Fix switch-true case-true narrowing to behave equivalently to default case #59459

Zzzen · 2024-07-29T16:20:56Z

… case

jakebailey · 2024-07-29T17:22:36Z

typescript-bot · 2024-07-29T17:22:40Z

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 · 2024-07-29T17:43:18Z

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

Everything looks the same!

You can check the log here.

typescript-bot · 2024-07-29T17:44:09Z

@jakebailey Here are the results of running the user tests with tsc comparing main and refs/pull/59459/merge:

Everything looks good!

typescript-bot · 2024-07-29T17:59:20Z

@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	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}	_{193,596k (± 0.95%)}	_{194,082k (± 1.00%)}	_~	_192,225k	_195,915k	_{p=1.000 n=6}
_{Parse Time}	_{1.56s (± 1.46%)}	_{1.57s (± 0.62%)}	_~	_1.56s	_1.58s	_{p=0.402 n=6}
_{Bind Time}	_{0.85s (± 0.98%)}	_{0.86s (± 1.20%)}	_~	_0.85s	_0.87s	_{p=0.923 n=6}
_{Check Time}	_{11.31s (± 0.15%)}	_{11.32s (± 0.41%)}	_~	_11.28s	_11.39s	_{p=0.936 n=6}
_{Emit Time}	_{3.25s (± 0.95%)}	_{3.25s (± 0.41%)}	_~	_3.24s	_3.27s	_{p=0.807 n=6}
_{Total Time}	_{16.97s (± 0.14%)}	_{17.01s (± 0.35%)}	_~	_16.94s	_17.09s	_{p=0.628 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}	_{1,221,118k (± 0.00%)}	_{1,221,082k (± 0.00%)}	_~	_1,220,983k	_1,221,146k	_{p=0.199 n=6}
_{Parse Time}	_{7.82s (± 0.46%)}	_{7.86s (± 0.92%)}	_~	_7.79s	_7.98s	_{p=0.571 n=6}
_{Bind Time}	_{2.20s (± 0.47%)}	_{2.21s (± 0.62%)}	_~	_2.19s	_2.23s	_{p=0.737 n=6}
_{Check Time}	_{36.27s (± 0.17%)}	_{36.43s (± 0.35%)}	_{+0.16s (+ 0.44%)}	_36.31s	_36.60s	_{p=0.037 n=6}
_{Emit Time}	_{17.78s (± 0.30%)}	_{17.82s (± 0.53%)}	_~	_17.70s	_17.94s	_{p=0.470 n=6}
_{Total Time}	_{64.08s (± 0.22%)}	_{64.31s (± 0.29%)}	_{+0.24s (+ 0.37%)}	_64.08s	_64.57s	_{p=0.037 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,438,572	_2,438,572	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,004,228	_1,004,228	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,410,578k (± 0.00%)}	_{2,410,583k (± 0.00%)}	_~	_2,410,545k	_2,410,667k	_{p=0.810 n=6}
_{Parse Time}	_{9.95s (± 0.32%)}	_{9.96s (± 0.21%)}	_~	_9.92s	_9.97s	_{p=0.466 n=6}
_{Bind Time}	_{2.49s (± 0.36%)}	_{2.48s (± 0.40%)}	_~	_2.47s	_2.49s	_{p=0.082 n=6}
_{Check Time}	_{89.50s (± 1.79%)}	_{89.43s (± 1.98%)}	_~	_87.91s	_92.07s	_{p=1.000 n=6}
_{Emit Time}	_{0.33s (± 1.24%)}	_{0.32s (± 3.05%)}	_~	_0.31s	_0.33s	_{p=0.213 n=6}
_{Total Time}	_{102.26s (± 1.55%)}	_{102.19s (± 1.73%)}	_~	_100.66s	_104.84s	_{p=0.936 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,227,797	_1,227,799	_{+2 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_265,144	_265,145	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,464,900k (± 7.40%)}	_{2,346,730k (± 0.01%)}	_~	_2,346,356k	_2,346,952k	_{p=0.378 n=6}
_{Parse Time}	_{6.01s (± 1.11%)}	_{5.98s (± 0.85%)}	_~	_5.91s	_6.04s	_{p=0.297 n=6}
_{Bind Time}	_{2.26s (± 0.53%)}	_{2.25s (± 0.65%)}	_~	_2.22s	_2.26s	_{p=0.072 n=6}
_{Check Time}	_{40.51s (± 0.55%)}	_{40.62s (± 0.55%)}	_~	_40.32s	_40.85s	_{p=0.298 n=6}
_{Emit Time}	_{3.95s (± 3.52%)}	_{3.97s (± 1.27%)}	_~	_3.91s	_4.05s	_{p=0.574 n=6}
_{Total Time}	_{52.74s (± 0.57%)}	_{52.80s (± 0.47%)}	_~	_52.43s	_53.08s	_{p=0.936 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,227,797	_1,227,799	_{+2 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_265,144	_265,145	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,420,265k (± 0.03%)}	_{2,420,227k (± 0.02%)}	_~	_2,419,216k	_2,420,751k	_{p=0.689 n=6}
_{Parse Time}	_{6.24s (± 0.68%)}	_{6.20s (± 0.89%)}	_~	_6.15s	_6.30s	_{p=0.199 n=6}
_{Bind Time}	_{2.03s (± 0.54%)}	_{2.06s (± 0.94%)}	_{+0.03s (+ 1.40%)}	_2.03s	_2.08s	_{p=0.019 n=6}
