Related to KT-20631: don't report redundant blank Unit in lambda

idea/src/org/jetbrains/kotlin/idea/inspections/RedundantUnitExpressionInspection.kt

@@ -21,6 +21,7 @@ import com.intellij.openapi.project.Project
 import com.intellij.psi.PsiElementVisitor
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
 
 class RedundantUnitExpressionInspection : AbstractKotlinInspection(), CleanupLocalInspectionTool {
     override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean, session: LocalInspectionToolSession): PsiElementVisitor {
@@ -36,6 +37,9 @@ class RedundantUnitExpressionInspection : AbstractKotlinInspection(), CleanupLoc
                 val parent = expression.parent
                 if (parent !is KtReturnExpression && parent !is KtBlockExpression) return
 
+                // Do not report just 'Unit' in function literals (return@label Unit is OK even in literals)
+                if (parent is KtBlockExpression && parent.getParentOfType<KtFunctionLiteral>(strict = true) != null) return
+
                 holder.registerProblem(expression,
                                        "Redundant 'Unit'",
                                        ProblemHighlightType.LIKE_UNUSED_SYMBOL,

idea/testData/inspectionsLocal/redundantUnitExpression/lambda.kt

@@ -0,0 +1,12 @@
+// PROBLEM: none
+
+fun <T> run(f: () -> T) = f()
+
+fun foo(s: String) = s
+
+fun test() {
+    run {
+        foo("Hello")
+        <caret>Unit
+    }
+}

idea/testData/inspectionsLocal/redundantUnitExpression/redundant2.kt

@@ -1,5 +0,0 @@
-fun test() {
-    val f: () -> Unit = {
-        <caret>Unit
-    }
-}

idea/testData/inspectionsLocal/redundantUnitExpression/redundant2.kt.after

@@ -1,4 +0,0 @@
-fun test() {
-    val f: () -> Unit = {
-    }
-}

idea/testData/inspectionsLocal/redundantUnitExpression/redundant3.kt

@@ -1,6 +0,0 @@
-fun test() {
-    val f: () -> Unit = {
-        <caret>Unit
-        Unit
-    }
-}

idea/testData/inspectionsLocal/redundantUnitExpression/redundant3.kt.after

@@ -1,5 +0,0 @@
-fun test() {
-    val f: () -> Unit = {
-        Unit
-    }
-}

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -1637,6 +1637,12 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/testData/inspectionsLocal/redundantUnitExpression"), Pattern.compile("^([\\w\\-_]+)\\.kt$"), TargetBackend.ANY, true);
         }
 
+        @TestMetadata("lambda.kt")
+        public void testLambda() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/redundantUnitExpression/lambda.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("notRedundant1.kt")
         public void testNotRedundant1() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/redundantUnitExpression/notRedundant1.kt");
@@ -1661,18 +1667,6 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             doTest(fileName);
         }
 
-        @TestMetadata("redundant2.kt")
-        public void testRedundant2() throws Exception {
-            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/redundantUnitExpression/redundant2.kt");
-            doTest(fileName);
-        }
-
-        @TestMetadata("redundant3.kt")
-        public void testRedundant3() throws Exception {
-            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/redundantUnitExpression/redundant3.kt");
-            doTest(fileName);
-        }
-
         @TestMetadata("redundant4.kt")
         public void testRedundant4() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/redundantUnitExpression/redundant4.kt");