Control flow analysis for element access with variable index by ahejlsberg · Pull Request #57847 · microsoft/TypeScript

Anders Hejlsberg (ahejlsberg) · 2024-03-19T14:32:02Z

With this PR we perform control flow analysis for element access expressions obj[key] where key is a const variable, or a let variable or parameter that is never targeted in an assignment. The intuition here is that even if the exact name of the property selected by key isn't known, any control flow analysis proof that involves obj[key] should hold in subsequent statements as long as obj and key aren't mutated,

Some examples:

functionf1(obj: Record<string,unknown>,key: string){if(typeofobj[key]==="string"){obj[key].toUpperCase();// Now ok, previously was error}}typeThing={a?: string,b?: number,c?: number};functionf2(obj: Thing,getKey: ()=>keyofThing){constkey=getKey();if(obj[key]!==undefined){if(typeofobj[key]==="string"){obj[key].toUpperCase();// Now ok, previously was error}if(typeofobj[key]==="number"){obj[key].toFixed();// Now ok, previously was error}}}functionf3<Kextendsstring>(obj: Record<K,string|undefined>,key: K){if(obj[key]){obj[key].toUpperCase();// Now ok, previously was error}}

Fixes#56389.

Anders Hejlsberg (ahejlsberg) · 2024-03-19T14:32:55Z

TypeScript Bot (@typescript-bot) test top200
TypeScript Bot (@typescript-bot) user test this
TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test this faster

TypeScript Bot (typescript-bot) · 2024-03-19T14:32:58Z

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

Command	Status	Results
`test top200`	✅ Started	👀 Results
`user test this`	✅ Started	👀 Results
`run dt`	✅ Started	✅ Results
`perf test this faster`	✅ Started	👀 Results

TypeScript Bot (typescript-bot) · 2024-03-19T14:53:13Z

Hey Anders Hejlsberg (@ahejlsberg), the results of running the DT tests are ready.
Everything looks the same!
You can check the log here.

TypeScript Bot (typescript-bot) · 2024-03-19T14:58:36Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the user test suite comparing main and refs/pull/57847/merge:

Something interesting changed - please have a look.

Details

webpack

tsconfig.types.json

[NEW] error TS2349: This expression is not callable.
- lib/stats/DefaultStatsPresetPlugin.js#L321

