Error on replacement character only in top-level scanning

[jakebailey]

This one came to me in the shower; everyone with this character "legally" in their files can only have put them into string literals or comments. If we just check this at the top level scan function, we'll never have a false positive because it'd definitely be a parse error at runtime. If any of the other scanner functions (e.g. scanIdentifier) see this character code, they're going to bail out anyway because it's an unexpected character, then this new case will hit.

I could also modify this to check only at the start of a file, but since we're now back in the switch-case where we process all of the other scanning, this isn't actually inefficient anymore.

Fixes #57930

[jakebailey]

@typescript-bot test it

[typescript-bot]

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
test top400	✅ Started	✅ Results
user test this	✅ Started	✅ Results
run dt	✅ Started
perf test this faster	✅ Started	👀 Results

[typescript-bot]

@jakebailey Here are the results of running the user tests comparing main and refs/pull/58227/merge:

Everything looks good!

[typescript-bot]

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

Here they are:

tsc

Comparison Report - baseline..pr

Metric	baseline	pr	Delta	Best	Worst	p-value
Angular - node (v18.15.0, x64)
Memory used	297,030k (± 0.01%)	297,024k (± 0.00%)	~	297,009k	297,037k	p=0.630 n=6
Parse Time	4.05s (± 0.30%)	4.05s (± 0.43%)	~	4.02s	4.07s	p=0.655 n=6
Bind Time	1.21s (± 0.69%)	1.22s (± 0.80%)	~	1.21s	1.24s	p=0.195 n=6
Check Time	12.13s (± 0.39%)	12.11s (± 0.39%)	~	12.05s	12.17s	p=0.630 n=6
Emit Time	10.51s (± 0.43%)	10.49s (± 0.39%)	~	10.44s	10.54s	p=0.373 n=6
Total Time	27.90s (± 0.15%)	27.86s (± 0.16%)	~	27.83s	27.95s	p=0.148 n=6
Compiler-Unions - node (v18.15.0, x64)
Memory used	192,423k (± 0.76%)	193,049k (± 0.96%)	~	191,738k	195,489k	p=0.936 n=6
Parse Time	1.36s (± 1.21%)	1.35s (± 0.00%)	~	1.35s	1.35s	p=0.293 n=6
Bind Time	0.72s (± 0.00%)	0.72s (± 0.00%)	~	0.72s	0.72s	p=1.000 n=6
Check Time	9.58s (± 0.41%)	9.52s (± 0.27%)	-0.06s (- 0.59%)	9.48s	9.55s	p=0.024 n=6
Emit Time	2.62s (± 0.64%)	2.63s (± 0.64%)	~	2.61s	2.65s	p=0.463 n=6
Total Time	14.27s (± 0.21%)	14.22s (± 0.18%)	-0.05s (- 0.35%)	14.19s	14.26s	p=0.019 n=6
mui-docs - node (v18.15.0, x64)
Memory used	1,751,177k (± 0.00%)	1,751,143k (± 0.00%)	~	1,751,098k	1,751,208k	p=0.298 n=6
Parse Time	6.84s (± 0.53%)	6.81s (± 0.51%)	~	6.77s	6.87s	p=0.293 n=6
Bind Time	2.29s (± 0.60%)	2.30s (± 1.58%)	~	2.27s	2.36s	p=0.511 n=6
Check Time	56.74s (± 0.22%)	56.69s (± 0.49%)	~	56.37s	57.14s	p=0.520 n=6
Emit Time	0.14s (± 4.51%)	0.14s (± 0.00%)	~	0.14s	0.14s	p=1.000 n=6
Total Time	66.01s (± 0.19%)	65.94s (± 0.47%)	~	65.56s	66.36s	p=0.810 n=6
self-build-src - node (v18.15.0, x64)
Memory used	2,307,811k (± 0.03%)	2,307,417k (± 0.02%)	~	2,306,858k	2,308,188k	p=0.230 n=6
Parse Time	5.00s (± 0.81%)	4.98s (± 0.89%)	~	4.93s	5.06s	p=0.423 n=6
Bind Time	1.87s (± 1.14%)	1.88s (± 1.05%)	~	1.85s	1.91s	p=0.681 n=6
Check Time	33.83s (± 0.35%)	33.88s (± 0.21%)	~	33.77s	33.99s	p=0.471 n=6
