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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"vm: `let` declaration no longer throws SyntaxError for non-configurable global property in vm context (regression in v26)","articleBody":"### Version\n\nv26.3.0\n\n### Platform\n\n```text\nDarwin 24.6.0 Darwin Kernel Version 24.6.0: xnu-11417.140.69.705.2~1/RELEASE_ARM64_T6041 arm64 (macOS, Apple Silicon)\n```\n\n### Subsystem\n\nvm\n\n### What steps will reproduce the bug?\n\nA let declaration that collides with a non-configurable property on a vm context's global object is no longer rejected with a SyntaxError. Save as repro.js and run with node repro.js:\n\n```js\nconst vm = require('vm');\nconst context = vm.createContext({});\n\n// Define a non-configurable (\"restricted\") property on the context global.\nvm.runInContext(\n  \"Object.defineProperty(this, 'foo', { value: 1, configurable: false });\",\n  context\n);\n\n// Per ECMA-262 GlobalDeclarationInstantiation step 3.d, a lexical\n// declaration colliding with a restricted global property must throw.\ntry {\n  vm.runInContext('let foo;', context);\n  console.log('NO ERROR (let foo; was accepted)');\n} catch (e) {\n  console.log('THREW:', e.constructor.name, '-', e.message);\n}\n```\n\n### How often does it reproduce? Is there a required condition?\n\n100% reproducible.\n\n### What is the expected behavior? Why is that the expected behavior?\n\n`let foo;` should throw a `SyntaxError`, because foo is a `non-configurable` own property of the global object. v24.12.0 behaves correctly: THREW: `SyntaxError - Identifier 'foo' has already been declared`\n\n### What do you see instead?\n\nOn v26.3.0 the declaration is silently accepted:  `NO ERROR (let foo; was accepted)`\n\n### Additional information\n\nFound via the test262 `language/global-code/script-decl-lex-restricted-global.js` case.","author":{"url":"https://github.com/hai-x","@type":"Person","name":"hai-x"},"datePublished":"2026-06-02T15:25:32.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/63715/node/issues/63715"}