TypeScript Bot (typescript-bot) · 2024-03-19T15:10:45Z

Anders Hejlsberg (@ahejlsberg)
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
_{Angular - node (v18.15.0, x64)}
_{Memory used}	_{295,747k (± 0.00%)}	_{295,762k (± 0.01%)}	_~	_295,722k	_295,797k	_{p=0.198 n=6}
_{Parse Time}	_{2.66s (± 0.28%)}	_{2.67s (± 0.31%)}	_~	_2.65s	_2.67s	_{p=0.432 n=6}
_{Bind Time}	_{0.83s (± 0.62%)}	_{0.83s (± 0.62%)}	_~	_0.82s	_0.83s	_{p=1.000 n=6}
_{Check Time}	_{8.21s (± 0.28%)}	_{8.19s (± 0.16%)}	_~	_8.17s	_8.21s	_{p=0.089 n=6}
_{Emit Time}	_{7.14s (± 0.26%)}	_{7.13s (± 0.33%)}	_~	_7.11s	_7.17s	_{p=0.518 n=6}
_{Total Time}	_{18.84s (± 0.15%)}	_{18.81s (± 0.09%)}	_~	_18.79s	_18.83s	_{p=0.164 n=6}
_{Compiler-Unions - node (v18.15.0, x64)}
_{Memory used}	_{192,638k (± 0.77%)}	_{193,221k (± 0.91%)}	_~	_191,920k	_195,508k	_{p=0.378 n=6}
_{Parse Time}	_{1.36s (± 1.20%)}	_{1.36s (± 0.40%)}	_~	_1.35s	_1.36s	_{p=0.360 n=6}
_{Bind Time}	_{0.72s (± 0.57%)}	_{0.72s (± 0.00%)}	_~	_0.72s	_0.72s	_{p=0.405 n=6}
_{Check Time}	_{9.52s (± 0.74%)}	_{9.48s (± 0.54%)}	_~	_9.42s	_9.54s	_{p=0.260 n=6}
_{Emit Time}	_{2.65s (± 0.41%)}	_{2.66s (± 0.19%)}	_{+0.01s (+ 0.50%)}	_2.66s	_2.67s	_{p=0.020 n=6}
_{Total Time}	_{14.26s (± 0.52%)}	_{14.22s (± 0.35%)}	_~	_14.16s	_14.28s	_{p=0.469 n=6}
_{Monaco - node (v18.15.0, x64)}
_{Memory used}	_{347,377k (± 0.01%)}	_{347,411k (± 0.00%)}	_~	_347,381k	_347,434k	_{p=0.065 n=6}
_{Parse Time}	_{2.47s (± 0.51%)}	_{2.48s (± 0.54%)}	_~	_2.46s	_2.50s	_{p=0.139 n=6}
_{Bind Time}	_{0.93s (± 0.44%)}	_{0.93s (± 0.56%)}	_~	_0.92s	_0.93s	_{p=0.595 n=6}
_{Check Time}	_{7.02s (± 0.40%)}	_{7.02s (± 0.50%)}	_~	_6.98s	_7.08s	_{p=1.000 n=6}
_{Emit Time}	_{4.06s (± 0.67%)}	_{4.08s (± 0.25%)}	_~	_4.06s	_4.09s	_{p=0.415 n=6}
_{Total Time}	_{14.47s (± 0.21%)}	_{14.50s (± 0.27%)}	_~	_14.47s	_14.57s	_{p=0.334 n=6}
_{TFS - node (v18.15.0, x64)}
_{Memory used}	_{302,758k (± 0.01%)}	_{302,755k (± 0.01%)}	_~	_302,734k	_302,782k	_{p=0.936 n=6}
_{Parse Time}	_{2.01s (± 0.88%)}	_{2.00s (± 0.68%)}	_~	_1.98s	_2.02s	_{p=0.805 n=6}
_{Bind Time}	_{1.01s (± 0.81%)}	_{1.00s (± 0.82%)}	_~	_0.99s	_1.01s	_{p=0.077 n=6}
_{Check Time}	_{6.34s (± 0.36%)}	_{6.32s (± 0.38%)}	_~	_6.29s	_6.36s	_{p=0.373 n=6}
_{Emit Time}	_{3.61s (± 0.21%)}	_{3.60s (± 0.91%)}	_~	_3.56s	_3.65s	_{p=0.566 n=6}
_{Total Time}	_{12.96s (± 0.17%)}	_{12.93s (± 0.38%)}	_~	_12.86s	_13.01s	_{p=0.225 n=6}
_{material-ui - node (v18.15.0, x64)}
_{Memory used}	_{511,373k (± 0.00%)}	_{511,377k (± 0.01%)}	_~	_511,349k	_511,407k	_{p=1.000 n=6}
_{Parse Time}	_{2.66s (± 0.46%)}	_{2.67s (± 0.28%)}	_~	_2.66s	_2.68s	_{p=0.062 n=6}
_{Bind Time}	_{0.98s (± 1.19%)}	_{0.98s (± 1.35%)}	_~	_0.96s	_1.00s	_{p=0.737 n=6}
_{Check Time}	_{17.34s (± 0.68%)}	_{17.31s (± 0.44%)}	_~	_17.21s	_17.41s	_{p=0.936 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{20.97s (± 0.53%)}	_{20.96s (± 0.33%)}	_~	_20.88s	_21.04s	_{p=1.000 n=6}
_{mui-docs - node (v18.15.0, x64)}
_{Memory used}	_{1,719,135k (± 0.00%)}	_{1,719,188k (± 0.00%)}	_{+54k (+ 0.00%)}	_1,719,155k	_1,719,222k	_{p=0.020 n=6}
_{Parse Time}	_{6.54s (± 0.21%)}	_{6.53s (± 0.51%)}	_~	_6.50s	_6.59s	_{p=0.373 n=6}
_{Bind Time}	_{2.35s (± 0.23%)}	_{2.36s (± 0.69%)}	_~	_2.35s	_2.39s	_{p=0.342 n=6}
_{Check Time}	_{56.29s (± 0.65%)}	_{56.21s (± 0.28%)}	_~	_56.01s	_56.41s	_{p=0.575 n=6}
_{Emit Time}	_{0.13s (± 0.00%)}	_{0.13s (± 0.00%)}	_~	_0.13s	_0.13s	_{p=1.000 n=6}
_{Total Time}	_{65.31s (± 0.56%)}	_{65.23s (± 0.25%)}	_~	_65.07s	_65.49s	_{p=0.689 n=6}
_{self-build-src - node (v18.15.0, x64)}
_{Memory used}	_{2,395,587k (± 0.03%)}	_{2,395,905k (± 0.03%)}	_~	_2,395,338k	_2,397,348k	_{p=0.298 n=6}
_{Parse Time}	_{4.99s (± 0.96%)}	_{5.01s (± 1.19%)}	_~	_4.96s	_5.12s	_{p=0.936 n=6}
_{Bind Time}	_{1.90s (± 0.87%)}	_{1.90s (± 1.20%)}	_~	_1.88s	_1.93s	_{p=0.933 n=6}
_{Check Time}	_{33.59s (± 0.22%)}	_{33.59s (± 0.31%)}	_~	_33.41s	_33.67s	_{p=1.000 n=6}
_{Emit Time}	_{2.71s (± 1.81%)}	_{2.70s (± 1.22%)}	_~	_2.67s	_2.75s	_{p=0.422 n=6}
_{Total Time}	_{43.21s (± 0.19%)}	_{43.23s (± 0.29%)}	_~	_43.08s	_43.39s	_{p=0.810 n=6}
_{self-compiler - node (v18.15.0, x64)}
_{Memory used}	_{416,099k (± 0.00%)}	_{416,158k (± 0.01%)}	_{+59k (+ 0.01%)}	_416,114k	_416,200k	_{p=0.005 n=6}
_{Parse Time}	_{2.82s (± 1.20%)}	_{2.81s (± 0.94%)}	_~	_2.76s	_2.83s	_{p=0.747 n=6}
_{Bind Time}	_{1.07s (± 0.70%)}	_{1.07s (± 0.92%)}	_~	_1.06s	_1.08s	_{p=1.000 n=6}
_{Check Time}	_{15.28s (± 0.23%)}	_{15.37s (± 0.22%)}	_{+0.08s (+ 0.55%)}	_15.32s	_15.41s	_{p=0.008 n=6}
_{Emit Time}	_{1.16s (± 1.01%)}	_{1.14s (± 0.66%)}	_{-0.02s (- 1.44%)}	_1.13s	_1.15s	_{p=0.032 n=6}
_{Total Time}	_{20.34s (± 0.08%)}	_{20.38s (± 0.19%)}	_{+0.05s (+ 0.23%)}	_20.34s	_20.44s	_{p=0.029 n=6}
_{vscode - node (v18.15.0, x64)}
_{Memory used}	_{2,883,825k (± 0.00%)}	_{2,884,003k (± 0.00%)}	_{+178k (+ 0.01%)}	_2,883,812k	_2,884,096k	_{p=0.031 n=6}
_{Parse Time}	_{10.82s (± 0.35%)}	_{10.83s (± 0.57%)}	_~	_10.76s	_10.91s	_{p=1.000 n=6}
_{Bind Time}	_{3.46s (± 0.68%)}	_{3.46s (± 0.30%)}	_~	_3.45s	_3.48s	_{p=0.494 n=6}
_{Check Time}	_{61.55s (± 0.41%)}	_{61.79s (± 0.63%)}	_~	_61.47s	_62.54s	_{p=0.298 n=6}
_{Emit Time}	_{17.06s (± 7.90%)}	_{16.99s (± 8.36%)}	_~	_16.30s	_19.89s	_{p=0.298 n=6}
_{Total Time}	_{92.88s (± 1.66%)}	_{93.07s (± 1.97%)}	_~	_92.07s	_96.80s	_{p=0.575 n=6}
_{webpack - node (v18.15.0, x64)}
_{Memory used}	_{408,036k (± 0.01%)}	_{408,075k (± 0.01%)}	_~	_408,013k	_408,146k	_{p=0.378 n=6}
_{Parse Time}	_{3.23s (± 0.32%)}	_{3.23s (± 0.25%)}	_~	_3.22s	_3.24s	_{p=0.270 n=6}
_{Bind Time}	_{1.38s (± 0.30%)}	_{1.37s (± 0.75%)}	_~	_1.36s	_1.38s	_{p=0.461 n=6}
_{Check Time}	_{14.27s (± 0.41%)}	_{14.31s (± 0.30%)}	_~	_14.27s	_14.37s	_{p=0.415 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{18.88s (± 0.34%)}	_{18.92s (± 0.28%)}	_~	_18.86s	_18.99s	_{p=0.521 n=6}
_{xstate - node (v18.15.0, x64)}
_{Memory used}	_{513,118k (± 0.02%)}	_{513,166k (± 0.02%)}	_~	_513,081k	_513,316k	_{p=0.689 n=6}
_{Parse Time}	_{3.28s (± 0.32%)}	_{3.28s (± 0.31%)}	_~	_3.26s	_3.29s	_{p=0.933 n=6}
_{Bind Time}	_{1.54s (± 0.34%)}	_{1.54s (± 0.41%)}	_~	_1.53s	_1.55s	_{p=0.386 n=6}
_{Check Time}	_{2.86s (± 0.68%)}	_{2.85s (± 0.90%)}	_~	_2.83s	_2.90s	_{p=0.517 n=6}
_{Emit Time}	_{0.07s (± 0.00%)}	_{0.07s (± 0.00%)}	_~	_0.07s	_0.07s	_{p=1.000 n=6}
_{Total Time}	_{7.75s (± 0.19%)}	_{7.75s (± 0.29%)}	_~	_7.73s	_7.79s	_{p=0.420 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

