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Suggest Did you mean 'typeof Foo' when using value Foo as a type #28975

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Suggest Did you mean 'typeof Foo' when using value Foo as a type#28975
Labels
Domain: Error MessagesThe issue relates to error messagingExperience EnhancementNoncontroversial enhancementsFixedA PR has been merged for this issueGood First IssueWell scoped, documented and has the green lightHelp WantedYou can do thisSuggestionAn idea for TypeScript
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Backlog

Description

@mohsen1
Mohsen Azimi (mohsen1)
opened on Dec 12, 2018
type Foo<T> = {}

const Something = []

type FooSomething = Foo<Something>
//                      ^
//                      Can not find name "Something"

Instead, suggest that Something is in the value space and user possibly meant typeof Something.

Search Terms

Error messages, type space, generics

Checklist

My suggestion meets these guidelines:

  • This wouldn't be a breaking change in existing TypeScript/JavaScript code
  • This wouldn't change the runtime behavior of existing JavaScript code
  • This could be implemented without emitting different JS based on the types of the expressions
  • This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
  • This feature would agree with the rest of TypeScript's Design Goals.

Activity

  1. Daniel Rosenwasser (DanielRosenwasser)
    added
    Help WantedYou can do this
    Good First IssueWell scoped, documented and has the green light
    Experience EnhancementNoncontroversial enhancements
    Domain: Error MessagesThe issue relates to error messaging
    on Dec 12, 2018
  2. Daniel Rosenwasser (DanielRosenwasser)
    changed the title [-]Suggest `Did you mean 'typeof Foo'` when using value Foo as a type argument[/-] [+]Suggest `Did you mean 'typeof Foo'` when using value Foo as a type[/+] on Dec 12, 2018

  3. DanielRosenwasser commented on Dec 12, 2018

    @DanielRosenwasser
    Daniel Rosenwasser (DanielRosenwasser)
    on Dec 12, 2018
    Member

    I think this is more general than a type argument; probably as a type in general.

  4. DanielRosenwasser commented on Dec 12, 2018

    @DanielRosenwasser
    Daniel Rosenwasser (DanielRosenwasser)
    on Dec 12, 2018
    Member

    Wesley Wigham (@weswigham) has some concerns regarding things like the following

    type FooInstance = { }

function Foo(): FooInstance {

}

// you probably don't want this to be corrected to 'typeof Foo'
type FooAlias = Foo;

  5. s-lambert commented on Dec 12, 2018

    @s-lambert
    Scott Lambert (s-lambert)
    on Dec 12, 2018

    But that code doesn't seem to work, it won't compile because you do need typeof Foo to assign it to a type.

  6. mohsen1 commented on Dec 12, 2018

    @mohsen1
    Mohsen Azimi (mohsen1)
    on Dec 12, 2018
    ContributorAuthor

    Daniel Rosenwasser (@DanielRosenwasser) I think you meant class Foo {} that works in both type and value spaces

  7. cpplearner commented on Dec 12, 2018

    @cpplearner
    S. B. Tam (cpplearner)
    on Dec 12, 2018

    Perhaps it's more likely that InstanceType<typeof Foo> is intended?

  8. suhailsinghbains commented on Jan 5, 2019

    @suhailsinghbains
    Suhail Singh Bains (suhailsinghbains)
    on Jan 5, 2019

    Hi, Can I please work on this issue, I am new here

  9. Ryan Cavanaugh (RyanCavanaugh)
    added
    SuggestionAn idea for TypeScript
    on Mar 7, 2019
  10. John Patterson (john-patterson)
    added 2 commits that reference this issue on Jul 24, 2019

    adds error message for using value as type argument

    dd7e79d

    adds error message for using value as type argument

    46f46a0
  11. Ryan Cavanaugh (RyanCavanaugh)
    added this to the Backlog milestone on Aug 16, 2019
  12. John Patterson (john-patterson)
    added a commit that references this issue on Aug 20, 2019

    adds error message for using value as type argument

    878ce4a
  13. John Patterson (john-patterson)
    added a commit that references this issue on Oct 12, 2019

    adds error message for using value as type argument

    8226955
  14. Andrew Casey (amcasey)
    added 2 commits that reference this issue on Mar 12, 2020

    adds error message for using value as type argument

    72a7d41

    adds error message for using value as type argument (#37359)

    9e97b00

  15. jtbandes commented on Apr 5, 2020

    @jtbandes
    Jacob Bandes-Storch (jtbandes)
    on Apr 5, 2020
    Contributor

    Andrew Casey (@amcasey) Should this issue be closed now as #37359 is merged? Looks like #32543 would have auto-closed this ticket but it was abandoned in favor of #37359.

  16. weswigham commented on Apr 5, 2020

    @weswigham
    Wesley Wigham (weswigham)
    on Apr 5, 2020
    Member

    Ah, yep.

  17. Wesley Wigham (weswigham)
    closed this as completedon Apr 5, 2020
  18. Wesley Wigham (weswigham)
    added
    FixedA PR has been merged for this issue
    on Apr 5, 2020
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