RedundantLetInspection: fix false negative for references

#KT-34603 Fixed

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

@@ -59,6 +59,7 @@ abstract class RedundantLetInspection : AbstractApplicabilityBasedInspection<KtC
             is KtDotQualifiedExpression -> bodyExpression.applyTo(element)
             is KtBinaryExpression -> bodyExpression.applyTo(element)
             is KtCallExpression -> bodyExpression.applyTo(element, lambdaExpression.functionLiteral, editor)
+            is KtSimpleNameExpression -> deleteCall(element)
         }
     }
 }
@@ -69,7 +70,11 @@ class SimpleRedundantLetInspection : RedundantLetInspection() {
         bodyExpression: PsiElement,
         lambdaExpression: KtLambdaExpression,
         parameterName: String
-    ): Boolean = if (bodyExpression is KtDotQualifiedExpression) bodyExpression.isApplicable(parameterName) else false
+    ): Boolean = when (bodyExpression) {
+        is KtDotQualifiedExpression -> bodyExpression.isApplicable(parameterName)
+        is KtSimpleNameExpression -> bodyExpression.text == parameterName
+        else -> false
+    }
 }
 
 class ComplexRedundantLetInspection : RedundantLetInspection() {
@@ -138,6 +143,16 @@ private fun KtDotQualifiedExpression.applyTo(element: KtCallExpression) {
     }
 }
 
+private fun deleteCall(element: KtCallExpression) {
+    val parent = element.parent as? KtDotQualifiedExpression
+    if (parent != null) {
+        val replacement = parent.selectorExpression?.takeIf { it != element } ?: parent.receiverExpression
+        parent.replace(replacement)
+    } else {
+        element.delete()
+    }
+}
+
 private fun KtCallExpression.applyTo(element: KtCallExpression, functionLiteral: KtFunctionLiteral, editor: Editor?) {
     val parent = element.parent as? KtQualifiedExpression
     val reference = functionLiteral.valueParameterReferences(this).firstOrNull()

idea/testData/inspectionsLocal/simpleRedundantLet/reference.kt

@@ -0,0 +1,3 @@
+// WITH_RUNTIME
+
+val a = 42.let<caret> { t -> t }.also { println(it) }

idea/testData/inspectionsLocal/simpleRedundantLet/reference.kt.after

@@ -0,0 +1,3 @@
+// WITH_RUNTIME
+
+val a = 42.also { println(it) }

idea/testData/inspectionsLocal/simpleRedundantLet/reference2.kt

@@ -0,0 +1,3 @@
+// WITH_RUNTIME
+
+val a = 42.let<caret> { it }

idea/testData/inspectionsLocal/simpleRedundantLet/reference2.kt.after

@@ -0,0 +1,3 @@
+// WITH_RUNTIME
+
+val a = 42

idea/testData/inspectionsLocal/simpleRedundantLet/reference3.kt

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun Int.foo() {
+    let<caret> { it }
+}

idea/testData/inspectionsLocal/simpleRedundantLet/reference3.kt.after

@@ -0,0 +1,4 @@
+// WITH_RUNTIME
+
+fun Int.foo() {
+}

idea/testData/inspectionsLocal/simpleRedundantLet/reference4.kt

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun Int.foo() {
+    let<caret> { it }.also(::println)
+}

idea/testData/inspectionsLocal/simpleRedundantLet/reference4.kt.after

@@ -0,0 +1,5 @@
+// WITH_RUNTIME
+
+fun Int.foo() {
+    also(::println)
+}

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

@@ -11650,6 +11650,26 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
             runTest("idea/testData/inspectionsLocal/simpleRedundantLet/receiverWithLambda2.kt");
         }
 
+        @TestMetadata("reference.kt")
+        public void testReference() throws Exception {
+            runTest("idea/testData/inspectionsLocal/simpleRedundantLet/reference.kt");
+        }
+
+        @TestMetadata("reference2.kt")
+        public void testReference2() throws Exception {
+            runTest("idea/testData/inspectionsLocal/simpleRedundantLet/reference2.kt");
+        }
+
+        @TestMetadata("reference3.kt")
+        public void testReference3() throws Exception {
+            runTest("idea/testData/inspectionsLocal/simpleRedundantLet/reference3.kt");
+        }
+
+        @TestMetadata("reference4.kt")
+        public void testReference4() throws Exception {
+            runTest("idea/testData/inspectionsLocal/simpleRedundantLet/reference4.kt");
+        }
+
         @TestMetadata("sameLets.kt")
         public void testSameLets() throws Exception {
             runTest("idea/testData/inspectionsLocal/simpleRedundantLet/sameLets.kt");