Angular - node (v18.15.0, x64)
Compiler-Unions - node (v18.15.0, x64)
Monaco - node (v18.15.0, x64)
TFS - node (v18.15.0, x64)
material-ui - node (v18.15.0, x64)
mui-docs - node (v18.15.0, x64)
self-build-src - node (v18.15.0, x64)
self-compiler - node (v18.15.0, x64)
vscode - node (v18.15.0, x64)
webpack - node (v18.15.0, x64)
xstate - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

TypeScript Bot (typescript-bot) · 2024-03-19T15:34:54Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the top-repos suite comparing main and refs/pull/57847/merge:

Something interesting changed - please have a look.

Details

microsoft/vscode

4 of 54 projects failed to build with the old tsc and were ignored

src/tsconfig.tsec.json

error TS2698: Spread types may only be created from object types.
- src/vs/workbench/api/node/proxyResolver.ts#L124
- src/vs/workbench/contrib/testing/common/testCoverage.ts#L43

src/tsconfig.json

error TS2698: Spread types may only be created from object types.
- src/vs/workbench/api/node/proxyResolver.ts#L124
- src/vs/workbench/contrib/testing/common/testCoverage.ts#L43

build/tsconfig.build.json

error TS2339: Property 'exports' does not exist on type 'never'.
- build/lib/bundle.ts#L440

react-navigation/react-navigation

9 of 14 projects failed to build with the old tsc and were ignored

tsconfig.json

error TS2349: This expression is not callable.
- packages/core/src/getStateFromPath.tsx#L635 in tsconfig.json

packages/core/tsconfig.build.json

error TS2349: This expression is not callable.
- packages/core/src/getStateFromPath.tsx#L635 in packages/core/tsconfig.build.json

Redocly/redoc

tsconfig.lib.json

error TS2698: Spread types may only be created from object types.
- src/services/OpenAPIParser.ts#L271

tsconfig.json

error TS2698: Spread types may only be created from object types.
- src/services/OpenAPIParser.ts#L271

ueberdosis/tiptap

3 of 8 projects failed to build with the old tsc and were ignored

tests/cypress/tsconfig.json

error TS2345: Argument of type 'RegExp' is not assignable to parameter of type 'string'.
- packages/core/src/utilities/objectIncludes.ts#L25

demos/tsconfig.vue-3.json

error TS2345: Argument of type 'RegExp' is not assignable to parameter of type 'string'.
- packages/core/src/utilities/objectIncludes.ts#L25

demos/tsconfig.vue-2.json

error TS2345: Argument of type 'RegExp' is not assignable to parameter of type 'string'.
- packages/core/src/utilities/objectIncludes.ts#L25

demos/tsconfig.react.json

error TS2345: Argument of type 'RegExp' is not assignable to parameter of type 'string'.
- packages/core/src/utilities/objectIncludes.ts#L25

demos/tsconfig.base.json

error TS2345: Argument of type 'RegExp' is not assignable to parameter of type 'string'.
- packages/core/src/utilities/objectIncludes.ts#L25

vercel/hyper

2 of 3 projects failed to build with the old tsc and were ignored

tsconfig.json

error TS2339: Property 'term' does not exist on type 'never'.
- lib/components/terms.tsx#L65 in tsconfig.json

xyflow/xyflow

5 of 6 projects failed to build with the old tsc and were ignored

packages/system/tsconfig.json

error TS2339: Property 'handleBounds' does not exist on type '{ z?: number | undefined; handleBounds?: NodeHandleBounds | undefined; isParent?: boolean | undefined; userProvidedNode: NodeBase<Record<string, unknown>, string>; } | undefined'.
- packages/system/src/xyhandle/utils.ts#L74

Jake Bailey (jakebailey) · 2024-03-19T16:04:56Z

Weird; reading some of the breaks, there seems to be a bug in this iteration of the PR where unrelated accesses are getting narrowed too.

declareconstkey: string;declareconstobj1: Record<string,number|undefined>;declareconstobj2: Record<string,number|undefined>;if(obj1[key]){constx=obj1[key];// ^?consty=obj2[key];// ^?}

Anders Hejlsberg (ahejlsberg) · 2024-03-19T16:48:17Z

Argh, I see what the issue is. Will fix.

Anders Hejlsberg (ahejlsberg) · 2024-03-19T17:31:09Z

TypeScript Bot (@typescript-bot) test top200
TypeScript Bot (@typescript-bot) user test this
TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test this faster

TypeScript Bot (typescript-bot) · 2024-03-19T17:31:12Z

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

Command	Status	Results
`test top200`	✅ Started	👀 Results
`user test this`	✅ Started	✅ Results
`run dt`	✅ Started	✅ Results
`perf test this faster`	✅ Started	👀 Results

TypeScript Bot (typescript-bot) · 2024-03-19T17:57:44Z

Hey Anders Hejlsberg (@ahejlsberg), the results of running the DT tests are ready.
Everything looks the same!
You can check the log here.

TypeScript Bot (typescript-bot) · 2024-03-19T17:58:27Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the user test suite comparing main and refs/pull/57847/merge:

Everything looks good!

