in operator shouldn't narrow {} originating in unknown

[Anders Hejlsberg (ahejlsberg)]

Fixes #50531.

This is a targeted fix for the exact issue in #50531. It doesn't address other known issues with the in operator.

[Anders Hejlsberg (ahejlsberg)]

TypeScript Bot (@typescript-bot) test this
TypeScript Bot (@typescript-bot) user test this inline
TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test faster
TypeScript Bot (@typescript-bot) test top100

[TypeScript Bot (typescript-bot)]

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the parallelized Definitely Typed test suite on this PR at 517777d. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the diff-based user code test suite on this PR at 517777d. You can monitor the build here.

Update: The results are in!

[TypeScript Bot (typescript-bot)]

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the extended test suite on this PR at 517777d. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the diff-based user code test suite on this PR at 517777d. You can monitor the build here.

Update: The results are in!

[TypeScript Bot (typescript-bot)]

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the abridged perf test suite on this PR at 517777d. You can monitor the build here.

Update: The results are in!

[TypeScript Bot (typescript-bot)]

Anders Hejlsberg (@ahejlsberg)
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..50610

Metric	main	50610	Delta	Best	Worst
Angular - node (v14.15.1, x64)
Memory used	338,741k (± 0.01%)	338,732k (± 0.01%)	-9k (- 0.00%)	338,679k	338,780k
Parse Time	2.08s (± 0.72%)	2.09s (± 1.27%)	+0.01s (+ 0.67%)	2.05s	2.16s
Bind Time	0.80s (± 1.52%)	0.79s (± 0.51%)	-0.01s (- 1.00%)	0.78s	0.80s
Check Time	5.84s (± 0.30%)	5.83s (± 0.48%)	-0.01s (- 0.24%)	5.78s	5.90s
Emit Time	6.18s (± 0.96%)	6.17s (± 0.52%)	-0.01s (- 0.16%)	6.10s	6.23s
Total Time	14.90s (± 0.48%)	14.88s (± 0.26%)	-0.01s (- 0.09%)	14.79s	14.98s
Compiler-Unions - node (v14.15.1, x64)
Memory used	192,975k (± 0.38%)	192,983k (± 0.39%)	+8k (+ 0.00%)	192,579k	195,996k
Parse Time	0.86s (± 1.15%)	0.85s (± 0.80%)	-0.00s (- 0.47%)	0.84s	0.87s
Bind Time	0.48s (± 1.03%)	0.49s (± 0.98%)	+0.00s (+ 0.41%)	0.48s	0.50s
Check Time	6.69s (± 0.60%)	6.73s (± 0.41%)	+0.03s (+ 0.51%)	6.67s	6.80s
Emit Time	2.41s (± 0.65%)	2.41s (± 0.62%)	+0.00s (+ 0.04%)	2.37s	2.43s
Total Time	10.44s (± 0.45%)	10.47s (± 0.28%)	+0.03s (+ 0.29%)	10.38s	10.53s
Monaco - node (v14.15.1, x64)
Memory used	326,527k (± 0.01%)	326,530k (± 0.01%)	+3k (+ 0.00%)	326,469k	326,562k
Parse Time	1.57s (± 0.68%)	1.57s (± 0.53%)	-0.00s (- 0.19%)	1.55s	1.58s
Bind Time	0.72s (± 0.50%)	0.72s (± 0.47%)	-0.00s (- 0.14%)	0.72s	0.73s
Check Time	5.72s (± 0.51%)	5.73s (± 0.31%)	+0.01s (+ 0.23%)	5.70s	5.77s
Emit Time	3.33s (± 0.87%)	3.30s (± 0.45%)	-0.04s (- 1.14%)	3.27s	3.33s
Total Time	11.35s (± 0.36%)	11.32s (± 0.30%)	-0.03s (- 0.25%)	11.25s	11.40s
TFS - node (v14.15.1, x64)
Memory used	289,647k (± 0.01%)	289,649k (± 0.01%)	+2k (+ 0.00%)	289,594k	289,681k
Parse Time	1.31s (± 0.81%)	1.30s (± 0.91%)	-0.00s (- 0.38%)	1.28s	1.34s
Bind Time	0.79s (± 0.51%)	0.80s (± 1.27%)	+0.00s (+ 0.51%)	0.78s	0.83s
Check Time	5.36s (± 0.43%)	5.34s (± 0.42%)	-0.02s (- 0.35%)	5.30s	5.39s
Emit Time	3.60s (± 1.19%)	3.56s (± 1.05%)	-0.03s (- 0.97%)	3.49s	3.68s
Total Time	11.06s (± 0.52%)	11.00s (± 0.48%)	-0.06s (- 0.56%)	10.88s	11.16s
material-ui - node (v14.15.1, x64)
Memory used	436,456k (± 0.00%)	436,461k (± 0.01%)	+5k (+ 0.00%)	436,416k	436,518k
Parse Time	1.86s (± 0.38%)	1.87s (± 0.56%)	+0.01s (+ 0.48%)	1.85s	1.89s
Bind Time	0.58s (± 0.63%)	0.58s (± 0.51%)	-0.00s (- 0.51%)	0.58s	0.59s
Check Time	12.86s (± 0.51%)	12.90s (± 0.80%)	+0.04s (+ 0.32%)	12.66s	13.21s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.30s (± 0.41%)	15.35s (± 0.64%)	+0.05s (+ 0.33%)	15.11s	15.64s
xstate - node (v14.15.1, x64)
Memory used	546,724k (± 0.00%)	546,737k (± 0.00%)	+13k (+ 0.00%)	546,714k	546,782k
Parse Time	2.60s (± 0.43%)	2.60s (± 0.52%)	-0.00s (- 0.12%)	2.58s	2.64s
Bind Time	0.97s (± 0.77%)	0.98s (± 0.85%)	+0.01s (+ 0.93%)	0.96s	1.00s
Check Time	1.53s (± 0.65%)	1.53s (± 0.68%)	-0.00s (- 0.13%)	1.51s	1.55s
Emit Time	0.07s (± 4.13%)	0.07s (± 3.14%)	-0.00s (- 1.39%)	0.07s	0.08s
Total Time	5.18s (± 0.31%)	5.18s (± 0.41%)	0.00s ( 0.00%)	5.13s	5.23s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-210-generic
Architecture	x64
Available Memory	16 GB
Available Memory	15 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