Emit Time	2.66s (± 1.29%)	2.67s (± 3.31%)	~	2.60s	2.84s	p=0.748 n=6
Total Time	43.38s (± 0.30%)	43.43s (± 0.45%)	~	43.26s	43.76s	p=1.000 n=6
self-build-src-public-api - node (v18.15.0, x64)
Memory used	2,382,584k (± 0.02%)	2,382,321k (± 0.01%)	~	2,381,851k	2,382,823k	p=0.230 n=6
Parse Time	5.09s (± 0.46%)	5.14s (± 0.79%)	~	5.09s	5.19s	p=0.128 n=6
Bind Time	1.72s (± 1.10%)	1.72s (± 0.73%)	~	1.70s	1.73s	p=1.000 n=6
Check Time	34.11s (± 0.34%)	34.13s (± 0.54%)	~	33.95s	34.48s	p=1.000 n=6
Emit Time	2.70s (± 0.41%)	2.70s (± 1.16%)	~	2.66s	2.74s	p=0.466 n=6
Total Time	43.66s (± 0.27%)	43.73s (± 0.52%)	~	43.45s	44.14s	p=0.689 n=6
self-compiler - node (v18.15.0, x64)
Memory used	419,427k (± 0.01%)	419,430k (± 0.01%)	~	419,388k	419,472k	p=1.000 n=6
Parse Time	4.19s (± 0.81%)	4.21s (± 0.49%)	~	4.17s	4.23s	p=0.744 n=6
Bind Time	1.60s (± 1.62%)	1.58s (± 0.96%)	~	1.56s	1.60s	p=0.463 n=6
Check Time	22.28s (± 0.46%)	22.35s (± 0.38%)	~	22.28s	22.49s	p=0.520 n=6
Emit Time	1.70s (± 1.26%)	1.70s (± 1.16%)	~	1.66s	1.71s	p=1.000 n=6
Total Time	29.76s (± 0.21%)	29.84s (± 0.35%)	~	29.74s	30.01s	p=0.334 n=6
ts-pre-modules - node (v18.15.0, x64)
Memory used	369,003k (± 0.01%)	369,006k (± 0.02%)	~	368,946k	369,188k	p=0.199 n=6
Parse Time	3.64s (± 0.22%)	3.68s (± 0.82%)	+0.03s (+ 0.91%)	3.64s	3.72s	p=0.049 n=6
Bind Time	1.91s (± 1.46%)	1.99s (± 0.86%)	🔻+0.08s (+ 4.09%)	1.97s	2.01s	p=0.005 n=6
Check Time	19.41s (± 0.47%)	19.40s (± 0.21%)	~	19.36s	19.48s	p=0.419 n=6
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	~	0.00s	0.00s	p=1.000 n=6
Total Time	24.96s (± 0.30%)	25.07s (± 0.27%)	+0.11s (+ 0.43%)	25.00s	25.19s	p=0.031 n=6
vscode - node (v18.15.0, x64)
Memory used	2,915,755k (± 0.00%)	2,915,672k (± 0.01%)	~	2,915,101k	2,915,852k	p=0.936 n=6
Parse Time	16.50s (± 0.28%)	16.52s (± 0.53%)	~	16.40s	16.65s	p=1.000 n=6
Bind Time	4.95s (± 0.66%)	4.94s (± 0.38%)	~	4.92s	4.97s	p=0.685 n=6
Check Time	88.26s (± 0.11%)	88.25s (± 0.27%)	~	87.96s	88.61s	p=0.936 n=6
Emit Time	23.79s (± 0.81%)	25.09s (± 8.02%)	~	23.74s	28.34s	p=0.261 n=6
Total Time	133.50s (± 0.20%)	134.79s (± 1.43%)	~	133.36s	137.93s	p=0.128 n=6
webpack - node (v18.15.0, x64)
Memory used	409,393k (± 0.01%)	409,468k (± 0.02%)	~	409,355k	409,593k	p=0.064 n=6
Parse Time	3.89s (± 0.66%)	3.95s (± 1.21%)	~	3.90s	4.01s	p=0.076 n=6
Bind Time	1.65s (± 0.66%)	1.66s (± 0.82%)	~	1.64s	1.68s	p=0.554 n=6
Check Time	16.94s (± 0.34%)	16.97s (± 0.38%)	~	16.88s	17.04s	p=0.575 n=6
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	~	0.00s	0.00s	p=1.000 n=6
Total Time	22.49s (± 0.28%)	22.57s (± 0.28%)	~	22.47s	22.66s	p=0.065 n=6
xstate-main - node (v18.15.0, x64)
Memory used	458,994k (± 0.01%)	458,999k (± 0.01%)	~	458,942k	459,049k	p=0.810 n=6
Parse Time	3.99s (± 0.22%)	4.01s (± 0.48%)	+0.02s (+ 0.54%)	4.00s	4.05s	p=0.015 n=6
Bind Time	1.46s (± 0.71%)	1.45s (± 1.07%)	~	1.43s	1.47s	p=0.182 n=6
Check Time	22.29s (± 0.22%)	22.28s (± 0.63%)	~	22.03s	22.42s	p=1.000 n=6
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	~	0.00s	0.00s	p=1.000 n=6
Total Time	27.75s (± 0.14%)	27.75s (± 0.58%)	~	27.46s	27.92s	p=0.688 n=6

