Fix getRecursionIdentity function to always return some identity

[ahejlsberg]

Fixes #43493.

[ahejlsberg]

This PR implements the fix I describe here. Basically, getRecursionIdentity now always returns some identity, which by default is the type itself.

The PR reverts the changes from #43435 since they're no longer required and don't fix the core issue. However, I'm keeping the tests from that PR.

Regarding the baseline changes, two tests that previously failed now succeed--as they did when they were originally created.

The mappedTypeRecursiveInference.ts test would previously fail with an Excessive stack depth comparing types... error. That error no longer occurs, which is good. However, instead the test involving XMLHttpRequest ultimately fails with Type_instantiation_is_excessively_deep_and_possibly_infinite, which is expected but takes about twice as long as our test timeout limit. For that reason, I've deleted that particular test.

[ahejlsberg]

@typescript-bot test this
@typescript-bot user test this
@typescript-bot run dt
@typescript-bot perf test this faster

[typescript-bot]

Heya @ahejlsberg, I've started to run the perf test suite on this PR at 90382b2. You can monitor the build here.

Update: The results are in!

[typescript-bot]

Heya @ahejlsberg, I've started to run the parallelized Definitely Typed test suite on this PR at 90382b2. You can monitor the build here.

[typescript-bot]

Heya @ahejlsberg, I've started to run the abridged perf test suite on this PR at 90382b2. You can monitor the build here.

Update: The results are in!

[typescript-bot]

Heya @ahejlsberg, I've started to run the parallelized community code test suite on this PR at 90382b2. You can monitor the build here.

[typescript-bot]

Heya @ahejlsberg, I've started to run the extended test suite on this PR at 90382b2. You can monitor the build here.

[typescript-bot]

@ahejlsberg
The results of the perf run you requested are in!

Here they are:

