fix(41621): fixUnusedIdentifier - allow deleting prefix/postfix unary operators

Author: a-tarasyuk

src/services/codefixes/fixUnusedIdentifier.ts

@@ -225,12 +225,11 @@ namespace ts.codefix {
     function deleteAssignments(changes: textChanges.ChangeTracker, sourceFile: SourceFile, token: Identifier, checker: TypeChecker) {
         FindAllReferences.Core.eachSymbolReferenceInFile(token, checker, sourceFile, (ref: Node) => {
             if (isPropertyAccessExpression(ref.parent) && ref.parent.name === ref) ref = ref.parent;
-            if (isBinaryExpression(ref.parent) && isExpressionStatement(ref.parent.parent) && ref.parent.left === ref) {
-                changes.delete(sourceFile, ref.parent.parent);
-            }
+            if (mayDeleteExpression(ref)) changes.delete(sourceFile, ref.parent.parent);
         });
     }
 
+
     function tryDeleteDeclarationWorker(token: Node, changes: textChanges.ChangeTracker, sourceFile: SourceFile, checker: TypeChecker, sourceFiles: readonly SourceFile[], program: Program, cancellationToken: CancellationToken, isFixAll: boolean): void {
         const { parent } = token;
         if (isParameter(parent)) {
@@ -327,4 +326,9 @@ namespace ts.codefix {
             parameters.slice(index + 1).every(p => isIdentifier(p.name) && !p.symbol.isReferenced) :
             index === parameters.length - 1;
     }
+
+    function mayDeleteExpression(node: Node) {
+        return ((isBinaryExpression(node.parent) && node.parent.left === node) ||
+            ((isPostfixUnaryExpression(node.parent) || isPrefixUnaryExpression(node.parent)) && node.parent.operand === node)) && isExpressionStatement(node.parent.parent);
+    }
 }

tests/cases/fourslash/codeFixUnusedIdentifier_all_delete.ts

@@ -56,6 +56,16 @@
 ////export const cls = class<T, U> { u: U; };
 ////export class Ctu<T, U> {}
 ////export type Length<T> = T extends ArrayLike<infer U> ? number : never; // Not affected, can't delete
+////
+////function f4() {
+////    let x = 1;
+////    x++;
+////    x--;
+////    let y = 1;
+////    ++x;
+////    --x;
+////}
+////f4();
 
 verify.codeFixAll({
     fixId: "unusedIdentifier_delete",
@@ -109,5 +119,9 @@ export type First<T> = T;
 export interface ISecond<U> { u: U; }
 export const cls = class<U> { u: U; };
 export class Ctu {}
-export type Length<T> = T extends ArrayLike<infer U> ? number : never; // Not affected, can't delete`,
+export type Length<T> = T extends ArrayLike<infer U> ? number : never; // Not affected, can't delete
+
+function f4() {
+}
+f4();`,
 });

tests/cases/fourslash/codeFixUnusedIdentifier_postfix_operator1.ts

@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+
+// @noUnusedLocals: true
+////function fn() {
+////   let x = 1;
+////   x++;
+////}
+
+verify.codeFix({
+    description: "Remove unused declaration for: 'x'",
+    newFileContent:
+`function fn() {
+}`
+});

tests/cases/fourslash/codeFixUnusedIdentifier_postfix_operator2.ts

@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+
+// @noUnusedLocals: true
+////function fn() {
+////   let x = 1;
+////   x--;
+////}
+
+verify.codeFix({
+    description: "Remove unused declaration for: 'x'",
+    newFileContent:
+`function fn() {
+}`
+});

tests/cases/fourslash/codeFixUnusedIdentifier_prefix_operator1.ts

@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+
+// @noUnusedLocals: true
+////function fn() {
+////   let x = 1;
+////   ++x;
+////}
+
+verify.codeFix({
+    description: "Remove unused declaration for: 'x'",
+    newFileContent:
+`function fn() {
+}`
+});

tests/cases/fourslash/codeFixUnusedIdentifier_prefix_operator2.ts

@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+
+// @noUnusedLocals: true
+////function fn() {
+////   let x = 1;
+////   --x;
+////}
+
+verify.codeFix({
+    description: "Remove unused declaration for: 'x'",
+    newFileContent:
+`function fn() {
+}`
+});