Microsoft/TypeScript

Error message displays computed name '[attr]' instead of key value

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#57,653 opened on Mar 5, 2024

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Description

🔎 Search Terms

computed property, error message

🕗 Version & Regression Information

  • This is the behavior in every version I tried, and I reviewed the FAQ for entries about computed properties

⏯ Playground Link

https://tsplay.dev/WyV2bw

💻 Code

type Unit =
  | {
      name: string;
      stength: number;
    }
  | {
      name: string;
      magic: number;
    };

const createUnit = (
  name: string,
  attr: "strength" | "magic",
  power: number,
): Unit => {
  return attr === "strength"
    ? { name, [attr]: power } // <-- error here
    : { name, [attr]: power };
};

🙁 Actual behavior

Error message displays "Object literal may only specify known properties, and '[attr]' does not exist in type 'Unit'".

🙂 Expected behavior

Error message should display that "strength" doesn't exist on Unit. (and possibly even recommend "stength" instead)

Additional information about the issue

No response

Contributor guide

Research direction
Investigate how TypeScript's checker resolves computed property names in object literals and how error messages are generated for excess properties. Look for where the symbolic name of the computed property is printed, and attempt to replace it with the actual key value.
Tech stack
typescript
Domain
compilers
Issue type
Bug
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
GitTypeScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65