System info unknown

Hosts

• node (v18.15.0, x64)

Scenarios

• Angular - node (v18.15.0, x64)
• Compiler-Unions - node (v18.15.0, x64)
• mui-docs - node (v18.15.0, x64)
• self-build-src - node (v18.15.0, x64)
• self-build-src-public-api - node (v18.15.0, x64)
• self-compiler - node (v18.15.0, x64)
• ts-pre-modules - node (v18.15.0, x64)
• vscode - node (v18.15.0, x64)
• webpack - node (v18.15.0, x64)
• xstate-main - node (v18.15.0, x64)

Benchmark	Name	Iterations
Current	pr	6
Baseline	baseline	6

Developer Information:

Download Benchmarks

[jakebailey]

@typescript-bot perf test this

[typescript-bot]

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
perf test this	✅ Started	👀 Results

[typescript-bot]

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

Here they are:

tsc

Comparison Report - baseline..pr

Metric	baseline	pr	Delta	Best	Worst	p-value
Angular - node (v18.15.0, x64)
Memory used	297,031k (± 0.01%)	297,036k (± 0.01%)	~	296,992k	297,057k	p=0.376 n=6
Parse Time	4.04s (± 0.34%)	4.05s (± 0.30%)	~	4.03s	4.06s	p=0.868 n=6
Bind Time	1.22s (± 0.80%)	1.22s (± 0.67%)	~	1.21s	1.23s	p=0.394 n=6
Check Time	12.12s (± 0.17%)	12.13s (± 0.28%)	~	12.10s	12.19s	p=1.000 n=6
Emit Time	10.53s (± 0.50%)	10.49s (± 0.29%)	~	10.46s	10.54s	p=0.334 n=6
Total Time	27.91s (± 0.21%)	27.88s (± 0.20%)	~	27.82s	27.97s	p=0.296 n=6
Compiler-Unions - node (v18.15.0, x64)
Memory used	191,770k (± 0.06%)	193,024k (± 0.97%)	~	191,792k	195,472k	p=0.173 n=6
Parse Time	2.02s (± 0.98%)	2.01s (± 1.65%)	~	1.95s	2.04s	p=1.000 n=6
Bind Time	1.07s (± 1.61%)	1.07s (± 0.97%)	~	1.05s	1.08s	p=0.870 n=6
Check Time	13.99s (± 0.39%)	13.97s (± 0.48%)	~	13.88s	14.05s	p=0.689 n=6
Emit Time	3.91s (± 3.03%)	3.85s (± 0.48%)	~	3.82s	3.87s	p=0.293 n=6
Total Time	20.98s (± 0.44%)	20.90s (± 0.43%)	~	20.76s	20.99s	p=0.196 n=6
mui-docs - node (v18.15.0, x64)
Memory used	1,751,097k (± 0.00%)	1,751,084k (± 0.00%)	~	1,751,029k	1,751,137k	p=0.521 n=6
Parse Time	9.95s (± 0.42%)	9.93s (± 0.33%)	~	9.88s	9.96s	p=0.258 n=6
Bind Time	3.33s (± 0.49%)	3.32s (± 0.62%)	~	3.29s	3.34s	p=0.466 n=6
Check Time	82.10s (± 0.38%)	81.83s (± 0.31%)	~	81.51s	82.11s	p=0.199 n=6
Emit Time	0.20s (± 2.62%)	0.20s (± 2.06%)	~	0.19s	0.20s	p=0.595 n=6
Total Time	95.57s (± 0.30%)	95.28s (± 0.30%)	~	94.94s	95.59s	p=0.173 n=6
self-build-src - node (v18.15.0, x64)
Memory used	2,308,046k (± 0.04%)	2,307,590k (± 0.03%)	~	2,306,487k	2,308,575k	p=0.471 n=6
Parse Time	7.39s (± 0.76%)	7.39s (± 0.88%)	~	7.32s	7.50s	p=0.689 n=6
Bind Time	2.76s (± 0.30%)	2.74s (± 1.02%)	~	2.71s	2.79s	p=0.064 n=6
Check Time	49.37s (± 0.98%)	49.31s (± 0.61%)	~	49.03s	49.83s	p=0.936 n=6
Emit Time	3.93s (± 2.37%)	3.91s (± 2.85%)	~	3.80s	4.10s	p=0.748 n=6
Total Time	63.48s (± 0.79%)	63.38s (± 0.59%)	~	62.99s	63.96s	p=0.689 n=6
self-build-src-public-api - node (v18.15.0, x64)
