ts-r
  • Error
  • Reported by the binder

TS2451

Cannot redeclare block-scoped variable '{0}'.

A let, const or class name is declared twice in the same scope. Rename one of them, or remove the duplicate.

What it means

Block-scoped declarations (let, const, class) can't share a name with another declaration in the same block. In script files (without imports or exports) the top-level scope is shared by every script, so the duplicate can be in another file.

Example

index.ts
export {};
let user = "ada";
let user = "grace";
ts-r-check -p tsconfig.json --pretty false ts-r output
index.ts(2,5): error TS2451: Cannot redeclare block-scoped variable 'user'.
index.ts(3,5): error TS2451: Cannot redeclare block-scoped variable 'user'.

Recorded by node scripts/verify-examples.mjs with ts-r built from commit 6deaf01. The example uses the default tsconfig: strict, target: es2022, module: esnext, moduleResolution: bundler.

How to fix

  • Rename one of the variables, or reassign instead of redeclaring: user = "grace".
  • If the clash is across script files, make the files modules by adding an import or export.