Support const assertions and unit type const variable references in constant expressions #59475

ahejlsberg · 2024-07-30T17:18:10Z

With this PR we permit constant expressions to contain const assertions and references to const variables with unit types:

const C00 = "a";
const C01 = "b" as const;
const C02: "c" = "c";
declare const C03: "d";

const enum E0 {
    A = C00,
    B = C01,  // Was error, now ok
    C = C02,  // Was error, now ok
    D = C03,  // Was error, now ok
}

const C10 = 1;
const C11 = 2 as const;
const C12: 3 = 3;
declare const C13: 4;

const enum E1 {
    A = C10,
    B = C11,  // Was error, now ok
    C = C12,  // Was error, now ok
    D = C13,  // Was error, now ok
}

Note that a const variable with a type annotation may be referenced in a constant expression only if the type annotation is a string or numeric literal. Other forms of types, such as named types or union types, are not supported.

Fixes #59346.

…pressions

ahejlsberg · 2024-07-30T17:18:24Z

@typescript-bot test it

typescript-bot · 2024-07-30T17:18:27Z

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

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

typescript-bot · 2024-07-30T17:39:37Z

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

Everything looks the same!

You can check the log here.

typescript-bot · 2024-07-30T17:44:40Z

@ahejlsberg Here are the results of running the user tests with tsc comparing main and refs/pull/59475/merge:

Everything looks good!

