Improvements to strictSubtypeRelation and getNarrowedType

[ahejlsberg]

This PR fixes a number of inconsistencies related to the strict subtype relation and user defined type predicate narrowing. Specifically:

• In the strict subtype relation, unknown is related to any but any is not related to unknown. Previously, the two were mutually related.
• In the strict subtype relation, a non-fresh object type is not related to a another object type if the first type is missing an index signature. Previously, it was possible for such types to be mutually related.
• In the subtype and strict subtype relations, given a signature S1 of the form (...args: A) => R, where A is any, any[], never, or never[], and R is any or unknown, and a signature S2 not of that form, S2 is related to S1 but S1 is not related to S2. Previously, it was possible for such signatures to be mutually related.
• The assignment expression x = y is has the same type as y with any object literal freshness preserved. Previously, object literal freshness was stripped.
• Narrowing by a user defined type predicate preserves the original type in the false branch for non-identical mutual subtypes.

The strict subtype relation primarily controls subtype reduction of union types. Subtype reduction occurs in control flow analysis and other situations that require determining a common supertype for multiple types. For example, given expressions a and b of type A and B, the element type of an array literal [a, b] is A if B is a subtype of A, B if A is a subtype of B, or A | B if neither is a subtype of the other. However, if A and B are mutual subtypes, the type chosen may ultimately depend on declaration order, which isn't desired. The goal of the strict subtype relation is to impose a stable ordering by eliminating mutual subtypes, and the first three rules above further that goal.

Fixes #50916.

[ahejlsberg]

@typescript-bot test this
@typescript-bot user test this inline
@typescript-bot run dt
@typescript-bot perf test faster
@typescript-bot test top100

[typescript-bot]

Heya @ahejlsberg, I've started to run the diff-based top-repos suite on this PR at 14985d4. 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 14985d4. You can monitor the build here.

[typescript-bot]

Heya @ahejlsberg, I've started to run the diff-based user code test suite on this PR at 14985d4. You can monitor the build here.

Update: The results are in!

[typescript-bot]

Heya @ahejlsberg, I've started to run the abridged perf test suite on this PR at 14985d4. You can monitor the build here.

Update: The results are in!

[typescript-bot]

Heya @ahejlsberg, I've started to run the extended test suite on this PR at 14985d4. You can monitor the build here.

[typescript-bot]

@ahejlsberg Here are the results of running the user test suite comparing main and refs/pull/52282/merge:

Everything looks good!

[typescript-bot]

Heya @ahejlsberg, I've run the RWC suite on this PR - assuming you're on the TS core team, you can view the resulting diff here.

[typescript-bot]

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

Here they are:

