 @@
 // !JVM_DEFAULT_MODE: compatibility
-// IGNORE_BACKEND: JVM_IR
 // TARGET_BACKEND: JVM
 // FILE: Simple.java
 

compiler/testData/codegen/box/jvm8/defaults/compatibility/simpleFunction.kt

@@ -1,5 +1,4 @@
 // !JVM_DEFAULT_MODE: compatibility
-// IGNORE_BACKEND: JVM_IR
 // TARGET_BACKEND: JVM
 // FILE: Simple.java
 

compiler/testData/codegen/box/jvm8/defaults/inlineProperty.kt

@@ -1,5 +1,4 @@
 // !JVM_DEFAULT_MODE: enable
-// IGNORE_BACKEND: JVM_IR
 // TARGET_BACKEND: JVM
 // JVM_TARGET: 1.8
 // WITH_RUNTIME

compiler/testData/writeFlags/jvm8/defaults/defaultProperty.kt

@@ -1,5 +1,4 @@
 // !JVM_DEFAULT_MODE: enable
-// IGNORE_BACKEND: JVM_IR
 // JVM_TARGET: 1.8
 // WITH_RUNTIME