Fix contextual discrimination for omitted members

[Erik Brinkman (erikbrinkman)]

The first attempt at fixing this issue caused a large regression on one
benchmark. This new PR addresses the regression by caching optional
members of union types when they're used for discrimination. This seems
to reduce the performance hit at the cost of some extra memory, but it's
not clear if the fix is worth this regression.

For context:
first related PR: #41759
original fix: #43633
fixes: #48298
reversion: #48426

I was able to reproduce the regression, but behavior on WSL ended up proving spotty, so in some tests the regression went mostly away (to 3%) on the material-ui docs benchmark. Other times it was closer to 10%. Ideally I'd like to see how this diff performs on all the benchmarks as is. I think further optimization is goin to require deeper caching, and there's an argument that maybe performing "correctly" in this case isn't worth the performance hit.

[Wesley Wigham (weswigham)]

TypeScript Bot (@typescript-bot) perf test this

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the perf test suite on this PR at caa081c. You can monitor the build here.

Update: The results are in!

[TypeScript Bot (typescript-bot)]

Wesley Wigham (@weswigham)
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..48448

Metric	main	48448	Delta	Best	Worst
Angular - node (v10.16.3, x64)
Memory used	356,681k (± 0.02%)	356,423k (± 0.02%)	-257k (- 0.07%)	356,252k	356,536k
Parse Time	2.07s (± 0.48%)	2.05s (± 0.57%)	-0.02s (- 1.01%)	2.03s	2.08s
Bind Time	0.87s (± 0.57%)	0.86s (± 0.57%)	-0.00s (- 0.23%)	0.85s	0.87s
Check Time	5.81s (± 0.65%)	5.79s (± 0.58%)	-0.02s (- 0.43%)	5.70s	5.84s
Emit Time	6.02s (± 0.64%)	5.99s (± 0.52%)	-0.04s (- 0.60%)	5.93s	6.05s
Total Time	14.77s (± 0.44%)	14.69s (± 0.34%)	-0.08s (- 0.53%)	14.63s	14.84s
Compiler-Unions - node (v10.16.3, x64)
Memory used	205,764k (± 0.03%)	205,746k (± 0.03%)	-18k (- 0.01%)	205,647k	205,980k
Parse Time	0.85s (± 0.76%)	0.85s (± 0.61%)	-0.00s (- 0.12%)	0.84s	0.86s
Bind Time	0.52s (± 1.00%)	0.52s (± 0.95%)	-0.00s (- 0.58%)	0.51s	0.53s
Check Time	8.01s (± 0.56%)	8.04s (± 0.96%)	+0.02s (+ 0.29%)	7.94s	8.34s
Emit Time	2.54s (± 1.82%)	2.52s (± 0.87%)	-0.03s (- 0.98%)	2.48s	2.59s
Total Time	11.93s (± 0.70%)	11.92s (± 0.81%)	-0.01s (- 0.04%)	11.78s	12.29s
Monaco - node (v10.16.3, x64)
Memory used	343,686k (± 0.01%)	343,600k (± 0.02%)	-86k (- 0.02%)	343,445k	343,784k
Parse Time	1.58s (± 1.11%)	1.58s (± 0.71%)	-0.00s (- 0.13%)	1.54s	1.59s
Bind Time	0.76s (± 0.88%)	0.76s (± 0.81%)	+0.00s (+ 0.53%)	0.75s	0.77s
Check Time	5.76s (± 0.33%)	5.76s (± 0.88%)	+0.00s (+ 0.07%)	5.61s	5.88s
Emit Time	3.24s (± 0.45%)	3.24s (± 0.66%)	-0.00s (- 0.06%)	3.19s	3.27s
Total Time	11.33s (± 0.36%)	11.34s (± 0.56%)	+0.00s (+ 0.03%)	11.18s	11.45s
TFS - node (v10.16.3, x64)
Memory used	305,268k (± 0.02%)	305,311k (± 0.02%)	+43k (+ 0.01%)	305,146k	305,469k
Parse Time	1.28s (± 0.47%)	1.28s (± 0.37%)	-0.00s (- 0.39%)	1.27s	1.29s
Bind Time	0.72s (± 0.72%)	0.72s (± 0.69%)	-0.00s (- 0.42%)	0.71s	0.73s
Check Time	5.26s (± 0.47%)	5.23s (± 0.60%)	-0.03s (- 0.61%)	5.17s	5.31s
Emit Time	3.44s (± 1.91%)	3.45s (± 1.06%)	+0.00s (+ 0.15%)	3.34s	3.52s
Total Time	10.70s (± 0.65%)	10.67s (± 0.49%)	-0.03s (- 0.27%)	10.55s	10.82s
material-ui - node (v10.16.3, x64)
Memory used	469,676k (± 0.01%)	476,270k (± 0.01%)	+6,593k (+ 1.40%)	476,195k	476,418k