Comparison Report - main..52282

Metric	main	52282	Delta	Best	Worst
Angular - node (v16.17.1, x64)
Memory used	358,311k (± 0.01%)	358,322k (± 0.01%)	+11k (+ 0.00%)	358,263k	358,361k
Parse Time	4.10s (± 0.58%)	4.12s (± 0.59%)	+0.01s (+ 0.33%)	4.09s	4.16s
Bind Time	1.25s (± 0.35%)	1.25s (± 0.45%)	-0.00s (- 0.03%)	1.25s	1.26s
Check Time	9.49s (± 0.50%)	9.49s (± 0.18%)	-0.00s (- 0.02%)	9.47s	9.51s
Emit Time	7.96s (± 0.25%)	7.94s (± 0.44%)	-0.02s (- 0.22%)	7.90s	8.00s
Total Time	22.81s (± 0.20%)	22.80s (± 0.18%)	-0.00s (- 0.01%)	22.72s	22.83s
Compiler-Unions - node (v16.17.1, x64)
Memory used	195,555k (± 0.96%)	191,823k (± 0.03%)	-3,732k (- 1.91%)	191,735k	191,901k
Parse Time	1.80s (± 1.25%)	1.81s (± 0.39%)	+0.01s (+ 0.31%)	1.80s	1.82s
Bind Time	0.85s (± 0.61%)	0.85s (± 0.72%)	+0.00s (+ 0.03%)	0.84s	0.86s
Check Time	10.24s (± 0.56%)	10.09s (± 0.99%)	-0.15s (- 1.44%)	9.94s	10.20s
Emit Time	3.13s (± 5.36%)	3.06s (± 2.08%)	-0.07s (- 2.26%)	3.01s	3.18s
Total Time	16.02s (± 1.05%)	15.81s (± 0.60%)	-0.21s (- 1.33%)	15.64s	15.91s
Monaco - node (v16.17.1, x64)
Memory used	345,118k (± 0.01%)	345,147k (± 0.01%)	+29k (+ 0.01%)	345,115k	345,172k
Parse Time	3.10s (± 1.05%)	3.10s (± 0.76%)	+0.00s (+ 0.01%)	3.08s	3.14s
Bind Time	1.11s (± 0.87%)	1.11s (± 0.79%)	-0.00s (- 0.38%)	1.10s	1.12s
Check Time	7.87s (± 0.09%)	7.93s (± 1.08%)	+0.05s (+ 0.66%)	7.85s	8.09s
Emit Time	4.57s (± 1.09%)	4.57s (± 2.05%)	+0.01s (+ 0.14%)	4.50s	4.76s
Total Time	16.66s (± 0.39%)	16.71s (± 1.09%)	+0.05s (+ 0.32%)	16.56s	17.07s
TFS - node (v16.17.1, x64)
Memory used	299,919k (± 0.01%)	299,918k (± 0.00%)	-1k (- 0.00%)	299,911k	299,924k
Parse Time	2.43s (± 1.35%)	2.42s (± 1.01%)	-0.01s (- 0.41%)	2.40s	2.46s
Bind Time	1.26s (± 1.06%)	1.26s (± 0.62%)	+0.00s (+ 0.26%)	1.25s	1.27s
Check Time	7.41s (± 0.40%)	7.44s (± 0.43%)	+0.03s (+ 0.38%)	7.40s	7.49s
Emit Time	4.23s (± 0.38%)	4.25s (± 0.52%)	+0.01s (+ 0.31%)	4.21s	4.27s
Total Time	15.34s (± 0.49%)	15.38s (± 0.31%)	+0.03s (+ 0.23%)	15.31s	15.45s
material-ui - node (v16.17.1, x64)
Memory used	475,709k (± 0.00%)	475,705k (± 0.00%)	-4k (- 0.00%)	475,666k	475,734k
Parse Time	3.65s (± 0.39%)	3.66s (± 0.26%)	+0.01s (+ 0.25%)	3.65s	3.68s
Bind Time	1.01s (± 0.51%)	1.01s (± 0.50%)	+0.00s (+ 0.40%)	1.00s	1.02s
Check Time	17.86s (± 0.22%)	18.05s (± 0.69%)	+0.18s (+ 1.01%)	17.90s	18.26s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	22.53s (± 0.17%)	22.72s (± 0.52%)	+0.19s (+ 0.85%)	22.57s	22.92s
xstate - node (v16.17.1, x64)
Memory used	543,991k (± 0.02%)	544,002k (± 0.01%)	+11k (+ 0.00%)	543,961k	544,099k
Parse Time	4.57s (± 0.37%)	4.60s (± 0.72%)	+0.03s (+ 0.65%)	4.57s	4.66s
Bind Time	1.79s (± 0.38%)	1.80s (± 0.18%)	+0.00s (+ 0.19%)	1.79s	1.80s
Check Time	2.93s (± 0.44%)	2.93s (± 0.54%)	+0.00s (+ 0.04%)	2.91s	2.95s
Emit Time	0.08s (± 6.09%)	0.08s (± 6.08%)	+0.00s (+ 0.10%)	0.08s	0.09s
Total Time	9.38s (± 0.20%)	9.42s (± 0.26%)	+0.03s (+ 0.37%)	9.39s	9.45s

System

Machine Name	ts-ci-ubuntu
Platform	linux 5.4.0-135-generic
Architecture	x64
Available Memory	16 GB
Available Memory	15 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

• node (v16.17.1, x64)

Scenarios

• Angular - node (v16.17.1, x64)
• Compiler-Unions - node (v16.17.1, x64)
• Monaco - node (v16.17.1, x64)
• TFS - node (v16.17.1, x64)
• material-ui - node (v16.17.1, x64)
• xstate - node (v16.17.1, x64)

Benchmark	Name	Iterations
Current	52282	6
Baseline	main	6

Developer Information:

Download Benchmark

[typescript-bot]

@ahejlsberg Here are the results of running the top-repos suite comparing main and refs/pull/52282/merge:

Something interesting changed - please have a look.

