RemoveExplicitTypeIntention: fix false positive for type aliases

#KT-33902 Fixed

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

@@ -22,6 +22,7 @@ import com.intellij.openapi.util.TextRange
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.idea.refactoring.addTypeArgumentsIfNeeded
 import org.jetbrains.kotlin.idea.refactoring.getQualifiedTypeArgumentList
+import org.jetbrains.kotlin.idea.references.mainReference
 import org.jetbrains.kotlin.idea.search.usagesSearch.descriptor
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.endOffset
@@ -68,7 +69,7 @@ class RemoveExplicitTypeIntention : SelfTargetingRangeIntention<KtCallableDeclar
 
             val initializer = (element as? KtDeclarationWithInitializer)?.initializer
 
-            if (!redundantTypeSpecification(element, initializer)) return null
+            if (!redundantTypeSpecification(element.typeReference, initializer)) return null
 
             return when {
                 initializer != null -> TextRange(element.startOffset, initializer.startOffset - 1)
@@ -78,18 +79,27 @@ class RemoveExplicitTypeIntention : SelfTargetingRangeIntention<KtCallableDeclar
             }
         }
 
-        fun redundantTypeSpecification(element: KtCallableDeclaration, initializer: KtExpression?): Boolean {
-            if (initializer == null) return true
+        tailrec fun redundantTypeSpecification(typeReference: KtTypeReference?, initializer: KtExpression?): Boolean {
+            if (initializer == null || typeReference == null) return true
             if (initializer !is KtLambdaExpression && initializer !is KtNamedFunction) return true
-            val functionType = element.typeReference?.typeElement as? KtFunctionType ?: return true
-            if (functionType.receiver != null) return false
-            if (functionType.parameters.isEmpty()) return true
-            val valueParameters = when (initializer) {
-                is KtLambdaExpression -> initializer.valueParameters
-                is KtNamedFunction -> initializer.valueParameters
-                else -> emptyList()
+            val typeElement = typeReference.typeElement ?: return true
+            return when (typeElement) {
+                is KtFunctionType -> {
+                    if (typeElement.receiver != null) return false
+                    if (typeElement.parameters.isEmpty()) return true
+                    val valueParameters = when (initializer) {
+                        is KtLambdaExpression -> initializer.valueParameters
+                        is KtNamedFunction -> initializer.valueParameters
+                        else -> emptyList()
+                    }
+                    valueParameters.isNotEmpty() && valueParameters.none { it.typeReference == null }
+                }
+                is KtUserType -> {
+                    val typeAlias = typeElement.referenceExpression?.mainReference?.resolve() as? KtTypeAlias ?: return true
+                    return redundantTypeSpecification(typeAlias.getTypeReference(), initializer)
+                }
+                else -> true
             }
-            return valueParameters.isNotEmpty() && valueParameters.none { it.typeReference == null }
         }
     }
 }

idea/src/org/jetbrains/kotlin/idea/quickfix/RemovePsiElementSimpleFix.kt

@@ -68,7 +68,7 @@ open class RemovePsiElementSimpleFix(element: PsiElement, private val text: Stri
     object RemoveVariableFactory : KotlinSingleIntentionActionFactory() {
         public override fun createAction(diagnostic: Diagnostic): KotlinQuickFixAction<PsiElement>? {
             val expression = diagnostic.psiElement.getNonStrictParentOfType<KtProperty>() ?: return null
-            if (!RemoveExplicitTypeIntention.redundantTypeSpecification(expression, expression.initializer)) return null
+            if (!RemoveExplicitTypeIntention.redundantTypeSpecification(expression.typeReference, expression.initializer)) return null
             return object : RemovePsiElementSimpleFix(expression, "Remove variable '${expression.name}'") {
                 override fun invoke(project: Project, editor: Editor?, file: KtFile) {
                     val initializer = expression.initializer

idea/testData/intentions/removeExplicitType/lambdaInitializerWithAlias.kt

@@ -0,0 +1,9 @@
+// IS_APPLICABLE: false
+
+typealias ValidationRule2 = (String, String) -> String
+typealias ValidationRule3 = ValidationRule2
+typealias ValidationRule4 = ValidationRule3
+
+fun getValidator(): ValidationRule4<caret> = { text, eventType ->
+    "abc"
+}

idea/testData/intentions/removeExplicitType/lambdaInitializerWithAlias2.kt

@@ -0,0 +1,5 @@
+typealias ValidationRule2 = String
+typealias ValidationRule3 = ValidationRule2
+typealias ValidationRule4 = ValidationRule3
+
+fun getValidator(): ValidationRule4<caret> = "abc"

idea/testData/intentions/removeExplicitType/lambdaInitializerWithAlias2.kt.after

@@ -0,0 +1,5 @@
+typealias ValidationRule2 = String
+typealias ValidationRule3 = ValidationRule2
+typealias ValidationRule4 = ValidationRule3
+
+fun getValidator() = "abc"

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

@@ -13367,6 +13367,16 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             runTest("idea/testData/intentions/removeExplicitType/lambdaInitializer5.kt");
         }
 
+        @TestMetadata("lambdaInitializerWithAlias.kt")
+        public void testLambdaInitializerWithAlias() throws Exception {
+            runTest("idea/testData/intentions/removeExplicitType/lambdaInitializerWithAlias.kt");
+        }
+
+        @TestMetadata("lambdaInitializerWithAlias2.kt")
+        public void testLambdaInitializerWithAlias2() throws Exception {
+            runTest("idea/testData/intentions/removeExplicitType/lambdaInitializerWithAlias2.kt");
+        }
+
         @TestMetadata("needTypeArgument.kt")
         public void testNeedTypeArgument() throws Exception {
             runTest("idea/testData/intentions/removeExplicitType/needTypeArgument.kt");