scala/scala3

Improve debugging support by implementing JSR-45

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#9,715 opened on Sep 3, 2020

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area:backendcompat:scala2help wanteditype:enhancement

Description

We should port https://github.com/scala/scala/pull/9121, note that unlike scala 2 we don't have a backend inliner (yet) but we do have inline def so we need to deal with positions coming from other files, this is currently handled by https://github.com/lampepfl/dotty/blob/cdfc76e2e5093dd8f70e1d582e38d2537494c0bb/compiler/src/dotty/tools/dotc/typer/Inliner.scala#L239-L240

Contributor guide

Tech stack
None
Domain
developer experiencetooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Scala compiler internalsJSR 45 specificationFamiliarity with dotty codebase
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
5
Research direction
Examine the referenced Scala 2 pull request (https://github.com/scala/scala/pull/9121) to understand how JSR 45 was implemented there. Study the current position handling in the Inliner at compiler/src/dotty/tools/dotc/typer/Inliner.scala lines 239-240. Determine how to adapt the logic to handle positions from inlined code, as Dotty uses inline def. Look at the existing debug information generation in the Dotty compiler to see where to incorporate the new line number mappings.