Details

marmelab/react-admin

22 of 23 projects failed to build with the old tsc and were ignored

packages/ra-core/tsconfig.json

• error TS2604: JSX element type 'Create' does not have any construct or call signatures.
  • packages/ra-core/src/core/Resource.tsx#L17
• error TS2604: JSX element type 'Show' does not have any construct or call signatures.
  • packages/ra-core/src/core/Resource.tsx#L23
• error TS2604: JSX element type 'Edit' does not have any construct or call signatures.
  • packages/ra-core/src/core/Resource.tsx#L29
• error TS2604: JSX element type 'List' does not have any construct or call signatures.
  • packages/ra-core/src/core/Resource.tsx#L35

ReactiveX/rxjs

8 of 13 projects failed to build with the old tsc and were ignored

src/tsconfig.cjs.spec.json

• error TS2339: Property 'next' does not exist on type 'Partial<Observer<T>> | ((value: T) => void)'.
  • src/internal/Subscriber.ts#L220
  • src/internal/Subscriber.ts#L220
• error TS2339: Property 'error' does not exist on type 'Partial<Observer<T>> | ((value: T) => void)'.
  • src/internal/Subscriber.ts#L221
  • src/internal/Subscriber.ts#L221
• error TS2339: Property 'complete' does not exist on type 'Partial<Observer<T>> | ((value: T) => void)'.
  • src/internal/Subscriber.ts#L222
  • src/internal/Subscriber.ts#L222
• error TS2322: Type 'Partial<Observer<T>> | ((value: T) => void)' is not assignable to type 'Partial<Observer<T>>'.
  • src/internal/Subscriber.ts#L226
• error TS2339: Property 'unsubscribe' does not exist on type 'Unsubscribable | (() => void)'.
  • src/internal/Subscription.ts#L214
• error TS2339: Property 'subscribe' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L121
• error TS2339: Property 'next' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L127
• error TS2339: Property 'complete' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L132
• error TS2339: Property 'error' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L137
• error TS2339: Property 'unsubscribe' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L142
• error TS2339: Property 'finalize' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L144

src/tsconfig.esm5.rollup.json

• error TS2339: Property 'next' does not exist on type 'Partial<Observer<T>> | ((value: T) => void)'.
  • src/internal/Subscriber.ts#L220
  • src/internal/Subscriber.ts#L220
• error TS2339: Property 'error' does not exist on type 'Partial<Observer<T>> | ((value: T) => void)'.
  • src/internal/Subscriber.ts#L221
  • src/internal/Subscriber.ts#L221
• error TS2339: Property 'complete' does not exist on type 'Partial<Observer<T>> | ((value: T) => void)'.
  • src/internal/Subscriber.ts#L222
  • src/internal/Subscriber.ts#L222
• error TS2322: Type 'Partial<Observer<T>> | ((value: T) => void)' is not assignable to type 'Partial<Observer<T>>'.
  • src/internal/Subscriber.ts#L226
• error TS2339: Property 'unsubscribe' does not exist on type 'Unsubscribable | (() => void)'.
  • src/internal/Subscription.ts#L214
• error TS2339: Property 'subscribe' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L121
• error TS2339: Property 'next' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L127
• error TS2339: Property 'complete' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L132
• error TS2339: Property 'error' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L137
• error TS2339: Property 'unsubscribe' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L142
• error TS2339: Property 'finalize' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L144

