Add language feature for inference compatibility mode

The feature is intended for updates in the inference algorithm
that change behaviour compared to the previous stable version.

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

@@ -358,6 +358,12 @@ abstract class CommonCompilerArguments : CommonToolArguments() {
     )
     var deserializeFakeOverrides: Boolean by FreezableVar(false)
 
+    @Argument(
+        value = "-Xinference-compatibility",
+        description = "Enable compatibility changes for generic type inference algorithm"
+    )
+    var inferenceCompatibility: Boolean by FreezableVar(false)
+
     open fun configureAnalysisFlags(collector: MessageCollector): MutableMap<AnalysisFlag<*>, Any> {
         return HashMap<AnalysisFlag<*>, Any>().apply {
             put(AnalysisFlags.skipMetadataVersionCheck, skipMetadataVersionCheck)
@@ -432,6 +438,10 @@ abstract class CommonCompilerArguments : CommonToolArguments() {
                 put(LanguageFeature.MixedNamedArgumentsInTheirOwnPosition, LanguageFeature.State.ENABLED)
             }
 
+            if (inferenceCompatibility) {
+                put(LanguageFeature.InferenceCompatibility, LanguageFeature.State.ENABLED)
+            }
+
             if (progressiveMode) {
                 LanguageFeature.values().filter { it.kind.enabledInProgressiveMode }.forEach {
                     // Don't overwrite other settings: users may want to turn off some particular

compiler/testData/cli/js/jsExtraHelp.out

@@ -44,6 +44,7 @@ where advanced options include:
   -Xexplicit-api={strict|warning|disable}
                              Force compiler to report errors on all public API declarations without explicit visibility or return type.
                              Use 'warning' level to issue warnings instead of errors.
+  -Xinference-compatibility  Enable compatibility changes for generic type inference algorithm
   -Xinline-classes           Enable experimental inline classes
   -Xintellij-plugin-root=<path> Path to the kotlin-compiler.jar or directory where IntelliJ configuration files can be found
   -Xlegacy-smart-cast-after-try Allow var smart casts despite assignment in try block

compiler/testData/cli/jvm/extraHelp.out

@@ -127,6 +127,7 @@ where advanced options include:
   -Xexplicit-api={strict|warning|disable}
                              Force compiler to report errors on all public API declarations without explicit visibility or return type.
                              Use 'warning' level to issue warnings instead of errors.
+  -Xinference-compatibility  Enable compatibility changes for generic type inference algorithm
   -Xinline-classes           Enable experimental inline classes
   -Xintellij-plugin-root=<path> Path to the kotlin-compiler.jar or directory where IntelliJ configuration files can be found
   -Xlegacy-smart-cast-after-try Allow var smart casts despite assignment in try block

compiler/util/src/org/jetbrains/kotlin/config/LanguageVersionSettings.kt

@@ -135,6 +135,7 @@ enum class LanguageFeature(
     DisableCompatibilityModeForNewInference(KOTLIN_1_5, defaultState = LanguageFeature.State.DISABLED),
     AdaptedCallableReferenceAgainstReflectiveType(KOTLIN_1_5, defaultState = LanguageFeature.State.DISABLED),
     ProhibitUsingNullableTypeParameterAgainstNotNullAnnotated(KOTLIN_1_5, kind = BUG_FIX),
+    InferenceCompatibility(KOTLIN_1_5, kind = BUG_FIX),
 
     // Temporarily disabled, see KT-27084/KT-22379
     SoundSmartcastFromLoopConditionForLoopAssignedVariables(sinceVersion = null, kind = BUG_FIX),