Parse Time	1.82s (± 0.64%)	1.81s (± 0.56%)	-0.01s (- 0.38%)	1.79s	1.83s
Bind Time	0.68s (± 0.77%)	0.68s (± 0.86%)	-0.00s (- 0.29%)	0.66s	0.69s
Check Time	14.28s (± 0.28%)	21.49s (± 1.05%)	🔻+7.22s (+50.54%)	20.93s	21.92s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	16.78s (± 0.26%)	23.99s (± 0.95%)	🔻+7.21s (+42.94%)	23.42s	24.43s
xstate - node (v10.16.3, x64)
Memory used	580,507k (± 1.90%)	570,779k (± 0.01%)	-9,728k (- 1.68%)	570,598k	570,898k
Parse Time	2.60s (± 0.39%)	2.58s (± 0.37%)	-0.02s (- 0.65%)	2.57s	2.61s
Bind Time	1.01s (± 0.81%)	1.01s (± 0.40%)	-0.00s (- 0.20%)	1.00s	1.02s
Check Time	1.53s (± 0.46%)	1.53s (± 0.34%)	-0.00s (- 0.13%)	1.52s	1.54s
Emit Time	0.07s (± 4.66%)	0.07s (± 3.14%)	-0.00s (- 2.74%)	0.07s	0.08s
Total Time	5.21s (± 0.36%)	5.19s (± 0.29%)	-0.02s (- 0.38%)	5.16s	5.23s
Angular - node (v12.1.0, x64)
Memory used	334,491k (± 0.02%)	334,199k (± 0.07%)	-292k (- 0.09%)	333,285k	334,431k
Parse Time	2.07s (± 0.28%)	2.08s (± 0.58%)	+0.00s (+ 0.10%)	2.05s	2.09s
Bind Time	0.83s (± 0.67%)	0.84s (± 1.14%)	+0.00s (+ 0.48%)	0.82s	0.87s
Check Time	5.66s (± 0.26%)	5.62s (± 0.75%)	-0.04s (- 0.76%)	5.56s	5.75s
Emit Time	6.33s (± 1.04%)	6.28s (± 0.90%)	-0.06s (- 0.93%)	6.18s	6.43s
Total Time	14.90s (± 0.43%)	14.81s (± 0.66%)	-0.09s (- 0.60%)	14.65s	15.11s
Compiler-Unions - node (v12.1.0, x64)
Memory used	193,061k (± 0.14%)	193,007k (± 0.13%)	-54k (- 0.03%)	192,623k	193,534k
Parse Time	0.84s (± 1.06%)	0.85s (± 1.29%)	+0.01s (+ 1.07%)	0.83s	0.88s
Bind Time	0.54s (± 1.20%)	0.54s (± 0.92%)	-0.00s (- 0.37%)	0.53s	0.55s
Check Time	7.49s (± 0.55%)	7.52s (± 0.61%)	+0.03s (+ 0.36%)	7.40s	7.64s
Emit Time	2.55s (± 1.33%)	2.55s (± 0.98%)	-0.01s (- 0.27%)	2.51s	2.61s
Total Time	11.43s (± 0.39%)	11.46s (± 0.58%)	+0.02s (+ 0.21%)	11.28s	11.60s
Monaco - node (v12.1.0, x64)
Memory used	326,509k (± 0.07%)	326,473k (± 0.07%)	-37k (- 0.01%)	325,818k	326,748k
Parse Time	1.57s (± 0.70%)	1.56s (± 0.85%)	-0.00s (- 0.26%)	1.54s	1.60s
Bind Time	0.74s (± 0.78%)	0.75s (± 1.11%)	+0.00s (+ 0.40%)	0.73s	0.77s
Check Time	5.60s (± 0.46%)	5.60s (± 0.51%)	0.00s ( 0.00%)	5.52s	5.65s
Emit Time	3.28s (± 1.41%)	3.29s (± 1.69%)	+0.01s (+ 0.46%)	3.21s	3.45s
Total Time	11.19s (± 0.52%)	11.21s (± 0.65%)	+0.01s (+ 0.12%)	11.04s	11.38s
TFS - node (v12.1.0, x64)
Memory used	289,907k (± 0.01%)	290,026k (± 0.03%)	+119k (+ 0.04%)	289,857k	290,284k
Parse Time	1.29s (± 0.82%)	1.31s (± 0.73%)	+0.01s (+ 0.85%)	1.28s	1.32s
Bind Time	0.71s (± 0.99%)	0.71s (± 0.70%)	-0.00s (- 0.42%)	0.70s	0.72s
Check Time	5.20s (± 0.45%)	5.19s (± 0.37%)	-0.02s (- 0.31%)	5.15s	5.24s
Emit Time	3.48s (± 0.71%)	3.50s (± 0.56%)	+0.01s (+ 0.37%)	3.46s	3.54s
Total Time	10.69s (± 0.35%)	10.70s (± 0.31%)	+0.01s (+ 0.12%)	10.62s	10.76s
material-ui - node (v12.1.0, x64)
Memory used	448,521k (± 0.08%)	455,355k (± 0.01%)	+6,834k (+ 1.52%)	455,264k	455,442k
Parse Time	1.81s (± 0.61%)	1.82s (± 0.62%)	+0.01s (+ 0.28%)	1.79s	1.84s
Bind Time	0.65s (± 0.85%)	0.64s (± 0.74%)	-0.01s (- 1.38%)	0.63s	0.65s
Check Time	13.05s (± 1.05%)	19.07s (± 1.60%)	🔻+6.02s (+46.13%)	18.56s	19.68s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.52s (± 0.91%)	21.54s (± 1.44%)	🔻+6.02s (+38.81%)	21.03s	22.14s
xstate - node (v12.1.0, x64)
Memory used	536,356k (± 0.02%)	536,463k (± 0.01%)	+106k (+ 0.02%)	536,363k	536,603k
