Cannot redeclare block-scoped variable
An attempt was made to declare a variable with 'let' or 'const' that has already been declared in the same scope.
- 1Declaring a variable with the same name twice in the same function or block.
- 2A variable name conflicts with a parameter name in the same function.
- 3A variable name conflicts with an imported module's member in the same scope.
A variable is declared twice in the same block.
const myVar = 1; const myVar = 2;
expected output
error TS2451: Cannot redeclare block-scoped variable 'myVar'.
Fix 1
Rename the variable
WHEN The variables should be distinct.
const myFirstVar = 1; const mySecondVar = 2;
Why this works
Using a unique name for the second declaration resolves the conflict.
Fix 2
Reassign the variable if declared with 'let'
WHEN The intent is to update the value.
let myVar = 1; myVar = 2;
Why this works
Reassignment is allowed for variables declared with 'let'.
✕ Use different blocks to scope the variables if it does not fit the logic
This can make the code harder to read and is not a clean solution if the variables belong in the same logical block.
microsoft/TypeScript src/compiler/diagnosticMessages.json
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