Discriminant of type never should never be matched

[ahejlsberg]

Fixes #50716.

[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'm starting to run the diff-based user code test suite on this PR at a2a00d5. Hold tight - I'll update this comment with the log link once the build has been queued.

Update: The results are in!

[typescript-bot]

Heya @ahejlsberg, I've started to run the extended test suite on this PR at a2a00d5. You can monitor the build here.

[typescript-bot]

Heya @ahejlsberg, I've started to run the parallelized Definitely Typed test suite on this PR at a2a00d5. You can monitor the build here.

[typescript-bot]

Heya @ahejlsberg, I've started to run the abridged perf test suite on this PR at a2a00d5. You can monitor the build here.

Update: The results are in!

[typescript-bot]

Heya @ahejlsberg, I'm starting to run the diff-based top-repos suite on this PR at a2a00d5. Hold tight - I'll update this comment with the log link once the build has been queued.

Update: The results are in!

[typescript-bot]

@ahejlsberg Here are the results of running the user test suite comparing main and refs/pull/50755/merge:

Everything looks good!

[typescript-bot]

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

Here they are:

Comparison Report - main..50755

Metric	main	50755	Delta	Best	Worst
Angular - node (v14.15.1, x64)
Memory used	338,915k (± 0.01%)	338,943k (± 0.01%)	+28k (+ 0.01%)	338,894k	339,028k
Parse Time	2.05s (± 0.36%)	2.06s (± 0.43%)	+0.01s (+ 0.44%)	2.03s	2.07s
Bind Time	0.80s (± 0.70%)	0.80s (± 0.42%)	+0.00s (+ 0.25%)	0.79s	0.81s
Check Time	5.83s (± 0.37%)	5.85s (± 0.48%)	+0.02s (+ 0.31%)	5.80s	5.94s
Emit Time	6.19s (± 0.57%)	6.20s (± 0.57%)	+0.01s (+ 0.24%)	6.14s	6.27s
Total Time	14.87s (± 0.32%)	14.92s (± 0.36%)	+0.05s (+ 0.32%)	14.79s	15.02s
Compiler-Unions - node (v14.15.1, x64)
Memory used	190,138k (± 0.01%)	190,130k (± 0.01%)	-9k (- 0.00%)	190,062k	190,172k
Parse Time	0.85s (± 0.53%)	0.85s (± 0.99%)	+0.00s (+ 0.35%)	0.84s	0.88s
Bind Time	0.49s (± 0.91%)	0.49s (± 0.98%)	-0.00s (- 0.20%)	0.48s	0.50s
Check Time	6.72s (± 0.47%)	6.71s (± 0.55%)	-0.01s (- 0.10%)	6.67s	6.83s
Emit Time	2.37s (± 0.75%)	2.36s (± 0.76%)	-0.01s (- 0.55%)	2.32s	2.39s
Total Time	10.43s (± 0.33%)	10.41s (± 0.45%)	-0.01s (- 0.13%)	10.34s	10.57s
Monaco - node (v14.15.1, x64)
Memory used	326,576k (± 0.01%)	326,578k (± 0.01%)	+2k (+ 0.00%)	326,508k	326,617k
Parse Time	1.58s (± 0.30%)	1.59s (± 0.91%)	+0.01s (+ 0.70%)	1.56s	1.63s
Bind Time	0.72s (± 0.69%)	0.73s (± 0.64%)	+0.01s (+ 0.69%)	0.72s	0.74s
Check Time	5.69s (± 0.44%)	5.74s (± 0.55%)	+0.05s (+ 0.95%)	5.67s	5.82s
Emit Time	3.31s (± 0.61%)	3.33s (± 0.41%)	+0.02s (+ 0.63%)	3.30s	3.35s
Total Time	11.30s (± 0.39%)	11.39s (± 0.31%)	+0.09s (+ 0.79%)	11.32s	11.46s
TFS - node (v14.15.1, x64)
Memory used	289,697k (± 0.01%)	289,687k (± 0.01%)	-10k (- 0.00%)	289,623k	289,732k
Parse Time	1.30s (± 0.94%)	1.30s (± 0.47%)	-0.00s (- 0.15%)	1.29s	1.31s
Bind Time	0.80s (± 1.12%)	0.78s (± 1.78%)	-0.02s (- 1.88%)	0.74s	0.80s
Check Time	5.34s (± 0.49%)	5.37s (± 0.50%)	+0.03s (+ 0.51%)	5.29s	5.43s
Emit Time	3.54s (± 0.47%)	3.53s (± 0.87%)	-0.01s (- 0.31%)	3.47s	3.60s
Total Time	10.98s (± 0.32%)	10.98s (± 0.47%)	-0.00s (- 0.02%)	10.86s	11.11s
material-ui - node (v14.15.1, x64)
Memory used	436,648k (± 0.01%)	436,580k (± 0.04%)	-68k (- 0.02%)	435,917k	436,703k
Parse Time	1.86s (± 0.55%)	1.88s (± 0.32%)	+0.02s (+ 0.91%)	1.86s	1.89s
Bind Time	0.58s (± 0.58%)	0.58s (± 0.99%)	0.00s ( 0.00%)	0.57s	0.60s
Check Time	12.82s (± 0.53%)	12.95s (± 0.63%)	+0.13s (+ 0.99%)	12.74s	13.10s
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	0.00s ( NaN%)	0.00s	0.00s
Total Time	15.27s (± 0.46%)	15.41s (± 0.57%)	+0.14s (+ 0.94%)	15.18s	15.56s
xstate - node (v14.15.1, x64)
Memory used	546,979k (± 0.00%)	546,984k (± 0.00%)	+5k (+ 0.00%)	546,957k	547,041k
Parse Time	2.60s (± 0.32%)	2.62s (± 0.60%)	+0.02s (+ 0.85%)	2.59s	2.65s
Bind Time	0.97s (± 0.91%)	0.98s (± 0.96%)	+0.01s (+ 0.72%)	0.96s	1.00s
Check Time	1.51s (± 0.34%)	1.53s (± 0.72%)	+0.02s (+ 1.06%)	1.50s	1.55s
Emit Time	0.07s (± 0.00%)	0.07s (± 0.00%)	0.00s ( 0.00%)	0.07s	0.07s
Total Time	5.15s (± 0.19%)	5.20s (± 0.47%)	+0.05s (+ 0.91%)	5.15s	5.26s

System

Machine Name	ts-ci-ubuntu
Platform	linux 4.4.0-210-generic
Architecture	x64
Available Memory	16 GB
Available Memory	15 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)
• xstate - node (v14.15.1, x64)

Benchmark	Name	Iterations
Current	50755	10
Baseline	main	10

Developer Information:

Download Benchmark

[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.

[andrewbranch]

Oops

[typescript-bot]

@ahejlsberg Here are the results of running the top-repos suite comparing main and refs/pull/50755/merge:

Everything looks good!