the tswhy logo: a question mark in a box

tswhy‽

A community effort to enrich TypeScript diagnostics.

Editing TS1021:

All diagnostics and fixes are authored in markdown. Propose any changes by editing the markdown. Additional fixes can be added. A preview of the rendered diagnostic will update when changes are made.

Once all proposed changes are made, the Propose button will submit the information and confirm raising the PR.

TS1021

An index signature must have a type annotation.

When defining an index signature, the signature must provide a type:

interface A {
  [a: string]
}

Fix: Provide a type.

To fix the error, provide a type. All other properties on the object must be assignable to this type:

interface A {
  [a: string]: string;
}
syntax-error