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!

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

c0b9fa9

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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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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