KT-10295: long enum (sealed) special case

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/Renderers.kt

@@ -411,11 +411,14 @@ object Renderers {
         append("(").append(renderTypes(inferenceErrorData.valueArgumentsTypes)).append(")")
     }
 
+    private val WHEN_MISSING_LIMIT = 7
+
     @JvmField val RENDER_WHEN_MISSING_CASES: Renderer<List<WhenMissingCase>> = Renderer {
         if (!it.hasUnknown) {
-            val list = it.map { "'$it'" }.joinToString(", ")
+            val list = it.take(WHEN_MISSING_LIMIT).map { "'$it'" }.joinToString(", ")
             val branches = if (it.size > 1) "branches" else "branch"
-            "$list $branches or 'else' branch instead"
+            val others = if (it.size > WHEN_MISSING_LIMIT) ", ..." else ""
+            "$list$others $branches or 'else' branch instead"
         }
         else {
             "'else' branch"

idea/testData/checker/WhenNonExhaustive.kt

@@ -28,6 +28,14 @@ fun whenOnEnum(c: Color) {
     }
 }
 
+enum class EnumInt {
+    A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15
+}
+
+fun whenOnLongEnum(i: EnumInt) = <error descr="[NO_ELSE_IN_WHEN] when expression must be exhaustive, add necessary 'A0', 'A1', 'A2', 'A3', 'A4', 'A5', 'A6', ... branches or 'else' branch instead">when</error> (i) {
+    EnumInt.A7 -> 7
+}
+
 sealed class Variant {
     object Singleton : Variant()