_{Check Time}	_{41.19s (± 0.18%)}	_{41.24s (± 0.15%)}	_~	_41.18s	_41.33s	_{p=0.336 n=6}
_{Emit Time}	_{4.04s (± 2.05%)}	_{4.12s (± 4.06%)}	_~	_3.94s	_4.39s	_{p=0.471 n=6}
_{Total Time}	_{53.51s (± 0.22%)}	_{53.64s (± 0.41%)}	_~	_53.42s	_53.94s	_{p=0.378 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_255,990	_255,992	_{+2 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_104,965	_104,966	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{427,931k (± 0.02%)}	_{427,944k (± 0.02%)}	_~	_427,849k	_428,065k	_{p=0.810 n=6}
_{Parse Time}	_{3.35s (± 0.40%)}	_{3.35s (± 0.56%)}	_~	_3.32s	_3.37s	_{p=0.565 n=6}
_{Bind Time}	_{1.30s (± 1.73%)}	_{1.32s (± 1.33%)}	_~	_1.29s	_1.33s	_{p=0.216 n=6}
_{Check Time}	_{17.96s (± 0.22%)}	_{17.91s (± 0.56%)}	_~	_17.75s	_18.06s	_{p=0.295 n=6}
_{Emit Time}	_{1.63s (± 1.05%)}	_{1.65s (± 1.56%)}	_~	_1.62s	_1.69s	_{p=0.169 n=6}
_{Total Time}	_{24.25s (± 0.26%)}	_{24.22s (± 0.58%)}	_~	_24.01s	_24.41s	_{p=0.809 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}	_{370,066k (± 0.05%)}	_{370,070k (± 0.03%)}	_~	_369,886k	_370,205k	_{p=0.936 n=6}
_{Parse Time}	_{3.43s (± 0.99%)}	_{3.43s (± 0.54%)}	_~	_3.41s	_3.46s	_{p=0.571 n=6}
_{Bind Time}	_{1.92s (± 0.85%)}	_{1.92s (± 1.22%)}	_~	_1.88s	_1.95s	_{p=1.000 n=6}
_{Check Time}	_{19.32s (± 0.36%)}	_{19.32s (± 0.24%)}	_~	_19.23s	_19.36s	_{p=1.000 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{24.67s (± 0.27%)}	_{24.67s (± 0.20%)}	_~	_24.58s	_24.73s	_{p=0.806 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₁₁	₁₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,988,169	_2,988,169	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,028,070	_1,028,070	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,112,793k (± 0.00%)}	_{3,112,801k (± 0.00%)}	_~	_3,112,704k	_3,112,918k	_{p=0.810 n=6}
_{Parse Time}	_{13.81s (± 0.37%)}	_{13.77s (± 0.28%)}	_~	_13.73s	_13.83s	_{p=0.171 n=6}
_{Bind Time}	_{4.33s (± 2.10%)}	_{4.33s (± 2.30%)}	_~	_4.27s	_4.53s	_{p=1.000 n=6}
_{Check Time}	_{79.52s (± 0.16%)}	_{79.24s (± 0.26%)}	_{-0.28s (- 0.35%)}	_79.01s	_79.61s	_{p=0.030 n=6}
_{Emit Time}	_{20.51s (± 0.35%)}	_{20.48s (± 0.45%)}	_~	_20.32s	_20.57s	_{p=0.810 n=6}
_{Total Time}	_{118.17s (± 0.12%)}	_{117.82s (± 0.20%)}	_{-0.35s (- 0.30%)}	_117.50s	_118.17s	_{p=0.020 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_267,567	_267,567	_~	_~	_~	_{p=1.000 n=6}
_Types	_109,077	_109,077	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{412,447k (± 0.02%)}	_{412,380k (± 0.00%)}	_{-67k (- 0.02%)}	_412,361k	_412,387k	_{p=0.044 n=6}
_{Parse Time}	_{3.17s (± 0.40%)}	_{3.17s (± 0.26%)}	_~	_3.16s	_3.18s	_{p=0.558 n=6}
_{Bind Time}	_{1.43s (± 0.53%)}	_{1.43s (± 0.28%)}	_~	_1.43s	_1.44s	_{p=0.389 n=6}
_{Check Time}	_{14.28s (± 0.60%)}	_{14.28s (± 0.32%)}	_~	_14.22s	_14.36s	_{p=0.872 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{18.88s (± 0.45%)}	_{18.89s (± 0.28%)}	_~	_18.82s	_18.98s	_{p=0.871 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_522,176	_522,176	_~	_~	_~	_{p=1.000 n=6}
_Types	_167,857	_167,857	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{457,701k (± 0.06%)}	_{457,896k (± 0.03%)}	_~	_457,782k	_458,054k	_{p=0.471 n=6}
_{Parse Time}	_{3.21s (± 0.43%)}	_{3.21s (± 0.87%)}	_~	_3.16s	_3.24s	_{p=0.746 n=6}
_{Bind Time}	_{1.20s (± 1.02%)}	_{1.20s (± 1.11%)}	_~	_1.18s	_1.21s	_{p=0.389 n=6}
_{Check Time}	_{17.71s (± 0.49%)}	_{17.70s (± 0.56%)}	_~	_17.61s	_17.83s	_{p=0.872 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{22.13s (± 0.37%)}	_{22.11s (± 0.50%)}	_~	_22.01s	_22.24s	_{p=0.936 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 · 2024-07-29T19:00:32Z

