Show more correct type hints

- Don't show hints containing error type as type parameter
 - Do not expand type aliases
 - Show base type for types of anonymous objects

 #KT-18369 Fixed
 #KT-18341 Fixed
 #KT-18343 Fixed

idea/src/org/jetbrains/kotlin/idea/parameterInfo/TypeHints.kt

@@ -23,18 +23,21 @@ import org.jetbrains.kotlin.descriptors.ConstructorDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.core.formatter.KotlinCodeStyleSettings
 import org.jetbrains.kotlin.idea.intentions.SpecifyTypeExplicitlyIntention
+import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.endOffset
 import org.jetbrains.kotlin.renderer.DescriptorRenderer
 import org.jetbrains.kotlin.renderer.RenderingFormat
 import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
 import org.jetbrains.kotlin.types.KotlinType
-import org.jetbrains.kotlin.types.isError
+import org.jetbrains.kotlin.types.typeUtil.containsError
+import org.jetbrains.kotlin.types.typeUtil.immediateSupertypes
 
 //hack to separate type presentation from param info presentation
 const val TYPE_INFO_PREFIX = "@TYPE@"
 private val typeRenderer = DescriptorRenderer.COMPACT_WITH_SHORT_TYPES.withOptions {
     textFormat = RenderingFormat.PLAIN
+    renderUnabbreviatedType = false
 }
 
 fun providePropertyTypeHint(elem: PsiElement): List<InlayInfo> {
@@ -47,8 +50,17 @@ fun providePropertyTypeHint(elem: PsiElement): List<InlayInfo> {
 }
 
 fun provideTypeHint(element: KtCallableDeclaration, offset: Int): List<InlayInfo> {
-    val type = SpecifyTypeExplicitlyIntention.getTypeForDeclaration(element)
-    return if (!type.isError && isUnclearType(type, element)) {
+    var type: KotlinType = SpecifyTypeExplicitlyIntention.getTypeForDeclaration(element).unwrap()
+    if (type.containsError()) return emptyList()
+    val name = type.constructor.declarationDescriptor?.name
+    if (name == SpecialNames.NO_NAME_PROVIDED) {
+        type = type.immediateSupertypes().singleOrNull() ?: return emptyList()
+    }
+    else if (name?.isSpecial == true) {
+        return emptyList()
+    }
+
+    return if (isUnclearType(type, element)) {
         val settings = CodeStyleSettingsManager.getInstance(element.project).currentSettings
                 .getCustomSettings(KotlinCodeStyleSettings::class.java)
 

idea/tests/org/jetbrains/kotlin/idea/parameterInfo/InlayTypeHintsTest.kt

@@ -56,4 +56,24 @@ class InlayTypeHintsTest : KotlinLightCodeInsightFixtureTestCase() {
         HintType.LOCAL_VARIABLE_HINT.option.set(true)
         check("""fun foo() { for (x: String in listOf("a")) { } }""")
     }
-}
+
+    fun testErrorType() {
+        HintType.PROPERTY_HINT.option.set(true)
+        check("""val x = arrayListOf<>()""")
+    }
+
+    fun testExpandedTypeAlias() {
+        HintType.PROPERTY_HINT.option.set(true)
+        check("""val x<hint text=": ArrayList<Int>" /> = arrayListOf(1)""")
+    }
+
+    fun testAnonymousObject() {
+        HintType.FUNCTION_HINT.option.set(true)
+        check("""val o = object : Iterable<Int> {
+                  override fun iterator()<hint text=": Iterator<Int>" /> = object : Iterator<Int> {
+                       override fun next()<hint text=": Int" /> = 1
+                       override fun hasNext()<hint text=": Boolean" /> = true
+                  }
+              }""")
+    }
+}