Unnecessary local variable: highlight with INFORMATION level when initializer has any multi-line blocks (#3359)

#KT-26752 Fixed

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

@@ -16,8 +16,10 @@
 
 package org.jetbrains.kotlin.idea.inspections
 
+import com.intellij.codeInspection.ProblemHighlightType
 import com.intellij.openapi.editor.Editor
 import com.intellij.openapi.project.Project
+import com.intellij.psi.impl.source.tree.LeafPsiElement
 import com.intellij.psi.search.LocalSearchScope
 import com.intellij.psi.search.searches.ReferencesSearch
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
@@ -27,15 +29,18 @@ import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToCall
 import org.jetbrains.kotlin.idea.core.NewDeclarationNameValidator
 import org.jetbrains.kotlin.idea.refactoring.inline.KotlinInlineValHandler
+import org.jetbrains.kotlin.idea.util.getLineCount
 import org.jetbrains.kotlin.idea.util.nameIdentifierTextRangeInThis
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.anyDescendantOfType
 import org.jetbrains.kotlin.psi.psiUtil.getNextSiblingIgnoringWhitespaceAndComments
 import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
 import org.jetbrains.kotlin.resolve.BindingContext.DECLARATION_TO_DESCRIPTOR
 import org.jetbrains.kotlin.resolve.BindingContext.REFERENCE_TARGET
 import org.jetbrains.kotlin.resolve.DescriptorToSourceUtils
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
+import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 
 class UnnecessaryVariableInspection : AbstractApplicabilityBasedInspection<KtProperty>(KtProperty::class.java) {
 
@@ -43,6 +48,11 @@ class UnnecessaryVariableInspection : AbstractApplicabilityBasedInspection<KtPro
 
     override fun inspectionHighlightRangeInElement(element: KtProperty) = element.nameIdentifierTextRangeInThis()
 
+    override fun inspectionHighlightType(element: KtProperty): ProblemHighlightType {
+        val hasMultiLineBlock = element.initializer?.hasMultiLineBlock() == true
+        return if (hasMultiLineBlock) ProblemHighlightType.INFORMATION else ProblemHighlightType.GENERIC_ERROR_OR_WARNING
+    }
+
     override fun inspectionText(element: KtProperty) = when (statusFor(element)) {
         Status.RETURN_ONLY -> KotlinBundle.message("variable.used.only.in.following.return.and.should.be.inlined")
         Status.EXACT_COPY -> KotlinBundle.message(
@@ -60,6 +70,11 @@ class UnnecessaryVariableInspection : AbstractApplicabilityBasedInspection<KtPro
         KotlinInlineValHandler(withPrompt = false).inlineElement(project, editor, element)
     }
 
+    private fun LeafPsiElement.startsMultilineBlock(): Boolean =
+        node.elementType == KtTokens.LBRACE && parent.safeAs<KtExpression>()?.getLineCount()?.let { it > 1 } == true
+
+    private fun KtExpression.hasMultiLineBlock(): Boolean = anyDescendantOfType<LeafPsiElement> { it.startsMultilineBlock() }
+
     companion object {
         private enum class Status {
             RETURN_ONLY,

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse.kt

@@ -0,0 +1,13 @@
+// HIGHLIGHT: INFORMATION
+fun test(b: Boolean): Int {
+    val <caret>result = if (b) {
+        foo()
+    } else {
+        bar()
+    }
+    return result
+}
+
+fun foo() = 1
+
+fun bar() = 2

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse.kt.after

@@ -0,0 +1,12 @@
+// HIGHLIGHT: INFORMATION
+fun test(b: Boolean): Int {
+    return if (b) {
+        foo()
+    } else {
+        bar()
+    }
+}
+
+fun foo() = 1
+
+fun bar() = 2

