Source Generator generated wrong code for regex `(?<=(abc)+?123)a` in .NET10

[longxya]

Description

visual studio 2026 Insiders given an error No such label 'LazyLoopBacktrack' within the scope of the goto statement for generated regex (?<=(abc)+?123)a and xxx(?<=(abc)+?123)a.

But work normally for generated regex (?<=(abc)+?123) and (?<=(abc)+?)a.

Reproduction Steps

internal partial class RegexTester
{
	[GeneratedRegex(@"(?<=(abc)+?123)a")]
	internal static partial Regex regexTestGenerate();
}

Expected behavior

Generate executable code.

Actual behavior

No such label 'LazyLoopBacktrack' within the scope of the goto statement.
Because in the source generated code, the LazyLoopBacktrack: and goto LazyLoopBacktrack; are separated by two layers of curly braces

Regression?

No response

Known Workarounds

No response

Configuration

No response

Other information

No response

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[eiriktsarpalis]

Is this a regression from .NET 9?

[longxya]

Is this a regression from .NET 9?

Source-generated code for (?<=(abc)+?123)a can run in .NET9, but the result may have some mistakes.

Similar compiled regex and source-generated regex exhibit such behavior(issue#117651) in .NET9.