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TypeScript 7.0.2 scanner does not advance on bare hash #64490
Description
Version
TypeScript 7.0.2
Reproduction
npm install typescript@7.0.2
node --input-type=module -e 'import { createScanner, LanguageVariant, SyntaxKind } from "typescript/unstable/ast"; const scanner=createScanner(false,LanguageVariant.Standard,"#"); for(let i=0;i<2;i++){const token=scanner.scan(); console.log(SyntaxKind[token], scanner.getTokenStart(), scanner.getTokenEnd())}'Actual output:
PrivateIdentifier 0 0
PrivateIdentifier 0 0
The scanner repeatedly returns the same non-EOF token without moving from offset 0. A loop that scans until EndOfFile therefore never terminates on a bare # (including when a later comment appears in the same source). Expected: scanning malformed input advances or returns EOF so consumers can terminate. A bare # followed by an identifier scans normally.
Activity
RyanCavanaugh commentedon Sep 28, 2026
Just calling
scanin a loop isn't going to give you anything meaningful; this isn't how to use that functiontypescript-automation commentedon Oct 1, 2026
This issue has been marked as "Unactionable" and has seen no recent activity. It has been automatically closed for house-keeping purposes.
YevheniiKotyrlo commentedon Oct 22, 2026
The 6.0.3 and Go scanners both move past the
#here: 6.0.3 increments inside its diagnostic call,error(Diagnostics.Invalid_character, pos++, charSize(ch)), and Go'sscanIdentifier(1, …)consumes it before reporting the same error. Theunstable/astcopy reports no diagnostics, and thepos++went with the call (scanner.ts), so as I read it this is a gap in the port, like #64135. Withpos++;aftertokenValue = "#";, the reproduction above printsPrivateIdentifier 0 1and thenEndOfFile 1 1.