typescript-bot · 2024-07-30T17:55:50Z

@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
_{Compiler-Unions - node (v18.15.0, x64)}
_Errors	₃₀	₃₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_62,153	_62,153	_~	_~	_~	_{p=1.000 n=6}
_Types	_50,242	_50,242	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{192,882k (± 0.74%)}	_{194,182k (± 0.97%)}	_{+1,301k (+ 0.67%)}	_192,303k	_196,019k	_{p=0.031 n=6}
_{Parse Time}	_{1.57s (± 0.52%)}	_{1.57s (± 1.02%)}	_~	_1.54s	_1.58s	_{p=0.796 n=6}
_{Bind Time}	_{0.86s (± 0.95%)}	_{0.85s (± 1.21%)}	_~	_0.84s	_0.87s	_{p=0.546 n=6}
_{Check Time}	_{11.36s (± 0.30%)}	_{11.39s (± 0.65%)}	_~	_11.31s	_11.50s	_{p=0.573 n=6}
_{Emit Time}	_{3.26s (± 1.09%)}	_{3.26s (± 0.93%)}	_~	_3.21s	_3.30s	_{p=1.000 n=6}
_{Total Time}	_{17.06s (± 0.15%)}	_{17.08s (± 0.55%)}	_~	_16.95s	_17.23s	_{p=0.687 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₇	₇	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_945,532	_945,532	_~	_~	_~	_{p=1.000 n=6}
_Types	_409,507	_409,507	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{1,221,116k (± 0.00%)}	_{1,221,146k (± 0.00%)}	_~	_1,221,115k	_1,221,202k	_{p=0.066 n=6}
_{Parse Time}	_{7.86s (± 0.76%)}	_{7.85s (± 0.63%)}	_~	_7.80s	_7.93s	_{p=0.686 n=6}
_{Bind Time}	_{2.22s (± 0.72%)}	_{2.21s (± 0.74%)}	_~	_2.19s	_2.24s	_{p=0.625 n=6}
_{Check Time}	_{36.35s (± 0.43%)}	_{36.36s (± 0.49%)}	_~	_36.22s	_36.68s	_{p=1.000 n=6}
_{Emit Time}	_{17.75s (± 0.62%)}	_{17.78s (± 0.97%)}	_~	_17.51s	_18.00s	_{p=0.748 n=6}
_{Total Time}	_{64.17s (± 0.36%)}	_{64.20s (± 0.39%)}	_~	_63.81s	_64.43s	_{p=1.000 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,439,121	_2,439,121	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,004,407	_1,004,407	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,410,535k (± 0.00%)}	_{2,410,556k (± 0.00%)}	_~	_2,410,517k	_2,410,630k	_{p=0.471 n=6}
_{Parse Time}	_{9.94s (± 0.21%)}	_{9.94s (± 0.20%)}	_~	_9.91s	_9.96s	_{p=0.807 n=6}
_{Bind Time}	_{2.49s (± 0.65%)}	_{2.49s (± 0.22%)}	_~	_2.48s	_2.49s	_{p=0.228 n=6}
_{Check Time}	_{89.24s (± 2.12%)}	_{89.04s (± 1.51%)}	_~	_88.06s	_91.61s	_{p=0.630 n=6}
_{Emit Time}	_{0.33s (± 2.29%)}	_{0.32s (± 2.79%)}	_~	_0.31s	_0.33s	_{p=0.149 n=6}
_{Total Time}	_{102.00s (± 1.85%)}	_{101.79s (± 1.32%)}	_~	_100.77s	_104.37s	_{p=0.689 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,227,815	_1,227,818	_{+3 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_265,152	_265,153	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,464,884k (± 7.42%)}	_{2,347,114k (± 0.03%)}	_~	_2,345,986k	_2,347,910k	_{p=0.936 n=6}
_{Parse Time}	_{5.97s (± 0.75%)}	_{5.91s (± 0.50%)}	_{-0.05s (- 0.92%)}	_5.88s	_5.96s	_{p=0.031 n=6}
_{Bind Time}	_{2.27s (± 0.66%)}	_{2.26s (± 1.03%)}	_~	_2.25s	_2.31s	_{p=0.120 n=6}
_{Check Time}	_{40.54s (± 0.54%)}	_{40.61s (± 0.27%)}	_~	_40.43s	_40.76s	_{p=0.689 n=6}
_{Emit Time}	_{3.93s (± 0.84%)}	_{3.94s (± 0.88%)}	_~	_3.88s	_3.98s	_{p=0.872 n=6}
_{Total Time}	_{52.73s (± 0.50%)}	_{52.74s (± 0.17%)}	_~	_52.66s	_52.89s	_{p=0.575 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,227,815	_1,227,818	_{+3 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_265,152	_265,153	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,420,353k (± 0.03%)}	_{2,420,621k (± 0.01%)}	_~	_2,420,189k	_2,421,053k	_{p=0.810 n=6}
_{Parse Time}	_{6.20s (± 0.83%)}	_{6.22s (± 0.67%)}	_~	_6.15s	_6.27s	_{p=0.520 n=6}
_{Bind Time}	_{2.04s (± 0.91%)}	_{2.03s (± 1.16%)}	_~	_1.98s	_2.04s	_{p=0.324 n=6}
_{Check Time}	_{41.24s (± 0.78%)}	_{41.19s (± 0.15%)}	_~	_41.11s	_41.28s	_{p=0.936 n=6}
_{Emit Time}	_{4.05s (± 1.53%)}	_{4.04s (± 2.54%)}	_~	_3.95s	_4.24s	_{p=0.421 n=6}
_{Total Time}	_{53.55s (± 0.54%)}	_{53.51s (± 0.36%)}	_~	_53.25s	_53.82s	_{p=0.936 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_255,990	_255,993	_{+3 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_104,965	_104,966	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{427,919k (± 0.02%)}	_{428,058k (± 0.05%)}	_~	_427,848k	_428,334k	_{p=0.471 n=6}
_{Parse Time}	_{3.35s (± 0.93%)}	_{3.37s (± 0.68%)}	_~	_3.34s	_3.39s	_{p=0.222 n=6}
_{Bind Time}	_{1.32s (± 0.57%)}	_{1.30s (± 1.33%)}	_{-0.02s (- 1.77%)}	_1.28s	_1.32s	_{p=0.036 n=6}
_{Check Time}	_{17.97s (± 0.27%)}	_{18.02s (± 0.34%)}	_~	_17.94s	_18.09s	_{p=0.335 n=6}
_{Emit Time}	_{1.64s (± 1.30%)}	_{1.66s (± 0.98%)}	_~	_1.64s	_1.68s	_{p=0.106 n=6}
_{Total Time}	_{24.29s (± 0.34%)}	_{24.34s (± 0.25%)}	_~	_24.27s	_24.41s	_{p=0.336 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₃₅	₃₅	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_224,931	_224,931	_~	_~	_~	_{p=1.000 n=6}
_Types	_94,146	_94,146	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{370,075k (± 0.02%)}	_{370,113k (± 0.05%)}	_~	_369,912k	_370,329k	_{p=0.936 n=6}
_{Parse Time}	_{3.45s (± 0.79%)}	_{3.43s (± 0.66%)}	_~	_3.40s	_3.45s	_{p=0.120 n=6}
_{Bind Time}	_{1.92s (± 0.71%)}	_{1.92s (± 0.51%)}	_~	_1.91s	_1.93s	_{p=0.611 n=6}
_{Check Time}	_{19.36s (± 0.30%)}	_{19.32s (± 0.50%)}	_~	_19.23s	_19.49s	_{p=0.261 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{24.74s (± 0.26%)}	_{24.67s (± 0.36%)}	_~	_24.57s	_24.82s	_{p=0.128 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₁₁	₁₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,989,199	_2,989,199	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,028,388	_1,028,428	_{+40 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{3,113,698k (± 0.00%)}	_{3,113,665k (± 0.00%)}	_~	_3,113,608k	_3,113,733k	_{p=0.230 n=6}
_{Parse Time}	_{13.82s (± 0.50%)}	_{13.81s (± 0.27%)}	_~	_13.78s	_13.87s	_{p=0.806 n=6}
_{Bind Time}	_{4.36s (± 2.67%)}	_{4.32s (± 2.22%)}	_~	_4.26s	_4.51s	_{p=0.464 n=6}
_{Check Time}	_{79.40s (± 0.35%)}	_{79.65s (± 0.50%)}	_~	_79.16s	_80.11s	_{p=0.378 n=6}
_{Emit Time}	_{20.57s (± 0.97%)}	_{20.60s (± 0.41%)}	_~	_20.44s	_20.68s	_{p=0.297 n=6}
_{Total Time}	_{118.16s (± 0.35%)}	_{118.39s (± 0.38%)}	_~	_117.69s	_118.96s	_{p=0.378 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_267,994	_267,994	_~	_~	_~	_{p=1.000 n=6}
_Types	_109,192	_109,192	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{412,899k (± 0.02%)}	_{412,944k (± 0.03%)}	_~	_412,849k	_413,149k	_{p=0.810 n=6}
_{Parse Time}	_{3.81s (± 0.59%)}	_{3.81s (± 0.45%)}	_~	_3.79s	_3.84s	_{p=0.806 n=6}
_{Bind Time}	_{1.72s (± 0.30%)}	_{1.71s (± 0.37%)}	_~	_1.70s	_1.72s	_{p=0.091 n=6}
_{Check Time}	_{16.87s (± 0.63%)}	_{16.91s (± 0.56%)}	_~	_16.81s	_17.08s	_{p=0.574 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{22.40s (± 0.47%)}	_{22.43s (± 0.41%)}	_~	_22.35s	_22.60s	_{p=0.423 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_535,921	_535,921	_~	_~	_~	_{p=1.000 n=6}
_Types	_176,733	_176,733	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{477,642k (± 0.06%)}	_{477,474k (± 0.09%)}	_~	_477,065k	_477,930k	_{p=0.378 n=6}
_{Parse Time}	_{2.80s (± 0.79%)}	_{2.79s (± 0.70%)}	_~	_2.76s	_2.81s	_{p=0.190 n=6}
_{Bind Time}	_{1.04s (± 0.50%)}	_{1.03s (± 1.13%)}	_~	_1.01s	_1.04s	_{p=0.523 n=6}
_{Check Time}	_{15.17s (± 0.25%)}	_{15.18s (± 0.53%)}	_~	_15.11s	_15.31s	_{p=0.871 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{19.01s (± 0.25%)}	_{19.00s (± 0.54%)}	_~	_18.89s	_19.15s	_{p=0.748 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 · 2024-07-30T19:03:22Z