Parse Time	2.54s (± 0.47%)	2.53s (± 0.44%)	-0.01s (- 0.28%)	2.51s	2.56s
Bind Time	1.04s (± 0.46%)	1.04s (± 0.54%)	-0.01s (- 0.48%)	1.03s	1.05s
Check Time	1.48s (± 0.63%)	1.48s (± 0.68%)	+0.00s (+ 0.13%)	1.46s	1.51s
Emit Time	0.07s (± 0.00%)	0.07s (± 3.14%)	+0.00s (+ 1.43%)	0.07s	0.08s
Total Time	5.14s (± 0.41%)	5.12s (± 0.38%)	-0.01s (- 0.29%)	5.09s	5.16s
Angular - node (v14.15.1, x64)
Memory used	332,740k (± 0.01%)	332,514k (± 0.01%)	-227k (- 0.07%)	332,472k	332,554k
Parse Time	2.04s (± 0.69%)	2.04s (± 0.86%)	+0.00s (+ 0.25%)	2.01s	2.10s
Bind Time	0.87s (± 0.42%)	0.87s (± 0.86%)	+0.00s (+ 0.12%)	0.86s	0.89s
Check Time	5.63s (± 0.54%)	5.62s (± 0.52%)	-0.01s (- 0.23%)	5.57s	5.70s
Emit Time	6.30s (± 0.71%)	6.36s (± 1.09%)	+0.06s (+ 0.98%)	6.24s	6.56s
Total Time	14.84s (± 0.54%)	14.89s (± 0.53%)	+0.05s (+ 0.36%)	14.77s	15.09s
Compiler-Unions - node (v14.15.1, x64)
Memory used	194,627k (± 0.49%)	193,966k (± 0.61%)	-661k (- 0.34%)	191,949k	195,297k
Parse Time	0.86s (± 0.46%)	0.86s (± 0.69%)	+0.00s (+ 0.46%)	0.85s	0.88s
Bind Time	0.57s (± 1.76%)	0.57s (± 0.66%)	-0.00s (- 0.35%)	0.56s	0.57s
Check Time	7.52s (± 0.57%)	7.55s (± 0.68%)	+0.03s (+ 0.40%)	7.45s	7.66s
Emit Time	2.50s (± 0.97%)	2.50s (± 0.93%)	+0.01s (+ 0.24%)	2.46s	2.57s
Total Time	11.45s (± 0.51%)	11.48s (± 0.53%)	+0.04s (+ 0.31%)	11.33s	11.61s
Monaco - node (v14.15.1, x64)
Memory used	325,421k (± 0.01%)	325,411k (± 0.00%)	-10k (- 0.00%)	325,386k	325,458k
Parse Time	1.59s (± 0.70%)	1.58s (± 0.71%)	-0.01s (- 0.57%)	1.55s	1.60s
Bind Time	0.78s (± 0.57%)	0.78s (± 0.79%)	+0.00s (+ 0.13%)	0.77s	0.79s
Check Time	5.52s (± 0.60%)	5.48s (± 0.48%)	-0.04s (- 0.71%)	5.43s	5.54s
Emit Time	3.33s (± 0.92%)	3.30s (± 0.90%)	-0.03s (- 0.81%)	3.25s	3.37s
Total Time	11.21s (± 0.47%)	11.14s (± 0.50%)	-0.07s (- 0.60%)	11.03s	11.28s
TFS - node (v14.15.1, x64)
Memory used	288,919k (± 0.01%)	288,917k (± 0.01%)	-2k (- 0.00%)	288,851k	288,993k
Parse Time	1.33s (± 1.01%)	1.34s (± 1.25%)	+0.01s (+ 1.06%)	1.30s	1.38s
Bind Time	0.74s (± 1.01%)	0.74s (± 0.67%)	-0.00s (- 0.14%)	0.73s	0.75s
Check Time	5.17s (± 0.41%)	5.16s (± 0.68%)	-0.00s (- 0.10%)	5.08s	5.23s
Emit Time	3.54s (± 1.88%)	3.56s (± 1.67%)	+0.02s (+ 0.51%)	3.39s	3.66s
Total Time	10.78s (± 0.76%)	10.80s (± 0.88%)	+0.02s (+ 0.21%)	10.52s	10.94s
material-ui - node (v14.15.1, x64)
Memory used	447,053k (± 0.01%)	453,656k (± 0.00%)	+6,603k (+ 1.48%)	453,607k	453,690k
Parse Time	1.87s (± 0.36%)	1.88s (± 0.53%)	+0.01s (+ 0.59%)	1.86s	1.90s
Bind Time	0.71s (± 0.73%)	0.71s (± 1.19%)	0.00s ( 0.00%)	0.69s	0.72s
Check Time	13.16s (± 0.47%)	19.08s (± 1.49%)	🔻+5.92s (+45.01%)	18.58s	19.62s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.73s (± 0.42%)	21.67s (± 1.32%)	🔻+5.94s (+37.73%)	21.16s	22.20s
xstate - node (v14.15.1, x64)
Memory used	534,095k (± 0.01%)	534,101k (± 0.00%)	+6k (+ 0.00%)	534,029k	534,150k
Parse Time	2.59s (± 0.56%)	2.60s (± 0.50%)	+0.01s (+ 0.39%)	2.56s	2.63s
Bind Time	1.15s (± 0.35%)	1.15s (± 0.87%)	+0.00s (+ 0.17%)	1.14s	1.18s
Check Time	1.52s (± 0.55%)	1.52s (± 0.55%)	0.00s ( 0.00%)	1.50s	1.54s
Emit Time	0.07s (± 0.00%)	0.07s (± 0.00%)	0.00s ( 0.00%)	0.07s	0.07s
Total Time	5.33s (± 0.31%)	5.34s (± 0.33%)	+0.01s (+ 0.11%)	5.30s	5.38s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-210-generic
Architecture	x64
Available Memory	16 GB
Available Memory	3 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

