Don't defer index types for non-generic substitution types by Andarist · Pull Request #61999 · microsoft/TypeScript

Andarist · 2025-07-06T12:12:33Z

Copilot

Pull Request Overview

This PR ensures that index types on non-generic substitution types are resolved immediately (instead of deferred), addressing #61728.

Added two new compiler tests to verify index lookups on non-generic substitution types.
Modified getIndexType in checker.ts to bypass deferral when both baseType and constraint are non-generic.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

File	Description
tests/cases/compiler/substitutionTypeNonGenericIndexType1.ts	Adds a test for boolean conditional index resolution on non-generic substitution types.
tests/cases/compiler/substitutionTypeNonGenericIndexType2.ts	Adds a test for `infer`-based index resolution on non-generic substitution types.
src/compiler/checker.ts	Updates `getIndexType` to immediately compute index types for non-generic substitutions.

Comments suppressed due to low confidence (3)

tests/cases/compiler/substitutionTypeNonGenericIndexType2.ts:1

[nitpick] Consider adding a reference to GitHub issue #61728 at the top of this test for consistency with related test files.

// @strict: true

tests/cases/compiler/substitutionTypeNonGenericIndexType2.ts:14

[nitpick] Consider adding additional test cases where either the baseType or the constraint is generic to ensure this new index type logic covers mixed generic scenarios.

const test: Test["rejectClose"] = "rejectClose";

jakebailey · 2025-12-04T04:38:36Z

@typescript-bot test it
@typescript-bot pack this

typescript-bot · 2025-12-04T04:38:40Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`pack this`	✅ Started	✅ Results
`test top400`	✅ Started	✅ Results
`user test this`	✅ Started	✅ Results
`run dt`	✅ Started	✅ Results
`perf test this faster`	✅ Started	👀 Results

typescript-bot · 2025-12-04T04:42:39Z

Hey @jakebailey, 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/166679/artifacts?artifactName=tgz&fileId=88C40553CBD26DF9E98DFD51DFBA9C2A38B2C0583A8FB0F8359BAF58E5856DDD02&fileName=/typescript-6.0.0-insiders.20251204.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@6.0.0-pr-61999-2".;

typescript-bot · 2025-12-04T05:01:16Z

Hey @jakebailey, the results of running the DT tests are ready.

Everything looks the same!

You can check the log here.

typescript-bot · 2025-12-04T05:07:55Z

@jakebailey Here are the results of running the user tests with tsc comparing main and refs/pull/61999/merge:

There were infrastructure failures potentially unrelated to your change:

1 instance of "Git clone failed"

Otherwise...

Everything looks good!

typescript-bot · 2025-12-04T05:41:47Z

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

Here they are:

