Do not covariantly mix in constraints from contravarrying positions

[Wesley Wigham (weswigham)]

When calculating substitutions within a conditional.

Fixes #43427

[Wesley Wigham (weswigham)]

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 faster

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the extended test suite on this PR at cb1833b. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the parallelized Definitely Typed test suite on this PR at cb1833b. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the abridged perf test suite on this PR at cb1833b. You can monitor the build here.

Update: The results are in!

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the parallelized community code test suite on this PR at cb1833b. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the perf test suite on this PR at cb1833b. 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 - master..43439

Metric	master	43439	Delta	Best	Worst
Angular - node (v10.16.3, x64)
Memory used	344,930k (± 0.02%)	344,947k (± 0.02%)	+17k (+ 0.00%)	344,782k	345,082k
Parse Time	1.95s (± 1.47%)	1.93s (± 0.55%)	-0.03s (- 1.43%)	1.91s	1.95s
Bind Time	0.84s (± 0.89%)	0.83s (± 0.82%)	-0.00s (- 0.36%)	0.82s	0.85s
Check Time	5.12s (± 0.53%)	5.10s (± 0.57%)	-0.02s (- 0.43%)	5.01s	5.16s
Emit Time	5.92s (± 0.58%)	5.91s (± 0.70%)	-0.01s (- 0.10%)	5.83s	6.01s
Total Time	13.83s (± 0.48%)	13.77s (± 0.48%)	-0.06s (- 0.45%)	13.65s	13.94s
Compiler-Unions - node (v10.16.3, x64)
Memory used	203,064k (± 0.15%)	203,295k (± 0.03%)	+230k (+ 0.11%)	203,144k	203,425k
Parse Time	0.79s (± 0.76%)	0.79s (± 1.67%)	+0.01s (+ 0.89%)	0.77s	0.84s
Bind Time	0.53s (± 1.27%)	0.53s (± 1.27%)	-0.00s (- 0.00%)	0.51s	0.54s
Check Time	7.50s (± 0.72%)	7.59s (± 0.73%)	+0.09s (+ 1.15%)	7.47s	7.70s
Emit Time	2.58s (± 0.86%)	2.60s (± 1.57%)	+0.02s (+ 0.89%)	2.52s	2.75s
Total Time	11.39s (± 0.58%)	11.51s (± 0.61%)	+0.12s (+ 1.01%)	11.34s	11.66s
Monaco - node (v10.16.3, x64)
Memory used	342,707k (± 0.02%)	342,696k (± 0.02%)	-12k (- 0.00%)	342,536k	342,819k
Parse Time	1.57s (± 1.47%)	1.56s (± 0.22%)	-0.01s (- 0.51%)	1.56s	1.57s
Bind Time	0.74s (± 1.17%)	0.74s (± 0.66%)	+0.00s (+ 0.27%)	0.74s	0.76s
Check Time	5.27s (± 0.38%)	5.28s (± 0.47%)	+0.01s (+ 0.23%)	5.23s	5.33s
Emit Time	3.14s (± 0.76%)	3.15s (± 0.65%)	+0.00s (+ 0.10%)	3.10s	3.18s
Total Time	10.72s (± 0.45%)	10.74s (± 0.34%)	+0.01s (+ 0.10%)	10.65s	10.81s
TFS - node (v10.16.3, x64)
Memory used	304,292k (± 0.02%)	304,301k (± 0.02%)	+9k (+ 0.00%)	304,196k	304,403k
Parse Time	1.22s (± 1.50%)	1.22s (± 0.74%)	-0.01s (- 0.49%)	1.20s	1.24s
Bind Time	0.70s (± 0.70%)	0.70s (± 0.88%)	-0.00s (- 0.43%)	0.68s	0.71s
Check Time	4.74s (± 0.35%)	4.75s (± 0.38%)	+0.01s (+ 0.19%)	4.72s	4.79s