TypeScript Bot (typescript-bot) · 2024-03-19T18:29:59Z

Anders Hejlsberg (@ahejlsberg)
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
_{Angular - node (v18.15.0, x64)}
_{Memory used}	_{295,750k (± 0.01%)}	_{295,777k (± 0.00%)}	_~	_295,765k	_295,788k	_{p=0.066 n=6}
_{Parse Time}	_{2.66s (± 0.37%)}	_{2.66s (± 0.50%)}	_~	_2.64s	_2.68s	_{p=0.654 n=6}
_{Bind Time}	_{0.83s (± 0.62%)}	_{0.83s (± 0.00%)}	_~	_0.83s	_0.83s	_{p=0.174 n=6}
_{Check Time}	_{8.20s (± 0.26%)}	_{8.19s (± 0.15%)}	_~	_8.17s	_8.20s	_{p=0.220 n=6}
_{Emit Time}	_{7.14s (± 0.23%)}	_{7.11s (± 0.23%)}	_{-0.03s (- 0.40%)}	_7.09s	_7.13s	_{p=0.028 n=6}
_{Total Time}	_{18.83s (± 0.21%)}	_{18.79s (± 0.14%)}	_~	_18.76s	_18.82s	_{p=0.075 n=6}
_{Compiler-Unions - node (v18.15.0, x64)}
_{Memory used}	_{193,151k (± 0.97%)}	_{192,675k (± 0.75%)}	_~	_191,914k	_195,612k	_{p=0.936 n=6}
_{Parse Time}	_{1.36s (± 0.40%)}	_{1.36s (± 1.02%)}	_~	_1.33s	_1.37s	_{p=0.663 n=6}
_{Bind Time}	_{0.72s (± 0.00%)}	_{0.72s (± 0.00%)}	_~	_0.72s	_0.72s	_{p=1.000 n=6}
_{Check Time}	_{9.49s (± 0.56%)}	_{9.48s (± 0.58%)}	_~	_9.41s	_9.58s	_{p=1.000 n=6}
_{Emit Time}	_{2.66s (± 0.66%)}	_{2.65s (± 0.34%)}	_~	_2.64s	_2.66s	_{p=0.198 n=6}
_{Total Time}	_{14.22s (± 0.32%)}	_{14.21s (± 0.35%)}	_~	_14.15s	_14.30s	_{p=0.936 n=6}
_{Monaco - node (v18.15.0, x64)}
_{Memory used}	_{347,386k (± 0.01%)}	_{347,403k (± 0.01%)}	_~	_347,380k	_347,435k	_{p=0.173 n=6}
_{Parse Time}	_{2.47s (± 0.98%)}	_{2.49s (± 0.00%)}	_~	_2.49s	_2.49s	_{p=0.128 n=6}
_{Bind Time}	_{0.94s (± 2.40%)}	_{0.93s (± 0.44%)}	_~	_0.92s	_0.93s	_{p=0.787 n=6}
_{Check Time}	_{7.02s (± 0.32%)}	_{7.00s (± 0.33%)}	_~	_6.98s	_7.04s	_{p=0.106 n=6}
_{Emit Time}	_{4.07s (± 0.41%)}	_{4.07s (± 0.30%)}	_~	_4.06s	_4.09s	_{p=0.616 n=6}
_{Total Time}	_{14.50s (± 0.13%)}	_{14.49s (± 0.26%)}	_~	_14.45s	_14.55s	_{p=0.332 n=6}
_{TFS - node (v18.15.0, x64)}
_{Memory used}	_{302,745k (± 0.01%)}	_{302,751k (± 0.01%)}	_~	_302,722k	_302,771k	_{p=0.378 n=6}
_{Parse Time}	_{2.00s (± 0.81%)}	_{2.01s (± 0.75%)}	_~	_2.00s	_2.04s	_{p=0.462 n=6}
_{Bind Time}	_{1.00s (± 0.98%)}	_{1.00s (± 1.03%)}	_~	_0.99s	_1.02s	_{p=0.452 n=6}
_{Check Time}	_{6.33s (± 0.60%)}	_{6.30s (± 0.21%)}	_~	_6.28s	_6.32s	_{p=0.221 n=6}
_{Emit Time}	_{3.60s (± 0.55%)}	_{3.60s (± 0.23%)}	_~	_3.59s	_3.61s	_{p=1.000 n=6}
_{Total Time}	_{12.93s (± 0.30%)}	_{12.92s (± 0.22%)}	_~	_12.89s	_12.97s	_{p=0.685 n=6}
_{material-ui - node (v18.15.0, x64)}
_{Memory used}	_{511,362k (± 0.00%)}	_{511,389k (± 0.00%)}	_{+27k (+ 0.01%)}	_511,377k	_511,417k	_{p=0.030 n=6}
_{Parse Time}	_{2.66s (± 0.58%)}	_{2.66s (± 0.31%)}	_~	_2.64s	_2.66s	_{p=0.242 n=6}
_{Bind Time}	_{0.99s (± 1.23%)}	_{0.99s (± 1.05%)}	_~	_0.97s	_1.00s	_{p=1.000 n=6}
_{Check Time}	_{17.33s (± 0.33%)}	_{17.29s (± 0.25%)}	_~	_17.23s	_17.36s	_{p=0.226 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{20.98s (± 0.26%)}	_{20.93s (± 0.23%)}	_~	_20.86s	_21.01s	_{p=0.125 n=6}
_{mui-docs - node (v18.15.0, x64)}
_{Memory used}	_{1,719,162k (± 0.00%)}	_{1,719,198k (± 0.00%)}	_~	_1,719,144k	_1,719,243k	_{p=0.066 n=6}
_{Parse Time}	_{6.52s (± 0.49%)}	_{6.53s (± 0.43%)}	_~	_6.50s	_6.57s	_{p=0.747 n=6}
_{Bind Time}	_{2.37s (± 0.56%)}	_{2.35s (± 0.35%)}	_~	_2.35s	_2.37s	_{p=0.052 n=6}
_{Check Time}	_{56.10s (± 0.42%)}	_{56.40s (± 0.42%)}	_{+0.30s (+ 0.54%)}	_56.12s	_56.75s	_{p=0.045 n=6}
_{Emit Time}	_{0.14s (± 4.05%)}	_{0.13s (± 0.00%)}	_~	_0.13s	_0.13s	_{p=0.071 n=6}
_{Total Time}	_{65.12s (± 0.36%)}	_{65.41s (± 0.39%)}	_~	_65.10s	_65.79s	_{p=0.093 n=6}
_{self-build-src - node (v18.15.0, x64)}
_{Memory used}	_{2,395,113k (± 0.03%)}	_{2,395,863k (± 0.02%)}	_~	_2,395,219k	_2,396,651k	_{p=0.128 n=6}
_{Parse Time}	_{4.98s (± 0.73%)}	_{4.98s (± 1.12%)}	_~	_4.94s	_5.08s	_{p=0.809 n=6}
_{Bind Time}	_{1.89s (± 0.72%)}	_{1.91s (± 0.63%)}	_{+0.02s (+ 1.06%)}	_1.90s	_1.93s	_{p=0.042 n=6}
_{Check Time}	_{33.64s (± 0.55%)}	_{33.64s (± 0.29%)}	_~	_33.49s	_33.79s	_{p=0.689 n=6}
_{Emit Time}	_{2.70s (± 2.05%)}	_{2.71s (± 1.18%)}	_~	_2.68s	_2.77s	_{p=1.000 n=6}
_{Total Time}	_{43.22s (± 0.55%)}	_{43.26s (± 0.21%)}	_~	_43.13s	_43.36s	_{p=0.378 n=6}
_{self-compiler - node (v18.15.0, x64)}
_{Memory used}	_{416,056k (± 0.00%)}	_{416,145k (± 0.01%)}	_{+89k (+ 0.02%)}	_416,120k	_416,178k	_{p=0.005 n=6}
_{Parse Time}	_{2.82s (± 0.66%)}	_{2.81s (± 0.52%)}	_~	_2.79s	_2.83s	_{p=0.368 n=6}
_{Bind Time}	_{1.07s (± 0.51%)}	_{1.07s (± 0.51%)}	_~	_1.06s	_1.07s	_{p=1.000 n=6}
_{Check Time}	_{15.27s (± 0.39%)}	_{15.37s (± 0.45%)}	_{+0.10s (+ 0.64%)}	_15.30s	_15.48s	_{p=0.029 n=6}
_{Emit Time}	_{1.14s (± 1.51%)}	_{1.15s (± 0.90%)}	_~	_1.13s	_1.16s	_{p=0.459 n=6}
_{Total Time}	_{20.30s (± 0.38%)}	_{20.39s (± 0.37%)}	_~	_20.30s	_20.52s	_{p=0.109 n=6}
_{vscode - node (v18.15.0, x64)}
_{Memory used}	_{2,884,099k (± 0.00%)}	_{2,884,245k (± 0.00%)}	_{+147k (+ 0.01%)}	_2,884,114k	_2,884,293k	_{p=0.013 n=6}
_{Parse Time}	_{10.81s (± 0.27%)}	_{10.81s (± 0.23%)}	_~	_10.77s	_10.84s	_{p=0.871 n=6}
_{Bind Time}	_{3.46s (± 0.47%)}	_{3.46s (± 0.24%)}	_~	_3.45s	_3.47s	_{p=0.458 n=6}
_{Check Time}	_{61.53s (± 0.21%)}	_{61.65s (± 0.39%)}	_~	_61.37s	_62.08s	_{p=0.297 n=6}
_{Emit Time}	_{16.44s (± 0.24%)}	_{17.12s (± 8.96%)}	_~	_16.41s	_20.25s	_{p=0.126 n=6}
_{Total Time}	_{92.24s (± 0.19%)}	_{93.05s (± 1.87%)}	_~	_92.13s	_96.60s	_{p=0.149 n=6}
_{webpack - node (v18.15.0, x64)}
_{Memory used}	_{408,093k (± 0.03%)}	_{408,112k (± 0.02%)}	_~	_408,031k	_408,214k	_{p=0.689 n=6}
_{Parse Time}	_{3.22s (± 0.46%)}	_{3.24s (± 0.50%)}	_~	_3.21s	_3.25s	_{p=0.139 n=6}
_{Bind Time}	_{1.38s (± 0.71%)}	_{1.38s (± 0.99%)}	_~	_1.36s	_1.40s	_{p=0.607 n=6}
_{Check Time}	_{14.31s (± 0.50%)}	_{14.31s (± 0.30%)}	_~	_14.23s	_14.34s	_{p=1.000 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{18.91s (± 0.40%)}	_{18.93s (± 0.19%)}	_~	_18.88s	_18.97s	_{p=0.688 n=6}
_{xstate - node (v18.15.0, x64)}
_{Memory used}	_{513,109k (± 0.01%)}	_{513,091k (± 0.01%)}	_~	_513,035k	_513,147k	_{p=0.810 n=6}
_{Parse Time}	_{3.28s (± 0.23%)}	_{3.27s (± 0.23%)}	_~	_3.26s	_3.28s	_{p=0.195 n=6}
_{Bind Time}	_{1.54s (± 0.41%)}	_{1.54s (± 0.49%)}	_~	_1.53s	_1.55s	_{p=0.718 n=6}
_{Check Time}	_{2.86s (± 0.64%)}	_{2.84s (± 1.02%)}	_~	_2.79s	_2.87s	_{p=0.145 n=6}
_{Emit Time}	_{0.07s (± 0.00%)}	_{0.07s (± 5.69%)}	_~	_0.07s	_0.08s	_{p=0.405 n=6}
_{Total Time}	_{7.76s (± 0.27%)}	_{7.73s (± 0.34%)}	_~	_7.69s	_7.76s	_{p=0.198 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