@jakebailey Here are the results of running the top 400 repos with tsc comparing main and refs/pull/59459/merge:

Everything looks good!

Firsh · 2025-06-26T22:00:09Z

Would this also fix this function's return type being inferred as number | undefined instead of just number?

type Circle = {
  kind: "circle";
  radius: number;
};

type Square = {
  kind: "square";
  sideLength: number;
};

type Shape = Circle | Square;

function calculateArea(shape: Shape) {
  switch (true) {
    case shape.kind === "circle": {
      return Math.PI * shape.radius * shape.radius;
    }
    case shape.kind === "square": {
      return shape.sideLength * shape.sideLength;
    }
  }
}

jakebailey · 2025-06-30T18:22:45Z

tests/cases/compiler/narrowByClauseExpressionInSwitchTrue11.ts

+// @noEmit: true
+
+function uhoh(input: string) : "A"|"B"|"C" {
+    switch (true) {


Awful, but, what about switch (false) + case false:?

Fix switch-true case-true narrowing to behave equivalently to default…

5731bdc

… case

typescript-bot added the For Backlog Bug PRs that fix a backlog bug label Jul 29, 2024

Merge branch 'main' into fix-switch-true

d0ed82b

jakebailey reviewed Jun 30, 2025

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Fix switch-true case-true narrowing to behave equivalently to default case #59459

Fix switch-true case-true narrowing to behave equivalently to default case #59459

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Fix switch-true case-true narrowing to behave equivalently to default case #59459

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Fix switch-true case-true narrowing to behave equivalently to default case #59459

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