Fix assignment of intersections to objects with optional properties #37195

ahejlsberg · 2020-03-03T22:40:05Z

We consider any intersection A & B assignable to a type T if either A or B is assignable to T. This can be problematic when T is an object type with optional properties. For example:

declare let x: { a?: number, b: string };
declare let y: { a: null, b: string };
declare let z: { a: null } & { b: string };

x = y;  // Error
x = z;  // No error!

The issue here is that because { b: string } is assignable to { a?: number, b: string } we also consider any intersection that includes { b: string } to be assignable--even if the intersection includes another type that conflicts with the optional a property.

With this PR we now require intersections of object types as a whole to be assignable to the target type. In other words, we treat { a: null } & { b: string} identically to { a: null, b: string } in relationships.

Fixes #36604.

ahejlsberg · 2020-03-03T22:41:07Z

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

typescript-bot · 2020-03-03T22:41:12Z

Heya @ahejlsberg, I've started to run the parallelized Definitely Typed test suite on this PR at f902f8a. You can monitor the build here.

typescript-bot · 2020-03-03T22:41:12Z

Heya @ahejlsberg, I've started to run the perf test suite on this PR at f902f8a. You can monitor the build here.

Update: The results are in!

typescript-bot · 2020-03-03T22:41:12Z

Heya @ahejlsberg, I've started to run the parallelized community code test suite on this PR at f902f8a. You can monitor the build here.

typescript-bot · 2020-03-03T22:41:12Z

Heya @ahejlsberg, I've started to run the extended test suite on this PR at f902f8a. You can monitor the build here.

typescript-bot · 2020-03-03T23:17:22Z

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

typescript-bot · 2020-03-03T23:18:08Z

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

Here they are:

Comparison Report - master..37195

_Metric	_master	₃₇₁₉₅	_Delta	_Best	_Worst
_{Angular - node (v10.16.3, x64)}
_{Memory used}	_{334,334k (± 0.05%)}	_{333,809k (± 0.03%)}	_{-525k (- 0.16%)}	_333,521k	_334,026k
_{Parse Time}	_{1.62s (± 0.61%)}	_{1.63s (± 0.80%)}	_{+0.00s (+ 0.25%)}	_1.60s	_1.65s
_{Bind Time}	_{0.89s (± 0.82%)}	_{0.90s (± 0.56%)}	_{+0.01s (+ 0.79%)}	_0.89s	_0.91s
_{Check Time}	_{4.70s (± 0.53%)}	_{4.74s (± 0.47%)}	_{+0.04s (+ 0.85%)}	_4.71s	_4.80s
_{Emit Time}	_{5.30s (± 0.48%)}	_{5.30s (± 0.62%)}	_{+0.00s (+ 0.08%)}	_5.23s	_5.36s
_{Total Time}	_{12.51s (± 0.28%)}	_{12.57s (± 0.39%)}	_{+0.06s (+ 0.48%)}	_12.48s	_12.67s
_{Monaco - node (v10.16.3, x64)}
_{Memory used}	_{335,259k (± 0.01%)}	_{335,245k (± 0.02%)}	_{-14k (- 0.00%)}	_335,082k	_335,358k
_{Parse Time}	_{1.25s (± 0.82%)}	_{1.26s (± 0.54%)}	_{+0.01s (+ 0.40%)}	_1.24s	_1.27s
_{Bind Time}	_{0.78s (± 0.94%)}	_{0.78s (± 0.44%)}	_{-0.00s (- 0.13%)}	_0.77s	_0.78s
_{Check Time}	_{4.72s (± 0.64%)}	_{4.71s (± 0.79%)}	_{-0.01s (- 0.13%)}	_4.63s	_4.80s
_{Emit Time}	_{2.93s (± 0.71%)}	_{2.95s (± 1.02%)}	_{+0.03s (+ 0.85%)}	_2.87s	_3.02s
_{Total Time}	_{9.67s (± 0.33%)}	_{9.70s (± 0.65%)}	_{+0.03s (+ 0.29%)}	_9.57s	_9.81s
_{TFS - node (v10.16.3, x64)}
_{Memory used}	_{299,484k (± 0.02%)}	_{299,485k (± 0.02%)}	_{+0k (+ 0.00%)}	_299,340k	_299,611k
_{Parse Time}	_{0.94s (± 0.59%)}	_{0.94s (± 0.50%)}	_{-0.00s (- 0.21%)}	_0.93s	_0.95s
_{Bind Time}	_{0.74s (± 0.49%)}	_{0.75s (± 0.69%)}	_{+0.01s (+ 0.94%)}	_0.74s	_0.77s
_{Check Time}	_{4.27s (± 0.49%)}	_{4.28s (± 0.43%)}	_{+0.01s (+ 0.12%)}	_4.25s	_4.32s
_{Emit Time}	_{3.03s (± 0.75%)}	_{3.06s (± 0.62%)}	_{+0.03s (+ 0.86%)}	_3.02s	_3.10s
_{Total Time}	_{8.99s (± 0.37%)}	_{9.02s (± 0.36%)}	_{+0.04s (+ 0.40%)}	_8.94s	_9.09s
_{material-ui - node (v10.16.3, x64)}
_{Memory used}	_{488,881k (± 0.01%)}	_{489,335k (± 0.01%)}	_{+455k (+ 0.09%)}	_489,193k	_489,441k
_{Parse Time}	_{1.77s (± 0.34%)}	_{1.77s (± 0.25%)}	_{-0.00s (- 0.17%)}	_1.76s	_1.78s
_{Bind Time}	_{0.68s (± 0.76%)}	_{0.69s (± 0.69%)}	_{+0.01s (+ 0.88%)}	_0.68s	_0.70s
_{Check Time}	_{13.62s (± 0.93%)}	_{13.64s (± 0.84%)}	_{+0.02s (+ 0.15%)}	_13.47s	_13.95s
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_{0.00s ( NaN%)}	_0.00s	_0.00s
_{Total Time}	_{16.08s (± 0.81%)}	_{16.10s (± 0.73%)}	_{+0.02s (+ 0.16%)}	_15.92s	_16.42s
_{Angular - node (v12.1.0, x64)}
_{Memory used}	_{309,968k (± 0.14%)}	_{309,625k (± 0.02%)}	_{-343k (- 0.11%)}	_309,460k	_309,721k
_{Parse Time}	_{1.58s (± 0.53%)}	_{1.58s (± 0.48%)}	_{-0.00s (- 0.25%)}	_1.56s	_1.59s
_{Bind Time}	_{0.87s (± 0.87%)}	_{0.87s (± 1.17%)}	_{+0.00s (+ 0.35%)}	_0.85s	_0.89s
_{Check Time}	_{4.62s (± 0.69%)}	_{4.62s (± 0.51%)}	_{0.00s ( 0.00%)}	_4.58s	_4.68s
_{Emit Time}	_{5.48s (± 1.25%)}	_{5.47s (± 0.82%)}	_{-0.01s (- 0.20%)}	_5.38s	_5.58s
_{Total Time}	_{12.54s (± 0.75%)}	_{12.53s (± 0.45%)}	_{-0.01s (- 0.06%)}	_12.40s	_12.64s
_{Monaco - node (v12.1.0, x64)}
_{Memory used}	_{315,184k (± 0.01%)}	_{315,196k (± 0.02%)}	_{+12k (+ 0.00%)}	_315,045k	_315,323k
