Revert assignability cases in getNarrowedType

[Orta Therox (orta)]

Added in #39258 - which caused too many breaks to ship, then skipped in #41849 as the assignability narrowing might still be valuable. However, we've got enough reports that this is probably worth dropping too.

re: #42225 - #41808#41984

[Wesley Wigham (weswigham)]

All of those reports seem to involve Array.isArray which was already reverted - Do we have a new test that can demonstrate what the desired behavior that motivates this change is? Since there's no new test with this PR?

[Orta Therox (orta)]

I think this still triggers odd outcomes:

• all of Compile errors in VS Code codebase with latest TS nightly  #42225 occurred after the revert had happened - this may be because I sent this PR to them prior Support the new 4.0 definition of isArray vscode#102413 (I'm gonna check that now)
• Issue with Array.isArray typeguard after upgrading from 4.1.2 to 4.1.3 #41984 has a case which seems specific to this assignability change

[Orta Therox (orta)]

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

[TypeScript Bot (typescript-bot)]

Heya Orta Therox (@orta), I've started to run the tarball bundle task on this PR at 21d55ad. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Orta Therox (@orta), I've started to run the perf test suite on this PR at 21d55ad. You can monitor the build here.

Update: The results are in!

[TypeScript Bot (typescript-bot)]

Heya Orta Therox (@orta), I've started to run the extended test suite on this PR at 21d55ad. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Orta Therox (@orta), I've started to run the parallelized community code test suite on this PR at 21d55ad. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Orta Therox (@orta), I've started to run the parallelized Definitely Typed test suite on this PR at 21d55ad. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Hey Orta Therox (@orta), 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/95375/artifacts?artifactName=tgz&fileId=C5F3AF448AAB717F04287FA15ADBF0B42820FB5E42B06DE060336F4780B61B7602&fileName=/typescript-4.2.0-insiders.20210209.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@4.2.0-pr-42231-8".;

[TypeScript Bot (typescript-bot)]

Orta Therox (@orta)
The results of the perf run you requested are in!

Here they are:

Comparison Report - master..42231

Metric	master	42231	Delta	Best	Worst
Angular - node (v10.16.3, x64)
Memory used	345,671k (± 0.03%)	345,668k (± 0.02%)	-3k (- 0.00%)	345,523k	345,776k
Parse Time	1.91s (± 0.65%)	1.91s (± 0.52%)	-0.00s (- 0.10%)	1.89s	1.93s
Bind Time	0.82s (± 0.72%)	0.82s (± 0.99%)	-0.00s (- 0.12%)	0.81s	0.84s
Check Time	4.96s (± 0.67%)	4.95s (± 0.50%)	-0.01s (- 0.30%)	4.89s	5.01s
Emit Time	5.26s (± 0.48%)	5.27s (± 0.46%)	+0.01s (+ 0.13%)	5.21s	5.33s
Total Time	12.96s (± 0.35%)	12.95s (± 0.36%)	-0.01s (- 0.11%)	12.80s	13.02s
Compiler-Unions - node (v10.16.3, x64)
Memory used	214,423k (± 0.06%)	214,434k (± 0.07%)	+10k (+ 0.00%)	213,914k	214,697k
Parse Time	0.78s (± 0.64%)	0.78s (± 0.63%)	+0.00s (+ 0.13%)	0.77s	0.79s
Bind Time	0.50s (± 0.73%)	0.50s (± 1.54%)	-0.00s (- 0.20%)	0.48s	0.51s
Check Time	10.60s (± 0.72%)	10.63s (± 0.74%)	+0.02s (+ 0.23%)	10.46s	10.86s
Emit Time	2.35s (± 0.99%)	2.33s (± 1.32%)	-0.01s (- 0.55%)	2.28s	2.41s
Total Time	14.22s (± 0.48%)	14.23s (± 0.58%)	+0.01s (+ 0.09%)	14.05s	14.44s
Monaco - node (v10.16.3, x64)
Memory used	355,231k (± 0.03%)	355,290k (± 0.02%)	+59k (+ 0.02%)	355,121k	355,417k
Parse Time	1.55s (± 0.57%)	1.55s (± 0.64%)	+0.00s (+ 0.00%)	1.53s	1.57s
Bind Time	0.72s (± 0.77%)	0.72s (± 0.90%)	+0.00s (+ 0.00%)	0.71s	0.74s
Check Time	5.10s (± 0.41%)	5.10s (± 0.56%)	-0.00s (- 0.02%)	5.07s	5.20s
Emit Time	2.81s (± 0.68%)	2.79s (± 0.81%)	-0.02s (- 0.75%)	2.74s	2.85s
Total Time	10.19s (± 0.37%)	10.17s (± 0.49%)	-0.02s (- 0.24%)	10.08s	10.32s
TFS - node (v10.16.3, x64)
Memory used	308,145k (± 0.02%)	308,198k (± 0.02%)	+53k (+ 0.02%)	308,110k	308,325k
Parse Time	1.20s (± 0.50%)	1.22s (± 0.92%)	+0.01s (+ 0.83%)	1.19s	1.25s
Bind Time	0.68s (± 0.69%)	0.68s (± 0.73%)	+0.00s (+ 0.74%)	0.68s	0.70s
Check Time	4.59s (± 0.40%)	4.62s (± 0.58%)	+0.03s (+ 0.59%)	4.55s	4.70s
Emit Time	2.96s (± 1.20%)	2.95s (± 1.04%)	-0.02s (- 0.57%)	2.87s	3.02s
Total Time	9.43s (± 0.46%)	9.46s (± 0.54%)	+0.03s (+ 0.29%)	9.38s	9.62s
material-ui - node (v10.16.3, x64)
Memory used	495,568k (± 0.02%)	495,574k (± 0.01%)	+6k (+ 0.00%)	495,477k	495,702k
Parse Time	1.99s (± 0.82%)	1.97s (± 0.67%)	-0.02s (- 0.95%)	1.95s	2.01s
Bind Time	0.66s (± 0.91%)	0.65s (± 0.89%)	-0.00s (- 0.31%)	0.64s	0.67s
Check Time	13.96s (± 0.55%)	13.88s (± 0.33%)	-0.08s (- 0.56%)	13.76s	13.95s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	16.61s (± 0.52%)	16.51s (± 0.31%)	-0.10s (- 0.60%)	16.37s	16.61s
Angular - node (v12.1.0, x64)
Memory used	323,216k (± 0.03%)	323,245k (± 0.03%)	+29k (+ 0.01%)	323,112k	323,563k