Memory used	2,382,814k (± 0.03%)	2,382,540k (± 0.04%)	~	2,381,419k	2,383,665k	p=0.471 n=6
Parse Time	6.19s (± 0.60%)	6.19s (± 0.87%)	~	6.12s	6.27s	p=0.936 n=6
Bind Time	2.07s (± 0.94%)	2.07s (± 1.31%)	~	2.03s	2.11s	p=1.000 n=6
Check Time	40.17s (± 0.23%)	40.22s (± 0.60%)	~	39.86s	40.58s	p=0.689 n=6
Emit Time	3.20s (± 1.93%)	3.15s (± 2.57%)	~	3.06s	3.25s	p=0.261 n=6
Total Time	51.63s (± 0.21%)	51.66s (± 0.57%)	~	51.17s	51.92s	p=0.575 n=6
self-compiler - node (v18.15.0, x64)
Memory used	419,495k (± 0.02%)	419,456k (± 0.01%)	~	419,404k	419,539k	p=0.297 n=6
Parse Time	4.17s (± 1.95%)	4.21s (± 0.28%)	~	4.19s	4.22s	p=0.513 n=6
Bind Time	1.62s (± 5.19%)	1.58s (± 0.96%)	~	1.56s	1.60s	p=0.124 n=6
Check Time	22.25s (± 0.20%)	22.28s (± 0.44%)	~	22.13s	22.39s	p=0.377 n=6
Emit Time	1.71s (± 1.67%)	1.72s (± 1.21%)	~	1.68s	1.73s	p=0.683 n=6
Total Time	29.76s (± 0.26%)	29.78s (± 0.26%)	~	29.67s	29.89s	p=0.421 n=6
ts-pre-modules - node (v18.15.0, x64)
Memory used	368,947k (± 0.01%)	368,980k (± 0.01%)	~	368,938k	369,024k	p=0.261 n=6
Parse Time	2.97s (± 1.18%)	2.96s (± 0.82%)	~	2.91s	2.98s	p=0.629 n=6
Bind Time	1.58s (± 1.85%)	1.63s (± 1.01%)	+0.04s (+ 2.74%)	1.60s	1.64s	p=0.015 n=6
Check Time	15.69s (± 0.30%)	15.70s (± 0.30%)	~	15.63s	15.74s	p=0.466 n=6
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	~	0.00s	0.00s	p=1.000 n=6
Total Time	20.23s (± 0.36%)	20.28s (± 0.35%)	~	20.17s	20.34s	p=0.227 n=6
vscode - node (v18.15.0, x64)
Memory used	2,915,712k (± 0.00%)	2,915,600k (± 0.01%)	~	2,915,374k	2,915,745k	p=0.128 n=6
Parse Time	13.41s (± 0.38%)	13.40s (± 0.20%)	~	13.37s	13.43s	p=0.469 n=6
Bind Time	4.07s (± 0.30%)	4.05s (± 0.30%)	~	4.04s	4.07s	p=0.182 n=6
Check Time	72.70s (± 0.44%)	72.57s (± 0.22%)	~	72.35s	72.76s	p=0.575 n=6
Emit Time	19.54s (± 0.64%)	21.45s (± 9.71%)	~	19.48s	23.37s	p=0.173 n=6
Total Time	109.72s (± 0.39%)	111.46s (± 1.83%)	~	109.40s	113.52s	p=0.230 n=6
webpack - node (v18.15.0, x64)
Memory used	409,392k (± 0.01%)	409,343k (± 0.02%)	~	409,271k	409,518k	p=0.128 n=6
Parse Time	3.26s (± 0.83%)	3.24s (± 0.79%)	~	3.20s	3.26s	p=0.511 n=6
Bind Time	1.38s (± 0.75%)	1.38s (± 0.65%)	~	1.37s	1.39s	p=0.673 n=6
Check Time	14.42s (± 0.20%)	14.40s (± 0.30%)	~	14.35s	14.45s	p=0.467 n=6
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	~	0.00s	0.00s	p=1.000 n=6
Total Time	19.06s (± 0.16%)	19.02s (± 0.18%)	~	18.97s	19.06s	p=0.126 n=6
xstate-main - node (v18.15.0, x64)
Memory used	458,921k (± 0.01%)	458,930k (± 0.01%)	~	458,892k	458,980k	p=0.689 n=6
Parse Time	2.69s (± 0.55%)	2.69s (± 0.43%)	~	2.67s	2.70s	p=0.666 n=6
Bind Time	0.98s (± 0.77%)	0.98s (± 0.00%)	~	0.98s	0.98s	p=0.598 n=6
Check Time	15.31s (± 0.20%)	15.35s (± 0.38%)	~	15.24s	15.40s	p=0.065 n=6
Emit Time	0.00s (± 0.00%)	0.00s (± 0.00%)	~	0.00s	0.00s	p=1.000 n=6
Total Time	18.98s (± 0.19%)	19.03s (± 0.39%)	~	18.88s	19.08s	p=0.065 n=6

