Support re-aliasing of type alias instantiations #42284

ahejlsberg · 2021-01-11T17:57:18Z

This PR continues the work in #42149 by supporting re-aliasing of type alias instantiations. For example:

type Thing<T> = { value: T };
type ArrayThing<U> = Thing<U[]>;
type StringArrayThing = ArrayThing<string>;

declare let t1: Thing<string[]>;     // Thing<string[]>
declare let t2: ArrayThing<string>;  // ArrayThing<string> (previously Thing<string[]>)
declare let t3: StringArrayThing;    // StringArrayThing (previously Thing<string[]>)

interface Item<T> { value: T }
type ArrayItem<U> = Item<U[]>;
type NumberArrayItem = ArrayItem<number>;

declare let t4: Item<number[]>;     // Item<number[]>
declare let t5: ArrayItem<number>;  // ArrayItem<number>
declare let t6: NumberArrayItem;    // NumberArrayItem (previously ArrayItem<number>)

function foo<T, K extends keyof T>(obj: T, key: K) {
    let x: Omit<T, K>;  // Omit<T, K> (previously Pick<T, Exclude<keyof T, K>>)
}

Previously, instantiations of aliased anonymous object, mapped, or conditional types with a new type alias would continue to display the original type alias in diagnostics, quick info, and declaration files. Now, re-aliasing of such types consistently adopts and displays the new type alias.

In addition, instantiations of distributive types (such as homomorphic mapped types and distributive conditional types) now properly preserve the original type alias when the instantiation results in a union type:

type A = { a: string };
type B = { b: string };

declare let p: Partial<A | B>;  // Partial<A | B> (previously Partial<A> | Partial<B>)

…tiations

ahejlsberg · 2021-01-11T18:16:56Z

@typescript-bot test this
@typescript-bot user test this
@typescript-bot run dt
@typescript-bot perf test this faster

typescript-bot · 2021-01-11T18:17:00Z

Heya @ahejlsberg, I've started to run the abridged perf test suite on this PR at 8ac7030. You can monitor the build here.

Update: The results are in!

typescript-bot · 2021-01-11T18:17:01Z

Heya @ahejlsberg, I've started to run the parallelized community code test suite on this PR at 8ac7030. You can monitor the build here.

typescript-bot · 2021-01-11T18:17:01Z

Heya @ahejlsberg, I've started to run the extended test suite on this PR at 8ac7030. You can monitor the build here.

typescript-bot · 2021-01-11T18:17:01Z

Heya @ahejlsberg, I've started to run the parallelized Definitely Typed test suite on this PR at 8ac7030. You can monitor the build here.

ahejlsberg · 2021-01-11T18:19:38Z

@robpalme This is the continuation PR I mentioned in #42149. Give it a try and let me know how it goes.

typescript-bot · 2021-01-11T18:30:15Z

@ahejlsberg
The results of the perf run you requested are in!

Here they are:

