Show pre-released 1.5 version in configuration preferences

^KT-44116 Fixed

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

@@ -324,6 +324,9 @@ enum class LanguageVersion(val major: Int, val minor: Int) : DescriptionAware {
     }
 }
 
+fun LanguageVersion.isStableOrReadyForPreview(): Boolean =
+    isStable || this == KOTLIN_1_5
+
 interface LanguageVersionSettings {
     fun getFeatureSupport(feature: LanguageFeature): LanguageFeature.State
 

idea/idea-jvm/src/org/jetbrains/kotlin/idea/quickfix/EnableUnsupportedFeatureFix.kt

@@ -17,6 +17,7 @@ import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.config.ApiVersion
 import org.jetbrains.kotlin.config.KotlinFacetSettingsProvider
 import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.config.isStableOrReadyForPreview
 import org.jetbrains.kotlin.diagnostics.Diagnostic
 import org.jetbrains.kotlin.diagnostics.Errors
 import org.jetbrains.kotlin.idea.KotlinJvmBundle
@@ -104,7 +105,7 @@ sealed class EnableUnsupportedFeatureFix(
             val apiVersionOnly = sinceVersion <= languageFeatureSettings.languageVersion &&
                     feature.sinceApiVersion > languageFeatureSettings.apiVersion
 
-            if (!sinceVersion.isStable && !ApplicationManager.getApplication().isInternal) {
+            if (!sinceVersion.isStableOrReadyForPreview() && !ApplicationManager.getApplication().isInternal) {
                 return null
             }
 

idea/idea-maven/src/org/jetbrains/kotlin/idea/maven/MavenCompletionProviders.kt

@@ -11,14 +11,15 @@ import org.jetbrains.idea.maven.plugins.api.MavenFixedValueReferenceProvider
 import org.jetbrains.kotlin.cli.common.arguments.DefaultValues
 import org.jetbrains.kotlin.config.JvmTarget
 import org.jetbrains.kotlin.config.LanguageVersion
+import org.jetbrains.kotlin.config.isStableOrReadyForPreview
 
 class MavenLanguageVersionsCompletionProvider : MavenFixedValueReferenceProvider(
-    LanguageVersion.values().filter { it.isStable || ApplicationManager.getApplication().isInternal }.map { it.versionString }
+    LanguageVersion.values().filter { it.isStableOrReadyForPreview() || ApplicationManager.getApplication().isInternal }.map { it.versionString }
         .toTypedArray()
 )
 
 class MavenApiVersionsCompletionProvider : MavenFixedValueReferenceProvider(
-    LanguageVersion.values().filter { it.isStable || ApplicationManager.getApplication().isInternal }.map { it.versionString }
+    LanguageVersion.values().filter { it.isStableOrReadyForPreview() || ApplicationManager.getApplication().isInternal }.map { it.versionString }
         .toTypedArray()
 )
 

idea/src/org/jetbrains/kotlin/idea/compiler/configuration/KotlinCompilerConfigurableTab.java

@@ -370,7 +370,7 @@ public class KotlinCompilerConfigurableTab implements SearchableConfigurable {
         apiVersionComboBox.addItem(VersionView.LatestStable.INSTANCE);
 
         for (LanguageVersion version : LanguageVersion.values()) {
-            if (version.isUnsupported() || !version.isStable() && !ApplicationManager.getApplication().isInternal()) {
+            if (version.isUnsupported() || !LanguageVersionSettingsKt.isStableOrReadyForPreview(version) && !ApplicationManager.getApplication().isInternal()) {
                 continue;
             }