Emit Time	3.28s (± 1.28%)	3.26s (± 1.39%)	-0.02s (- 0.49%)	3.11s	3.33s
Total Time	9.95s (± 0.55%)	9.93s (± 0.56%)	-0.02s (- 0.19%)	9.75s	10.04s
material-ui - node (v10.16.3, x64)
Memory used	465,575k (± 0.02%)	465,481k (± 0.01%)	-95k (- 0.02%)	465,364k	465,622k
Parse Time	2.03s (± 2.15%)	2.01s (± 0.41%)	-0.03s (- 1.33%)	1.98s	2.02s
Bind Time	0.66s (± 1.13%)	0.66s (± 1.33%)	-0.00s (- 0.45%)	0.64s	0.67s
Check Time	14.29s (± 0.54%)	14.35s (± 0.54%)	+0.06s (+ 0.41%)	14.17s	14.50s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	16.99s (± 0.59%)	17.01s (± 0.49%)	+0.03s (+ 0.16%)	16.81s	17.17s
Angular - node (v12.1.0, x64)
Memory used	322,756k (± 0.03%)	322,720k (± 0.02%)	-37k (- 0.01%)	322,556k	322,875k
Parse Time	1.93s (± 0.72%)	1.92s (± 0.31%)	-0.01s (- 0.52%)	1.90s	1.93s
Bind Time	0.81s (± 0.76%)	0.81s (± 0.61%)	+0.00s (+ 0.37%)	0.81s	0.83s
Check Time	5.00s (± 0.37%)	5.01s (± 0.34%)	+0.01s (+ 0.22%)	4.97s	5.04s
Emit Time	5.99s (± 0.65%)	5.97s (± 0.60%)	-0.02s (- 0.40%)	5.92s	6.09s
Total Time	13.73s (± 0.38%)	13.71s (± 0.32%)	-0.02s (- 0.16%)	13.66s	13.86s
Compiler-Unions - node (v12.1.0, x64)
Memory used	190,573k (± 0.11%)	190,171k (± 0.20%)	-402k (- 0.21%)	189,188k	190,903k
Parse Time	0.76s (± 0.49%)	0.77s (± 0.68%)	+0.00s (+ 0.52%)	0.76s	0.78s
Bind Time	0.53s (± 0.65%)	0.53s (± 0.71%)	-0.00s (- 0.38%)	0.52s	0.53s
Check Time	7.03s (± 0.60%)	7.02s (± 0.81%)	-0.00s (- 0.03%)	6.92s	7.14s
Emit Time	2.55s (± 0.90%)	2.56s (± 1.01%)	+0.01s (+ 0.47%)	2.50s	2.60s
Total Time	10.86s (± 0.57%)	10.88s (± 0.57%)	+0.02s (+ 0.16%)	10.77s	11.00s
Monaco - node (v12.1.0, x64)
Memory used	325,050k (± 0.03%)	325,115k (± 0.03%)	+64k (+ 0.02%)	324,909k	325,421k
Parse Time	1.55s (± 1.09%)	1.54s (± 0.75%)	-0.00s (- 0.26%)	1.51s	1.57s
Bind Time	0.72s (± 0.92%)	0.72s (± 1.03%)	+0.00s (+ 0.00%)	0.71s	0.74s
Check Time	5.12s (± 0.63%)	5.10s (± 0.44%)	-0.01s (- 0.23%)	5.05s	5.17s
Emit Time	3.10s (± 0.64%)	3.08s (± 0.52%)	-0.02s (- 0.55%)	3.05s	3.12s
Total Time	10.48s (± 0.47%)	10.45s (± 0.34%)	-0.03s (- 0.28%)	10.38s	10.52s
TFS - node (v12.1.0, x64)
Memory used	288,770k (± 0.03%)	288,773k (± 0.02%)	+3k (+ 0.00%)	288,575k	288,893k
Parse Time	1.21s (± 0.83%)	1.21s (± 0.84%)	-0.01s (- 0.41%)	1.19s	1.23s
Bind Time	0.69s (± 0.75%)	0.70s (± 0.71%)	+0.01s (+ 0.72%)	0.69s	0.71s
Check Time	4.66s (± 0.49%)	4.69s (± 0.63%)	+0.03s (+ 0.60%)	4.64s	4.75s
Emit Time	3.15s (± 0.60%)	3.17s (± 0.76%)	+0.02s (+ 0.60%)	3.10s	3.22s
Total Time	9.71s (± 0.44%)	9.76s (± 0.42%)	+0.05s (+ 0.54%)	9.69s	9.88s
material-ui - node (v12.1.0, x64)
Memory used	443,735k (± 0.01%)	443,496k (± 0.09%)	-240k (- 0.05%)	442,362k	443,865k
Parse Time	2.02s (± 0.66%)	2.02s (± 0.44%)	-0.00s (- 0.00%)	2.00s	2.04s
Bind Time	0.64s (± 0.73%)	0.64s (± 1.25%)	+0.00s (+ 0.31%)	0.63s	0.66s