• node (v10.16.3, x64)
• node (v12.1.0, x64)
• node (v14.15.1, x64)

Scenarios

• Angular - node (v10.16.3, x64)
• Angular - node (v12.1.0, x64)
• Angular - node (v14.15.1, x64)
• Compiler-Unions - node (v10.16.3, x64)
• Compiler-Unions - node (v12.1.0, x64)
• Compiler-Unions - node (v14.15.1, x64)
• Monaco - node (v10.16.3, x64)
• Monaco - node (v12.1.0, x64)
• Monaco - node (v14.15.1, x64)
• TFS - node (v10.16.3, x64)
• TFS - node (v12.1.0, x64)
• TFS - node (v14.15.1, x64)
• material-ui - node (v10.16.3, x64)
• material-ui - node (v12.1.0, x64)
• material-ui - node (v14.15.1, x64)
• xstate - node (v10.16.3, x64)
• xstate - node (v12.1.0, x64)
• xstate - node (v14.15.1, x64)

Benchmark	Name	Iterations
Current	48448	10
Baseline	main	10

Developer Information:

Download Benchmark

[Wesley Wigham (weswigham)]

Oof, this is still reporting a 50% check time regression in material-ui.

[Erik Brinkman (erikbrinkman)]

TypeScript Bot (@typescript-bot) perf test this

[Erik Brinkman (erikbrinkman)]

The "problem" is that material-ui has some types that are large unions ~700 types, and at least some have ~100 optional types. discriminateTypeByDiscriminableItems has complexity O(number of types in union x number of discriminators) and they way I naively implemented this extension required checking all of them. This new version only adds member names that discriminate against different sets of types in the union. This trick doesn't change the worst case complexity of this change, but it should prevent common / degenerate cases like material-ui.

It's not clear to me that the performance could be improved any more, so if it's still bad somehow, or is deemed too complex for the handful of edge cases it helps, I'm cool with abandoning in.

As an implementation side note, I needed a way to hash subsets of the union type, and I did this by forming a string with space delimited indices. This works, but I'm not sure if there's a better way to achieve this same result.

[Wesley Wigham (weswigham)]

TypeScript Bot (@typescript-bot) perf test this

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the perf test suite on this PR at cd00855. You can monitor the build here.

Update: The results are in!

[Wesley Wigham (weswigham)]

As an implementation side note, I needed a way to hash subsets of the union type, and I did this by forming a string with space delimited indices. This works, but I'm not sure if there's a better way to achieve this same result.

getTypeListId already exists and has a similar implementation. Slightly more compressed for long runs of consecutive type ids.