Comparison Report - master..42284

_Metric	_master	₄₂₂₈₄	_Delta	_Best	_Worst
_{Angular - node (v12.1.0, x64)}
_{Memory used}	_{324,053k (± 0.02%)}	_{324,025k (± 0.02%)}	_{-28k (- 0.01%)}	_323,871k	_324,182k
_{Parse Time}	_{1.98s (± 0.66%)}	_{1.99s (± 0.84%)}	_{+0.01s (+ 0.50%)}	_1.95s	_2.01s
_{Bind Time}	_{0.81s (± 0.92%)}	_{0.82s (± 1.35%)}	_{+0.00s (+ 0.49%)}	_0.81s	_0.86s
_{Check Time}	_{4.88s (± 0.33%)}	_{4.88s (± 0.58%)}	_{+0.01s (+ 0.21%)}	_4.82s	_4.94s
_{Emit Time}	_{5.51s (± 0.77%)}	_{5.51s (± 0.61%)}	_{-0.00s (- 0.02%)}	_5.46s	_5.59s
_{Total Time}	_{13.18s (± 0.43%)}	_{13.21s (± 0.50%)}	_{+0.03s (+ 0.21%)}	_13.06s	_13.36s
_{Compiler-Unions - node (v12.1.0, x64)}
_{Memory used}	_{200,247k (± 0.08%)}	_{200,294k (± 0.07%)}	_{+47k (+ 0.02%)}	_199,982k	_200,507k
_{Parse Time}	_{0.78s (± 0.77%)}	_{0.77s (± 0.98%)}	_{-0.00s (- 0.00%)}	_0.76s	_0.79s
_{Bind Time}	_{0.50s (± 0.66%)}	_{0.50s (± 1.04%)}	_{-0.00s (- 0.20%)}	_0.49s	_0.51s
_{Check Time}	_{9.94s (± 1.06%)}	_{9.92s (± 0.79%)}	_{-0.02s (- 0.17%)}	_9.75s	_10.15s
_{Emit Time}	_{2.37s (± 0.97%)}	_{2.36s (± 1.29%)}	_{-0.01s (- 0.42%)}	_2.30s	_2.46s
_{Total Time}	_{13.58s (± 0.74%)}	_{13.55s (± 0.70%)}	_{-0.03s (- 0.23%)}	_13.34s	_13.75s
_{Monaco - node (v12.1.0, x64)}
_{Memory used}	_{337,446k (± 0.03%)}	_{337,473k (± 0.01%)}	_{+27k (+ 0.01%)}	_337,335k	_337,541k
_{Parse Time}	_{1.59s (± 0.30%)}	_{1.58s (± 0.56%)}	_{-0.00s (- 0.31%)}	_1.57s	_1.61s
_{Bind Time}	_{0.70s (± 1.08%)}	_{0.70s (± 0.64%)}	_{-0.01s (- 0.99%)}	_0.69s	_0.71s
_{Check Time}	_{4.95s (± 0.46%)}	_{4.94s (± 0.43%)}	_{-0.01s (- 0.12%)}	_4.88s	_4.98s
_{Emit Time}	_{2.88s (± 0.60%)}	_{2.89s (± 0.42%)}	_{+0.01s (+ 0.38%)}	_2.86s	_2.91s
_{Total Time}	_{10.12s (± 0.24%)}	_{10.11s (± 0.36%)}	_{-0.01s (- 0.06%)}	_9.99s	_10.16s
_{TFS - node (v12.1.0, x64)}
_{Memory used}	_{292,356k (± 0.02%)}	_{292,396k (± 0.02%)}	_{+41k (+ 0.01%)}	_292,282k	_292,533k
_{Parse Time}	_{1.25s (± 0.76%)}	_{1.25s (± 0.71%)}	_{-0.01s (- 0.64%)}	_1.23s	_1.26s
_{Bind Time}	_{0.65s (± 0.73%)}	_{0.65s (± 0.86%)}	_{-0.01s (- 0.77%)}	_0.64s	_0.66s
_{Check Time}	_{4.54s (± 0.70%)}	_{4.52s (± 0.54%)}	_{-0.02s (- 0.51%)}	_4.47s	_4.58s
_{Emit Time}	_{2.95s (± 0.89%)}	_{2.94s (± 0.72%)}	_{-0.00s (- 0.14%)}	_2.90s	_2.98s
_{Total Time}	_{9.40s (± 0.52%)}	_{9.36s (± 0.42%)}	_{-0.04s (- 0.37%)}	_9.28s	_9.45s
_{material-ui - node (v12.1.0, x64)}
_{Memory used}	_{478,950k (± 0.07%)}	_{473,781k (± 0.01%)}	_{-5,169k (- 1.08%)}	_473,585k	_473,886k
_{Parse Time}	_{2.08s (± 0.73%)}	_{2.07s (± 0.54%)}	_{-0.02s (- 0.91%)}	_2.04s	_2.09s
_{Bind Time}	_{0.65s (± 0.73%)}	_{0.64s (± 0.69%)}	_{-0.00s (- 0.77%)}	_0.63s	_0.65s
_{Check Time}	_{12.49s (± 0.90%)}	_{12.51s (± 0.71%)}	_{+0.02s (+ 0.14%)}	_12.28s	_12.72s
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_{0.00s ( NaN%)}	_0.00s	_0.00s
_{Total Time}	_{15.23s (± 0.65%)}	_{15.22s (± 0.62%)}	_{-0.00s (- 0.03%)}	_14.98s	_15.44s