_{Parse Time}	_{1.20s (± 0.40%)}	_{1.20s (± 0.79%)}	_{+0.00s (+ 0.08%)}	_1.19s	_1.23s
_{Bind Time}	_{0.74s (± 1.10%)}	_{0.75s (± 1.27%)}	_{+0.00s (+ 0.40%)}	_0.73s	_0.78s
_{Check Time}	_{4.55s (± 0.26%)}	_{4.56s (± 0.43%)}	_{+0.01s (+ 0.31%)}	_4.53s	_4.61s
_{Emit Time}	_{2.96s (± 0.72%)}	_{2.95s (± 0.79%)}	_{-0.01s (- 0.27%)}	_2.90s	_3.01s
_{Total Time}	_{9.46s (± 0.28%)}	_{9.47s (± 0.47%)}	_{+0.01s (+ 0.11%)}	_9.39s	_9.60s
_{TFS - node (v12.1.0, x64)}
_{Memory used}	_{281,780k (± 0.02%)}	_{281,777k (± 0.03%)}	_{-3k (- 0.00%)}	_281,601k	_281,955k
_{Parse Time}	_{0.92s (± 0.79%)}	_{0.93s (± 0.82%)}	_{+0.00s (+ 0.33%)}	_0.91s	_0.94s
_{Bind Time}	_{0.71s (± 0.97%)}	_{0.71s (± 0.81%)}	_{+0.00s (+ 0.71%)}	_0.70s	_0.72s
_{Check Time}	_{4.18s (± 0.72%)}	_{4.20s (± 0.40%)}	_{+0.02s (+ 0.55%)}	_4.17s	_4.25s
_{Emit Time}	_{3.08s (± 1.35%)}	_{3.09s (± 0.59%)}	_{+0.01s (+ 0.19%)}	_3.05s	_3.13s
_{Total Time}	_{8.89s (± 0.57%)}	_{8.93s (± 0.30%)}	_{+0.04s (+ 0.45%)}	_8.86s	_8.97s
_{material-ui - node (v12.1.0, x64)}
_{Memory used}	_{466,312k (± 0.02%)}	_{466,828k (± 0.01%)}	_{+516k (+ 0.11%)}	_466,730k	_466,905k
_{Parse Time}	_{1.74s (± 0.33%)}	_{1.76s (± 0.45%)}	_{+0.02s (+ 0.86%)}	_1.74s	_1.78s
_{Bind Time}	_{0.62s (± 0.95%)}	_{0.63s (± 0.64%)}	_{+0.01s (+ 0.80%)}	_0.62s	_0.64s
_{Check Time}	_{12.05s (± 0.54%)}	_{12.20s (± 0.80%)}	_{+0.15s (+ 1.26%)}	_11.99s	_12.38s
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_{0.00s ( NaN%)}	_0.00s	_0.00s
_{Total Time}	_{14.41s (± 0.46%)}	_{14.59s (± 0.69%)}	_{+0.17s (+ 1.20%)}	_14.37s	_14.77s
_{Angular - node (v8.9.0, x64)}
_{Memory used}	_{329,366k (± 0.01%)}	_{328,925k (± 0.02%)}	_{-441k (- 0.13%)}	_328,754k	_329,071k
_{Parse Time}	_{2.11s (± 0.32%)}	_{2.10s (± 0.29%)}	_{-0.01s (- 0.28%)}	_2.09s	_2.12s
_{Bind Time}	_{0.92s (± 0.87%)}	_{0.92s (± 0.43%)}	_{-0.00s (- 0.11%)}	_0.91s	_0.93s
_{Check Time}	_{5.51s (± 0.44%)}	_{5.52s (± 0.82%)}	_{+0.00s (+ 0.04%)}	_5.43s	_5.62s
_{Emit Time}	_{6.23s (± 0.90%)}	_{6.26s (± 1.03%)}	_{+0.03s (+ 0.42%)}	_6.04s	_6.36s
_{Total Time}	_{14.78s (± 0.43%)}	_{14.80s (± 0.61%)}	_{+0.02s (+ 0.14%)}	_14.61s	_15.01s
_{Monaco - node (v8.9.0, x64)}
_{Memory used}	_{333,576k (± 0.02%)}	_{333,533k (± 0.01%)}	_{-43k (- 0.01%)}	_333,456k	_333,625k
_{Parse Time}	_{1.54s (± 0.66%)}	_{1.54s (± 0.46%)}	_{+0.00s (+ 0.20%)}	_1.53s	_1.56s
_{Bind Time}	_{0.90s (± 0.66%)}	_{0.90s (± 1.33%)}	_{+0.01s (+ 0.78%)}	_0.87s	_0.93s
_{Check Time}	_{5.40s (± 0.60%)}	_{5.42s (± 0.61%)}	_{+0.02s (+ 0.31%)}	_5.32s	_5.47s
_{Emit Time}	_{3.55s (± 0.56%)}	_{3.55s (± 0.37%)}	_{+0.01s (+ 0.17%)}	_3.53s	_3.59s
_{Total Time}	_{11.38s (± 0.36%)}	_{11.41s (± 0.43%)}	_{+0.03s (+ 0.25%)}	_11.31s	_11.54s
_{TFS - node (v8.9.0, x64)}
_{Memory used}	_{298,881k (± 0.02%)}	_{298,895k (± 0.02%)}	_{+13k (+ 0.00%)}	_298,777k	_299,060k
_{Parse Time}	_{1.25s (± 0.53%)}	_{1.26s (± 0.47%)}	_{+0.00s (+ 0.24%)}	_1.24s	_1.27s
_{Bind Time}	_{0.75s (± 0.69%)}	_{0.75s (± 0.64%)}	_{-0.00s (- 0.53%)}	_0.74s	_0.76s
_{Check Time}	_{4.83s (± 1.44%)}	_{4.82s (± 0.79%)}	_{-0.00s (- 0.08%)}	_4.75s	_4.96s