Angular - node (v18.15.0, x64)
Compiler-Unions - node (v18.15.0, x64)
Monaco - node (v18.15.0, x64)
TFS - node (v18.15.0, x64)
material-ui - node (v18.15.0, x64)
mui-docs - node (v18.15.0, x64)
self-build-src - node (v18.15.0, x64)
self-compiler - node (v18.15.0, x64)
vscode - node (v18.15.0, x64)
webpack - node (v18.15.0, x64)
xstate - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

Anders Hejlsberg (ahejlsberg) · 2024-03-19T18:36:51Z

TypeScript Bot (@typescript-bot) perf test this faster

TypeScript Bot (typescript-bot) · 2024-03-19T18:36:54Z

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

Command	Status	Results
`perf test this faster`	✅ Started	👀 Results

TypeScript Bot (typescript-bot) · 2024-03-19T18:47:44Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the top-repos suite comparing main and refs/pull/57847/merge:

Something interesting changed - please have a look.

Details

xyflow/xyflow

5 of 6 projects failed to build with the old tsc and were ignored

packages/system/tsconfig.json

error TS2339: Property 'handleBounds' does not exist on type '{ z?: number | undefined; handleBounds?: NodeHandleBounds | undefined; isParent?: boolean | undefined; userProvidedNode: NodeBase<Record<string, unknown>, string>; } | undefined'.
- packages/system/src/xyhandle/utils.ts#L74

Jake Bailey (jakebailey) · 2024-03-19T20:05:33Z

TypeScript Bot (@typescript-bot) pack this

TypeScript Bot (typescript-bot) · 2024-03-19T20:05:35Z

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

Command	Status	Results
`pack this`	✅ Started	✅ Results

TypeScript Bot (typescript-bot) · 2024-03-19T20:10:06Z

Hey Jake Bailey (@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/160607/artifacts?artifactName=tgz&fileId=FCCE8FB0B7250696E9C38855366CC2296FF63CC26FF4295ECFB451B5CF87FE3B02&fileName=/typescript-5.5.0-insiders.20240319.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@5.5.0-pr-57847-18".;

Anders Hejlsberg (ahejlsberg) · 2024-03-19T21:50:26Z

Tests and performance look good. This is ready for a review.

Jake Bailey (jakebailey) · 2024-03-19T22:49:51Z

+ }
+ if (isElementAccessExpression(source) && isElementAccessExpression(target) && isIdentifier(source.argumentExpression) && isIdentifier(target.argumentExpression)) {
+ const symbol = getResolvedSymbol(source.argumentExpression);
+ if (symbol === getResolvedSymbol(target.argumentExpression) && (isConstantVariable(symbol) || isParameterOrMutableLocalVariable(symbol) && !isSymbolAssigned(symbol))) {


Does it make more sense to do isPastLastAssignment using a more specific location? How does this PR interact with #56908?