Check Time	12.99s (± 0.63%)	13.00s (± 0.96%)	+0.01s (+ 0.08%)	12.75s	13.28s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.65s (± 0.53%)	15.67s (± 0.80%)	+0.01s (+ 0.10%)	15.41s	15.95s
Angular - node (v14.15.1, x64)
Memory used	321,275k (± 0.08%)	321,412k (± 0.01%)	+137k (+ 0.04%)	321,373k	321,490k
Parse Time	1.94s (± 0.51%)	1.92s (± 0.27%)	-0.02s (- 0.88%)	1.91s	1.93s
Bind Time	0.86s (± 0.72%)	0.86s (± 0.35%)	-0.00s (- 0.12%)	0.85s	0.86s
Check Time	5.05s (± 0.75%)	5.04s (± 0.62%)	-0.01s (- 0.22%)	4.96s	5.12s
Emit Time	6.37s (± 1.09%)	6.32s (± 1.67%)	-0.05s (- 0.75%)	6.23s	6.73s
Total Time	14.22s (± 0.73%)	14.14s (± 0.74%)	-0.08s (- 0.53%)	13.99s	14.52s
Compiler-Unions - node (v14.15.1, x64)
Memory used	189,309k (± 0.13%)	189,402k (± 0.01%)	+93k (+ 0.05%)	189,360k	189,453k
Parse Time	0.80s (± 0.42%)	0.81s (± 0.69%)	+0.01s (+ 0.62%)	0.80s	0.82s
Bind Time	0.56s (± 0.53%)	0.56s (± 0.40%)	+0.00s (+ 0.18%)	0.55s	0.56s
Check Time	7.13s (± 0.90%)	7.13s (± 0.55%)	-0.01s (- 0.11%)	7.04s	7.24s
Emit Time	2.57s (± 1.28%)	2.56s (± 0.63%)	-0.00s (- 0.19%)	2.54s	2.60s
Total Time	11.06s (± 0.69%)	11.05s (± 0.43%)	-0.01s (- 0.10%)	10.96s	11.20s
Monaco - node (v14.15.1, x64)
Memory used	324,037k (± 0.01%)	324,017k (± 0.01%)	-20k (- 0.01%)	323,958k	324,048k
Parse Time	1.57s (± 0.92%)	1.57s (± 0.53%)	+0.00s (+ 0.00%)	1.56s	1.59s
Bind Time	0.74s (± 0.46%)	0.75s (± 0.49%)	+0.00s (+ 0.40%)	0.74s	0.75s
Check Time	5.06s (± 0.48%)	5.07s (± 0.43%)	+0.01s (+ 0.14%)	5.03s	5.14s
Emit Time	3.20s (± 0.71%)	3.19s (± 0.91%)	-0.01s (- 0.22%)	3.14s	3.25s
Total Time	10.58s (± 0.38%)	10.59s (± 0.49%)	+0.01s (+ 0.08%)	10.48s	10.74s
TFS - node (v14.15.1, x64)
Memory used	287,697k (± 0.01%)	287,702k (± 0.01%)	+5k (+ 0.00%)	287,645k	287,762k
Parse Time	1.27s (± 1.04%)	1.26s (± 0.80%)	-0.01s (- 0.63%)	1.24s	1.29s
Bind Time	0.72s (± 0.62%)	0.72s (± 0.82%)	+0.00s (+ 0.28%)	0.71s	0.74s
Check Time	4.69s (± 0.41%)	4.71s (± 0.48%)	+0.02s (+ 0.47%)	4.65s	4.74s
Emit Time	3.25s (± 0.51%)	3.27s (± 0.71%)	+0.02s (+ 0.49%)	3.24s	3.34s
Total Time	9.93s (± 0.39%)	9.97s (± 0.31%)	+0.04s (+ 0.35%)	9.89s	10.05s
material-ui - node (v14.15.1, x64)
Memory used	441,883k (± 0.06%)	441,876k (± 0.06%)	-8k (- 0.00%)	440,748k	442,033k
Parse Time	2.09s (± 0.45%)	2.10s (± 0.69%)	+0.00s (+ 0.14%)	2.05s	2.12s
Bind Time	0.69s (± 0.98%)	0.70s (± 0.71%)	+0.00s (+ 0.29%)	0.69s	0.71s
Check Time	13.01s (± 0.51%)	13.08s (± 1.05%)	+0.07s (+ 0.51%)	12.85s	13.51s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.80s (± 0.45%)	15.87s (± 0.89%)	+0.07s (+ 0.45%)	15.63s	16.30s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-206-generic
Architecture	x64
Available Memory	16 GB
Available Memory	10 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	43439	10
Baseline	master	10