System

_{Machine Name}	_ts-ci-ubuntu
_Platform	_{linux 4.4.0-197-generic}
_Architecture	_x64
_{Available Memory}	_{16 GB}
_{Available Memory}	_{4 GB}
_CPUs	_{4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz}

Hosts

node (v12.1.0, x64)

Scenarios

Angular - node (v12.1.0, x64)
Compiler-Unions - node (v12.1.0, x64)
Monaco - node (v12.1.0, x64)
TFS - node (v12.1.0, x64)
material-ui - node (v12.1.0, x64)

_Benchmark	_Name	_Iterations
_Current	₄₂₂₈₄	₁₀
_Baseline	_master	₁₀

typescript-bot · 2021-01-11T19:11:23Z

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

ahejlsberg · 2021-01-11T19:32:33Z

Tests all look good, only changes are improved diagnostics. Performance is unaffected.

DanielRosenwasser · 2021-01-11T19:40:19Z

@typescript-bot pack this

typescript-bot · 2021-01-11T19:40:23Z

Heya @DanielRosenwasser, I've started to run the tarball bundle task on this PR at 8ac7030. You can monitor the build here.

typescript-bot · 2021-01-11T19:56:40Z

Hey @DanielRosenwasser, I've packed this into an installable tgz. You can install it for testing by referencing it in your package.json like so:

{
    "devDependencies": {
        "typescript": "https://typescript.visualstudio.com/cf7ac146-d525-443c-b23c-0d58337efebc/_apis/build/builds/93139/artifacts?artifactName=tgz&fileId=4FE49FBE4115C3F38EC02DE524EF9087A6729DD9744C9B257007FE5D69F77D1202&fileName=/typescript-4.2.0-insiders.20210111.tgz"
    }
}

and then running npm install.

There is also a playground for this build and an npm module you can use via "typescript": "npm:@typescript-deploys/pr-build@4.2.0-pr-42284-11".;

DanielRosenwasser · 2021-01-11T19:38:49Z

tests/baselines/reference/conditionalTypes1.errors.txt

+!!! error TS2322:     Type 'keyof T' is not assignable to type 'T[keyof T] extends Function ? never : keyof T'.
+!!! error TS2322:       Type 'string | number | symbol' is not assignable to type 'T[keyof T] extends Function ? never : keyof T'.
+!!! error TS2322:         Type 'string' is not assignable to type 'T[keyof T] extends Function ? never : keyof T'.
+!!! error TS2322:           Type 'keyof T' is not assignable to type 'never'.
+!!! error TS2322:             Type 'string | number | symbol' is not assignable to type 'never'.
+!!! error TS2322:               Type 'string' is not assignable to type 'never'.


Why's this happening? What was avoiding the elaboration before?

Sounds like we can't avoid re-elaboration based on type IDs

robpalme · 2021-01-12T10:19:35Z

@ahejlsberg This is even better than the previous attempt 🎉

As before, there are no inlining/size regressions - I reviewed every changed line and this PR is a pure win. This PR improves upon 2c2d06d by also handling aliases to Record and Pick<obj, union>.

// Previous: 2c2d06
  myRecordProp: Record<string, any>;
  myObjectProp: Pick<{
      lotsOfProps,
    }, "red" | "green" | "blue
  >;

...is replaced by...

