Fold initializer & if to elvis: add test, rename tests, simplify code

Enhancement for KT-27016

idea/src/org/jetbrains/kotlin/idea/intentions/FoldInitializerAndIfToElvisIntention.kt

@@ -23,7 +23,9 @@ import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiWhiteSpace
 import com.intellij.psi.search.LocalSearchScope
 import com.intellij.psi.search.searches.ReferencesSearch
+import org.jetbrains.kotlin.descriptors.VariableDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
+import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
 import org.jetbrains.kotlin.idea.core.replaced
 import org.jetbrains.kotlin.idea.core.setType
 import org.jetbrains.kotlin.idea.inspections.IntentionBasedInspection
@@ -147,11 +149,7 @@ class FoldInitializerAndIfToElvisIntention :
 
             if (typeReference != null) {
                 val checkedType = ifExpression.analyze(BodyResolveMode.PARTIAL)[BindingContext.TYPE, typeReference]
-                val variableTypeReference = prevStatement.typeReference
-                val variableType = if (variableTypeReference != null)
-                    prevStatement.analyze(BodyResolveMode.PARTIAL)[BindingContext.TYPE, variableTypeReference]
-                else
-                    SpecifyTypeExplicitlyIntention.getTypeForDeclaration(prevStatement)
+                val variableType = (prevStatement.resolveToDescriptorIfAny() as? VariableDescriptor)?.type
                 if (checkedType != null && variableType != null && !checkedType.isSubtypeOf(variableType)) return null
             }
 

idea/testData/intentions/foldInitializerAndIfToElvis/IsSideTypeFake.kt

@@ -0,0 +1,21 @@
+// IS_APPLICABLE: false
+interface A {
+    fun a() {}
+}
+
+open class B : A {
+    fun b() {}
+}
+
+interface C : A {
+    fun c() {}
+}
+
+fun test() {
+    val b = B()
+    if (<caret>b !is C) {
+        return
+    }
+    b.b()
+    b.c()
+}

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -8729,6 +8729,26 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             runTest("idea/testData/intentions/foldInitializerAndIfToElvis/ifStatementPriority.kt");
         }
 
+        @TestMetadata("IsSameType.kt")
+        public void testIsSameType() throws Exception {
+            runTest("idea/testData/intentions/foldInitializerAndIfToElvis/IsSameType.kt");
+        }
+
+        @TestMetadata("IsSideTypeFake.kt")
+        public void testIsSideTypeFake() throws Exception {
+            runTest("idea/testData/intentions/foldInitializerAndIfToElvis/IsSideTypeFake.kt");
+        }
+
+        @TestMetadata("IsSubType.kt")
+        public void testIsSubType() throws Exception {
+            runTest("idea/testData/intentions/foldInitializerAndIfToElvis/IsSubType.kt");
+        }
+
+        @TestMetadata("IsSuperTypeFake.kt")
+        public void testIsSuperTypeFake() throws Exception {
+            runTest("idea/testData/intentions/foldInitializerAndIfToElvis/IsSuperTypeFake.kt");
+        }
+
         @TestMetadata("MultiStatementBlock.kt")
         public void testMultiStatementBlock() throws Exception {
             runTest("idea/testData/intentions/foldInitializerAndIfToElvis/MultiStatementBlock.kt");
@@ -8749,21 +8769,6 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             runTest("idea/testData/intentions/foldInitializerAndIfToElvis/NotIsNullableType.kt");
         }
 
-        @TestMetadata("NotIsSameType.kt")
-        public void testNotIsSameType() throws Exception {
-            runTest("idea/testData/intentions/foldInitializerAndIfToElvis/NotIsSameType.kt");
-        }
-
-        @TestMetadata("NotIsSubType.kt")
-        public void testNotIsSubType() throws Exception {
-            runTest("idea/testData/intentions/foldInitializerAndIfToElvis/NotIsSubType.kt");
-        }
-
-        @TestMetadata("NotIsSuperType.kt")
-        public void testNotIsSuperType() throws Exception {
-            runTest("idea/testData/intentions/foldInitializerAndIfToElvis/NotIsSuperType.kt");
-        }
-
         @TestMetadata("OtherVar1.kt")
         public void testOtherVar1() throws Exception {
             runTest("idea/testData/intentions/foldInitializerAndIfToElvis/OtherVar1.kt");