tsc

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-Unions - node (v18.15.0, x64)}
_Errors	₁	₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_62,370	_62,370	_~	_~	_~	_{p=1.000 n=6}
_Types	_50,387	_50,387	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{195,063k (± 0.97%)}	_{192,710k (± 0.10%)}	_~	_192,602k	_193,076k	_{p=0.092 n=6}
_{Parse Time}	_{1.30s (± 0.69%)}	_{1.30s (± 0.58%)}	_~	_1.29s	_1.31s	_{p=0.798 n=6}
_{Bind Time}	_{0.75s (± 0.54%)}	_0.75s	_~	_~	_~	_{p=0.405 n=6}
_{Check Time}	_{9.89s (± 0.18%)}	_{9.89s (± 0.52%)}	_~	_9.84s	_9.97s	_{p=0.748 n=6}
_{Emit Time}	_{2.74s (± 0.63%)}	_{2.73s (± 0.56%)}	_~	_2.70s	_2.74s	_{p=0.323 n=6}
_{Total Time}	_{14.68s (± 0.17%)}	_{14.67s (± 0.37%)}	_~	_14.62s	_14.74s	_{p=0.572 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₂	₂	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_956,048	_956,048	_~	_~	_~	_{p=1.000 n=6}
_Types	_415,904	_415,904	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{1,255,277k (± 0.00%)}	_{1,255,251k (± 0.01%)}	_~	_1,255,190k	_1,255,353k	_{p=0.230 n=6}
_{Parse Time}	_{7.99s (± 0.73%)}	_{8.01s (± 0.97%)}	_~	_7.94s	_8.13s	_{p=0.574 n=6}
_{Bind Time}	_{2.37s (± 0.83%)}	_{2.36s (± 0.32%)}	_~	_2.35s	_2.37s	_{p=0.405 n=6}
_{Check Time}	_{38.74s (± 0.19%)}	_{38.89s (± 0.24%)}	_{+0.15s (+ 0.39%)}	_38.74s	_38.98s	_{p=0.037 n=6}
_{Emit Time}	_{17.94s (± 0.50%)}	_{17.93s (± 0.49%)}	_~	_17.81s	_18.03s	_{p=0.809 n=6}
_{Total Time}	_{67.05s (± 0.13%)}	_{67.18s (± 0.23%)}	_~	_66.90s	_67.37s	_{p=0.128 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,722,106	_2,722,106	_~	_~	_~	_{p=1.000 n=6}
_Types	_937,535	_937,535	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,050,995k (± 0.00%)}	_{3,050,980k (± 0.00%)}	_~	_3,050,893k	_3,051,084k	_{p=0.936 n=6}
_{Parse Time}	_{8.54s (± 0.17%)}	_{8.54s (± 0.18%)}	_~	_8.52s	_8.55s	_{p=0.933 n=6}
_{Bind Time}	_{2.32s (± 0.70%)}	_{2.32s (± 0.57%)}	_~	_2.30s	_2.33s	_{p=0.869 n=6}
_{Check Time}	_{93.05s (± 0.39%)}	_{93.06s (± 0.71%)}	_~	_92.51s	_94.20s	_{p=0.873 n=6}
_{Emit Time}	_{0.31s (± 3.15%)}	_{0.31s (± 2.44%)}	_~	_0.30s	_0.32s	_{p=0.652 n=6}
_{Total Time}	_{104.23s (± 0.36%)}	_{104.24s (± 0.62%)}	_~	_103.71s	_105.33s	_{p=0.936 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,251,654	_1,251,654	_~	_~	_~	_{p=1.000 n=6}
_Types	_259,840	_259,840	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,392,908k (± 0.03%)}	_{2,574,802k (±11.82%)}	_~	_2,392,575k	_3,121,215k	_{p=0.173 n=6}
_{Parse Time}	_{5.19s (± 0.80%)}	_{5.21s (± 1.54%)}	_~	_5.12s	_5.32s	_{p=0.630 n=6}
_{Bind Time}	_{1.82s (± 0.22%)}	_{1.82s (± 1.59%)}	_~	_1.77s	_1.85s	_{p=0.608 n=6}
_{Check Time}	_{35.49s (± 0.28%)}	_{35.46s (± 0.96%)}	_~	_34.90s	_35.94s	_{p=1.000 n=6}
_{Emit Time}	_{2.99s (± 2.45%)}	_{3.02s (± 1.49%)}	_~	_2.98s	_3.09s	_{p=0.689 n=6}
_{Total Time}	_{45.51s (± 0.14%)}	_{45.53s (± 0.68%)}	_~	_45.12s	_46.03s	_{p=1.000 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,251,654	_1,251,654	_~	_~	_~	_{p=1.000 n=6}
_Types	_259,840	_259,840	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,459,526k (± 0.02%)}	_{2,459,616k (± 0.02%)}	_~	_2,458,812k	_2,460,216k	_{p=0.689 n=6}
_{Parse Time}	_{5.33s (± 0.84%)}	_{5.34s (± 0.40%)}	_~	_5.31s	_5.37s	_{p=0.747 n=6}
_{Bind Time}	_{1.87s (± 1.04%)}	_{1.86s (± 0.22%)}	_~	_1.85s	_1.86s	_{p=0.210 n=6}
_{Check Time}	_{35.59s (± 0.57%)}	_{35.53s (± 0.29%)}	_~	_35.38s	_35.68s	_{p=0.575 n=6}
_{Emit Time}	_{3.07s (± 0.73%)}	_{3.07s (± 1.59%)}	_~	_3.01s	_3.15s	_{p=0.873 n=6}
_{Total Time}	_{45.86s (± 0.50%)}	_{45.82s (± 0.23%)}	_~	_45.68s	_45.96s	_{p=0.689 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_264,287	_264,287	_~	_~	_~	_{p=1.000 n=6}
