Native API createSourceFile panics for numeric literals whose normalized text is longer than the source #65451

🔎 Search Terms

stringtable, createSourceFile panic, slice bounds, numeric literal encoder

🕗 Version & Regression Information

Reproduces with typescript@7.1.0-beta and typescript@7.1.0-dev.20261111.1 on Linux x64, using Node.js 24.20.0.

Also reproduces in an unmodified local build of current main, commit ad24728023c52ef6a92a278046cdb69621048365 (7.1.0-dev), built with node node_modules/hereby/bin/hereby.js build.

The first affected version has not been identified. This concerns the native typescript/sync API. I reviewed the FAQ and found no entry covering this crash.

⏯ Playground Link

Not applicable: this reproduces through the native API's source-file serialization.

💻 Code

Install an exact affected version:

npm install typescript@7.1.0-dev.20261111.1

Save as repro.cjs and run node repro.cjs:

const { API } = require('typescript/sync');
const api = new API();
try {
  api.createSourceFile('a.ts', '.1');
} finally {
  api.close();
}

🙁 Actual behavior

The call throws an error containing the server panic:

panic: runtime error: slice bounds out of range [-1:]
.../internal/api/encoder.(*stringTable).add
    .../internal/api/encoder/stringtable.go:41
.../internal/api/encoder.recordExtendedData_NumericLiteral
    .../internal/api/encoder/encoder.go:936

Replacing .1 with 1e3 or 1e9 also panics. 1e2, 1, and 0 succeed. Each input was tested in a separate API instance/process.

🙂 Expected behavior

Return a source-file syntax tree for these valid numeric expressions without a panic.

Additional information about the issue

The numeric literal's normalized text can be longer than its original spelling:

recordExtendedData_NumericLiteral passes the normalized text and original positions to stringTable.add. The latter computes start := end - len(text) and slices fileText[start:end] before checking whether the slice matches the text. In these examples start is negative, so the existing fallback for text that cannot be reused from the source is never reached.

Source inspected at commit ad24728023c52ef6a92a278046cdb69621048365: