ts-r
  • Error
  • Reported by the lexer and parser

TS8011

Type arguments can only be used in TypeScript files.

Type arguments like `f<string>()` appear in a JavaScript file. Remove them.

What it means

Explicit type arguments on calls, new expressions and heritage clauses are TypeScript syntax and can't appear in a .js file.

ts-r's parser reports this code when it reads .js files with tsc's rules for TypeScript syntax in JavaScript. ts-r-check doesn't report it yet: today it parses .js files with the plain JavaScript grammar and reports a syntax error at the same place instead.

Example

index.js
class Store extends Map<string, number> {}
cargo run -p ts_r_parser --example dump -- index.js --ts-in-js report ts-r output
index.js(1,25): error TS8011: Type arguments can only be used in TypeScript files.

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

  • Remove the type arguments; describe them with JSDoc (@extends {Map<string, number>}) if you want them checked.
  • Rename the file to .ts if it's meant to be TypeScript.