_{Emit Time}	_{3.34s (± 1.92%)}	_{3.37s (± 1.36%)}	_{+0.03s (+ 0.84%)}	_3.22s	_3.45s
_{Total Time}	_{10.17s (± 0.32%)}	_{10.20s (± 0.43%)}	_{+0.03s (+ 0.28%)}	_10.08s	_10.29s
_{material-ui - node (v8.9.0, x64)}
_{Memory used}	_{494,722k (± 0.01%)}	_{495,296k (± 0.01%)}	_{+574k (+ 0.12%)}	_495,176k	_495,416k
_{Parse Time}	_{2.11s (± 0.53%)}	_{2.10s (± 0.81%)}	_{-0.01s (- 0.38%)}	_2.07s	_2.13s
_{Bind Time}	_{0.82s (± 1.35%)}	_{0.82s (± 1.96%)}	_{+0.00s (+ 0.24%)}	_0.78s	_0.86s
_{Check Time}	_{19.54s (± 0.47%)}	_{19.62s (± 0.54%)}	_{+0.08s (+ 0.41%)}	_19.38s	_19.87s
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_{0.00s ( NaN%)}	_0.00s	_0.00s
_{Total Time}	_{22.46s (± 0.47%)}	_{22.54s (± 0.50%)}	_{+0.08s (+ 0.36%)}	_22.29s	_22.78s
_{Angular - node (v8.9.0, x86)}
_{Memory used}	_{188,954k (± 0.03%)}	_{188,772k (± 0.02%)}	_{-182k (- 0.10%)}	_188,696k	_188,862k
_{Parse Time}	_{2.05s (± 0.77%)}	_{2.06s (± 0.48%)}	_{+0.01s (+ 0.29%)}	_2.04s	_2.08s
_{Bind Time}	_{1.07s (± 1.10%)}	_{1.07s (± 0.69%)}	_{+0.00s (+ 0.09%)}	_1.05s	_1.08s
_{Check Time}	_{5.07s (± 0.95%)}	_{5.07s (± 0.40%)}	_{-0.00s (- 0.04%)}	_5.03s	_5.12s
_{Emit Time}	_{6.19s (± 1.27%)}	_{6.21s (± 1.36%)}	_{+0.02s (+ 0.26%)}	_6.09s	_6.50s
_{Total Time}	_{14.38s (± 0.92%)}	_{14.40s (± 0.55%)}	_{+0.02s (+ 0.17%)}	_14.26s	_14.65s
_{Monaco - node (v8.9.0, x86)}
_{Memory used}	_{189,214k (± 0.02%)}	_{189,226k (± 0.02%)}	_{+12k (+ 0.01%)}	_189,146k	_189,290k
_{Parse Time}	_{1.58s (± 0.99%)}	_{1.59s (± 0.94%)}	_{+0.01s (+ 0.69%)}	_1.57s	_1.63s
_{Bind Time}	_{0.77s (± 0.87%)}	_{0.77s (± 0.58%)}	_{+0.00s (+ 0.13%)}	_0.76s	_0.78s
_{Check Time}	_{5.35s (± 1.51%)}	_{5.35s (± 1.78%)}	_{-0.00s (- 0.07%)}	_5.11s	_5.49s
_{Emit Time}	_{3.01s (± 3.38%)}	_{3.02s (± 3.99%)}	_{+0.01s (+ 0.43%)}	_2.83s	_3.29s
_{Total Time}	_{10.71s (± 0.33%)}	_{10.73s (± 0.54%)}	_{+0.02s (+ 0.18%)}	_10.57s	_10.85s
_{TFS - node (v8.9.0, x86)}
_{Memory used}	_{170,430k (± 0.02%)}	_{170,430k (± 0.03%)}	_{-0k (- 0.00%)}	_170,316k	_170,510k
_{Parse Time}	_{1.28s (± 0.73%)}	_{1.28s (± 0.90%)}	_{+0.00s (+ 0.23%)}	_1.27s	_1.31s
_{Bind Time}	_{0.72s (± 0.77%)}	_{0.72s (± 0.83%)}	_{-0.00s (- 0.28%)}	_0.71s	_0.73s
_{Check Time}	_{4.62s (± 1.13%)}	_{4.64s (± 0.73%)}	_{+0.02s (+ 0.48%)}	_4.57s	_4.73s
_{Emit Time}	_{2.99s (± 1.87%)}	_{2.97s (± 1.00%)}	_{-0.02s (- 0.60%)}	_2.90s	_3.03s
_{Total Time}	_{9.61s (± 0.58%)}	_{9.60s (± 0.63%)}	_{-0.00s (- 0.01%)}	_9.47s	_9.70s
_{material-ui - node (v8.9.0, x86)}
_{Memory used}	_{277,168k (± 0.02%)}	_{277,417k (± 0.02%)}	_{+249k (+ 0.09%)}	_277,320k	_277,496k
_{Parse Time}	_{2.17s (± 0.38%)}	_{2.18s (± 0.63%)}	_{+0.00s (+ 0.14%)}	_2.14s	_2.21s
_{Bind Time}	_{0.69s (± 1.16%)}	_{0.68s (± 1.95%)}	_{-0.00s (- 0.58%)}	_0.67s	_0.73s
_{Check Time}	_{17.72s (± 0.80%)}	_{17.70s (± 0.53%)}	_{-0.03s (- 0.16%)}	_17.53s	_17.90s
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_{0.00s ( NaN%)}	_0.00s	_0.00s
_{Total Time}	_{20.58s (± 0.69%)}	_{20.55s (± 0.48%)}	_{-0.03s (- 0.16%)}	_20.37s	_20.75s