Developer Information:

Download Benchmark

[TypeScript Bot (typescript-bot)]

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

Here they are:

Comparison Report - master..43439

Metric	master	43439	Delta	Best	Worst
Angular - node (v14.15.1, x64)
Memory used	321,275k (± 0.08%)	321,251k (± 0.08%)	-24k (- 0.01%)	320,241k	321,430k
Parse Time	1.94s (± 0.51%)	1.93s (± 0.56%)	-0.01s (- 0.36%)	1.91s	1.96s
Bind Time	0.86s (± 0.72%)	0.86s (± 0.55%)	-0.00s (- 0.23%)	0.85s	0.87s
Check Time	5.05s (± 0.75%)	5.04s (± 0.63%)	-0.01s (- 0.28%)	4.97s	5.10s
Emit Time	6.37s (± 1.09%)	6.31s (± 0.60%)	-0.06s (- 1.02%)	6.27s	6.45s
Total Time	14.22s (± 0.73%)	14.13s (± 0.40%)	-0.09s (- 0.62%)	14.04s	14.29s
Compiler-Unions - node (v14.15.1, x64)
Memory used	189,309k (± 0.13%)	189,409k (± 0.01%)	+101k (+ 0.05%)	189,368k	189,447k
Parse Time	0.80s (± 0.42%)	0.80s (± 0.77%)	-0.00s (- 0.50%)	0.79s	0.81s
Bind Time	0.56s (± 0.53%)	0.55s (± 0.67%)	-0.00s (- 0.54%)	0.55s	0.56s
Check Time	7.13s (± 0.90%)	7.07s (± 0.52%)	-0.06s (- 0.87%)	6.98s	7.17s
Emit Time	2.57s (± 1.28%)	2.56s (± 0.85%)	-0.01s (- 0.47%)	2.51s	2.62s
Total Time	11.06s (± 0.69%)	10.98s (± 0.38%)	-0.08s (- 0.76%)	10.89s	11.09s
Monaco - node (v14.15.1, x64)
Memory used	324,037k (± 0.01%)	324,040k (± 0.01%)	+3k (+ 0.00%)	323,998k	324,076k
Parse Time	1.57s (± 0.92%)	1.56s (± 0.64%)	-0.02s (- 1.08%)	1.54s	1.58s
Bind Time	0.74s (± 0.46%)	0.74s (± 0.66%)	+0.00s (+ 0.13%)	0.73s	0.75s
Check Time	5.06s (± 0.48%)	5.04s (± 0.40%)	-0.01s (- 0.30%)	4.99s	5.08s
Emit Time	3.20s (± 0.71%)	3.17s (± 0.86%)	-0.03s (- 1.06%)	3.12s	3.24s
Total Time	10.58s (± 0.38%)	10.52s (± 0.28%)	-0.06s (- 0.60%)	10.44s	10.60s
TFS - node (v14.15.1, x64)
Memory used	287,697k (± 0.01%)	287,699k (± 0.01%)	+2k (+ 0.00%)	287,630k	287,752k
Parse Time	1.27s (± 1.04%)	1.26s (± 0.74%)	-0.01s (- 0.79%)	1.24s	1.29s
Bind Time	0.72s (± 0.62%)	0.72s (± 0.95%)	-0.01s (- 0.83%)	0.71s	0.74s
Check Time	4.69s (± 0.41%)	4.68s (± 0.38%)	-0.00s (- 0.11%)	4.64s	4.72s
Emit Time	3.25s (± 0.51%)	3.25s (± 0.31%)	-0.01s (- 0.25%)	3.23s	3.28s
Total Time	9.93s (± 0.39%)	9.90s (± 0.29%)	-0.03s (- 0.28%)	9.86s	9.97s
material-ui - node (v14.15.1, x64)
Memory used	441,883k (± 0.06%)	441,996k (± 0.00%)	+113k (+ 0.03%)	441,939k	442,014k
Parse Time	2.09s (± 0.45%)	2.09s (± 0.64%)	-0.00s (- 0.05%)	2.05s	2.11s