Parse Time	1.91s (± 0.61%)	1.91s (± 0.73%)	+0.00s (+ 0.00%)	1.88s	1.94s
Bind Time	0.80s (± 0.72%)	0.80s (± 1.06%)	-0.00s (- 0.50%)	0.78s	0.82s
Check Time	4.86s (± 0.62%)	4.88s (± 1.25%)	+0.02s (+ 0.47%)	4.81s	5.09s
Emit Time	5.46s (± 1.50%)	5.44s (± 1.15%)	-0.02s (- 0.44%)	5.33s	5.63s
Total Time	13.03s (± 0.70%)	13.03s (± 0.70%)	-0.00s (- 0.02%)	12.85s	13.22s
Compiler-Unions - node (v12.1.0, x64)
Memory used	199,843k (± 0.07%)	199,848k (± 0.06%)	+6k (+ 0.00%)	199,519k	200,033k
Parse Time	0.77s (± 0.97%)	0.76s (± 0.95%)	-0.01s (- 1.42%)	0.75s	0.79s
Bind Time	0.50s (± 1.04%)	0.50s (± 0.80%)	0.00s ( 0.00%)	0.49s	0.51s
Check Time	9.76s (± 1.17%)	9.67s (± 0.89%)	-0.09s (- 0.92%)	9.46s	9.92s
Emit Time	2.37s (± 1.12%)	2.35s (± 1.02%)	-0.02s (- 0.84%)	2.28s	2.40s
Total Time	13.40s (± 1.00%)	13.28s (± 0.71%)	-0.12s (- 0.90%)	13.07s	13.56s
Monaco - node (v12.1.0, x64)
Memory used	337,509k (± 0.02%)	337,503k (± 0.01%)	-5k (- 0.00%)	337,432k	337,614k
Parse Time	1.53s (± 0.92%)	1.52s (± 0.44%)	-0.01s (- 0.65%)	1.51s	1.54s
Bind Time	0.71s (± 0.52%)	0.71s (± 0.70%)	-0.00s (- 0.00%)	0.70s	0.72s
Check Time	4.91s (± 0.43%)	4.88s (± 0.39%)	-0.04s (- 0.71%)	4.83s	4.92s
Emit Time	2.85s (± 0.65%)	2.85s (± 0.70%)	+0.00s (+ 0.18%)	2.82s	2.90s
Total Time	10.00s (± 0.45%)	9.96s (± 0.33%)	-0.04s (- 0.38%)	9.89s	10.02s
TFS - node (v12.1.0, x64)
Memory used	292,357k (± 0.03%)	292,340k (± 0.02%)	-16k (- 0.01%)	292,260k	292,552k
Parse Time	1.22s (± 0.62%)	1.22s (± 0.53%)	+0.00s (+ 0.16%)	1.20s	1.23s
Bind Time	0.65s (± 0.75%)	0.65s (± 1.35%)	-0.00s (- 0.15%)	0.63s	0.68s
Check Time	4.50s (± 0.53%)	4.50s (± 0.70%)	-0.00s (- 0.02%)	4.44s	4.59s
Emit Time	2.93s (± 1.52%)	2.94s (± 0.70%)	+0.01s (+ 0.24%)	2.89s	2.98s
Total Time	9.30s (± 0.53%)	9.31s (± 0.49%)	+0.01s (+ 0.09%)	9.17s	9.40s
material-ui - node (v12.1.0, x64)
Memory used	472,634k (± 0.05%)	472,811k (± 0.01%)	+178k (+ 0.04%)	472,715k	472,947k
Parse Time	2.00s (± 0.58%)	2.00s (± 0.76%)	-0.00s (- 0.00%)	1.96s	2.03s
Bind Time	0.64s (± 0.69%)	0.64s (± 1.18%)	+0.00s (+ 0.31%)	0.62s	0.65s
Check Time	12.51s (± 0.72%)	12.45s (± 0.81%)	-0.06s (- 0.46%)	12.33s	12.83s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.15s (± 0.64%)	15.09s (± 0.70%)	-0.06s (- 0.37%)	14.94s	15.48s
Angular - node (v14.15.1, x64)
Memory used	321,841k (± 0.01%)	321,831k (± 0.01%)	-10k (- 0.00%)	321,794k	321,879k
Parse Time	1.90s (± 0.39%)	1.90s (± 0.61%)	+0.00s (+ 0.11%)	1.88s	1.93s
Bind Time	0.85s (± 0.88%)	0.84s (± 0.79%)	-0.00s (- 0.47%)	0.83s	0.86s
Check Time	4.83s (± 0.21%)	4.85s (± 0.47%)	+0.02s (+ 0.44%)	4.81s	4.92s
Emit Time	5.48s (± 0.67%)	5.47s (± 0.43%)	-0.02s (- 0.29%)	5.42s	5.53s