_Types	_104,051	_104,051	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{443,264k (± 0.01%)}	_{443,310k (± 0.01%)}	_~	_443,248k	_443,353k	_{p=0.128 n=6}
_{Parse Time}	_{3.52s (± 1.09%)}	_{3.53s (± 0.77%)}	_~	_3.50s	_3.57s	_{p=0.466 n=6}
_{Bind Time}	_{1.40s (± 1.11%)}	_{1.38s (± 0.54%)}	_{-0.02s (- 1.31%)}	_1.37s	_1.39s	_{p=0.015 n=6}
_{Check Time}	_{19.23s (± 0.55%)}	_{19.19s (± 0.40%)}	_~	_19.12s	_19.28s	_{p=0.419 n=6}
_{Emit Time}	_{1.53s (± 1.01%)}	_{1.54s (± 0.82%)}	_~	_1.53s	_1.56s	_{p=0.328 n=6}
_{Total Time}	_{25.68s (± 0.50%)}	_{25.65s (± 0.41%)}	_~	_25.53s	_25.76s	_{p=0.810 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₇₂	₇₂	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_225,493	_225,493	_~	_~	_~	_{p=1.000 n=6}
_Types	_94,373	_94,373	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{370,150k (± 0.02%)}	_{370,304k (± 0.07%)}	_~	_370,061k	_370,595k	_{p=0.689 n=6}
_{Parse Time}	_{2.84s (± 1.73%)}	_{2.82s (± 0.86%)}	_~	_2.80s	_2.86s	_{p=0.627 n=6}
_{Bind Time}	_{1.64s (± 1.09%)}	_{1.64s (± 1.26%)}	_~	_1.63s	_1.67s	_{p=0.931 n=6}
_{Check Time}	_{16.59s (± 0.41%)}	_{16.60s (± 0.43%)}	_~	_16.50s	_16.69s	_{p=1.000 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{21.07s (± 0.37%)}	_{21.07s (± 0.29%)}	_~	_20.99s	_21.15s	_{p=0.871 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₁₁	₁₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_4,076,919	_4,076,919	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,284,323	_1,284,323	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,862,422k (± 0.00%)}	_{3,862,556k (± 0.00%)}	_{+134k (+ 0.00%)}	_3,862,445k	_3,862,722k	_{p=0.020 n=6}
_{Parse Time}	_{15.62s (± 0.76%)}	_{15.66s (± 0.79%)}	_~	_15.53s	_15.86s	_{p=0.748 n=6}
_{Bind Time}	_{5.24s (± 0.79%)}	_{5.25s (± 1.31%)}	_~	_5.20s	_5.38s	_{p=0.748 n=6}
_{Check Time}	_{113.90s (± 2.73%)}	_{113.27s (± 2.88%)}	_~	_109.85s	_118.60s	_{p=0.575 n=6}
_{Emit Time}	_{40.80s (±14.01%)}	_{41.39s (± 7.53%)}	_~	_38.43s	_45.48s	_{p=0.575 n=6}
_{Total Time}	_{175.56s (± 4.99%)}	_{175.58s (± 3.35%)}	_~	_169.44s	_182.56s	_{p=0.936 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₄₀	₄₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_380,758	_380,758	_~	_~	_~	_{p=1.000 n=6}
_Types	_166,811	_166,811	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{540,886k (± 0.02%)}	_{540,864k (± 0.02%)}	_~	_540,779k	_541,004k	_{p=0.689 n=6}
_{Parse Time}	_{4.72s (± 0.69%)}	_{4.73s (± 0.56%)}	_~	_4.70s	_4.77s	_{p=0.808 n=6}
_{Bind Time}	_{2.02s (± 1.24%)}	_{2.03s (± 0.91%)}	_~	_2.02s	_2.07s	_{p=0.404 n=6}
_{Check Time}	_{23.02s (± 0.68%)}	_{22.99s (± 0.41%)}	_~	_22.85s	_23.13s	_{p=0.574 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{29.77s (± 0.60%)}	_{29.75s (± 0.28%)}	_~	_29.64s	_29.86s	_{p=0.688 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₃₀	₃₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_692,951	_692,951	_~	_~	_~	_{p=1.000 n=6}
_Types	_210,425	_210,425	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{589,064k (± 0.01%)}	_{588,971k (± 0.03%)}	_~	_588,802k	_589,124k	_{p=0.471 n=6}
_{Parse Time}	_{4.17s (± 0.82%)}	_{4.15s (± 0.47%)}	_~	_4.13s	_4.18s	_{p=0.331 n=6}
_{Bind Time}	_{1.39s (± 1.24%)}	_{1.41s (± 1.10%)}	_~	_1.39s	_1.43s	_{p=0.086 n=6}
_{Check Time}	_{20.83s (± 1.38%)}	_{21.10s (± 2.01%)}	_~	_20.67s	_21.52s	_{p=0.228 n=6}
_{Emit Time}	_{0.01s (±77.38%)}	_0.00s	_{🟩-0.01s (-100.00%)}	_~	_~	_{p=0.025 n=6}
_{Total Time}	_{26.39s (± 1.16%)}	_{26.68s (± 1.68%)}	_~	_26.21s	_27.12s	_{p=0.298 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