src/tsconfig.types.json

• error TS2339: Property 'unsubscribe' does not exist on type 'Unsubscribable | (() => void)'.
  • src/internal/Subscription.ts#L214 in src/tsconfig.types.json
• error TS2339: Property 'next' does not exist on type 'Partial<Observer<T>> | ((value: T) => void)'.
  • src/internal/Subscriber.ts#L220 in src/tsconfig.types.json
  • src/internal/Subscriber.ts#L220 in src/tsconfig.types.json
• error TS2339: Property 'error' does not exist on type 'Partial<Observer<T>> | ((value: T) => void)'.
  • src/internal/Subscriber.ts#L221 in src/tsconfig.types.json
  • src/internal/Subscriber.ts#L221 in src/tsconfig.types.json
• error TS2339: Property 'complete' does not exist on type 'Partial<Observer<T>> | ((value: T) => void)'.
  • src/internal/Subscriber.ts#L222 in src/tsconfig.types.json
  • src/internal/Subscriber.ts#L222 in src/tsconfig.types.json
• error TS2322: Type 'Partial<Observer<T>> | ((value: T) => void)' is not assignable to type 'Partial<Observer<T>>'.
  • src/internal/Subscriber.ts#L226 in src/tsconfig.types.json
• error TS2339: Property 'subscribe' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L121 in src/tsconfig.types.json
• error TS2339: Property 'next' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L127 in src/tsconfig.types.json
• error TS2339: Property 'complete' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L132 in src/tsconfig.types.json
• error TS2339: Property 'error' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L137 in src/tsconfig.types.json
• error TS2339: Property 'unsubscribe' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L142 in src/tsconfig.types.json
• error TS2339: Property 'finalize' does not exist on type 'Partial<TapObserver<T>> | ((value: T) => void)'.
  • src/internal/operators/tap.ts#L144 in src/tsconfig.types.json

vuejs/vue

7 of 8 projects failed to build with the old tsc and were ignored

tsconfig.json

• error TS2339: Property 'get' does not exist on type 'Record<string, any> | (() => any)'.
  • src/core/instance/state.ts#L232
  • src/core/instance/state.ts#L235
• error TS2339: Property 'cache' does not exist on type 'Record<string, any> | (() => any)'.
  • src/core/instance/state.ts#L233
• error TS2339: Property 'set' does not exist on type 'Record<string, any> | (() => any)'.
  • src/core/instance/state.ts#L237
• error TS2345: Argument of type 'string | (() => any)' is not assignable to parameter of type 'string'.
  • src/core/observer/watcher.ts#L115
• error TS2578: Unused '@ts-expect-error' directive.
  • src/core/vdom/create-component.ts#L238
• error TS2339: Property 'slot' does not exist on type 'VNodeData | {}'.
  • src/core/vdom/create-functional-component.ts#L171
• error TS2339: Property 'transition' does not exist on type 'VNodeData | {}'.
  • src/platforms/web/runtime/components/transition-group.ts#L72
  • src/platforms/web/runtime/components/transition.ts#L153
• error TS2339: Property 'loader' does not exist on type 'AsyncComponentOptions | (() => any)'.
  • src/v3/apiAsyncComponent.ts#L39
• error TS2339: Property 'loadingComponent' does not exist on type 'AsyncComponentOptions | (() => any)'.
  • src/v3/apiAsyncComponent.ts#L40
• error TS2339: Property 'errorComponent' does not exist on type 'AsyncComponentOptions | (() => any)'.
  • src/v3/apiAsyncComponent.ts#L41
• error TS2339: Property 'delay' does not exist on type 'AsyncComponentOptions | (() => any)'.
  • src/v3/apiAsyncComponent.ts#L42
• error TS2339: Property 'timeout' does not exist on type 'AsyncComponentOptions | (() => any)'.
  • src/v3/apiAsyncComponent.ts#L43
• error TS2339: Property 'suspensible' does not exist on type 'AsyncComponentOptions | (() => any)'.
  • src/v3/apiAsyncComponent.ts#L44
• error TS2339: Property 'onError' does not exist on type 'AsyncComponentOptions | (() => any)'.
  • src/v3/apiAsyncComponent.ts#L45

[ahejlsberg]

@typescript-bot test this
@typescript-bot user test this inline
@typescript-bot run dt
@typescript-bot perf test faster
@typescript-bot test top100

[typescript-bot]

Heya @ahejlsberg, I've started to run the diff-based user code test suite on this PR at d7a80c4. 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 d7a80c4. You can monitor the build here.

[typescript-bot]

Heya @ahejlsberg, I've started to run the abridged perf test suite on this PR at d7a80c4. You can monitor the build here.

Update: The results are in!

[typescript-bot]

Heya @ahejlsberg, I've started to run the extended test suite on this PR at d7a80c4. You can monitor the build here.

[typescript-bot]

Heya @ahejlsberg, I've started to run the diff-based top-repos suite on this PR at d7a80c4. You can monitor the build here.

Update: The results are in!

[typescript-bot]

@ahejlsberg Here are the results of running the user test suite comparing main and refs/pull/52282/merge:

Everything looks good!