System info unknown

Hosts

• node (v18.15.0, x64)

Scenarios

• Angular - node (v18.15.0, x64)
• Compiler-Unions - node (v18.15.0, x64)
• mui-docs - node (v18.15.0, x64)
• self-build-src - node (v18.15.0, x64)
• self-build-src-public-api - node (v18.15.0, x64)
• self-compiler - node (v18.15.0, x64)
• ts-pre-modules - node (v18.15.0, x64)
• vscode - node (v18.15.0, x64)
• webpack - node (v18.15.0, x64)
• xstate-main - node (v18.15.0, x64)

Benchmark	Name	Iterations
Current	pr	6
Baseline	baseline	6

tsserver

Comparison Report - baseline..pr

Metric	baseline	pr	Delta	Best	Worst	p-value
Compiler-UnionsTSServer - node (v18.15.0, x64)
Req 1 - updateOpen	2,341ms (± 0.91%)	2,357ms (± 0.64%)	~	2,340ms	2,382ms	p=0.128 n=6
Req 2 - geterr	5,191ms (± 2.38%)	5,192ms (± 1.42%)	~	5,109ms	5,296ms	p=0.810 n=6
Req 3 - references	284ms (± 0.78%)	286ms (± 2.08%)	~	280ms	297ms	p=0.935 n=6
Req 4 - navto	227ms (± 1.06%)	227ms (± 1.00%)	~	224ms	230ms	p=0.870 n=6
Req 5 - completionInfo count	1,357 (± 0.00%)	1,357 (± 0.00%)	~	1,357	1,357	p=1.000 n=6
Req 5 - completionInfo	83ms (± 8.58%)	83ms (± 8.81%)	~	76ms	92ms	p=0.933 n=6
CompilerTSServer - node (v18.15.0, x64)
Req 1 - updateOpen	2,486ms (± 0.95%)	2,481ms (± 0.81%)	~	2,449ms	2,509ms	p=0.936 n=6
Req 2 - geterr	3,953ms (± 1.40%)	3,912ms (± 1.98%)	~	3,837ms	3,994ms	p=0.748 n=6
Req 3 - references	299ms (± 1.55%)	303ms (± 1.95%)	~	296ms	310ms	p=0.374 n=6
Req 4 - navto	227ms (± 0.48%)	228ms (± 0.36%)	~	227ms	229ms	p=0.197 n=6
Req 5 - completionInfo count	1,519 (± 0.00%)	1,519 (± 0.00%)	~	1,519	1,519	p=1.000 n=6
Req 5 - completionInfo	76ms (± 6.23%)	79ms (± 6.97%)	~	72ms	84ms	p=0.413 n=6
xstateTSServer - node (v18.15.0, x64)
Req 1 - updateOpen	3,918ms (± 0.27%)	3,911ms (± 0.39%)	~	3,896ms	3,930ms	p=0.470 n=6
Req 2 - geterr	2,215ms (± 1.08%)	2,198ms (± 1.00%)	~	2,171ms	2,225ms	p=0.173 n=6
Req 3 - references	182ms (± 2.26%)	182ms (± 0.73%)	~	181ms	184ms	p=0.807 n=6
