Show lambda return hints only once in one-liner ifs (KT-27802)

#KT-27802 Fixed

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

@@ -8,6 +8,7 @@ package org.jetbrains.kotlin.idea.parameterInfo
 import com.intellij.codeInsight.hints.InlayInfo
 import com.intellij.psi.PsiWhiteSpace
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
+import org.jetbrains.kotlin.idea.intentions.branchedTransformations.isOneLiner
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
@@ -15,7 +16,15 @@ import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import org.jetbrains.kotlin.resolve.bindingContextUtil.isUsedAsResultOfLambda
 
 fun provideLambdaReturnValueHints(expression: KtExpression): List<InlayInfo> {
-    if (expression is KtIfExpression || expression is KtWhenExpression || expression is KtBlockExpression) {
+    if (expression is KtWhenExpression || expression is KtBlockExpression) {
+        return emptyList()
+    }
+
+    if (expression is KtIfExpression && !expression.isOneLiner()) {
+        return emptyList()
+    }
+
+    if (expression.getParentOfType<KtIfExpression>(true)?.isOneLiner() == true) {
         return emptyList()
     }
 

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

@@ -19,6 +19,10 @@ internal fun JavaCodeInsightTestFixture.checkHintType(text: String, hintType: Hi
     configureByText("A.kt", text.trimIndent())
     doHighlighting()
 
+    checkHintType(hintType)
+}
+
+internal fun JavaCodeInsightTestFixture.checkHintType(hintType: HintType) {
     val hintInfo = getHintInfoFromProvider(caretOffset, file, editor)
     Assert.assertNotNull("No hint available at caret", hintInfo)
     Assert.assertEquals(hintType.option.name, (hintInfo as HintInfo.OptionInfo).optionName)

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

@@ -5,11 +5,9 @@
 
 package org.jetbrains.kotlin.idea.parameterInfo
 
-import com.intellij.codeInsight.hints.HintInfo
 import org.jetbrains.kotlin.idea.test.KotlinLightCodeInsightFixtureTestCase
 import org.jetbrains.kotlin.idea.test.KotlinLightProjectDescriptor
 import org.jetbrains.kotlin.idea.test.KotlinWithJdkAndRuntimeLightProjectDescriptor
-import org.junit.Assert
 
 class LambdaImplicitHintsTest : KotlinLightCodeInsightFixtureTestCase() {
     override fun getProjectDescriptor(): KotlinLightProjectDescriptor = KotlinWithJdkAndRuntimeLightProjectDescriptor.INSTANCE

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

@@ -15,18 +15,10 @@ class LambdaReturnValueHintsTest : KotlinLightCodeInsightFixtureTestCase() {
     fun check(text: String) {
         myFixture.configureByText("A.kt", text.trimIndent())
         myFixture.testInlays()
-    }
 
-    fun testHintType() {
-        myFixture.checkHintType(
-            """
-            val x = run {
-                println("foo")
-                <caret>1
-            }
-            """,
-            HintType.LAMBDA_RETURN_EXPRESSION
-        )
+        if (myFixture.editor.caretModel.offset != 0) {
+            myFixture.checkHintType(HintType.LAMBDA_RETURN_EXPRESSION)
+        }
     }
 
     fun testSimple() {
@@ -34,7 +26,7 @@ class LambdaReturnValueHintsTest : KotlinLightCodeInsightFixtureTestCase() {
             """
             val x = run {
                 println("foo")
-                <hint text="^run" />1
+                <caret><hint text="^run" />1
             }
             """
         )
@@ -65,6 +57,17 @@ class LambdaReturnValueHintsTest : KotlinLightCodeInsightFixtureTestCase() {
         )
     }
 
+    fun testOneLineIf() {
+        check(
+            """
+            val x = run {
+                println(1)
+                <caret><hint text="^run"/>if (true) 1 else { 0 }
+            }
+            """
+        )
+    }
+
     fun testWhen() {
         check(
             """