Fix -Xuse-mixed-named-arguments compiler arg

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/CommonCompilerArguments.kt

@@ -311,7 +311,7 @@ abstract class CommonCompilerArguments : CommonToolArguments() {
         value = "-Xuse-mixed-named-arguments",
         description = "Enable Support named arguments in their own position even if the result appears as mixed"
     )
-    val useMixedNamedArguments: Boolean by FreezableVar(false)
+    var useMixedNamedArguments: Boolean by FreezableVar(false)
 
     @Argument(value = "-Xdisable-default-scripting-plugin", description = "Do not enable scripting plugin by default")
     var disableDefaultScriptingPlugin: Boolean by FreezableVar(false)

compiler/testData/cli/jvm/useMixedNamedArgumentsFlag.args

@@ -0,0 +1,5 @@
+$TESTDATA_DIR$/useMixedNamedArgumentsFlag.kt
+-Xuse-mixed-named-arguments
+-Xnew-inference
+-d
+$TEMP_DIR$

compiler/testData/cli/jvm/useMixedNamedArgumentsFlag.kt

@@ -0,0 +1,5 @@
+fun foo(x: Int, y: Int, z: Int) {}
+
+fun test() {
+    foo(1, y = 2, 3)
+}

compiler/testData/cli/jvm/useMixedNamedArgumentsFlag.out

@@ -0,0 +1,12 @@
+warning: some JAR files in the classpath have the Kotlin Runtime library bundled into them. This may cause difficult to debug problems if there's a different version of the Kotlin Runtime library in the classpath. Consider removing these libraries from the classpath
+dist/kotlinc/lib/kotlin-reflect.jar: warning: library has Kotlin runtime bundled into it
+compiler/testData/cli/jvm/useMixedNamedArgumentsFlag.kt:1:9: warning: parameter 'x' is never used
+fun foo(x: Int, y: Int, z: Int) {}
+        ^
+compiler/testData/cli/jvm/useMixedNamedArgumentsFlag.kt:1:17: warning: parameter 'y' is never used
+fun foo(x: Int, y: Int, z: Int) {}
+                ^
+compiler/testData/cli/jvm/useMixedNamedArgumentsFlag.kt:1:25: warning: parameter 'z' is never used
+fun foo(x: Int, y: Int, z: Int) {}
+                        ^
+OK

compiler/tests/org/jetbrains/kotlin/cli/CliTestGenerated.java

@@ -645,6 +645,11 @@ public class CliTestGenerated extends AbstractCliTest {
             runTest("compiler/testData/cli/jvm/unsupportedTypeAlias.args");
         }
 
+        @TestMetadata("useMixedNamedArgumentsFlag.args")
+        public void testUseMixedNamedArgumentsFlag() throws Exception {
+            runTest("compiler/testData/cli/jvm/useMixedNamedArgumentsFlag.args");
+        }
+
         @TestMetadata("warningJdkWithNoJdk.args")
         public void testWarningJdkWithNoJdk() throws Exception {
             runTest("compiler/testData/cli/jvm/warningJdkWithNoJdk.args");