[typescript-bot]

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

Here they are:

Comparison Report - main..52282

Metric	main	52282	Delta	Best	Worst
Angular - node (v16.17.1, x64)
Memory used	358,348k (± 0.01%)	358,145k (± 0.01%)	-203k (- 0.06%)	358,095k	358,205k
Parse Time	4.10s (± 0.43%)	4.09s (± 0.25%)	-0.02s (- 0.37%)	4.07s	4.10s
Bind Time	1.25s (± 0.39%)	1.25s (± 0.71%)	+0.00s (+ 0.03%)	1.24s	1.27s
Check Time	9.47s (± 0.41%)	9.51s (± 0.38%)	+0.04s (+ 0.42%)	9.46s	9.56s
Emit Time	7.97s (± 0.26%)	7.97s (± 0.68%)	-0.00s (- 0.05%)	7.92s	8.06s
Total Time	22.80s (± 0.15%)	22.82s (± 0.37%)	+0.03s (+ 0.11%)	22.73s	22.96s
Compiler-Unions - node (v16.17.1, x64)
Memory used	193,926k (± 0.03%)	192,283k (± 0.73%)	-1,643k (- 0.85%)	191,608k	195,141k
Parse Time	1.80s (± 1.18%)	1.81s (± 0.80%)	+0.02s (+ 0.93%)	1.79s	1.84s
Bind Time	0.85s (± 0.59%)	0.85s (± 0.56%)	-0.00s (- 0.00%)	0.85s	0.86s
Check Time	10.27s (± 0.42%)	10.09s (± 0.72%)	-0.17s (- 1.70%)	10.02s	10.19s
Emit Time	3.03s (± 1.10%)	3.04s (± 0.43%)	+0.00s (+ 0.05%)	3.02s	3.05s
Total Time	15.95s (± 0.29%)	15.79s (± 0.39%)	-0.16s (- 1.03%)	15.72s	15.87s
Monaco - node (v16.17.1, x64)
Memory used	345,126k (± 0.01%)	345,149k (± 0.02%)	+23k (+ 0.01%)	345,068k	345,198k
Parse Time	3.10s (± 1.17%)	3.10s (± 0.53%)	+0.00s (+ 0.05%)	3.08s	3.13s
Bind Time	1.11s (± 0.66%)	1.11s (± 1.28%)	+0.01s (+ 0.57%)	1.09s	1.13s
Check Time	7.88s (± 0.32%)	7.91s (± 0.56%)	+0.03s (+ 0.42%)	7.84s	7.95s
Emit Time	4.53s (± 0.75%)	4.53s (± 0.80%)	+0.01s (+ 0.16%)	4.49s	4.60s
Total Time	16.60s (± 0.46%)	16.65s (± 0.41%)	+0.05s (+ 0.29%)	16.56s	16.76s
TFS - node (v16.17.1, x64)
Memory used	299,929k (± 0.00%)	299,939k (± 0.00%)	+11k (+ 0.00%)	299,922k	299,954k
Parse Time	2.43s (± 0.88%)	2.44s (± 0.84%)	+0.01s (+ 0.37%)	2.40s	2.46s
Bind Time	1.27s (± 0.62%)	1.27s (± 0.68%)	-0.00s (- 0.03%)	1.26s	1.28s
Check Time	7.42s (± 0.36%)	7.44s (± 0.42%)	+0.02s (+ 0.28%)	7.41s	7.48s
Emit Time	4.25s (± 1.22%)	4.26s (± 0.57%)	+0.01s (+ 0.14%)	4.24s	4.29s
Total Time	15.37s (± 0.41%)	15.40s (± 0.26%)	+0.04s (+ 0.24%)	15.35s	15.45s
material-ui - node (v16.17.1, x64)
Memory used	475,698k (± 0.01%)	475,695k (± 0.00%)	-3k (- 0.00%)	475,684k	475,711k
Parse Time	3.66s (± 0.27%)	3.66s (± 0.29%)	+0.00s (+ 0.04%)	3.65s	3.68s
Bind Time	1.02s (± 0.40%)	1.02s (± 0.77%)	-0.00s (- 0.03%)	1.00s	1.03s
Check Time	17.92s (± 0.80%)	17.90s (± 0.44%)	-0.02s (- 0.13%)	17.82s	18.01s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	22.60s (± 0.66%)	22.58s (± 0.38%)	-0.02s (- 0.10%)	22.48s	22.70s
xstate - node (v16.17.1, x64)
Memory used	543,932k (± 0.01%)	543,978k (± 0.01%)	+46k (+ 0.01%)	543,924k	544,042k
Parse Time	4.57s (± 0.44%)	4.58s (± 0.44%)	+0.02s (+ 0.33%)	4.55s	4.60s
Bind Time	1.79s (± 0.86%)	1.79s (± 0.30%)	+0.00s (+ 0.25%)	1.79s	1.80s
Check Time	2.94s (± 0.73%)	2.93s (± 0.75%)	-0.01s (- 0.31%)	2.90s	2.96s
Emit Time	0.08s (± 6.19%)	0.08s (± 6.44%)	+0.00s (+ 1.97%)	0.08s	0.09s
Total Time	9.39s (± 0.30%)	9.39s (± 0.22%)	+0.00s (+ 0.02%)	9.37s	9.43s