Req 4 - navto	530ms (± 0.88%)	533ms (± 1.57%)	~	520ms	543ms	p=0.520 n=6
Req 5 - completionInfo count	2,079 (± 0.00%)	2,079 (± 0.00%)	~	2,079	2,079	p=1.000 n=6
Req 5 - completionInfo	448ms (± 1.78%)	450ms (± 1.26%)	~	444ms	458ms	p=0.628 n=6

System info unknown

Hosts

• node (v18.15.0, x64)

Scenarios

• CompilerTSServer - node (v18.15.0, x64)
• Compiler-UnionsTSServer - node (v18.15.0, x64)
• xstateTSServer - node (v18.15.0, x64)

Benchmark	Name	Iterations
Current	pr	6
Baseline	baseline	6

startup

Comparison Report - baseline..pr

Metric	baseline	pr	Delta	Best	Worst	p-value
tsc-startup - node (v18.15.0, x64)
Execution time	154.57ms (± 0.18%)	154.39ms (± 0.19%)	-0.19ms (- 0.12%)	153.34ms	159.79ms	p=0.000 n=600
tsserver-startup - node (v18.15.0, x64)
Execution time	230.15ms (± 0.17%)	230.23ms (± 0.15%)	+0.08ms (+ 0.03%)	228.69ms	235.09ms	p=0.004 n=600
tsserverlibrary-startup - node (v18.15.0, x64)
Execution time	224.36ms (± 0.16%)	224.13ms (± 0.16%)	-0.23ms (- 0.10%)	222.66ms	231.05ms	p=0.000 n=600
typescript-startup - node (v18.15.0, x64)
Execution time	224.28ms (± 0.16%)	224.30ms (± 0.15%)	~	222.79ms	227.15ms	p=0.442 n=600

System info unknown

Hosts

• node (v18.15.0, x64)

Scenarios

• tsc-startup - node (v18.15.0, x64)
• tsserver-startup - node (v18.15.0, x64)
• tsserverlibrary-startup - node (v18.15.0, x64)
• typescript-startup - node (v18.15.0, x64)

Benchmark	Name	Iterations
Current	pr	6
Baseline	baseline	6

Developer Information:

Download Benchmarks

[typescript-bot]

@jakebailey Here are the results of running the top 400 repos comparing main and refs/pull/58227/merge:

Everything looks good!

[jakebailey]

@typescript-bot run dt

[typescript-bot]

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
run dt	✅ Started	✅ Results

[typescript-bot]

Hey @jakebailey, the results of running the DT tests are ready.

Everything looks the same!

You can check the log here.

[wooorm]

Thanks Jake!