[TypeScript Bot (typescript-bot)]

Wesley Wigham (@weswigham)
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..48448

Metric	main	48448	Delta	Best	Worst
Angular - node (v10.16.3, x64)
Memory used	356,681k (± 0.02%)	356,443k (± 0.02%)	-237k (- 0.07%)	356,321k	356,603k
Parse Time	2.07s (± 0.48%)	2.08s (± 0.40%)	+0.00s (+ 0.14%)	2.05s	2.09s
Bind Time	0.87s (± 0.57%)	0.87s (± 0.69%)	-0.00s (- 0.12%)	0.86s	0.88s
Check Time	5.81s (± 0.65%)	5.84s (± 0.36%)	+0.03s (+ 0.57%)	5.80s	5.89s
Emit Time	6.02s (± 0.64%)	6.04s (± 0.71%)	+0.01s (+ 0.23%)	5.95s	6.16s
Total Time	14.77s (± 0.44%)	14.82s (± 0.39%)	+0.05s (+ 0.33%)	14.71s	14.97s
Compiler-Unions - node (v10.16.3, x64)
Memory used	205,764k (± 0.03%)	205,820k (± 0.04%)	+56k (+ 0.03%)	205,662k	205,965k
Parse Time	0.85s (± 0.76%)	0.85s (± 0.61%)	-0.00s (- 0.12%)	0.84s	0.86s
Bind Time	0.52s (± 1.00%)	0.52s (± 1.00%)	+0.00s (+ 0.39%)	0.51s	0.53s
Check Time	8.01s (± 0.56%)	8.02s (± 0.54%)	+0.00s (+ 0.04%)	7.94s	8.14s
Emit Time	2.54s (± 1.82%)	2.51s (± 0.89%)	-0.03s (- 1.22%)	2.47s	2.57s
Total Time	11.93s (± 0.70%)	11.90s (± 0.46%)	-0.03s (- 0.23%)	11.77s	12.05s
Monaco - node (v10.16.3, x64)
Memory used	343,686k (± 0.01%)	343,676k (± 0.03%)	-10k (- 0.00%)	343,409k	343,847k
Parse Time	1.58s (± 1.11%)	1.59s (± 0.63%)	+0.01s (+ 0.76%)	1.57s	1.61s
Bind Time	0.76s (± 0.88%)	0.76s (± 0.85%)	+0.00s (+ 0.13%)	0.74s	0.77s
Check Time	5.76s (± 0.33%)	5.76s (± 0.38%)	+0.01s (+ 0.10%)	5.71s	5.80s
Emit Time	3.24s (± 0.45%)	3.25s (± 0.87%)	+0.01s (+ 0.22%)	3.17s	3.32s
Total Time	11.33s (± 0.36%)	11.35s (± 0.42%)	+0.02s (+ 0.19%)	11.25s	11.49s
TFS - node (v10.16.3, x64)
Memory used	305,268k (± 0.02%)	305,330k (± 0.01%)	+62k (+ 0.02%)	305,234k	305,393k
Parse Time	1.28s (± 0.47%)	1.29s (± 0.82%)	+0.00s (+ 0.08%)	1.27s	1.32s
Bind Time	0.72s (± 0.72%)	0.72s (± 0.66%)	-0.00s (- 0.28%)	0.71s	0.73s
Check Time	5.26s (± 0.47%)	5.24s (± 0.51%)	-0.02s (- 0.34%)	5.18s	5.28s
Emit Time	3.44s (± 1.91%)	3.44s (± 0.91%)	-0.00s (- 0.06%)	3.35s	3.53s
Total Time	10.70s (± 0.65%)	10.69s (± 0.54%)	-0.02s (- 0.17%)	10.58s	10.81s
material-ui - node (v10.16.3, x64)
Memory used	469,676k (± 0.01%)	465,079k (± 0.01%)	-4,598k (- 0.98%)	464,971k	465,192k
Parse Time	1.82s (± 0.64%)	1.83s (± 0.60%)	+0.01s (+ 0.49%)	1.80s	1.85s
Bind Time	0.68s (± 0.77%)	0.68s (± 0.70%)	+0.00s (+ 0.59%)	0.67s	0.69s
Check Time	14.28s (± 0.28%)	14.94s (± 0.64%)	+0.66s (+ 4.65%)	14.70s	15.16s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	16.78s (± 0.26%)	17.46s (± 0.59%)	+0.67s (+ 4.00%)	17.19s	17.69s
xstate - node (v10.16.3, x64)
Memory used	580,507k (± 1.90%)	571,511k (± 0.02%)	-8,996k (- 1.55%)	571,274k	571,894k
Parse Time	2.60s (± 0.39%)	2.59s (± 0.26%)	-0.01s (- 0.31%)	2.58s	2.61s
Bind Time	1.01s (± 0.81%)	1.02s (± 0.58%)	+0.00s (+ 0.30%)	1.00s	1.03s
Check Time	1.53s (± 0.46%)	1.54s (± 0.82%)	+0.01s (+ 0.65%)	1.51s	1.56s
Emit Time	0.07s (± 4.66%)	0.07s (± 3.14%)	-0.00s (- 2.74%)	0.07s	0.08s
