Check for unused locals in commonjs modules (#19612)

src/compiler/checker.ts

@@ -23158,7 +23158,7 @@ namespace ts {
 
                 checkDeferredNodes();
 
-                if (isExternalModule(node)) {
+                if (isExternalOrCommonJsModule(node)) {
                     registerForUnusedIdentifiersCheck(node);
                 }
 

tests/baselines/reference/commonJsUnusedLocals.errors.txt

@@ -0,0 +1,9 @@
+/a.js(1,7): error TS6133: 'x' is declared but its value is never read.
+
+
+==== /a.js (1 errors) ====
+    const x = 0;
+          ~
+!!! error TS6133: 'x' is declared but its value is never read.
+    exports.y = 1;
+    

tests/baselines/reference/commonJsUnusedLocals.symbols

@@ -0,0 +1,9 @@
+=== /a.js ===
+const x = 0;
+>x : Symbol(x, Decl(a.js, 0, 5))
+
+exports.y = 1;
+>exports.y : Symbol(y, Decl(a.js, 0, 12))
+>exports : Symbol(y, Decl(a.js, 0, 12))
+>y : Symbol(y, Decl(a.js, 0, 12))
+

tests/baselines/reference/commonJsUnusedLocals.types

@@ -0,0 +1,12 @@
+=== /a.js ===
+const x = 0;
+>x : 0
+>0 : 0
+
+exports.y = 1;
+>exports.y = 1 : 1
+>exports.y : number
+>exports : typeof "/a"
+>y : number
+>1 : 1
+

tests/cases/compiler/commonJsUnusedLocals.ts

@@ -0,0 +1,8 @@
+// @noUnusedLocals: true
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+
+// @Filename: /a.js
+const x = 0;
+exports.y = 1;