// Master: Using PR#42284
  myRecordProp: MyRecordType;
  myObjectProp: MyColorsOnly<{
      lotsOfProps,
    }
  >;

On the large package I referred to in previous reports, this PR results in a further 10KB decrease vs the previous attempt, i.e the Record & Pick changes explains the 10KB win. Meaning the net effect of this PR is now:

50 declaration files out of 394 were affected by this PR
Net size of all declaration files shrank by 41KB
- 50 files shrank (total size of these files reduced by 41KB from 585KB to 544KB)
- 0 files grew

* New aliases for type alias instantiations * New aliases for conditional, mapped, and anonymous object type instantiations * Accept new baselines * Fix issues with re-aliasing * Accept new baselines

ahejlsberg added 5 commits January 8, 2021 16:33

New aliases for type alias instantiations

a4a47db

New aliases for conditional, mapped, and anonymous object type instan…

0c6dfb7

…tiations

Accept new baselines

54da2a4

Fix issues with re-aliasing

1b0d12e

Accept new baselines

8ac7030

typescript-bot assigned ahejlsberg Jan 11, 2021

typescript-bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Jan 11, 2021

typescript-bot mentioned this pull request Jan 11, 2021

🤖 User test baselines have changed for newAliasesForInstantiatedTypes typescript-bot/TypeScript#131

Open

ahejlsberg requested review from weswigham, rbuckton, DanielRosenwasser and RyanCavanaugh January 11, 2021 19:30

DanielRosenwasser approved these changes Jan 11, 2021

View reviewed changes

ahejlsberg merged commit c456bbd into master Jan 11, 2021

DanielRosenwasser deleted the newAliasesForInstantiatedTypes branch January 12, 2021 00:20

Kingwl mentioned this pull request Jan 12, 2021

Add inlay hints support #42089

Merged

10 tasks

sandersn mentioned this pull request Jan 13, 2021

jquery has batch-only inference error after re-aliasing support (##42284) #42317

Closed

danvk mentioned this pull request Jan 13, 2021

TS 4.2 beta preserves "keyof" expressions in type display #42322

Closed

ahejlsberg mentioned this pull request Jan 22, 2021

react-redux: conditional type inference from alias fails after re-alias support in #42284 #42421

Closed

DanielRosenwasser added this to the TypeScript 4.2.0 milestone Jan 22, 2021

DanielRosenwasser mentioned this pull request Jan 28, 2021

Use homomorphic templated type for Omit #42524

Closed

ahejlsberg mentioned this pull request Mar 29, 2021

Conditional type inference regression in 4.2* #43192

Closed

amcasey mentioned this pull request Apr 13, 2021

React HOCs generate extremely large and incorrect .d.ts declaration files, regression from 4.1.3 #43622

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DanielRosenwasser mentioned this pull request Apr 20, 2021

Design Meeting Notes, 4/14/2021 #43743

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ahejlsberg mentioned this pull request May 26, 2021

TS 4.2: Type alias differs from original type #44119

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jakebailey mentioned this pull request Oct 7, 2021

Lengthy type being shown instead of alias microsoft/pylance-release#1914

Closed

jcalz mentioned this pull request Mar 1, 2022

Conditional type evaluation of type aliases produces different result than their equivalent substitution #48070

Open

rbuckton mentioned this pull request Apr 5, 2022

Write more useful types in .types test outputs #48578

Merged

RyanCavanaugh mentioned this pull request Apr 19, 2022

Infer operator returning container type instead of applied generic #48772

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ahejlsberg mentioned this pull request Sep 12, 2023

Method infers the wrong type when passing a value that is typealiased that uses union and intersection types #55648

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ddurschlag mentioned this pull request Oct 12, 2023

Improve type readability (fix type alias propagation, allow aliasing inferred types) #45954

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Support re-aliasing of type alias instantiations #42284

Support re-aliasing of type alias instantiations #42284

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Support re-aliasing of type alias instantiations #42284

Support re-aliasing of type alias instantiations #42284

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