Total Time	13.06s (± 0.33%)	13.07s (± 0.21%)	+0.01s (+ 0.08%)	13.00s	13.12s
Compiler-Unions - node (v14.15.1, x64)
Memory used	200,912k (± 0.60%)	200,781k (± 0.55%)	-131k (- 0.07%)	199,058k	202,893k
Parse Time	0.80s (± 0.60%)	0.80s (± 1.13%)	+0.00s (+ 0.25%)	0.78s	0.82s
Bind Time	0.53s (± 0.76%)	0.53s (± 0.63%)	+0.00s (+ 0.19%)	0.52s	0.54s
Check Time	9.67s (± 0.33%)	9.65s (± 0.45%)	-0.02s (- 0.24%)	9.56s	9.75s
Emit Time	2.34s (± 0.88%)	2.33s (± 1.09%)	-0.00s (- 0.04%)	2.28s	2.40s
Total Time	13.33s (± 0.31%)	13.31s (± 0.38%)	-0.02s (- 0.18%)	13.21s	13.43s
Monaco - node (v14.15.1, x64)
Memory used	336,871k (± 0.01%)	336,866k (± 0.01%)	-5k (- 0.00%)	336,827k	336,937k
Parse Time	1.55s (± 0.67%)	1.56s (± 0.71%)	+0.01s (+ 0.52%)	1.54s	1.59s
Bind Time	0.73s (± 0.81%)	0.73s (± 0.55%)	-0.00s (- 0.41%)	0.72s	0.74s
Check Time	4.86s (± 0.43%)	4.85s (± 0.55%)	-0.02s (- 0.35%)	4.78s	4.90s
Emit Time	2.91s (± 0.80%)	2.92s (± 0.63%)	+0.02s (+ 0.55%)	2.89s	2.98s
Total Time	10.06s (± 0.33%)	10.06s (± 0.33%)	+0.00s (+ 0.05%)	9.97s	10.11s
TFS - node (v14.15.1, x64)
Memory used	291,526k (± 0.01%)	291,536k (± 0.01%)	+10k (+ 0.00%)	291,497k	291,623k
Parse Time	1.25s (± 1.13%)	1.24s (± 0.78%)	-0.01s (- 0.96%)	1.22s	1.27s
Bind Time	0.69s (± 0.98%)	0.69s (± 0.84%)	-0.00s (- 0.14%)	0.68s	0.71s
Check Time	4.49s (± 0.43%)	4.49s (± 0.55%)	+0.00s (+ 0.09%)	4.44s	4.53s
Emit Time	3.06s (± 0.89%)	3.05s (± 0.52%)	-0.01s (- 0.46%)	3.01s	3.09s
Total Time	9.50s (± 0.37%)	9.47s (± 0.36%)	-0.03s (- 0.27%)	9.39s	9.54s
material-ui - node (v14.15.1, x64)
Memory used	471,374k (± 0.06%)	471,372k (± 0.06%)	-2k (- 0.00%)	470,254k	471,533k
Parse Time	2.06s (± 0.81%)	2.05s (± 0.78%)	-0.01s (- 0.29%)	2.02s	2.08s
Bind Time	0.70s (± 0.92%)	0.70s (± 0.64%)	-0.00s (- 0.57%)	0.69s	0.71s
Check Time	12.58s (± 0.84%)	12.60s (± 0.72%)	+0.01s (+ 0.10%)	12.43s	12.83s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.34s (± 0.70%)	15.35s (± 0.55%)	+0.01s (+ 0.04%)	15.21s	15.60s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-198-generic
Architecture	x64
Available Memory	16 GB
Available Memory	8 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)

Benchmark	Name	Iterations
Current	42231	10
Baseline	master	10

[TypeScript Bot (typescript-bot)]

The user suite test run you requested has finished and failed. I've opened a PR with the baseline diff from master.

[Orta Therox (orta)]

I'm heading out for the night, not sure if getting Anders' sign off is a blocker, if it's not can one of you two merge?

[Daniel Rosenwasser (DanielRosenwasser)]

Thanks Orta Therox (@orta)!