Comparison Report - master..43527

Metric	master	43527	Delta	Best	Worst
Angular - node (v10.16.3, x64)
Memory used	344,904k (± 0.02%)	344,867k (± 0.03%)	-37k (- 0.01%)	344,706k	345,193k
Parse Time	1.93s (± 0.41%)	1.93s (± 0.45%)	+0.00s (+ 0.21%)	1.92s	1.95s
Bind Time	0.83s (± 0.87%)	0.83s (± 0.41%)	+0.00s (+ 0.12%)	0.83s	0.84s
Check Time	5.09s (± 0.26%)	5.10s (± 0.62%)	+0.01s (+ 0.28%)	5.06s	5.19s
Emit Time	5.91s (± 0.60%)	5.92s (± 0.89%)	+0.00s (+ 0.02%)	5.85s	6.08s
Total Time	13.76s (± 0.31%)	13.78s (± 0.46%)	+0.02s (+ 0.15%)	13.66s	13.92s
Compiler-Unions - node (v10.16.3, x64)
Memory used	203,345k (± 0.03%)	203,340k (± 0.04%)	-5k (- 0.00%)	203,197k	203,530k
Parse Time	0.78s (± 0.43%)	0.78s (± 0.93%)	-0.00s (- 0.13%)	0.77s	0.80s
Bind Time	0.52s (± 1.13%)	0.52s (± 1.06%)	-0.00s (- 0.38%)	0.51s	0.53s
Check Time	7.46s (± 0.58%)	7.47s (± 0.32%)	+0.01s (+ 0.13%)	7.41s	7.52s
Emit Time	2.60s (± 1.35%)	2.57s (± 0.96%)	-0.03s (- 1.04%)	2.53s	2.64s
Total Time	11.37s (± 0.55%)	11.35s (± 0.30%)	-0.02s (- 0.21%)	11.29s	11.41s
Monaco - node (v10.16.3, x64)
Memory used	342,642k (± 0.02%)	342,650k (± 0.02%)	+9k (+ 0.00%)	342,541k	342,804k
Parse Time	1.55s (± 0.52%)	1.56s (± 0.49%)	+0.00s (+ 0.32%)	1.54s	1.57s
Bind Time	0.74s (± 0.92%)	0.74s (± 0.49%)	0.00s ( 0.00%)	0.73s	0.74s
Check Time	5.26s (± 0.65%)	5.24s (± 0.42%)	-0.02s (- 0.30%)	5.19s	5.28s
Emit Time	3.12s (± 0.41%)	3.10s (± 0.39%)	-0.02s (- 0.61%)	3.08s	3.14s
Total Time	10.67s (± 0.37%)	10.64s (± 0.17%)	-0.03s (- 0.28%)	10.60s	10.68s
TFS - node (v10.16.3, x64)
Memory used	304,257k (± 0.02%)	304,314k (± 0.02%)	+57k (+ 0.02%)	304,164k	304,406k
Parse Time	1.21s (± 0.48%)	1.20s (± 0.57%)	-0.00s (- 0.25%)	1.19s	1.22s
Bind Time	0.70s (± 0.93%)	0.70s (± 1.19%)	-0.00s (- 0.43%)	0.67s	0.71s
Check Time	4.72s (± 0.54%)	4.72s (± 0.61%)	+0.00s (+ 0.11%)	4.66s	4.78s
Emit Time	3.25s (± 1.05%)	3.22s (± 1.29%)	-0.04s (- 1.17%)	3.13s	3.29s
Total Time	9.87s (± 0.38%)	9.84s (± 0.41%)	-0.04s (- 0.39%)	9.75s	9.96s
material-ui - node (v10.16.3, x64)
Memory used	465,406k (± 0.02%)	465,540k (± 0.01%)	+133k (+ 0.03%)	465,431k	465,679k
Parse Time	2.00s (± 0.70%)	2.00s (± 0.70%)	+0.00s (+ 0.10%)	1.98s	2.05s
Bind Time	0.66s (± 0.98%)	0.66s (± 0.71%)	+0.00s (+ 0.30%)	0.65s	0.67s
Check Time	14.22s (± 0.36%)	14.19s (± 0.39%)	-0.03s (- 0.18%)	14.10s	14.32s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	16.88s (± 0.29%)	16.85s (± 0.37%)	-0.03s (- 0.15%)	16.76s	17.03s
Angular - node (v12.1.0, x64)
Memory used	322,629k (± 0.03%)	322,648k (± 0.02%)	+19k (+ 0.01%)	322,433k	322,774k
Parse Time	1.92s (± 0.52%)	1.91s (± 0.43%)	-0.00s (- 0.16%)	1.90s	1.93s
Bind Time	0.81s (± 0.55%)	0.81s (± 0.42%)	-0.00s (- 0.12%)	0.80s	0.81s
Check Time	5.00s (± 0.45%)	4.99s (± 0.52%)	-0.01s (- 0.26%)	4.95s	5.06s
Emit Time	5.97s (± 0.41%)	6.05s (± 1.63%)	+0.08s (+ 1.32%)	5.93s	6.41s
Total Time	13.69s (± 0.31%)	13.75s (± 0.82%)	+0.06s (+ 0.44%)	13.61s	14.14s
Compiler-Unions - node (v12.1.0, x64)
Memory used	190,339k (± 0.16%)	190,026k (± 0.22%)	-313k (- 0.16%)	189,129k	190,898k
Parse Time	0.77s (± 0.89%)	0.77s (± 0.58%)	+0.00s (+ 0.26%)	0.76s	0.78s
Bind Time	0.53s (± 0.95%)	0.53s (± 1.23%)	+0.00s (+ 0.57%)	0.52s	0.55s
Check Time	6.95s (± 0.38%)	7.00s (± 0.45%)	+0.05s (+ 0.71%)	6.94s	7.09s
Emit Time	2.53s (± 0.89%)	2.57s (± 1.52%)	+0.04s (+ 1.58%)	2.48s	2.70s
Total Time	10.76s (± 0.38%)	10.86s (± 0.45%)	+0.10s (+ 0.91%)	10.77s	10.98s
Monaco - node (v12.1.0, x64)
Memory used	325,088k (± 0.02%)	325,015k (± 0.02%)	-73k (- 0.02%)	324,807k	325,168k
Parse Time	1.53s (± 0.71%)	1.53s (± 0.53%)	-0.00s (- 0.13%)	1.52s	1.55s
