FuelLabs/sway

DCA improvements

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#6,007 opened on May 14, 2024

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 (2 comments) (0 reactions) (1 assignee)Rust (61,702 stars) (5,421 forks)batch import
DCAgood first issue

Description

I think there is room for improvement on our DCA. For example, the screenshot below shows how rustc considers: A, T and f to be dead, because no "live code" actually uses them.

image

We, on the other hand, consider the mere presence of impls enough for them to not be dead.

image

Remove the impl and we now correctly mark this as dead. But the error message is not as clear as rustc's, which says the struct is never "constructed".

image image

This is all done at sway-core/src/control_flow_analysis/dead_code_analysis.rs and seems a candidate for "good first issue".

Contributor guide

Tech stack
rust
Domain
toolingdeveloper experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
RustSway compiler basicsdead code analysis concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
Start by examining the dead code analysis logic in sway core/src/control flow analysis/dead code analysis.rs. Compare its behavior with rustc's DCA, particularly how rustc marks items as dead based on usage. Then modify the logic to detect and report dead items with clearer error messages similar to rustc's 'never constructed' phrasing.