Bind Time	0.69s (± 0.98%)	0.69s (± 0.86%)	-0.00s (- 0.00%)	0.68s	0.70s
Check Time	13.01s (± 0.51%)	13.04s (± 0.59%)	+0.03s (+ 0.22%)	12.88s	13.20s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.80s (± 0.45%)	15.83s (± 0.49%)	+0.03s (+ 0.17%)	15.68s	16.02s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-206-generic
Architecture	x64
Available Memory	16 GB
Available Memory	10 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)

Benchmark	Name	Iterations
Current	43439	10
Baseline	master	10

Developer Information:

Download Benchmark

[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.

[Ryan Cavanaugh (RyanCavanaugh)]

TypeScript Bot (@typescript-bot) pack this

[TypeScript Bot (typescript-bot)]

Heya Ryan Cavanaugh (@RyanCavanaugh), I've started to run the tarball bundle task on this PR at cb1833b. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Hey Ryan Cavanaugh (@RyanCavanaugh), 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/99765/artifacts?artifactName=tgz&fileId=3F0E740F4C6B9374DE9E9EAC3D681D2988529BF5808C1BCBC3B8A5D211957FAC02&fileName=/typescript-4.3.0-insiders.20210330.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@4.3.0-pr-43439-11".;

[Wesley Wigham (weswigham)]

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

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the parallelized Definitely Typed test suite on this PR at 6abbc96. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the parallelized community code test suite on this PR at 6abbc96. You can monitor the build here.

[Anders Hejlsberg (ahejlsberg)]

Looks like you still need to accept the test suite baseline changes. Otherwise, looks good, assuming it doesn't break anything in the other test suites.

[Wesley Wigham (weswigham)]

There's one DT change left I wanna adjust this to not hit - I think I'll adjust this so substitutes on type variables continue to always occur, regardless of position.

[Wesley Wigham (weswigham)]

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

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the parallelized Definitely Typed test suite on this PR at c392b0f. You can monitor the build here.

[TypeScript Bot (typescript-bot)]

Heya Wesley Wigham (@weswigham), I've started to run the parallelized community code test suite on this PR at c392b0f. You can monitor the build here.