Keyword completion: do not suggest const except inside top level or object

#KT-23026 Fixed
#KT-29840 Fixed

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

@@ -407,11 +407,27 @@ object KeywordCompletion {
 
                         is KtObjectDeclaration -> if (ownerDeclaration.isObjectLiteral()) KotlinTarget.OBJECT_LITERAL else KotlinTarget.OBJECT
 
-                        else -> return true
+                        else -> return keywordTokenType != CONST_KEYWORD
                     }
 
                     if (!ModifierCheckerCore.isPossibleParentTarget(keywordTokenType, parentTarget, languageVersionSettings)) return false
 
+                    if (keywordTokenType == CONST_KEYWORD) {
+                        return when (parentTarget) {
+                            KotlinTarget.OBJECT -> true
+                            KotlinTarget.FILE -> {
+                                val prevSiblings = elementAt.parent.siblings(withItself = false, forward = false)
+                                val hasLineBreak = prevSiblings
+                                    .takeWhile { it is PsiWhiteSpace || it.isSemicolon() }
+                                    .firstOrNull { it.text.contains("\n") || it.isSemicolon() } != null
+                                hasLineBreak || prevSiblings.none {
+                                    it !is PsiWhiteSpace && !it.isSemicolon() && it !is KtImportList && it !is KtPackageDirective
+                                }
+                            }
+                            else -> false
+                        }
+                    }
+
                     return true
                 }
             }
@@ -423,6 +439,8 @@ object KeywordCompletion {
         }
     }
 
+    private fun PsiElement.isSemicolon() = node.elementType == KtTokens.SEMICOLON
+
     private fun isErrorElementBefore(token: PsiElement): Boolean {
         for (leaf in token.prevLeafs) {
             if (leaf is PsiWhiteSpace || leaf is PsiComment) continue

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

@@ -0,0 +1,4 @@
+class Foo <caret> {
+}
+
+// EXIST:  constructor

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

@@ -39,7 +39,6 @@ class MouseMovedEventArgs
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST:  typealias
 // EXIST:  expect

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

@@ -38,7 +38,6 @@ class A {
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST:  typealias
 // EXIST:  expect

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

@@ -24,7 +24,6 @@ annotation class Test {
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST:  typealias
 // EXIST:  expect

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

@@ -36,7 +36,6 @@ public class Test {
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST:  typealias
 // EXIST:  expect

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

@@ -30,7 +30,6 @@ class TestClass {
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST:  typealias
 // EXIST:  expect

idea/idea-completion/testData/keywords/InEnumScope2.kt

@@ -24,7 +24,6 @@ enum class Test {
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST: fun
 // EXIST:  typealias

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

@@ -26,7 +26,6 @@ interface Test {
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST:  typealias
 // EXIST:  expect

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

@@ -17,6 +17,5 @@ class TestSample(<caret>)
 // EXIST: actual
 /* TODO: keywords below should not be here*/
 // EXIST: abstract
-// EXIST: const val
 // EXIST: lateinit var
 // NOTHING_ELSE

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

@@ -38,7 +38,6 @@ class Some {
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST:  typealias
 // EXIST:  expect

idea/idea-completion/testData/keywords/PropertyAccessors2.kt

@@ -38,7 +38,6 @@ class Some {
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST:  typealias
 // EXIST:  expect

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

@@ -36,7 +36,6 @@ class Some {
 // EXIST:  tailrec
 // EXIST:  external
 // EXIST:  annotation class
-// EXIST:  const val
 // EXIST:  suspend
 // EXIST:  typealias
 // EXIST:  expect

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

@@ -25,6 +25,11 @@ public class KeywordCompletionTestGenerated extends AbstractKeywordCompletionTes
         KotlinTestUtils.runTest(this::doTest, TargetBackend.ANY, testDataFilePath);
     }
 
+    @TestMetadata("AfterClassName.kt")
+    public void testAfterClassName() throws Exception {
+        runTest("idea/idea-completion/testData/keywords/AfterClassName.kt");
+    }
+
     @TestMetadata("AfterClassProperty.kt")
     public void testAfterClassProperty() throws Exception {
         runTest("idea/idea-completion/testData/keywords/AfterClassProperty.kt");