• node (v14.15.1, x64)

Scenarios

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

Benchmark	Name	Iterations
Current	50610	10
Baseline	main	10

Developer Information:

Download Benchmark

[TypeScript Bot (typescript-bot)]

Anders Hejlsberg (@ahejlsberg) Here are the results of running the user test suite comparing main and refs/pull/50610/merge:

Everything looks good!

[TypeScript Bot (typescript-bot)]

Anders Hejlsberg (@ahejlsberg) Here are the results of running the top-repos suite comparing main and refs/pull/50610/merge:

Everything looks good!

[Andrew Branch (andrewbranch)]

TypeScript Bot (@typescript-bot) cherry-pick this to release-4.8

[TypeScript Bot (typescript-bot)]

Heya Andrew Branch (@andrewbranch), I've started to run the task to cherry-pick this into release-4.8 on this PR at 517777d. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Hey Andrew Branch (@andrewbranch), I've opened #50612 for you.

[Bruce Pascoe (fatcerberus)]

What was the cause of #50531? It’s weird that unknown -> {} got narrowed by in but a directly-typed {} didn’t.

[Andrew Branch (andrewbranch)]

It’s that weird declaredType !== type condition—we discussed rewriting that whole set of conditions for 4.9 such that in only filters object types out of unions by property when there’s more than one object-like type in the declared type. There was also some discussion about whether to do anything if the property tested by in doesn’t exist in any of the object-like types in the union. (Anders Hejlsberg (@ahejlsberg) can probably better explain where we landed.)