Initial tests for type hints; don't show hint when type is obvious

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

@@ -19,9 +19,11 @@ package org.jetbrains.kotlin.idea.parameterInfo
 import com.intellij.codeInsight.hints.InlayInfo
 import com.intellij.psi.PsiElement
 import com.intellij.psi.codeStyle.CodeStyleSettingsManager
+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.psi.KtCallableDeclaration
+import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.endOffset
 import org.jetbrains.kotlin.renderer.DescriptorRenderer
 import org.jetbrains.kotlin.renderer.RenderingFormat
@@ -46,7 +48,7 @@ fun providePropertyTypeHint(elem: PsiElement): List<InlayInfo> {
 
 fun provideTypeHint(element: KtCallableDeclaration, offset: Int): List<InlayInfo> {
     val type = SpecifyTypeExplicitlyIntention.getTypeForDeclaration(element)
-    return if (!type.isError) {
+    return if (!type.isError && isUnclearType(type, element)) {
         val settings = CodeStyleSettingsManager.getInstance(element.project).currentSettings
                 .getCustomSettings(KotlinCodeStyleSettings::class.java)
 
@@ -66,3 +68,18 @@ fun provideTypeHint(element: KtCallableDeclaration, offset: Int): List<InlayInfo
     }
 }
 
+private fun isUnclearType(type: KotlinType, element: KtCallableDeclaration): Boolean {
+    if (element is KtProperty) {
+        val initializer = element.initializer ?: return true
+        if (initializer is KtConstantExpression || initializer is KtStringTemplateExpression) return false
+        if (initializer is KtCallExpression) {
+            val bindingContext = element.analyze()
+            val resolvedCall = initializer.getResolvedCall(bindingContext)
+            val constructorDescriptor = resolvedCall?.candidateDescriptor as? ConstructorDescriptor
+            if (constructorDescriptor != null && constructorDescriptor.constructedClass.declaredTypeParameters.isEmpty()) {
+                return false
+            }
+        }
+    }
+    return true
+}

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

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2010-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.idea.parameterInfo
+
+import org.jetbrains.kotlin.idea.test.KotlinLightCodeInsightFixtureTestCase
+import org.jetbrains.kotlin.idea.test.KotlinWithJdkAndRuntimeLightProjectDescriptor
+
+class InlayTypeHintsTest : KotlinLightCodeInsightFixtureTestCase() {
+    override fun getProjectDescriptor() = KotlinWithJdkAndRuntimeLightProjectDescriptor.INSTANCE
+
+    fun check(text: String) {
+        myFixture.configureByText("A.kt", text)
+        myFixture.testInlays()
+    }
+
+    fun testLocalVariableType() {
+        HintType.LOCAL_VARIABLE_HINT.option.set(true)
+        check("""fun foo() { val a<hint text=": List<String>" /> = listOf("a") }""")
+    }
+
+    fun testPropertyType() {
+        HintType.PROPERTY_HINT.option.set(true)
+        check("""val a<hint text=": List<String>" /> = listOf("a")""")
+    }
+
+    fun testConstInitializerType() {
+        HintType.PROPERTY_HINT.option.set(true)
+        check("""val a = 1""")
+    }
+
+    fun testConstructorWithoutTypeParametersType() {
+        HintType.PROPERTY_HINT.option.set(true)
+        check("""val a = Any()""")
+    }
+}