GeezerVison

I already tried to make Omit its own type, but then we ran into #31190

Does this new implementation avoid that issue?

Daniel Rosenwasser (@DanielRosenwasser) this version preserves modifiers, unlike yours, as the mapped type is homomorphic; the 3rd type parameter is used to ensure such.

I'm generally not a fan of using type parameter defaults as an ad-hoc mechanism to introduce in-situ type aliases as it clutters the declaration output and quickinfo. I still think we should introduce some mechanism for in-situ type aliases to address this, similar to a let..in expression, i.e.:

type Omit<T, K extends keyof any> = 
  type Keys = Exclude<keyof T, K> in
  {
    [P in Keys]: T[P];
  };

Wesley Wigham (@weswigham) do you want to discuss this more, or look for a variant solution? If not, I'd like to close this PR to keep the number of open PRs manageable.

Did we wanna discuss our preferred approach here? Extra syntax for local type aliases and better default type parameter elision could both be ways forward here.

Wesley Wigham (@weswigham) should we keep looking for fixes for this PR or close it?

Daniel Rosenwasser (@DanielRosenwasser) Ron Buckton (@rbuckton) Nathan Shively-Sanders (@sandersn) Anders Hejlsberg (@ahejlsberg) I've changed this to use the template form to preserve the alias, as suggested by ExE Boss (@ExE-Boss). I had to make the tiniest change to templated mapped type comparisons to get the tests to pass, however.

Wesley Wigham (@weswigham)
Looks like tests/cases/conformance/types/literal/templateLiteralTypes1.ts is failing because the errors baseline has changed: https://github.com/microsoft/TypeScript/pull/37608/checks?check_run_id=1295283520#step:7:99

I could swear c2f4d8a should have fixed that when I ran it locally...

Oh wait, that's a different test that I just didn't notice was failing locally. Heh. Hold on.

Fixed. Notable: Our linter breaks because

Error: D:\Github\TypeScript\src\lib\es5.d.ts:1485:18  Parsing error: ']' expected.

We might need to update eslint? Or wait until the RC is out with the template mapped types to get parsing support for them in the linter? I'm unsure what, exactly, needs to go out before it'll lint without error.

TypeScript Bot (@typescript-bot) pack this
TypeScript Bot (@typescript-bot) test this
TypeScript Bot (@typescript-bot) user test this
TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test this

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the tarball bundle task on this PR at 636005e. You can monitor the build here.

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the parallelized community code test suite on this PR at 636005e. You can monitor the build here.

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the perf test suite on this PR at 636005e. You can monitor the build here.

Update: The results are in!

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the parallelized Definitely Typed test suite on this PR at 636005e. You can monitor the build here.

Heya Daniel Rosenwasser (@DanielRosenwasser), I've started to run the extended test suite on this PR at 636005e. You can monitor the build here.

Daniel Rosenwasser (@DanielRosenwasser)
The results of the perf run you requested are in!

The user suite test run you requested has finished and failed. I've opened a PR with the baseline diff from master.

This should also have “Fixes #31104” in the PR description.

I'm gonna say this is superseded by #42524 now~