Bind Time	0.72s (± 0.56%)	0.72s (± 0.66%)	-0.00s (- 0.28%)	0.71s	0.73s
Check Time	5.07s (± 0.50%)	5.08s (± 0.50%)	+0.01s (+ 0.18%)	5.02s	5.13s
Emit Time	3.08s (± 0.47%)	3.08s (± 0.30%)	-0.00s (- 0.06%)	3.06s	3.10s
Total Time	10.40s (± 0.25%)	10.41s (± 0.27%)	+0.00s (+ 0.03%)	10.34s	10.45s
TFS - node (v12.1.0, x64)
Memory used	288,785k (± 0.02%)	288,733k (± 0.02%)	-52k (- 0.02%)	288,555k	288,884k
Parse Time	1.21s (± 0.58%)	1.21s (± 0.90%)	+0.00s (+ 0.08%)	1.19s	1.23s
Bind Time	0.69s (± 0.68%)	0.69s (± 1.01%)	+0.00s (+ 0.14%)	0.68s	0.71s
Check Time	4.64s (± 0.57%)	4.67s (± 0.53%)	+0.03s (+ 0.67%)	4.61s	4.72s
Emit Time	3.16s (± 0.63%)	3.16s (± 0.61%)	-0.01s (- 0.22%)	3.11s	3.20s
Total Time	9.71s (± 0.44%)	9.73s (± 0.45%)	+0.02s (+ 0.23%)	9.64s	9.82s
material-ui - node (v12.1.0, x64)
Memory used	443,470k (± 0.06%)	443,502k (± 0.09%)	+32k (+ 0.01%)	442,452k	443,844k
Parse Time	2.03s (± 0.55%)	2.02s (± 0.44%)	-0.00s (- 0.15%)	2.00s	2.04s
Bind Time	0.64s (± 0.53%)	0.64s (± 0.90%)	+0.00s (+ 0.47%)	0.63s	0.65s
Check Time	12.84s (± 0.49%)	12.88s (± 0.77%)	+0.04s (+ 0.34%)	12.75s	13.16s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.51s (± 0.38%)	15.54s (± 0.61%)	+0.04s (+ 0.25%)	15.41s	15.81s
Angular - node (v14.15.1, x64)
Memory used	321,325k (± 0.01%)	321,364k (± 0.01%)	+39k (+ 0.01%)	321,309k	321,402k
Parse Time	1.93s (± 0.42%)	1.92s (± 0.31%)	-0.01s (- 0.78%)	1.90s	1.93s
Bind Time	0.86s (± 0.47%)	0.86s (± 0.35%)	-0.00s (- 0.12%)	0.85s	0.86s
Check Time	4.99s (± 0.55%)	5.00s (± 0.67%)	+0.01s (+ 0.20%)	4.93s	5.10s
Emit Time	6.29s (± 0.55%)	6.30s (± 0.53%)	+0.01s (+ 0.11%)	6.23s	6.36s
Total Time	14.08s (± 0.29%)	14.08s (± 0.36%)	0.00s ( 0.00%)	13.96s	14.17s
Compiler-Unions - node (v14.15.1, x64)
Memory used	189,403k (± 0.02%)	189,397k (± 0.01%)	-6k (- 0.00%)	189,353k	189,463k
Parse Time	0.80s (± 0.72%)	0.80s (± 1.21%)	+0.00s (+ 0.12%)	0.79s	0.83s
Bind Time	0.55s (± 0.40%)	0.55s (± 0.62%)	+0.00s (+ 0.36%)	0.55s	0.56s
Check Time	7.05s (± 0.47%)	7.03s (± 0.54%)	-0.02s (- 0.23%)	6.94s	7.09s
Emit Time	2.55s (± 0.54%)	2.54s (± 1.02%)	-0.01s (- 0.55%)	2.50s	2.62s
Total Time	10.96s (± 0.37%)	10.93s (± 0.36%)	-0.03s (- 0.25%)	10.82s	10.98s
Monaco - node (v14.15.1, x64)
Memory used	324,044k (± 0.01%)	324,039k (± 0.01%)	-5k (- 0.00%)	324,004k	324,089k
Parse Time	1.56s (± 0.37%)	1.56s (± 0.52%)	+0.00s (+ 0.19%)	1.55s	1.58s
Bind Time	0.74s (± 0.49%)	0.74s (± 0.66%)	0.00s ( 0.00%)	0.74s	0.76s
Check Time	5.03s (± 0.44%)	5.02s (± 0.40%)	-0.00s (- 0.06%)	4.99s	5.07s
Emit Time	3.17s (± 0.53%)	3.17s (± 0.57%)	-0.01s (- 0.19%)	3.12s	3.21s
Total Time	10.50s (± 0.29%)	10.50s (± 0.41%)	-0.00s (- 0.01%)	10.42s	10.62s
TFS - node (v14.15.1, x64)
Memory used	287,658k (± 0.01%)	287,669k (± 0.01%)	+11k (+ 0.00%)	287,585k	287,742k
Parse Time	1.26s (± 0.67%)	1.27s (± 1.23%)	+0.01s (+ 0.48%)	1.23s	1.30s
Bind Time	0.71s (± 0.63%)	0.72s (± 0.46%)	+0.01s (+ 1.12%)	0.71s	0.73s
Check Time	4.65s (± 0.40%)	4.67s (± 0.45%)	+0.01s (+ 0.24%)	4.62s	4.72s
Emit Time	3.24s (± 0.45%)	3.25s (± 0.67%)	+0.01s (+ 0.31%)	3.21s	3.32s
Total Time	9.86s (± 0.22%)	9.90s (± 0.33%)	+0.03s (+ 0.32%)	9.83s	9.96s
material-ui - node (v14.15.1, x64)
Memory used	441,589k (± 0.08%)	441,900k (± 0.06%)	+311k (+ 0.07%)	440,906k	442,054k
Parse Time	2.09s (± 0.75%)	2.09s (± 0.46%)	+0.00s (+ 0.00%)	2.07s	2.11s
Bind Time	0.69s (± 0.80%)	0.69s (± 0.84%)	-0.01s (- 0.72%)	0.68s	0.70s
Check Time	13.04s (± 0.82%)	13.03s (± 0.90%)	-0.00s (- 0.01%)	12.88s	13.45s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.82s (± 0.72%)	15.81s (± 0.69%)	-0.01s (- 0.03%)	15.67s	16.20s

