From 23b3eb685fa358e3ae7e4cdf94349b570d6d8e08 Mon Sep 17 00:00:00 2001
From: Oleksandr T <oleksandr.tarasiuk@outlook.com>
Date: Mon, 30 Nov 2020 23:58:47 +0200
Subject: [PATCH] fix(41621): fixUnusedIdentifier - allow deleting
 prefix/postfix unary operators (#41624)

---
 src/services/codefixes/fixUnusedIdentifier.ts      |  7 ++++++-
 .../codeFixUnusedIdentifier_postfix_operator1.ts   | 14 ++++++++++++++
 .../codeFixUnusedIdentifier_postfix_operator2.ts   | 14 ++++++++++++++
 .../codeFixUnusedIdentifier_prefix_operator1.ts    | 14 ++++++++++++++
 .../codeFixUnusedIdentifier_prefix_operator2.ts    | 14 ++++++++++++++
 5 files changed, 62 insertions(+), 1 deletion(-)
 create mode 100644 tests/cases/fourslash/codeFixUnusedIdentifier_postfix_operator1.ts
 create mode 100644 tests/cases/fourslash/codeFixUnusedIdentifier_postfix_operator2.ts
 create mode 100644 tests/cases/fourslash/codeFixUnusedIdentifier_prefix_operator1.ts
 create mode 100644 tests/cases/fourslash/codeFixUnusedIdentifier_prefix_operator2.ts

diff --git a/src/services/codefixes/fixUnusedIdentifier.ts b/src/services/codefixes/fixUnusedIdentifier.ts
index 19956a097d9..db7e0550e9a 100644
--- a/src/services/codefixes/fixUnusedIdentifier.ts
+++ b/src/services/codefixes/fixUnusedIdentifier.ts
@@ -225,7 +225,7 @@ namespace ts.codefix {
         if (isIdentifier(token)) {
             FindAllReferences.Core.eachSymbolReferenceInFile(token, checker, sourceFile, (ref: Node) => {
                 if (isPropertyAccessExpression(ref.parent) && ref.parent.name === ref) ref = ref.parent;
-                if (!isFixAll && isBinaryExpression(ref.parent) && isExpressionStatement(ref.parent.parent) && ref.parent.left === ref) {
+                if (!isFixAll && mayDeleteExpression(ref)) {
                     changes.delete(sourceFile, ref.parent.parent);
                 }
             });
@@ -332,4 +332,9 @@ 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);
+    }
 }
diff --git a/tests/cases/fourslash/codeFixUnusedIdentifier_postfix_operator1.ts b/tests/cases/fourslash/codeFixUnusedIdentifier_postfix_operator1.ts
new file mode 100644
index 00000000000..5d6526a627a
--- /dev/null
+++ b/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() {
+}`
+});
diff --git a/tests/cases/fourslash/codeFixUnusedIdentifier_postfix_operator2.ts b/tests/cases/fourslash/codeFixUnusedIdentifier_postfix_operator2.ts
new file mode 100644
index 00000000000..5390baceeac
--- /dev/null
+++ b/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() {
+}`
+});
diff --git a/tests/cases/fourslash/codeFixUnusedIdentifier_prefix_operator1.ts b/tests/cases/fourslash/codeFixUnusedIdentifier_prefix_operator1.ts
new file mode 100644
index 00000000000..b79d64686cd
--- /dev/null
+++ b/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() {
+}`
+});
diff --git a/tests/cases/fourslash/codeFixUnusedIdentifier_prefix_operator2.ts b/tests/cases/fourslash/codeFixUnusedIdentifier_prefix_operator2.ts
new file mode 100644
index 00000000000..fa5e437bccd
--- /dev/null
+++ b/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() {
+}`
+});