Exclude keywords from completion if the corresponding feature is unsupported by the language level selected for the module

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/KeywordCompletion.kt

@@ -20,7 +20,7 @@ import com.intellij.codeInsight.completion.InsertHandler
 import com.intellij.codeInsight.completion.InsertionContext
 import com.intellij.codeInsight.lookup.LookupElement
 import com.intellij.codeInsight.lookup.LookupElementBuilder
-import com.intellij.openapi.project.Project
+import com.intellij.openapi.module.ModuleUtilCore
 import com.intellij.psi.PsiComment
 import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiErrorElement
@@ -30,10 +30,13 @@ import com.intellij.psi.filters.position.LeftNeighbour
 import com.intellij.psi.filters.position.PositionElementFilter
 import com.intellij.psi.tree.IElementType
 import com.intellij.psi.tree.TokenSet
+import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.config.LanguageVersionSettingsImpl
 import org.jetbrains.kotlin.descriptors.annotations.KotlinTarget
 import org.jetbrains.kotlin.descriptors.annotations.KotlinTarget.*
 import org.jetbrains.kotlin.idea.completion.handlers.WithTailInsertHandler
 import org.jetbrains.kotlin.idea.completion.handlers.createKeywordConstructLookupElement
+import org.jetbrains.kotlin.idea.project.languageVersionSettings
 import org.jetbrains.kotlin.lexer.KtKeywordToken
 import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.lexer.KtTokens
@@ -255,7 +258,7 @@ object KeywordCompletion {
                                        position: PsiElement): (KtKeywordToken) -> Boolean {
         val offset = position.getStartOffsetInAncestor(contextElement)
         val truncatedContext = contextElement.text!!.substring(0, offset)
-        return buildFilterByText(prefixText + truncatedContext, contextElement.project)
+        return buildFilterByText(prefixText + truncatedContext, position)
     }
 
     private fun buildFilterWithReducedContext(prefixText: String,
@@ -263,12 +266,12 @@ object KeywordCompletion {
                                               position: PsiElement): (KtKeywordToken) -> Boolean {
         val builder = StringBuilder()
         buildReducedContextBefore(builder, position, contextElement)
-        return buildFilterByText(prefixText + builder.toString(), position.project)
+        return buildFilterByText(prefixText + builder.toString(), position)
     }
 
 
-    private fun buildFilterByText(prefixText: String, project: Project): (KtKeywordToken) -> Boolean {
-        val psiFactory = KtPsiFactory(project)
+    private fun buildFilterByText(prefixText: String, position: PsiElement): (KtKeywordToken) -> Boolean {
+        val psiFactory = KtPsiFactory(position.project)
         return fun (keywordTokenType): Boolean {
             val postfix = if (prefixText.endsWith("@")) ":X Y.Z" else " X"
             val file = psiFactory.createFile(prefixText + keywordTokenType.value + postfix)
@@ -281,6 +284,8 @@ object KeywordCompletion {
 
                 isErrorElementBefore(elementAt) -> return false
 
+                !isSupportedAtLanguageLevel(keywordTokenType, position) -> return false
+
                 keywordTokenType !is KtModifierKeywordToken -> return true
 
                 else -> {
@@ -356,6 +361,17 @@ object KeywordCompletion {
         }
     }
 
+    private fun isSupportedAtLanguageLevel(keyword: KtKeywordToken, position: PsiElement): Boolean {
+        val languageVersionSettings = ModuleUtilCore.findModuleForPsiElement(position)?.languageVersionSettings ?: LanguageVersionSettingsImpl.DEFAULT
+        val feature = when (keyword) {
+            KtTokens.TYPE_ALIAS_KEYWORD -> LanguageFeature.TypeAliases
+            KtTokens.HEADER_KEYWORD, KtTokens.IMPL_KEYWORD -> LanguageFeature.MultiPlatformProjects
+            KtTokens.SUSPEND_KEYWORD -> LanguageFeature.Coroutines
+            else -> return true
+        }
+        return languageVersionSettings.supportsFeature(feature)
+    }
+
     // builds text within scope (or from the start of the file) before position element excluding almost all declarations
     private fun buildReducedContextBefore(builder: StringBuilder, position: PsiElement, scope: PsiElement?) {
         if (position == scope) return

idea/idea-completion/testData/keywords/AfterClasses_LangLevel10.kt

@@ -0,0 +1,37 @@
+class A {
+    fun foo() {
+        bar()
+    }
+}
+
+class B {
+    fun bar() {
+        foo()
+    }
+}
+
+<caret>
+
+// EXIST:  abstract
+// EXIST:  class
+// EXIST:  enum class
+// EXIST:  final
+// EXIST:  fun
+// EXIST:  internal
+// EXIST:  object
+// EXIST:  open
+// EXIST:  private
+// EXIST:  public
+// EXIST:  interface
+// EXIST:  val
+// EXIST:  var
+// EXIST:  operator
+// EXIST:  infix
+// EXIST:  sealed
+// EXIST:  data
+// EXIST:  inline
+// EXIST:  tailrec
+// EXIST:  external
+// EXIST:  annotation class
+// EXIST:  const
+// NOTHING_ELSE

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/AbstractKeywordCompletionTest.kt

@@ -20,6 +20,7 @@ import com.intellij.codeInsight.completion.CompletionType
 import com.intellij.codeInsight.lookup.LookupElement
 import org.jetbrains.kotlin.idea.completion.KeywordLookupObject
 import org.jetbrains.kotlin.idea.test.KotlinLightProjectDescriptor
+import org.jetbrains.kotlin.idea.test.KotlinProjectDescriptorWithFacet
 import org.jetbrains.kotlin.resolve.jvm.platform.JvmPlatform
 
 abstract class AbstractKeywordCompletionTest : KotlinFixtureCompletionBaseTestCase() {
@@ -32,7 +33,12 @@ abstract class AbstractKeywordCompletionTest : KotlinFixtureCompletionBaseTestCa
         return items.filter { it.`object` is KeywordLookupObject }.toTypedArray()
     }
 
-    override fun getProjectDescriptor() = KotlinLightProjectDescriptor.INSTANCE
+    override fun getProjectDescriptor(): KotlinLightProjectDescriptor {
+        if ("LangLevel10" in fileName()) {
+            return KotlinProjectDescriptorWithFacet.KOTLIN_10
+        }
+        return KotlinLightProjectDescriptor.INSTANCE
+    }
 
     override fun defaultInvocationCount() = 1
 }

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/KeywordCompletionTestGenerated.java

@@ -44,6 +44,12 @@ public class KeywordCompletionTestGenerated extends AbstractKeywordCompletionTes
         doTest(fileName);
     }
 
+    @TestMetadata("AfterClasses_LangLevel10.kt")
+    public void testAfterClasses_LangLevel10() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/idea-completion/testData/keywords/AfterClasses_LangLevel10.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("AfterDot.kt")
     public void testAfterDot() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("idea/idea-completion/testData/keywords/AfterDot.kt");