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	43527	10
Baseline	master	10

Developer Information:

Download Benchmark

[typescript-bot]

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

[typescript-bot]

@ahejlsberg
The results of the perf run you requested are in!

Here they are:

Comparison Report - master..43527

Metric	master	43527	Delta	Best	Worst
Angular - node (v14.15.1, x64)
Memory used	321,325k (± 0.01%)	321,364k (± 0.01%)	+39k (+ 0.01%)	321,280k	321,438k
Parse Time	1.93s (± 0.42%)	1.93s (± 0.49%)	+0.00s (+ 0.00%)	1.91s	1.95s
Bind Time	0.86s (± 0.47%)	0.86s (± 0.52%)	+0.00s (+ 0.35%)	0.85s	0.87s
Check Time	4.99s (± 0.55%)	5.02s (± 0.70%)	+0.02s (+ 0.48%)	4.94s	5.08s
Emit Time	6.29s (± 0.55%)	6.33s (± 0.64%)	+0.04s (+ 0.57%)	6.26s	6.45s
Total Time	14.08s (± 0.29%)	14.14s (± 0.48%)	+0.06s (+ 0.45%)	14.00s	14.31s
Compiler-Unions - node (v14.15.1, x64)
Memory used	189,403k (± 0.02%)	189,410k (± 0.01%)	+8k (+ 0.00%)	189,354k	189,460k
Parse Time	0.80s (± 0.72%)	0.80s (± 1.11%)	+0.00s (+ 0.50%)	0.79s	0.83s
Bind Time	0.55s (± 0.40%)	0.56s (± 0.53%)	+0.01s (+ 1.27%)	0.55s	0.56s
Check Time	7.05s (± 0.47%)	7.06s (± 0.53%)	+0.01s (+ 0.14%)	6.99s	7.13s
Emit Time	2.55s (± 0.54%)	2.54s (± 0.57%)	-0.01s (- 0.51%)	2.51s	2.57s
Total Time	10.96s (± 0.37%)	10.96s (± 0.41%)	+0.01s (+ 0.05%)	10.88s	11.06s
Monaco - node (v14.15.1, x64)
Memory used	324,044k (± 0.01%)	324,027k (± 0.01%)	-17k (- 0.01%)	323,996k	324,060k
Parse Time	1.56s (± 0.37%)	1.57s (± 0.42%)	+0.01s (+ 0.83%)	1.56s	1.59s
Bind Time	0.74s (± 0.49%)	0.75s (± 0.64%)	+0.00s (+ 0.40%)	0.74s	0.76s
Check Time	5.03s (± 0.44%)	5.04s (± 0.50%)	+0.01s (+ 0.20%)	4.98s	5.10s
Emit Time	3.17s (± 0.53%)	3.20s (± 0.94%)	+0.03s (+ 0.88%)	3.15s	3.30s
Total Time	10.50s (± 0.29%)	10.55s (± 0.48%)	+0.05s (+ 0.50%)	10.47s	10.68s
TFS - node (v14.15.1, x64)
Memory used	287,658k (± 0.01%)	287,663k (± 0.01%)	+6k (+ 0.00%)	287,607k	287,742k
Parse Time	1.26s (± 0.67%)	1.26s (± 0.99%)	+0.00s (+ 0.24%)	1.23s	1.28s
Bind Time	0.71s (± 0.63%)	0.72s (± 0.97%)	+0.01s (+ 0.98%)	0.71s	0.74s
Check Time	4.65s (± 0.40%)	4.69s (± 0.58%)	+0.03s (+ 0.71%)	4.63s	4.76s
Emit Time	3.24s (± 0.45%)	3.27s (± 0.74%)	+0.04s (+ 1.08%)	3.21s	3.32s
Total Time	9.86s (± 0.22%)	9.94s (± 0.50%)	+0.08s (+ 0.79%)	9.82s	10.05s
material-ui - node (v14.15.1, x64)
Memory used	441,589k (± 0.08%)	441,894k (± 0.06%)	+306k (+ 0.07%)	440,880k	442,064k
Parse Time	2.09s (± 0.75%)	2.10s (± 0.58%)	+0.01s (+ 0.34%)	2.07s	2.12s
Bind Time	0.69s (± 0.80%)	0.70s (± 0.86%)	+0.00s (+ 0.43%)	0.68s	0.70s
Check Time	13.04s (± 0.82%)	13.11s (± 0.85%)	+0.08s (+ 0.61%)	12.86s	13.44s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.82s (± 0.72%)	15.91s (± 0.75%)	+0.09s (+ 0.57%)	15.63s	16.26s

