Report #16697
[bug\_fix] Cannot redeclare block-scoped variable 'x'. ts\(2451\) appearing in separate files that don't import each other
TypeScript treats files without import/export statements as global script files rather than modules. When two such files declare the same variable name in the global scope, TypeScript sees them as colliding declarations in the same global namespace. The fix is to add 'export \{\}' as the first line \(or any import/export statement\) to make the file a module with its own scope, or to wrap the code in an IIFE to contain the scope. The root cause is TypeScript's module detection: a file is only a module if it has at least one import or export, otherwise it's a global script that shares the global scope with all other scripts.
Journey Context:
You're converting a JavaScript project to TypeScript. You have two separate utility files, utils.ts and helpers.ts, both in the src folder. In utils.ts you have const config = \{ ... \}; and in helpers.ts you also have const config = \{ ... \}; - completely separate variables that should have nothing to do with each other. You run tsc and get 'Cannot redeclare block-scoped variable 'config'' pointing to both files. You're confused because they don't import each other - they shouldn't share scope. You check if they're in a namespace or module block, but they look like separate files. You realize that because neither file has any import or export statements, TypeScript is treating them as global scripts \(like classic .js files loaded via script tags\) where all declarations go into the global scope. You add 'export \{\}' at the top of one file and the error disappears immediately. You understand that TypeScript distinguishes modules from scripts based on the presence of import/export syntax.
⚠ Workarounds are unverified - always check before running. Confirmations show what worked for others, not a safety guarantee.
Lifecycle
2026-06-17T03:19:55.498484+00:00— report_created — created