Introduce subject to when: suggest for qualified, not for obj / constant

#KT-18772 Fixed

idea/src/org/jetbrains/kotlin/idea/intentions/branchedTransformations/branchedTransformationUtils.kt

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.idea.intentions.branchedTransformations
 
 import org.jetbrains.kotlin.idea.core.replaced
+import org.jetbrains.kotlin.idea.references.mainReference
 import org.jetbrains.kotlin.idea.util.CommentSaver
 import org.jetbrains.kotlin.idea.util.psi.patternMatching.matches
 import org.jetbrains.kotlin.lexer.KtTokens
@@ -48,7 +49,10 @@ fun KtWhenExpression.getSubjectToIntroduce(): KtExpression? {
             if (condition !is KtWhenConditionWithExpression) return null
 
             val candidate = condition.expression?.getWhenConditionSubjectCandidate() ?: return null
-            if (candidate !is KtNameReferenceExpression && candidate !is KtThisExpression) return null
+            if (candidate !is KtNameReferenceExpression
+                && (candidate as? KtQualifiedExpression)?.selectorExpression !is KtNameReferenceExpression
+                && candidate !is KtThisExpression
+            ) return null
 
             if (lastCandidate == null) {
                 lastCandidate = candidate
@@ -66,12 +70,14 @@ private fun KtExpression?.getWhenConditionSubjectCandidate(): KtExpression? = wh
 
     is KtBinaryExpression -> {
         val lhs = left
+        val rhs = right
         when (operationToken) {
             KtTokens.IN_KEYWORD, KtTokens.NOT_IN -> lhs
-            KtTokens.EQEQ -> lhs as? KtNameReferenceExpression ?: right
+            KtTokens.EQEQ ->
+                lhs?.takeIf { it.hasCandidateNameReferenceExpression() } ?: rhs?.takeIf { it.hasCandidateNameReferenceExpression() }
             KtTokens.OROR -> {
                 val leftCandidate = lhs.getWhenConditionSubjectCandidate()
-                val rightCandidate = right.getWhenConditionSubjectCandidate()
+                val rightCandidate = rhs.getWhenConditionSubjectCandidate()
                 if (leftCandidate.matches(rightCandidate)) leftCandidate else null
             }
             else -> null
@@ -82,6 +88,15 @@ private fun KtExpression?.getWhenConditionSubjectCandidate(): KtExpression? = wh
     else -> null
 }
 
+private fun KtExpression.hasCandidateNameReferenceExpression(): Boolean {
+    val nameReferenceExpression = this as? KtNameReferenceExpression
+        ?: (this as? KtQualifiedExpression)?.selectorExpression as? KtNameReferenceExpression
+        ?: return false
+    val resolved = nameReferenceExpression.mainReference.resolve()
+    if (resolved is KtObjectDeclaration || (resolved as? KtProperty)?.hasModifier(KtTokens.CONST_KEYWORD) == true) return false
+    return true
+}
+
 fun KtWhenExpression.introduceSubject(): KtWhenExpression? {
     val subject = getSubjectToIntroduce() ?: return null
 

idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified.kt

@@ -0,0 +1,13 @@
+import Platform.JvmPlatform
+
+sealed class Platform {
+    object JvmPlatform : Platform()
+    class Another(val name: String) : Platform()
+}
+
+class ModuleInfo(val platform: Platform)
+
+fun foo(moduleInfo: ModuleInfo) = <caret>when {
+    moduleInfo.platform == JvmPlatform -> 1
+    else -> 0
+}

idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified.kt.after

@@ -0,0 +1,13 @@
+import Platform.JvmPlatform
+
+sealed class Platform {
+    object JvmPlatform : Platform()
+    class Another(val name: String) : Platform()
+}
+
+class ModuleInfo(val platform: Platform)
+
+fun foo(moduleInfo: ModuleInfo) = <caret>when (moduleInfo.platform) {
+    JvmPlatform -> 1
+    else -> 0
+}

idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified2.kt

@@ -0,0 +1,13 @@
+import Platform.JvmPlatform
+
+sealed class Platform {
+    object JvmPlatform : Platform()
+    class Another(val name: String) : Platform()
+}
+
+class ModuleInfo(val platform: Platform)
+
+fun foo(moduleInfo: ModuleInfo) = <caret>when {
+    JvmPlatform == moduleInfo.platform -> 1
+    else -> 0
+}

idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified2.kt.after

@@ -0,0 +1,13 @@
+import Platform.JvmPlatform
+
+sealed class Platform {
+    object JvmPlatform : Platform()
+    class Another(val name: String) : Platform()
+}
+
+class ModuleInfo(val platform: Platform)
+
+fun foo(moduleInfo: ModuleInfo) = <caret>when (moduleInfo.platform) {
+    JvmPlatform -> 1
+    else -> 0
+}

idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified3.kt

@@ -0,0 +1,11 @@
+class Foo {
+    val bar = 1
+}
+
+fun test(foo: Foo): Int {
+    return <caret>when {
+        foo.bar == 1 -> 10
+        foo.bar == 2 -> 20
+        else -> 30
+    }
+}

idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified3.kt.after

@@ -0,0 +1,11 @@
+class Foo {
+    val bar = 1
+}
+
+fun test(foo: Foo): Int {
+    return <caret>when (foo.bar) {
+        1 -> 10
+        2 -> 20
+        else -> 30
+    }
+}

idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified4.kt

@@ -0,0 +1,14 @@
+class Foo {
+    val bar = 1
+}
+
+const val A = 1
+const val B = 2
+
+fun test(foo: Foo): Int {
+    return <caret>when {
+        A == foo.bar -> 10
+        B == foo.bar -> 20
+        else -> 30
+    }
+}

idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified4.kt.after

@@ -0,0 +1,14 @@
+class Foo {
+    val bar = 1
+}
+
+const val A = 1
+const val B = 2
+
+fun test(foo: Foo): Int {
+    return <caret>when (foo.bar) {
+        A -> 10
+        B -> 20
+        else -> 30
+    }
+}

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

@@ -824,6 +824,26 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
                 runTest("idea/testData/inspectionsLocal/branched/introduceWhenSubject/lineBreaksAndComments.kt");
             }
 
+            @TestMetadata("qualified.kt")
+            public void testQualified() throws Exception {
+                runTest("idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified.kt");
+            }
+
+            @TestMetadata("qualified2.kt")
+            public void testQualified2() throws Exception {
+                runTest("idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified2.kt");
+            }
+
+            @TestMetadata("qualified3.kt")
+            public void testQualified3() throws Exception {
+                runTest("idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified3.kt");
+            }
+
+            @TestMetadata("qualified4.kt")
+            public void testQualified4() throws Exception {
+                runTest("idea/testData/inspectionsLocal/branched/introduceWhenSubject/qualified4.kt");
+            }
+
             @TestMetadata("this.kt")
             public void testThis() throws Exception {
                 runTest("idea/testData/inspectionsLocal/branched/introduceWhenSubject/this.kt");