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	43527	10
Baseline	master	10

Developer Information:

Download Benchmark

[ahejlsberg]

Tests all look good, performance is unaffected.

[andrewbranch]

Makes sense 👍

[weswigham]

which is expected but takes about twice as long as our test timeout limit. For that reason, I've deleted that particular test.

That doesn't seem like a good outcome - a reverse mapped type over something with a pointer to a deep type hierarchy adding 40s to a compilation seems unacceptable to me? I just tested it out - #42485 can bring the runtime of that test down from 27s to 3s. Still not great (3s for a single call on a beefy machine?), but fixes it by an order of magnitude and definitely makes it keepable as a test.

[ahejlsberg]

I'm not sure I understand how #42485 helps. Before the fix in this PR we'd end up hitting the panic limit at 100 recursive invocations and output an Excessive stack depth comparing types... diagnostic, which prints the two types. This happed relatively quickly, but it is nonetheless wrong behavior.

With the PR we keep successfully relating types until we get to 50 levels of instantiations and then stop--but without printing any types, so #42485 wouldn't affect anything. It takes longer for this to occur but that isn't surprising given the very large number of types XMLHpptRequest touches if you recursively iterate over all of its properties.

[weswigham]

This test (from 7bd6eaf):

let xhr: XMLHttpRequest;
const out2 = foo(xhr);
out2.responseXML
out2.responseXML.activeElement.className.length

you said you removed from this PR because after this PR, it takes an excessive time to typecheck. I can see that - on my machine it typechecks in 27s and issues a (bogus! The tree of possible reverse-mapped types is in fact finite!) error TS2589: Type instantiation is excessively deep and possibly infinite.. If you merge this PR and #42485 (which caches reverse mapped types much better than we do today via two means: 1. actually caching the lazily inferred property types (today we repeat inference on every property lookup!) and 2. identifying that repeated indexing on the template of a reverse mapped type is that same as the base and transforming the type as such as explained in this comment, allowing caching to be shared as inference descends into a tree of types), the erroneous error goes away and typecheck time gets reduced by an order of magnitude.

Discussing perf of deleted test

[ahejlsberg]

@weswigham I thought #42485 was just about fixing type printback, but great that it also improves performance. Let's get it merged before this PR and then we can keep the test.