Unfortunately not that simple. We would need to know that all narrowing operations for obj[key] occur past the last assignment to key which would require an additional CFA graph walk. We don't have that issue in #56908 because the only location we care about is the location where the arrow function is created.

Makes sense; I really need to prototype the idea I had to make that efficient enough for us to do, but I've lost that brainwave ☹️
Can you add a test in the vein of #56908 in terms of what closures do? Something like: Playground Link (which does behave properly I think)

Can you add a test in the vein of...
Such a test wouldn't show anything. The new analysis in #56908 only affects references to local variables, not references to properties, so there are no changes across closure boundaries with this PR.

Anders Hejlsberg (ahejlsberg) · 2024-03-20T14:05:01Z

TypeScript Bot (@typescript-bot) perf test this faster

TypeScript Bot (typescript-bot) · 2024-03-20T14:05:04Z

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

Command	Status	Results
`perf test this faster`	✅ Started	👀 Results

TypeScript Bot (typescript-bot) · 2024-03-20T14:40:09Z

Anders Hejlsberg (@ahejlsberg)
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
_{Angular - node (v18.15.0, x64)}
_{Memory used}	_{295,752k (± 0.00%)}	_{295,764k (± 0.01%)}	_~	_295,727k	_295,787k	_{p=0.199 n=6}
_{Parse Time}	_{2.67s (± 0.28%)}	_{2.66s (± 0.39%)}	_~	_2.65s	_2.68s	_{p=0.351 n=6}
_{Bind Time}	_{0.83s (± 0.76%)}	_{0.83s (± 0.76%)}	_~	_0.82s	_0.84s	_{p=1.000 n=6}
_{Check Time}	_{8.20s (± 0.28%)}	_{8.21s (± 0.29%)}	_~	_8.17s	_8.24s	_{p=0.459 n=6}
_{Emit Time}	_{7.11s (± 0.19%)}	_{7.11s (± 0.43%)}	_~	_7.07s	_7.15s	_{p=0.745 n=6}
_{Total Time}	_{18.81s (± 0.21%)}	_{18.82s (± 0.21%)}	_~	_18.78s	_18.88s	_{p=0.686 n=6}
_{Compiler-Unions - node (v18.15.0, x64)}
_{Memory used}	_{192,684k (± 0.79%)}	_{193,228k (± 0.93%)}	_~	_191,955k	_195,545k	_{p=0.689 n=6}
_{Parse Time}	_{1.36s (± 1.29%)}	_{1.36s (± 1.10%)}	_~	_1.34s	_1.38s	_{p=0.932 n=6}
_{Bind Time}	_{0.72s (± 0.57%)}	_{0.72s (± 0.00%)}	_~	_0.72s	_0.72s	_{p=0.405 n=6}
_{Check Time}	_{9.54s (± 0.59%)}	_{9.53s (± 0.69%)}	_~	_9.45s	_9.60s	_{p=1.000 n=6}
_{Emit Time}	_{2.66s (± 0.39%)}	_{2.66s (± 0.19%)}	_~	_2.65s	_2.66s	_{p=0.794 n=6}
_{Total Time}	_{14.28s (± 0.44%)}	_{14.27s (± 0.43%)}	_~	_14.19s	_14.33s	_{p=0.935 n=6}
_{Monaco - node (v18.15.0, x64)}
_{Memory used}	_{347,381k (± 0.01%)}	_{347,410k (± 0.00%)}	_{+29k (+ 0.01%)}	_347,396k	_347,428k	_{p=0.020 n=6}
_{Parse Time}	_{2.48s (± 0.59%)}	_{2.48s (± 0.49%)}	_~	_2.46s	_2.49s	_{p=0.867 n=6}
_{Bind Time}	_{0.93s (± 0.44%)}	_{0.92s (± 0.59%)}	_~	_0.92s	_0.93s	_{p=0.282 n=6}
_{Check Time}	_{7.02s (± 0.43%)}	_{7.03s (± 0.11%)}	_~	_7.02s	_7.04s	_{p=0.368 n=6}
_{Emit Time}	_{4.07s (± 0.63%)}	_{4.07s (± 0.55%)}	_~	_4.05s	_4.11s	_{p=0.800 n=6}
_{Total Time}	_{14.50s (± 0.42%)}	_{14.50s (± 0.18%)}	_~	_14.48s	_14.55s	_{p=1.000 n=6}
_{TFS - node (v18.15.0, x64)}
_{Memory used}	_{302,745k (± 0.01%)}	_{302,759k (± 0.01%)}	_~	_302,715k	_302,814k	_{p=0.575 n=6}
_{Parse Time}	_{2.01s (± 0.70%)}	_{2.00s (± 1.41%)}	_~	_1.97s	_2.05s	_{p=0.293 n=6}
_{Bind Time}	_{1.01s (± 1.02%)}	_{1.00s (± 0.52%)}	_~	_0.99s	_1.00s	_{p=0.069 n=6}
_{Check Time}	_{6.33s (± 0.45%)}	_{6.33s (± 0.60%)}	_~	_6.28s	_6.39s	_{p=0.630 n=6}
_{Emit Time}	_{3.61s (± 0.29%)}	_{3.60s (± 0.46%)}	_~	_3.58s	_3.62s	_{p=0.559 n=6}
_{Total Time}	_{12.96s (± 0.26%)}	_{12.93s (± 0.41%)}	_~	_12.87s	_13.01s	_{p=0.261 n=6}
_{material-ui - node (v18.15.0, x64)}
_{Memory used}	_{509,905k (± 0.00%)}	_{509,929k (± 0.00%)}	_{+24k (+ 0.00%)}	_509,910k	_509,954k	_{p=0.020 n=6}
_{Parse Time}	_{2.66s (± 0.73%)}	_{2.66s (± 0.44%)}	_~	_2.64s	_2.67s	_{p=0.869 n=6}
_{Bind Time}	_{0.99s (± 1.18%)}	_{0.98s (± 1.23%)}	_~	_0.97s	_1.00s	_{p=0.323 n=6}