Total Time	5.21s (± 0.36%)	5.22s (± 0.39%)	+0.01s (+ 0.13%)	5.18s	5.26s
Angular - node (v12.1.0, x64)
Memory used	334,491k (± 0.02%)	334,276k (± 0.03%)	-215k (- 0.06%)	334,036k	334,420k
Parse Time	2.07s (± 0.28%)	2.07s (± 0.83%)	-0.00s (- 0.14%)	2.03s	2.10s
Bind Time	0.83s (± 0.67%)	0.84s (± 1.08%)	+0.01s (+ 0.84%)	0.82s	0.86s
Check Time	5.66s (± 0.26%)	5.70s (± 0.44%)	+0.04s (+ 0.64%)	5.63s	5.73s
Emit Time	6.33s (± 1.04%)	6.34s (± 1.14%)	+0.00s (+ 0.05%)	6.23s	6.56s
Total Time	14.90s (± 0.43%)	14.95s (± 0.58%)	+0.05s (+ 0.32%)	14.81s	15.19s
Compiler-Unions - node (v12.1.0, x64)
Memory used	193,061k (± 0.14%)	193,401k (± 0.05%)	+340k (+ 0.18%)	193,174k	193,625k
Parse Time	0.84s (± 1.06%)	0.85s (± 1.11%)	+0.00s (+ 0.36%)	0.83s	0.87s
Bind Time	0.54s (± 1.20%)	0.54s (± 0.89%)	-0.00s (- 0.19%)	0.53s	0.55s
Check Time	7.49s (± 0.55%)	7.54s (± 0.41%)	+0.04s (+ 0.57%)	7.47s	7.61s
Emit Time	2.55s (± 1.33%)	2.56s (± 1.42%)	+0.01s (+ 0.35%)	2.49s	2.65s
Total Time	11.43s (± 0.39%)	11.49s (± 0.48%)	+0.05s (+ 0.48%)	11.35s	11.62s
Monaco - node (v12.1.0, x64)
Memory used	326,509k (± 0.07%)	326,604k (± 0.06%)	+95k (+ 0.03%)	325,923k	326,851k
Parse Time	1.57s (± 0.70%)	1.55s (± 0.82%)	-0.01s (- 0.96%)	1.52s	1.58s
Bind Time	0.74s (± 0.78%)	0.74s (± 0.66%)	+0.00s (+ 0.13%)	0.73s	0.75s
Check Time	5.60s (± 0.46%)	5.62s (± 0.44%)	+0.02s (+ 0.39%)	5.55s	5.66s
Emit Time	3.28s (± 1.41%)	3.28s (± 0.64%)	+0.00s (+ 0.06%)	3.24s	3.34s
Total Time	11.19s (± 0.52%)	11.21s (± 0.24%)	+0.01s (+ 0.13%)	11.14s	11.25s
TFS - node (v12.1.0, x64)
Memory used	289,907k (± 0.01%)	289,911k (± 0.07%)	+4k (+ 0.00%)	289,160k	290,093k
Parse Time	1.29s (± 0.82%)	1.29s (± 0.69%)	-0.00s (- 0.08%)	1.27s	1.31s
Bind Time	0.71s (± 0.99%)	0.71s (± 0.73%)	+0.00s (+ 0.28%)	0.70s	0.72s
Check Time	5.20s (± 0.45%)	5.17s (± 0.66%)	-0.03s (- 0.60%)	5.09s	5.25s
Emit Time	3.48s (± 0.71%)	3.48s (± 0.83%)	-0.00s (- 0.09%)	3.42s	3.56s
Total Time	10.69s (± 0.35%)	10.66s (± 0.53%)	-0.03s (- 0.29%)	10.53s	10.80s
material-ui - node (v12.1.0, x64)
Memory used	448,521k (± 0.08%)	444,144k (± 0.01%)	-4,377k (- 0.98%)	444,043k	444,212k
Parse Time	1.81s (± 0.61%)	1.83s (± 0.37%)	+0.01s (+ 0.66%)	1.81s	1.84s
Bind Time	0.65s (± 0.85%)	0.65s (± 0.89%)	-0.00s (- 0.31%)	0.64s	0.67s
Check Time	13.05s (± 1.05%)	13.40s (± 0.55%)	+0.35s (+ 2.67%)	13.24s	13.58s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.52s (± 0.91%)	15.88s (± 0.47%)	+0.36s (+ 2.31%)	15.71s	16.03s
xstate - node (v12.1.0, x64)
Memory used	536,356k (± 0.02%)	537,078k (± 0.01%)	+722k (+ 0.13%)	536,994k	537,257k
Parse Time	2.54s (± 0.47%)	2.54s (± 0.48%)	+0.00s (+ 0.12%)	2.50s	2.56s
Bind Time	1.04s (± 0.46%)	1.05s (± 0.64%)	+0.00s (+ 0.38%)	1.04s	1.06s
Check Time	1.48s (± 0.63%)	1.48s (± 0.59%)	+0.00s (+ 0.07%)	1.46s	1.50s
Emit Time	0.07s (± 0.00%)	0.07s (± 0.00%)	0.00s ( 0.00%)	0.07s	0.07s
Total Time	5.14s (± 0.41%)	5.14s (± 0.29%)	+0.00s (+ 0.04%)	5.11s	5.17s
Angular - node (v14.15.1, x64)
