reviews

Author: yeonjuan

Diff for: packages/eslint-plugin/src/rules/no-base-to-string.ts

@@ -240,18 +240,8 @@ export default createRule<Options, MessageIds>({
                 return;
               }
 
-              for (const part of typeParts) {
-                const typeArg = checker.getTypeArguments(
-                  part as ts.TypeReference,
-                )[0];
-
-                const certainty = getToStringCertainty(node, typeArg);
-
-                if (certainty !== Usefulness.Always) {
-                  checkExpression(memberExpr.object, typeArg, 'baseArrayJoin');
-                  return;
-                }
-              }
+              const typeArg = type.getNumberIndexType();
+              checkExpression(memberExpr.object, typeArg, 'baseArrayJoin');
             },
           }
         : undefined),

Diff for: packages/eslint-plugin/tests/rules/no-base-to-string.test.ts

@@ -455,6 +455,23 @@ String(...objects);
       ],
       options: [{ checkArrayJoin: true }],
     },
+    {
+      code: `
+        class Foo {}
+        const tuple: [string, Foo] = ['string', new Foo()];
+        tuple.join('');
+      `,
+      errors: [
+        {
+          data: {
+            certainty: 'will',
+            name: 'tuple',
+          },
+          messageId: 'baseArrayJoin',
+        },
+      ],
+      options: [{ checkArrayJoin: true }],
+    },
     {
       code: `
         class Foo {}
@@ -472,5 +489,29 @@ String(...objects);
       ],
       options: [{ checkArrayJoin: true }],
     },
+    {
+      code: `
+        class Foo {}
+        const tuple: [string, Foo] = ['string', new Foo()];
+        tuple.join('');
+      `,
+      errors: [
+        {
+          data: {
+            certainty: 'will',
+            name: 'tuple',
+          },
+          messageId: 'baseArrayJoin',
+        },
+      ],
+      languageOptions: {
+        parserOptions: {
+          project: './tsconfig.noUncheckedIndexedAccess.json',
+          projectService: false,
+          tsconfigRootDir: rootDir,
+        },
+      },
+      options: [{ checkArrayJoin: true }],
+    },
   ],
 });