Microsoft/TypeScript

Typescript Autocompletion Not Working For Function Overloads

Open

#26,892 opened on Sep 5, 2018

View on GitHub
 (9 comments) (6 reactions) (0 assignees)TypeScript (48,455 stars) (6,726 forks)batch import
Experience EnhancementHelp WantedSuggestion

Description

From @MartinLoeper on August 29, 2018 13:27

  • VSCode Version: 1.25.1 1dfc5e557209371715f655691b1235b6b26a06be x64
  • OS Version: Linux version 4.15.0-32-generic Ubuntu

Steps to Reproduce:
I provided a small example of the issue (see screenshot below).

  1. Create a function with two overloads
  2. Try to invoke this function
  3. Once you typed in the first parameter, the IDE recognizes that it matches the first overload's signature. However, the auto-completion suggest the literals for both overloads.

I expect the auto-completion to show "BW" and "BY" only!

_005

Does this issue occur when all extensions are disabled?: Yes

The code:


export class MomentHolidayFactory {
    public a(input: Germany, second: GermanState): string;
    public a(input: Austria, second: AustrianState): string;

    public a(input: Country, second: State): string {
        return "test";
    }

    public holidays() {
        this.a("de", ""
    }
}

type Country = Germany & Austria;
type Germany = "de" | "De" | "DE" | "germany";
type Austria = "Au" | "au" | "AU" | "austria";

type State = GermanState & AustrianState;
type GermanState = "BW" | "BY";
type AustrianState = "Stmk" | "Vbg";

Copied from original issue: Microsoft/vscode#57509

Contributor guide

Tech stack
typescript
Domain
developer experiencetooling
Issue type
bug
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.
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
TypeScriptunderstanding of function overloads
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the TypeScript language service completion logic. The issue is that when a function has overloads, the completions for literal types are not filtered by the overload that matches the already typed arguments. Look at the CompletionEntry or related code in the TypeScript compiler source, specifically around overload resolution during completion. Analyze the current behavior and propose a fix to filter completions based on the appropriate overload signature.