facebookarchive/prepack

Implement switch statement for abstract values

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#1,378 opened on Jan 30, 2018

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abstractbootcampedenhancementhelp wantedlevel 4 (hard)priority: lowtest needed

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Description

Let v be an abstract value, then

switch(expr) { case 'a': {...; break;} case 'b': {...; break;} default: {...; break;} }

should not give an error but should have the same outcome as let v = expr; if (v === 'a') {...} else if (v === 'b') {...} else {...};

To tackle this task, first look at how the if statement is implemented for abstract conditions, then implement the switch case accordingly. Start with the simplest scenario, such as the one in the example above, then look at the complications that arise when a case falls through to the next case because there is no break in its code block.

Remember to update the path conditions and bear in mind that fall throughs complicate this.

Contributor guide

Research direction
Study how if statements handle abstract conditions in the Prepack codebase. Then implement switch statement by modeling the case clauses similarly, handling fall through by accumulating path conditions.
Tech stack
javascript
Domain
tooling
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.
1-2 days
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
JavaScriptGit
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70