System

_{Machine Name}	_ts-ci-ubuntu
_Platform	_{linux 4.4.0-166-generic}
_Architecture	_x64
_{Available Memory}	_{16 GB}
_{Available Memory}	_{1 GB}
_CPUs	_{4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz}

Hosts

node (v10.16.3, x64)
node (v12.1.0, x64)
node (v8.9.0, x64)
node (v8.9.0, x86)

Scenarios

Angular - node (v10.16.3, x64)
Angular - node (v12.1.0, x64)
Angular - node (v8.9.0, x64)
Angular - node (v8.9.0, x86)
Monaco - node (v10.16.3, x64)
Monaco - node (v12.1.0, x64)
Monaco - node (v8.9.0, x64)
Monaco - node (v8.9.0, x86)
TFS - node (v10.16.3, x64)
TFS - node (v12.1.0, x64)
TFS - node (v8.9.0, x64)
TFS - node (v8.9.0, x86)
material-ui - node (v10.16.3, x64)
material-ui - node (v12.1.0, x64)
material-ui - node (v8.9.0, x64)
material-ui - node (v8.9.0, x86)

_Benchmark	_Name	_Iterations
_Current	₃₇₁₉₅	₁₀
_Baseline	_master	₁₀

ahejlsberg · 2020-03-04T00:36:27Z

@typescript-bot run dt

typescript-bot · 2020-03-04T00:37:16Z

Heya @ahejlsberg, I've started to run the parallelized Definitely Typed test suite on this PR at f902f8a. You can monitor the build here.

ahejlsberg · 2020-03-04T20:57:20Z

@typescript-bot user test this

typescript-bot · 2020-03-04T20:57:29Z

Heya @ahejlsberg, I've started to run the parallelized community code test suite on this PR at 1a5911a. You can monitor the build here.

weswigham · 2020-03-04T21:00:43Z

So, notably, this does not fix #36637 because that has a generic T involved, right?

ahejlsberg · 2020-03-04T21:02:29Z

So, notably, this does not fix #36637 because that has a generic T involved, right?

That's right.

typescript-bot · 2020-03-04T21:28:53Z

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

ahejlsberg · 2020-03-04T23:14:02Z

@weswigham Can you take a look at the last user test suite run and tell me which of those are preexisting conditions, or how I might find out? The office-ui-fabric-react is for sure a new issue, but I don't know about the rest.

weswigham · 2020-03-04T23:43:24Z

Can you take a look at the last user test suite run and tell me which of those are preexisting conditions, or how I might find out? The office-ui-fabric-react is for sure a new issue, but I don't know about the rest.

Looking over #37219 and #37203 , looks like just the office-ui-fabric-react ones are new.

ahejlsberg · 2020-03-05T00:18:42Z

Summarizing test runs: No change in RWC and DT and no appreciable perf impact. New errors in the office-ui-fabric-react user test project are indeed legitimate errors that we didn't catch before.

So, this PR is technically a breaking change because we find new issues.