Compiler-Unions - node (v18.15.0, x64)
angular-1 - node (v18.15.0, x64)
mui-docs - node (v18.15.0, x64)
self-build-src - node (v18.15.0, x64)
self-build-src-public-api - node (v18.15.0, x64)
self-compiler - node (v18.15.0, x64)
ts-pre-modules - node (v18.15.0, x64)
vscode - node (v18.15.0, x64)
webpack - node (v18.15.0, x64)
xstate-main - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

typescript-bot · 2025-12-04T06:04:05Z

@jakebailey Here are the results of running the top 400 repos with tsc comparing main and refs/pull/61999/merge:

Everything looks good!

typescript-bot · 2026-03-24T21:22:01Z

With 6.0 out as the final release vehicle for this codebase, we're closing all PRs that don't fit the merge criteria for post-6.0 patches. If you think this was a mistake and this PR fits the post-6.0 patch criteria, please post to the 6.0 iteration issue with details (specifically, which PR and which patch criteria it satisfies).

Next steps for PRs:

For crash bugfixes or language service improvements, PRs are currently accepted at the typescript-go repo
Changes to type system behavior should wait until after 7.0, at which point mainline TypeScript development will resume in this repository with the Go codebase
Library file updates (lib.d.ts etc) continue to live in this repo or the DOM Generator repo as appropriate

Don't defer index types for non-generic substitution types

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Copilot AI review requested due to automatic review settings July 6, 2025 12:12

github-project-automation bot moved this to Not started in PR Backlog Jul 6, 2025

github-project-automation bot added this to PR Backlog Jul 6, 2025

typescript-bot added For Backlog Bug PRs that fix a backlog bug labels Jul 6, 2025

Copilot AI reviewed Jul 6, 2025

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LukeAbby mentioned this pull request Dec 3, 2025

Broken assignability and quick info due to erroneously deferring keyof T since #51621 microsoft/typescript-go#2186

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typescript-bot closed this Mar 24, 2026

github-project-automation bot moved this from Not started to Done in PR Backlog Mar 24, 2026

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Don't defer index types for non-generic substitution types#61999

Don't defer index types for non-generic substitution types#61999
Andarist wants to merge 1 commit intomicrosoft:mainfrom
Andarist:fix/dont-defer-index-types-on-non-generic-substitutions

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