Microsoft/TypeScript

'Omit' should alias a distinct mapped type (for display purposes)

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#31,104 opened on Apr 24, 2019

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 (8 comments) (5 reactions) (1 assignee)TypeScript (48,455 stars) (6,726 forks)batch import
Effort: ModerateExperience EnhancementFix AvailableHelp WantedSuggestion

Description

Today, Omit will expand to Pick<Exclude<...>, ...> in quick info, error messages, etc. which is gross.

By defining Omit as its own conditional type, we can get a slightly nicer display, though it will introduce duplication of code between the two helpers.

Contributor guide

Tech stack
typescript
Domain
developer experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
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.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
TypeScript type systemconditional typesmapped typesPull request process
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate the current definition of Omit in TypeScript's standard library (likely in src/lib/es5.d.ts) and understand how it gets expanded in type display (quickInfo, error messages). Consider creating a new conditional type alias for Omit and modifying the type printer to recognize it. Evaluate the duplication impact. See comments in issue #31104 for discussion.