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse2.kt

@@ -0,0 +1,9 @@
+// HIGHLIGHT: GENERIC_ERROR_OR_WARNING
+fun test(b: Boolean): Int {
+    val <caret>result = if (b) foo() else bar()
+    return result
+}
+
+fun foo() = 1
+
+fun bar() = 2

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse2.kt.after

@@ -0,0 +1,8 @@
+// HIGHLIGHT: GENERIC_ERROR_OR_WARNING
+fun test(b: Boolean): Int {
+    return if (b) foo() else bar()
+}
+
+fun foo() = 1
+
+fun bar() = 2

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse3.kt

@@ -0,0 +1,12 @@
+// HIGHLIGHT: GENERIC_ERROR_OR_WARNING
+fun test(b: Boolean): Int {
+    val <caret>result = if (b)
+        foo()
+    else
+        bar()
+    return result
+}
+
+fun foo() = 1
+
+fun bar() = 2

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse3.kt.after

@@ -0,0 +1,11 @@
+// HIGHLIGHT: GENERIC_ERROR_OR_WARNING
+fun test(b: Boolean): Int {
+    return if (b)
+        foo()
+    else
+        bar()
+}
+
+fun foo() = 1
+
+fun bar() = 2

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse4.kt

@@ -0,0 +1,14 @@
+// HIGHLIGHT: GENERIC_ERROR_OR_WARNING
+fun test(b: Boolean): Int {
+    val <caret>result = if (b)
+        baz { foo() }
+    else
+        baz { bar() }
+    return result
+}
+
+fun foo() = 1
+
+fun bar() = 2
+
+fun baz(f: () -> Int) = f()

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse4.kt.after

@@ -0,0 +1,13 @@
+// HIGHLIGHT: GENERIC_ERROR_OR_WARNING
+fun test(b: Boolean): Int {
+    return if (b)
+        baz { foo() }
+    else
+        baz { bar() }
+}
+
+fun foo() = 1
+
+fun bar() = 2
+
+fun baz(f: () -> Int) = f()

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse5.kt

@@ -0,0 +1,18 @@
+// HIGHLIGHT: INFORMATION
+fun test(b: Boolean): Int {
+    val <caret>result = if (b)
+        baz {
+            foo()
+        }
+    else
+        baz {
+            bar()
+        }
+    return result
+}
+
+fun foo() = 1
+
+fun bar() = 2
+
+fun baz(f: () -> Int) = f()

idea/testData/inspectionsLocal/unnecessaryVariable/ifElse5.kt.after

@@ -0,0 +1,17 @@
+// HIGHLIGHT: INFORMATION
+fun test(b: Boolean): Int {
+    return if (b)
+        baz {
+            foo()
+        }
+    else
+        baz {
+            bar()
+        }
+}
+
+fun foo() = 1
+
+fun bar() = 2
+
+fun baz(f: () -> Int) = f()

idea/testData/inspectionsLocal/unnecessaryVariable/lambda.kt

@@ -0,0 +1,9 @@
+// HIGHLIGHT: GENERIC_ERROR_OR_WARNING
+fun test(): Int {
+    val <caret>result = foo { bar() }
+    return result
+}
+
+fun foo(f: () -> Int) = f()
+
+fun bar() = 1

idea/testData/inspectionsLocal/unnecessaryVariable/lambda.kt.after

@@ -0,0 +1,8 @@
+// HIGHLIGHT: GENERIC_ERROR_OR_WARNING
+fun test(): Int {
+    return foo { bar() }
+}
+
+fun foo(f: () -> Int) = f()
+
+fun bar() = 1

idea/testData/inspectionsLocal/unnecessaryVariable/lambda2.kt

@@ -0,0 +1,11 @@
+// HIGHLIGHT: INFORMATION
+fun test(): Int {
+    val <caret>result = foo {
+        bar()
+    }
+    return result
+}
+
+fun foo(f: () -> Int) = f()
+
+fun bar() = 1

