[Bug]: property access on negative number isn't preserved as negative number in the output

[Andarist]

💻

• Would you like to work on a fix?

How are you using Babel?

Programmatic API (babel.transform, babel.parse)

Input code

const result = require("@babel/core").transformSync(
  `
  export default 'hello';
`,
  {
    plugins: [
      function (babel) {
        const { types: t } = babel;

        return {
          visitor: {
            StringLiteral(path) {
              path.replaceWith(
                t.unaryExpression(
                  "typeof",
                  t.callExpression(
                    t.memberExpression(
                      t.numericLiteral(-1),
                      t.identifier("toString")
                    ),
                    []
                  )
                )
              );
            },
          },
        };
      },
    ],
  }
);

console.log(result.code);

Configuration file name

No response

Configuration

none

Current and expected behavior

current

export default typeof -1 .toString(); // evaluated as 'number'

expected

export default typeof (-1).toString(); // evaluated as 'string'

Environment

System:
OS: macOS 12.3
Binaries:
Node: 20.2.0 - ~/Library/Caches/fnm_multishells/2251_1687933194251/bin/node
Yarn: 1.22.17 - /usr/local/bin/yarn
npm: 9.6.6 - ~/Library/Caches/fnm_multishells/2251_1687933194251/bin/npm
pnpm: 7.27.1 - ~/Library/pnpm/pnpm
npmPackages:
@babel/core: ^7.22.9 => 7.22.9

Possible solution

wrap negative numbers in member expressions with parentheses

Additional context

No response

[nicolo-ribaudo]

-1 is a t.unaryExpression("-", t.numericLiteral(1)), not a t.numericLiteral(-1). JavaScript does not have literals for negative numbers.

https://astexplorer.net/#/gist/6861e112ab5faa5d7b0f4078b627c29a/ac7ca72bc22445946003404a371fbb51b1a6d5e6

We should add some validation to the numericLiteral function.

[JLHwung]

Should we also apply the non-negative restriction to t.bigIntLiteral and t.decimalLiteral? Though the value accepts string only, but we can always check if it starts with -.

[nicolo-ribaudo]

Maybe we could also start requiring the number to be a bigint rather than a string (in babel 8), given that it's now supported everywhere.