Merge pull request #90266 from bolinfest/match-only-at-line-start

Fixes microsoft/monaco-editor#1818: check matchOnlyAtLineStart when e…

src/vs/editor/standalone/common/monarch/monarchLexer.ts

@@ -501,7 +501,7 @@ export class MonarchTokenizer implements modes.ITokenizationSupport {
 			}
 
 			let result = line.search(regex);
-			if (result === -1) {
+			if (result === -1 || (result !== 0 && rule.matchOnlyAtLineStart)) {
 				continue;
 			}