System

Machine Name	ts-ci-ubuntu
Platform	linux 5.4.0-135-generic
Architecture	x64
Available Memory	16 GB
Available Memory	15 GB
CPUs	4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz

Hosts

• node (v16.17.1, x64)

Scenarios

• Angular - node (v16.17.1, x64)
• Compiler-Unions - node (v16.17.1, x64)
• Monaco - node (v16.17.1, x64)
• TFS - node (v16.17.1, x64)
• material-ui - node (v16.17.1, x64)
• xstate - node (v16.17.1, x64)

Benchmark	Name	Iterations
Current	52282	6
Baseline	main	6

Developer Information:

Download Benchmark

[DanielRosenwasser]

@typescript-bot top200

[jakebailey]

Before we approve/merge this, can we make sure that cases like those listed in various replies to #48840 (and #52387) are all tested to be working with their desired behaviors?

[ahejlsberg]

@jakebailey This PR doesn't change anything with regards to #48840 and #52387.

[ahejlsberg]

@typescript-bot test top200

[ahejlsberg]

@DanielRosenwasser I don't think there's such a thing as test200 in typescript-bot. The results of test100 are here and, as we discussed, are acceptable.

[jakebailey]

@jakebailey This PR doesn't change anything with regards to #48840 and #52387.

I guess I shouldn't have mentioned the PR as I think it drew the focus away from what I actually wanted checked. I meant that the issue thread (#48840) has some discussion as to what constitutes a top-function-type, which is changing in this PR via isTopSignature.

I'll just pack this PR and test it.

@typescript-bot pack this

[typescript-bot]

Heya @jakebailey, I've started to run the tarball bundle task on this PR at e249498. You can monitor the build here.

[typescript-bot]

Hey @jakebailey, 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/145789/artifacts?artifactName=tgz&fileId=6D0BA089D05A85084C1DC8BBF2F77939D48C21AA802E40F6C6C93CD6D630F5C802&fileName=/typescript-5.0.0-insiders.20230207.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/[email protected]".;

[jakebailey]

Okay, the things I wanted to test appear to work fine, or at least have not changed behavior from 4.9 anyhow.

[DanielRosenwasser]

Would you be able to add tests that demonstrate the ordering among supertypey functions?

type A = (...args: any) => unknown;
type B = (...args: any[]) => unknown;
type C = (...args: never) => unknown;
type D = (...args: never[]) => unknown;
type E = () => unknown;

type FnTypes = A | B | C | D | E;

declare function isSomeFunc<T>(x: any): x is T;

function checkA(f: FnTypes) {
    if (isSomeFunc<A>(f)) {
        f
    }
    else {
        f
    }
    f
}

function checkB(f: FnTypes) {
    if (isSomeFunc<B>(f)) {
        f
    }
    else {
        f
    }
    f
}

function checkC(f: FnTypes) {
    if (isSomeFunc<C>(f)) {
        f
    }
    else {
        f
    }
    f
}

function checkD(f: FnTypes) {
    if (isSomeFunc<D>(f)) {
        f
    }
    else {
        f
    }
    f
}

function checkE(f: FnTypes) {
    if (isSomeFunc<E>(f)) {
        f
    }
    else {
        f
    }
    f
}

[ahejlsberg]

@DanielRosenwasser More tests added.