Memory used	332,740k (± 0.01%)	332,513k (± 0.01%)	-227k (- 0.07%)	332,425k	332,617k
Parse Time	2.04s (± 0.69%)	2.04s (± 0.37%)	-0.00s (- 0.25%)	2.02s	2.05s
Bind Time	0.87s (± 0.42%)	0.88s (± 0.68%)	+0.01s (+ 1.15%)	0.87s	0.89s
Check Time	5.63s (± 0.54%)	5.66s (± 0.50%)	+0.03s (+ 0.48%)	5.62s	5.75s
Emit Time	6.30s (± 0.71%)	6.32s (± 0.61%)	+0.02s (+ 0.30%)	6.24s	6.38s
Total Time	14.84s (± 0.54%)	14.89s (± 0.40%)	+0.06s (+ 0.37%)	14.76s	15.05s
Compiler-Unions - node (v14.15.1, x64)
Memory used	194,627k (± 0.49%)	194,649k (± 0.50%)	+22k (+ 0.01%)	191,951k	195,382k
Parse Time	0.86s (± 0.46%)	0.86s (± 0.69%)	+0.00s (+ 0.46%)	0.85s	0.88s
Bind Time	0.57s (± 1.76%)	0.56s (± 1.05%)	-0.00s (- 0.53%)	0.55s	0.58s
Check Time	7.52s (± 0.57%)	7.55s (± 0.49%)	+0.03s (+ 0.47%)	7.47s	7.63s
Emit Time	2.50s (± 0.97%)	2.51s (± 0.63%)	+0.02s (+ 0.60%)	2.47s	2.55s
Total Time	11.45s (± 0.51%)	11.50s (± 0.42%)	+0.05s (+ 0.43%)	11.40s	11.60s
Monaco - node (v14.15.1, x64)
Memory used	325,421k (± 0.01%)	325,425k (± 0.01%)	+4k (+ 0.00%)	325,383k	325,453k
Parse Time	1.59s (± 0.70%)	1.59s (± 0.57%)	+0.00s (+ 0.25%)	1.57s	1.61s
Bind Time	0.78s (± 0.57%)	0.78s (± 0.79%)	+0.00s (+ 0.13%)	0.76s	0.79s
Check Time	5.52s (± 0.60%)	5.52s (± 0.53%)	+0.00s (+ 0.05%)	5.46s	5.58s
Emit Time	3.33s (± 0.92%)	3.31s (± 0.45%)	-0.02s (- 0.48%)	3.29s	3.34s
Total Time	11.21s (± 0.47%)	11.20s (± 0.36%)	-0.01s (- 0.06%)	11.12s	11.29s
TFS - node (v14.15.1, x64)
Memory used	288,919k (± 0.01%)	288,914k (± 0.01%)	-5k (- 0.00%)	288,864k	288,955k
Parse Time	1.33s (± 1.01%)	1.32s (± 1.26%)	-0.00s (- 0.08%)	1.30s	1.37s
Bind Time	0.74s (± 1.01%)	0.74s (± 1.00%)	+0.00s (+ 0.41%)	0.73s	0.76s
Check Time	5.17s (± 0.41%)	5.16s (± 0.46%)	-0.01s (- 0.15%)	5.10s	5.21s
Emit Time	3.54s (± 1.88%)	3.54s (± 2.12%)	-0.00s (- 0.06%)	3.39s	3.69s
Total Time	10.78s (± 0.76%)	10.77s (± 0.76%)	-0.01s (- 0.08%)	10.60s	10.96s
material-ui - node (v14.15.1, x64)
Memory used	447,053k (± 0.01%)	442,269k (± 0.08%)	-4,784k (- 1.07%)	441,317k	442,567k
Parse Time	1.87s (± 0.36%)	1.87s (± 0.60%)	+0.01s (+ 0.27%)	1.85s	1.89s
Bind Time	0.71s (± 0.73%)	0.71s (± 0.87%)	0.00s ( 0.00%)	0.70s	0.72s
Check Time	13.16s (± 0.47%)	13.52s (± 1.15%)	+0.36s (+ 2.70%)	13.24s	13.94s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.73s (± 0.42%)	16.10s (± 0.98%)	+0.36s (+ 2.30%)	15.79s	16.52s
xstate - node (v14.15.1, x64)
Memory used	534,095k (± 0.01%)	534,794k (± 0.01%)	+700k (+ 0.13%)	534,728k	534,848k
Parse Time	2.59s (± 0.56%)	2.59s (± 0.66%)	+0.01s (+ 0.39%)	2.56s	2.62s
Bind Time	1.15s (± 0.35%)	1.15s (± 0.66%)	+0.00s (+ 0.35%)	1.14s	1.17s
Check Time	1.52s (± 0.55%)	1.53s (± 0.50%)	+0.01s (+ 0.92%)	1.52s	1.55s
Emit Time	0.07s (± 0.00%)	0.07s (± 0.00%)	0.00s ( 0.00%)	0.07s	0.07s
Total Time	5.33s (± 0.31%)	5.36s (± 0.33%)	+0.02s (+ 0.45%)	5.31s	5.39s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-210-generic
Architecture	x64
Available Memory	16 GB
Available Memory	3 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

