Microsoft/TypeScript

Optimize constructing type nodes from types

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#34,776 opened on Oct 28, 2019

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 (0 comments) (2 reactions) (0 assignees)TypeScript (48,455 stars) (6,726 forks)batch import
BugDomain: PerformanceHelp Wanted

Description

Originally posted by @weswigham in https://github.com/microsoft/TypeScript/issues/34119#issuecomment-545640573

Yep, looking at the traces I see pretty much all the time spent in trySymbolTable and getAliasForSymbolInContainer, which are workers user for calculating visible symbol chains. The whole process is uncached and quite naive right now (it's pretty much the same as it was since TS 1.8, but we rely on it more and more). It has been on my backlog as something that needs to be rewritten with a better more cacheable structure for perf.

There's also a fair chunk of time spent in GC and in path component-related operations that might also need some optimization - I'm guessing the large number of import types we manufacture require a large number of path calculations which end up making a lot of garbage - some caching may be in order here.

Contributor guide

Tech stack
typescript
Domain
performancetooling
Issue type
performance
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.
mostly clear
Prerequisites
TypeScript compiler architecturecaching patternsperformance analysis
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
10
Research direction
Investigate the current implementation of `trySymbolTable` and `getAliasForSymbolInContainer` in the TypeScript compiler source to understand how visible symbol chains are computed. Identify where caching can be introduced to reduce repeated computations. Also analyze path related operations for import types to reduce garbage collection overhead. Refer to the linked comment for additional context.