DanielRosenwasser · 2020-03-05T00:20:49Z

@typescript-bot pack this

typescript-bot · 2020-03-05T00:20:55Z

Heya @DanielRosenwasser, I've started to run the tarball bundle task on this PR at 1a5911a. You can monitor the build here.

typescript-bot · 2020-03-05T00:35:53Z

Hey @DanielRosenwasser, 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/67180/artifacts?artifactName=tgz&fileId=8A4B17A3BD0AA9909034921D0F3C3FBDFFB9B06D33543D6718C4F38A9CAA8A6602&fileName=/typescript-3.9.0-insiders.20200305.tgz"
    }
}

and then running npm install.

There is also a playground for this build.

DanielRosenwasser · 2020-03-05T01:46:03Z

CC @dzearing @JasonGore, it looks like this change will cause issues for Fabric. It looks like tightening the declarations of

https://github.com/OfficeDev/office-ui-fabric-react/blob/e5c9f2bea83a4b9b0a82d303682c2ea093036c83/packages/fluentui/react-proptypes/src/index.ts#L436-L463

to use PropTypes.oneOf([...]) with the appropriate string literals for design will fix it. To try it out, I'd recommend using the above build.

ahejlsberg added 6 commits March 3, 2020 12:19

Treat intersections of only objects as a single object in relations

37d539d

Exclude intersections containing non-inferrable types

583ca83

Accept new baselines

1e114d2

Update test

0a207cc

Accept new baselines

adeb532

Add tests

f902f8a

typescript-bot mentioned this pull request Mar 3, 2020

🤖 User test baselines have changed for fix36604 #37200

Closed

ahejlsberg added 2 commits March 3, 2020 16:42

Merge branch 'master' into fix36604

669797a

Merge branch 'master' into fix36604

1a5911a

typescript-bot mentioned this pull request Mar 4, 2020

🤖 User test baselines have changed for fix36604 #37219

Closed

ahejlsberg added the Breaking Change Would introduce errors in existing code label Mar 5, 2020

This was referenced Mar 13, 2020

Design Meeting Notes, 3/6/2020 #37388

Closed

Design Meeting Notes, 3/13/2020 #37389

Closed

ahejlsberg merged commit b8baf48 into master Mar 14, 2020

ahejlsberg deleted the fix36604 branch March 14, 2020 16:46

ahejlsberg mentioned this pull request Mar 23, 2020

Extra check in assignment of intersections with generic constituents #37537

Merged

This was referenced Mar 31, 2020

[3.9.0-beta] OR'd types seem to get ANDed because of assertions #37659

Closed

Reduce away intersections that aren't assignable to constituents in CFA #37724

Closed

ekilah mentioned this pull request Apr 1, 2020

Can assign types even though interface field overriden using Omit #36604

Closed

weswigham mentioned this pull request Apr 8, 2020

New error: Excessive stack depth comparing types #37600

Closed

kitsonk mentioned this pull request Apr 29, 2020

TS 3.9 - No overload matches this call #38241

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DanielRosenwasser mentioned this pull request May 5, 2020

Regression: Intersection of array and tuple not assignable to tuple #38348

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ahejlsberg mentioned this pull request May 7, 2020

Exclude arrays and tuples from full intersection property check #38395

Merged

kitsonk mentioned this pull request May 13, 2020

Omit breaks in 3.9.2 #38531

Closed

RomainMuller mentioned this pull request May 13, 2020

3.9 regression: TS2322 error around assignment of an inferred intersection to a union #38542

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x87 mentioned this pull request May 14, 2020

3.9 Regression Merge Types #38571

Closed

fox1t mentioned this pull request May 14, 2020

Got error TS2315 with recently released TS 3.9 sinclairzx81/typebox#24

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KasparEtter mentioned this pull request Jun 3, 2020

TS 3.9.3 breaks HOC around generic class-based components that worked with TS 3.8.3 #38910

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brendankenny mentioned this pull request Jul 27, 2020

tests: update to typescript 3.9.7 GoogleChrome/lighthouse#11158

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github-actions bot mentioned this pull request Aug 14, 2022

Remove span tag in title and unnecessary TOC in Ko microsoft/TypeScript-Website-Localizations#164

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jakebailey mentioned this pull request Jul 9, 2023

Intersection with mapped never type allows incompatible optional assignments #19927

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Fix assignment of intersections to objects with optional properties #37195

Fix assignment of intersections to objects with optional properties #37195

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Fix assignment of intersections to objects with optional properties #37195

Fix assignment of intersections to objects with optional properties #37195

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