• node (v10.16.3, x64)
• node (v12.1.0, x64)
• node (v14.15.1, x64)

Scenarios

• Angular - node (v10.16.3, x64)
• Angular - node (v12.1.0, x64)
• Angular - node (v14.15.1, x64)
• Compiler-Unions - node (v10.16.3, x64)
• Compiler-Unions - node (v12.1.0, x64)
• Compiler-Unions - node (v14.15.1, x64)
• Monaco - node (v10.16.3, x64)
• Monaco - node (v12.1.0, x64)
• Monaco - node (v14.15.1, x64)
• TFS - node (v10.16.3, x64)
• TFS - node (v12.1.0, x64)
• TFS - node (v14.15.1, x64)
• material-ui - node (v10.16.3, x64)
• material-ui - node (v12.1.0, x64)
• material-ui - node (v14.15.1, x64)
• xstate - node (v10.16.3, x64)
• xstate - node (v12.1.0, x64)
• xstate - node (v14.15.1, x64)

Benchmark	Name	Iterations
Current	48448	10
Baseline	main	10

Developer Information:

Download Benchmark

[Wesley Wigham (weswigham)]

Well, that's much better, that's for sure. 2-5% worse is a lot better than 30-50% worse.

[Erik Brinkman (erikbrinkman)]

It was a good thing this was reverted, because the PR is actually unsound, and it was caught from the local serve build. The problem is a few fold, and so I'm writing here to seek guidance. As a general note, I'm unsure how this should function in exactOptionalPropertyTypes land.

The original PR sought to add any discriminable property of any optional property of any element of the union type as a discriminator checking for assignability to undefined. This concept had some performance hits that I was able to address, but there was actually an underlying bug in the test. If an "unrelated" type had optional members, those would still get added to the discriminator list. However in discriminateTypeByDiscriminableItems if a type doesn't have that property, it's immediately marked as not discriminable. This vaguely makes sense, but doesn't actually align with what this was trying to do, which is inherently check for assignability to undefined as a way to check for missing member as part of a discriminated union. I tried defaulting to undefined in discriminateTypeByDiscriminableItems but that created a few other problems.

Either way, this premise of checking for assignability to undefined of optional members is actually flawed. In principle what we actually want to is check for all potential properties in the union type that are missing from the original object for their assignability to missing. Ignoring exactOptionalPropertyTypes this should be possible to do by checking assignability to undefined, but as currently written, this would need a new path discriminateTypeByDiscriminableItems and seems potentially error prone, and potentially very expensive.

As I write this, another idea comes to mind, which seems less "correct" but may still be able to achieve the ideal result: In principle this is still meant to help figure out "discriminated unions", so instead of caching all properties, or all optional properties, we could specifically look for optional discriminated unions, e.g. the property is optional on one type and non-optional on any other members. By itself this will still fail on the union of two disjoint optional discriminated unions (which seems unlikely). But instead of checking all discriminators we check them independently for the set of types they discriminate against. Worst case this could be really bad, but I think in most common usages it might not even require an extra check.

I'm curious as to general thoughts on these different approaches. I realize this isn't very important, so maybe I'm overthinking this.

[Erik Brinkman (erikbrinkman)]

After some more experimentation, I think the goal of the PR as stated is out of line with the way typescript handles discriminant unions, and the current handling is sufficient. I'll open up an issue (or search to see if one exists) about better union discrimination.