Report InvalidMappingColumn on tsc generated source map

Reproduce

$ source-map-explorer test.js
test.js
  Your source map refers to generated column 21 on line 1, but the source only contains 21 column(s) on that line.
  Check that you are using the correct source map.

test.js

console.log('hello');
console.log('world');
//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJmaWxlIjoidGVzdC5qcyIsInNvdXJjZVJvb3QiOiIiLCJzb3VyY2VzIjpbInRlc3QudHMiXSwibmFtZXMiOltdLCJtYXBwaW5ncyI6IkFBQUEsT0FBTyxDQUFDLEdBQUcsQ0FBQyxPQUFPLENBQUMsQ0FBQztBQUNyQixPQUFPLENBQUMsR0FBRyxDQUFDLE9BQU8sQ0FBQyxDQUFDIn0=

Root cause

Typescript emits mappings for end-of-line characters, which breaks the boundary checks in source-map-explorer.

This issue has been reported as https://github.com/microsoft/TypeScript/issues/34695. However, even if it’s fixed in next ts release, there will be code generated by earlier versions of tsc around, that source-map-explorer won’t be able to process.

Moreover, though it doesn’t seem to be an ordinary input to source-map-explorer, such mapping can easily propagate its way to the final bundle and breaks source-map-explorer eventually.

[Fi1osof]

Got

Your source map refers to generated column 27 on line 1, but the source only contains 26 column(s) on that line.
  Check that you are using the correct source map.

Ubuntu 20, source-map-explorer@2.5.0

[heygrady]

Is this likely the line in question?

https://github.com/danvk/source-map-explorer/blob/c007f361a363465437eca94f81e4dfe0152b562f/src/explore.ts#L109