Support for Source Maps

[CeylonMigrationBot]

The JavaScript backend should support producing JavaScript source maps in addition to the JavaScript code, so that browser debuggers can support Ceylon.

This will require modifying the JavaScript backend to record which source position maps to what JavaScript output, as we produce the output.

As the SourceMap specification is quite hairy, a good understanding of it is a prerequisite. This work should be incremental and start with only supporting certain Ast tree elements (like a typical helloworld), to validate on each addition that it works.

Ideally, a test framework should also be developped to test the produced output every time we add new support, and to make sure compiler changes don't regress.

[@lfryc] The SourceMap is technique for mapping a in-browser debugger to actual source in given language:

Source Map Revision 3 Proposal http://goo.gl/PgynY

Video on the subject: https://plus.google.com/u/1/110412141990454266397/posts/Nvr6Se6eAPh?utm_source=html5weekly&utm_medium=email

[Migrated from ceylon/ceylon-js#67]

[CeylonMigrationBot]

[@drochetti] +1 for source maps

[CeylonMigrationBot]

[@quintesse] Moved to 1.0

[CeylonMigrationBot]

[@chochos] Moving to 1.1

[CeylonMigrationBot]

[@lfryc] This feature request is duplicated by #2736