_{Check Time}	_{17.23s (± 0.24%)}	_{17.27s (± 0.33%)}	_~	_17.19s	_17.33s	_{p=0.296 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{20.89s (± 0.23%)}	_{20.91s (± 0.28%)}	_~	_20.84s	_20.98s	_{p=0.372 n=6}
_{mui-docs - node (v18.15.0, x64)}
_{Memory used}	_{1,719,252k (± 0.00%)}	_{1,719,223k (± 0.00%)}	_~	_1,719,141k	_1,719,297k	_{p=0.575 n=6}
_{Parse Time}	_{6.54s (± 0.43%)}	_{6.55s (± 0.74%)}	_~	_6.50s	_6.64s	_{p=0.872 n=6}
_{Bind Time}	_{2.36s (± 0.38%)}	_{2.38s (± 0.52%)}	_{+0.02s (+ 0.64%)}	_2.37s	_2.40s	_{p=0.025 n=6}
_{Check Time}	_{56.41s (± 0.23%)}	_{56.32s (± 0.47%)}	_~	_55.88s	_56.58s	_{p=0.810 n=6}
_{Emit Time}	_{0.13s (± 0.00%)}	_{0.13s (± 3.87%)}	_~	_0.13s	_0.14s	_{p=0.174 n=6}
_{Total Time}	_{65.45s (± 0.21%)}	_{65.38s (± 0.34%)}	_~	_65.03s	_65.58s	_{p=0.630 n=6}
_{self-build-src - node (v18.15.0, x64)}
_{Memory used}	_{2,395,320k (± 0.04%)}	_{2,394,952k (± 0.04%)}	_~	_2,393,869k	_2,395,740k	_{p=0.575 n=6}
_{Parse Time}	_{4.99s (± 0.58%)}	_{5.04s (± 1.02%)}	_~	_4.96s	_5.10s	_{p=0.077 n=6}
_{Bind Time}	_{1.91s (± 0.88%)}	_{1.90s (± 0.98%)}	_~	_1.88s	_1.93s	_{p=0.516 n=6}
_{Check Time}	_{33.69s (± 0.48%)}	_{33.71s (± 0.24%)}	_~	_33.60s	_33.80s	_{p=0.689 n=6}
_{Emit Time}	_{2.72s (± 1.49%)}	_{2.69s (± 1.32%)}	_~	_2.65s	_2.74s	_{p=0.375 n=6}
_{Total Time}	_{43.33s (± 0.40%)}	_{43.35s (± 0.17%)}	_~	_43.26s	_43.44s	_{p=0.810 n=6}
_{self-compiler - node (v18.15.0, x64)}
_{Memory used}	_{416,071k (± 0.01%)}	_{416,145k (± 0.01%)}	_{+75k (+ 0.02%)}	_416,120k	_416,177k	_{p=0.005 n=6}
_{Parse Time}	_{2.82s (± 0.65%)}	_{2.84s (± 0.66%)}	_~	_2.82s	_2.87s	_{p=0.122 n=6}
_{Bind Time}	_{1.07s (± 0.59%)}	_{1.07s (± 0.51%)}	_~	_1.06s	_1.07s	_{p=0.201 n=6}
_{Check Time}	_{15.28s (± 0.22%)}	_{15.33s (± 0.18%)}	_{+0.04s (+ 0.27%)}	_15.30s	_15.36s	_{p=0.043 n=6}
_{Emit Time}	_{1.14s (± 1.43%)}	_{1.14s (± 1.11%)}	_~	_1.13s	_1.16s	_{p=0.567 n=6}
_{Total Time}	_{20.32s (± 0.16%)}	_{20.36s (± 0.18%)}	_{+0.05s (+ 0.23%)}	_20.32s	_20.42s	_{p=0.034 n=6}
_{vscode - node (v18.15.0, x64)}
_{Memory used}	_{2,886,074k (± 0.00%)}	_{2,886,262k (± 0.00%)}	_{+189k (+ 0.01%)}	_2,886,173k	_2,886,342k	_{p=0.005 n=6}
_{Parse Time}	_{10.86s (± 0.46%)}	_{10.84s (± 0.37%)}	_~	_10.80s	_10.91s	_{p=0.808 n=6}
_{Bind Time}	_{3.47s (± 0.42%)}	_{3.46s (± 0.22%)}	_~	_3.45s	_3.47s	_{p=0.102 n=6}
_{Check Time}	_{61.33s (± 0.32%)}	_{61.46s (± 0.32%)}	_~	_61.25s	_61.67s	_{p=0.378 n=6}
_{Emit Time}	_{16.50s (± 0.79%)}	_{16.42s (± 0.26%)}	_~	_16.35s	_16.47s	_{p=0.148 n=6}
_{Total Time}	_{92.16s (± 0.33%)}	_{92.19s (± 0.24%)}	_~	_91.91s	_92.45s	_{p=0.936 n=6}
_{webpack - node (v18.15.0, x64)}
_{Memory used}	_{408,070k (± 0.02%)}	_{408,120k (± 0.02%)}	_~	_408,023k	_408,217k	_{p=0.378 n=6}
_{Parse Time}	_{3.23s (± 0.51%)}	_{3.23s (± 0.46%)}	_~	_3.21s	_3.24s	_{p=0.684 n=6}
_{Bind Time}	_{1.38s (± 0.00%)}	_{1.38s (± 0.75%)}	_~	_1.36s	_1.39s	_{p=0.599 n=6}
_{Check Time}	_{14.29s (± 0.17%)}	_{14.29s (± 0.22%)}	_~	_14.23s	_14.32s	_{p=0.935 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{18.90s (± 0.18%)}	_{18.90s (± 0.17%)}	_~	_18.86s	_18.94s	_{p=1.000 n=6}
_{xstate - node (v18.15.0, x64)}
_{Memory used}	_{513,109k (± 0.01%)}	_{513,102k (± 0.01%)}	_~	_512,985k	_513,143k	_{p=0.810 n=6}
_{Parse Time}	_{3.27s (± 0.27%)}	_{3.27s (± 0.41%)}	_~	_3.25s	_3.29s	_{p=0.801 n=6}
_{Bind Time}	_{1.54s (± 0.54%)}	_{1.54s (± 0.26%)}	_~	_1.54s	_1.55s	_{p=0.527 n=6}
_{Check Time}	_{2.85s (± 0.63%)}	_{2.85s (± 0.65%)}	_~	_2.83s	_2.88s	_{p=0.628 n=6}
_{Emit Time}	_{0.07s (± 0.00%)}	_{0.07s (± 0.00%)}	_~	_0.07s	_0.07s	_{p=1.000 n=6}
_{Total Time}	_{7.75s (± 0.21%)}	_{7.74s (± 0.18%)}	_~	_7.73s	_7.76s	_{p=1.000 n=6}

System info unknown

Hosts

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_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

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Illia Panasenko (ipanasenko) · 2024-06-11T19:30:52Z

Hi. I'm not sure if it's okay to ask here or I should rather open new discussion, so sorry in advance.

