Merge pull request #13100 from Microsoft/unusedLocalsInSpread

 Do not report error on unused removed property from object spread when its module member

Author: sheetalkamat

src/compiler/checker.ts

@@ -16899,7 +16899,7 @@ namespace ts {
                     if (!local.isReferenced && !local.exportSymbol) {
                         for (const declaration of local.declarations) {
                             if (!isAmbientModule(declaration)) {
-                                error(declaration.name, Diagnostics._0_is_declared_but_never_used, local.name);
+                                errorUnusedLocal(declaration.name, local.name);
                             }
                         }
                     }

tests/baselines/reference/unusedLocalsAndObjectSpread2.errors.txt

@@ -0,0 +1,29 @@
+tests/cases/compiler/unusedLocalsAndObjectSpread2.ts(6,6): error TS6133: 'rest' is declared but never used.
+tests/cases/compiler/unusedLocalsAndObjectSpread2.ts(9,10): error TS6133: 'foo' is declared but never used.
+tests/cases/compiler/unusedLocalsAndObjectSpread2.ts(13,8): error TS6133: 'rest' is declared but never used.
+
+
+==== tests/cases/compiler/unusedLocalsAndObjectSpread2.ts (3 errors) ====
+    
+    declare let props: any;
+    const {
+        children, // here!
+        active: _a, // here!
+      ...rest,
+         ~~~~
+!!! error TS6133: 'rest' is declared but never used.
+    } = props;
+    
+    function foo() {
+             ~~~
+!!! error TS6133: 'foo' is declared but never used.
+        const {
+            children,
+            active: _a,
+        ...rest,
+           ~~~~
+!!! error TS6133: 'rest' is declared but never used.
+      } = props;
+    }
+    
+    export const asdf = 123;

tests/baselines/reference/unusedLocalsAndObjectSpread2.js

@@ -0,0 +1,37 @@
+//// [unusedLocalsAndObjectSpread2.ts]
+
+declare let props: any;
+const {
+    children, // here!
+    active: _a, // here!
+  ...rest,
+} = props;
+
+function foo() {
+    const {
+        children,
+        active: _a,
+    ...rest,
+  } = props;
+}
+
+export const asdf = 123;
+
+//// [unusedLocalsAndObjectSpread2.js]
+"use strict";
+var __rest = (this && this.__rest) || function (s, e) {
+    var t = {};
+    for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p) && e.indexOf(p) < 0)
+        t[p] = s[p];
+    if (s != null && typeof Object.getOwnPropertySymbols === "function")
+        for (var i = 0, p = Object.getOwnPropertySymbols(s); i < p.length; i++) if (e.indexOf(p[i]) < 0)
+            t[p[i]] = s[p[i]];
+    return t;
+};
+var children = props.children, // here!
+_a = props.active, // here!
+rest = __rest(props, ["children", "active"]);
+function foo() {
+    var children = props.children, _a = props.active, rest = __rest(props, ["children", "active"]);
+}
+exports.asdf = 123;

tests/cases/compiler/unusedLocalsAndObjectSpread2.ts

@@ -0,0 +1,18 @@
+//@noUnusedLocals:true
+
+declare let props: any;
+const {
+    children, // here!
+    active: _a, // here!
+  ...rest,
+} = props;
+
+function foo() {
+    const {
+        children,
+        active: _a,
+    ...rest,
+  } = props;
+}
+
+export const asdf = 123;