idea/testData/inspectionsLocal/unnecessaryVariable/lambda2.kt.after

@@ -0,0 +1,10 @@
+// HIGHLIGHT: INFORMATION
+fun test(): Int {
+    return foo {
+        bar()
+    }
+}
+
+fun foo(f: () -> Int) = f()
+
+fun bar() = 1

idea/testData/inspectionsLocal/unnecessaryVariable/try.kt

@@ -0,0 +1,13 @@
+// HIGHLIGHT: INFORMATION
+fun test(): Int {
+    val <caret>result = try {
+        foo()
+    } finally {
+        bar()
+    }
+    return result
+}
+
+fun foo() = 1
+
+fun bar() {}

idea/testData/inspectionsLocal/unnecessaryVariable/try.kt.after

@@ -0,0 +1,12 @@
+// HIGHLIGHT: INFORMATION
+fun test(): Int {
+    return try {
+        foo()
+    } finally {
+        bar()
+    }
+}
+
+fun foo() = 1
+
+fun bar() {}

idea/testData/inspectionsLocal/unnecessaryVariable/when.kt

@@ -0,0 +1,12 @@
+// HIGHLIGHT: INFORMATION
+fun test(i: Int): Int {
+    val <caret>result = when (i) {
+        1 -> foo()
+        else -> bar()
+    }
+    return result
+}
+
+fun foo() = 1
+
+fun bar() = 2

idea/testData/inspectionsLocal/unnecessaryVariable/when.kt.after

@@ -0,0 +1,11 @@
+// HIGHLIGHT: INFORMATION
+fun test(i: Int): Int {
+    return when (i) {
+        1 -> foo()
+        else -> bar()
+    }
+}
+
+fun foo() = 1
+
+fun bar() = 2

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

@@ -14083,11 +14083,46 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/unnecessaryVariable/copyOfVar.kt");
         }
 
+        @TestMetadata("ifElse.kt")
+        public void testIfElse() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unnecessaryVariable/ifElse.kt");
+        }
+
+        @TestMetadata("ifElse2.kt")
+        public void testIfElse2() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unnecessaryVariable/ifElse2.kt");
+        }
+
+        @TestMetadata("ifElse3.kt")
+        public void testIfElse3() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unnecessaryVariable/ifElse3.kt");
+        }
+
+        @TestMetadata("ifElse4.kt")
+        public void testIfElse4() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unnecessaryVariable/ifElse4.kt");
+        }
+
+        @TestMetadata("ifElse5.kt")
+        public void testIfElse5() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unnecessaryVariable/ifElse5.kt");
+        }
+
         @TestMetadata("it.kt")
         public void testIt() throws Exception {
             runTest("idea/testData/inspectionsLocal/unnecessaryVariable/it.kt");
         }
 
+        @TestMetadata("lambda.kt")
+        public void testLambda() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unnecessaryVariable/lambda.kt");
+        }
+
+        @TestMetadata("lambda2.kt")
+        public void testLambda2() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unnecessaryVariable/lambda2.kt");
+        }
+
         @TestMetadata("override.kt")
         public void testOverride() throws Exception {
             runTest("idea/testData/inspectionsLocal/unnecessaryVariable/override.kt");
@@ -14118,11 +14153,21 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/unnecessaryVariable/topLevelCopy.kt");
         }
 
+        @TestMetadata("try.kt")
+        public void testTry() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unnecessaryVariable/try.kt");
+        }
+
         @TestMetadata("varCopy.kt")
         public void testVarCopy() throws Exception {
             runTest("idea/testData/inspectionsLocal/unnecessaryVariable/varCopy.kt");
         }
 
+        @TestMetadata("when.kt")
+        public void testWhen() throws Exception {
+            runTest("idea/testData/inspectionsLocal/unnecessaryVariable/when.kt");
+        }
+
         @TestMetadata("whenSubject.kt")
         public void testWhenSubject() throws Exception {
             runTest("idea/testData/inspectionsLocal/unnecessaryVariable/whenSubject.kt");