Do you think the following type narrowing using in should work as well?
I have a Record with predefined keys in it, and I expected that if in returns true, then animal can only be of Animal type.
https://www.typescriptlang.org/play/?#code/C4TwDgpgBAggdgSwLYEMA2UC8UDkBjFYHKAH1wBMB7Ac2LJwCMEAncnAbgCg9K4BnYFBSJUaAAooA7nwCyKMAC4oAJQg9WAHnjJ0AGihwArkgYRmAPixQA3pyhQCwBQBZddqFWou39pqyUATG4AvlzcvAJQABaUknJwIBLSVgAUwjpoSgLMCHDUAJRKRiZmWJa29ggAZlBpIuhQuUL14lKy8vk27vbMEMCGzHDNGUntYADa6aIAulz2wZzuvf2DUACScFW5CKBcwUA

I think this might be related to this feature.

Joost Koehoorn (JoostK) · 2024-06-11T20:07:17Z

Hi. I'm not sure if it's okay to ask here or I should rather open new discussion, so sorry in advance.
Do you think the following type narrowing using in should work as well? I have a Record with predefined keys in it, and I expected that if in returns true, then animal can only be of Animal type. https://www.typescriptlang.org/play/?#code/C4TwDgpgBAggdgSwLYEMA2UC8UDkBjFYHKAH1wBMB7Ac2LJwCMEAncnAbgCg9K4BnYFBSJUaAAooA7nwCyKMAC4oAJQg9WAHnjJ0AGihwArkgYRmAPixQA3pyhQCwBQBZddqFWou39pqyUATG4AvlzcvAJQABaUknJwIBLSVgAUwjpoSgLMCHDUAJRKRiZmWJa29ggAZlBpIuhQuUL14lKy8vk27vbMEMCGzHDNGUntYADa6aIAulz2wZzuvf2DUACScFW5CKBcwUA
I think this might be related to this feature.

That error is correct and desirable: the index signature only specifies that properties in Animal (i.e. 'cat' | 'dog' | 'bird') have a number value, it does not specify a type for any other properties. Since TypeScript does not have strict types it's fine for a Record<Animal, number> to also have other properties, as demonstrated in this playground. If the animal parameter is changed from type string to Animal then TypeScript no longer reports an error for the implementation of howManyPaws, while correctly preventing the monkey from requesting its number of paws.

Illia Panasenko (ipanasenko) · 2024-06-11T20:14:17Z

I see. Big thank you for an explanation

Dima Kharitonov (geakstr) · 2024-06-24T18:13:39Z

Hi and thank you for your work! Trying to clarify for myself this statement "The intuition here is that even if the exact name of the property selected by key isn't known, any control flow analysis proof that involves obj[key] should hold in subsequent statements as long as obj and key aren't mutated" from the PR description.

Here I mutate obj and TS 5.5.2 doesn't throw errors:

function f1(obj: Record<string, unknown>, key: string) {
if (typeof obj[key] === "string") {
delete obj[key];
obj[key].toUpperCase(); // ok
}
}

Is this "expected"?

Anders Hejlsberg (ahejlsberg) added 3 commits March 18, 2024 21:17

CFA for obj[key] where key is constant variable or parameter
aed5fc0

Accept new baselines
8676121

Add tests
2ce7c15

TypeScript Bot (typescript-bot) assigned Anders Hejlsberg (ahejlsberg)Mar 19, 2024

TypeScript Bot (typescript-bot) added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Mar 19, 2024

Anders Hejlsberg (ahejlsberg) requested review from Daniel Rosenwasser (DanielRosenwasser) and Ryan Cavanaugh (RyanCavanaugh)March 19, 2024 15:22

Mateusz Burzyński (Andarist) mentioned this pull request Mar 19, 2024
Narrow down non-const enity name expressions within element access expressions #56392
Closed

Fully compare references
95818c0

Minor optimization
aa68fd8

Emanuel Hoogeveen (ehoogeveen-medweb) mentioned this pull request Mar 19, 2024
Design Meeting Notes, 3/19/2024 #57856
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Jake Bailey (jakebailey) reviewed Mar 19, 2024
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Gabriela Araujo Britto (gabritto) approved these changes Mar 21, 2024
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Anders Hejlsberg (ahejlsberg) merged commit a22aaf0 into mainMar 26, 2024

Anders Hejlsberg (ahejlsberg) deleted the fix56389 branch March 26, 2024 20:40

Ryan Cavanaugh (RyanCavanaugh) mentioned this pull request Apr 18, 2024
[NewErrors] 5.5.0-dev.20240414 vs 5.4.5 #58189
Open

Mateusz Burzyński (Andarist) mentioned this pull request Jun 7, 2024
instanceof has been used and there is a type inference error #58793
Closed

Grant Dickinson (grant-d) mentioned this pull request Jun 7, 2024
Narrowing for constant indexed access fails on array getter #58803
Closed

Rix (rixtox) mentioned this pull request Jun 10, 2024
Control flow analysis for element access with variable index doesn't account for async race condition #58822
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Aleksey Bobyr (Alexsey) mentioned this pull request Jun 16, 2024
TypeScript 5.5 "Control Flow Narrowing for Constant Indexed Accesses" is not working #58883
Closed

Martin Johns (MartinJohns) mentioned this pull request Jun 22, 2024
let indexes using noUncheckedIndexedAccess in TS 5.5.2 #58972
Closed

Jongsun Suh (MajorLift) mentioned this pull request Jul 18, 2024
[assets-contract-controller] Apply messenger pattern and remove inheritance from BaseControllerV1MetaMask/core#4397
Merged
3 tasks

Joe Calzaretta (jcalz) mentioned this pull request Jul 22, 2024
Presence of export affects narrowing #59393
Closed

Jake Bailey (jakebailey) mentioned this pull request Jul 25, 2024
Fixes issue 10530 #46121
Closed

Philip Waritschlager (phil294) mentioned this pull request Oct 15, 2024
Discriminant property type guard not applied with bracket notation #10530
Closed

Mateusz Burzyński (Andarist) mentioned this pull request Dec 9, 2024
Control flow analysis for element access with variable constant-like index in for statements #60715
Closed

Joe Calzaretta (jcalz) mentioned this pull request Feb 14, 2025
Narrow object property indexed by bracket notation when the key is a known literal type, regardless of where the key comes from #61176
Open
6 tasks

This was referenced Mar 10, 2025
'in' does not remove undefined from indexed value (with noUncheckedIndexedAccess) #61389
Open
Improve narrowing by in operator under noUncheckedIndexedAccess for variable properties #61393
Closed

Joe Calzaretta (jcalz) mentioned this pull request Jun 27, 2025
Inconsistent type when using noUncheckedIndexedAccess#61957
Closed

Matt Kantor (mkantor) mentioned this pull request Aug 13, 2025
Add definite assignment checks for interacting with noUncheckedIndexAccess#47998
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5 tasks

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