JVM IR: fix monitorEnterMonitorExit.kt

After an inaccurate merge of 31936890 and d6ed93b2, this test was now
failing with the newly added assertion. It seems that currently the best
way to handle it would be to special-case these two methods in
SyntheticAccessorLowering.kt.

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

@@ -48,7 +48,7 @@ internal class SyntheticAccessorLowering(val context: JvmBackendContext) : IrEle
         irFile.transformChildrenVoid(this)
 
         for (accessor in pendingAccessorsToAdd) {
-            assert(accessor.file == irFile) {
+            assert(accessor.fileOrNull == irFile || accessor.isAllowedToBeAddedToForeignFile()) {
                 "SyntheticAccessorLowering should not attempt to modify other files!\n" +
                         "While lowering this file: ${irFile.render()}\n" +
                         "Trying to add this accessor: ${accessor.render()}"
@@ -560,4 +560,10 @@ internal class SyntheticAccessorLowering(val context: JvmBackendContext) : IrEle
             else -> true
         }
     }
+
+    // monitorEnter/monitorExit are the only functions which are accessed "illegally" (see kotlin/util/Synchronized.kt).
+    // Since they are intrinsified in the codegen, SyntheticAccessorLowering should not crash on attempt to add accessors for them.
+    private fun IrFunction.isAllowedToBeAddedToForeignFile(): Boolean =
+        (name.asString() == "access\$monitorEnter" || name.asString() == "access\$monitorExit") &&
+                context.irIntrinsics.getIntrinsic(symbol) != null
 }

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrUtils.kt

@@ -600,16 +600,17 @@ private fun IrMemberAccessExpression.copyTypeAndValueArgumentsFrom(
     }
 }
 
-val IrDeclaration.file: IrFile
-    get() = parent.let {
-        when (it) {
-            is IrFile -> it
-            is IrPackageFragment -> TODO("Unknown file")
-            is IrDeclaration -> it.file
-            else -> TODO("Unexpected declaration parent")
-        }
+val IrDeclaration.fileOrNull: IrFile?
+    get() = when (val parent = parent) {
+        is IrFile -> parent
+        is IrPackageFragment -> null
+        is IrDeclaration -> parent.fileOrNull
+        else -> TODO("Unexpected declaration parent")
     }
 
+val IrDeclaration.file: IrFile
+    get() = fileOrNull ?: TODO("Unknown file")
+
 val IrFunction.allTypeParameters: List<IrTypeParameter>
     get() = if (this is IrConstructor)
         parentAsClass.typeParameters + typeParameters