@ahejlsberg Here are the results of running the top 400 repos with tsc comparing main and refs/pull/59475/merge:

Everything looks good!

daniele-orlando · 2025-01-24T16:59:04Z

@RyanCavanaugh Hi dear TypeScript maintainers, this MR is pending since 6 months and it is blocking the resolution of issue #59346, which had a milestone of TypeScript 5.7.0, which has been clearly missed.

Can we get it merged?

Friend-LGA · 2025-01-28T17:18:33Z

I also would love to see this merged

P.S.: looks like all tests have successfully passed loooong time ago... Can someone review this MR already, please?

daniele-orlando · 2025-02-19T19:12:34Z

@RyanCavanaugh Is there any hope to see this merge request merged sooner or later? 6 months have passed and it is blocked for no explained reason.

cc: @jakebailey @andrewbranch @DanielRosenwasser

IainSAP · 2025-04-02T09:07:14Z

Please approve and merge...thx!

ahejlsberg added 4 commits July 30, 2024 09:28

Allow const assertions in constant expressions

e0036e6

Allow references to const variables with literal types in constant ex…

2e0d0fc

…pressions

Add tests

4a6d9fd

Include declaration emit in tests

e713577

typescript-bot assigned ahejlsberg Jul 30, 2024

typescript-bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Jul 30, 2024

ahejlsberg requested a review from RyanCavanaugh July 30, 2024 17:18

MartinJohns mentioned this pull request Jan 28, 2025

Not possible to use const string as enum value #61064

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Support const assertions and unit type const variable references in constant expressions #59475

Support const assertions and unit type const variable references in constant expressions #59475

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Support const assertions and unit type const variable references in constant expressions #59475

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Support const assertions and unit type const variable references in constant expressions #59475

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