Fix compilation failure from regex source generator with some lazy loops#118132
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stephentoub merged 1 commit intodotnet:mainfrom Jul 28, 2025
Merged
Fix compilation failure from regex source generator with some lazy loops#118132stephentoub merged 1 commit intodotnet:mainfrom
stephentoub merged 1 commit intodotnet:mainfrom
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Because of some possible complicated control flow, the compiler thinks these variables are not deterministically initialized.
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Pull Request Overview
This PR fixes a compilation failure in the regex source generator that occurs with specific lazy loop constructs. The issue stems from the compiler's inability to determine that certain variables are definitively initialized due to complex control flow patterns in generated code.
- Moves variable declarations for lazy loop position tracking variables to a more appropriate scope
- Adds comprehensive test cases to verify the fix works for problematic regex patterns with lazy loops and alternations
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/libraries/System.Text.RegularExpressions/gen/RegexGenerator.Emitter.cs | Fixes variable initialization issue by moving declarations to additionalDeclarations and separating assignment |
| src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/Regex.Match.Tests.cs | Adds test cases for regex patterns that previously caused compilation failures |
src/libraries/System.Text.RegularExpressions/gen/RegexGenerator.Emitter.cs
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MihaZupan
approved these changes
Jul 28, 2025
This was referenced Jul 28, 2025
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Because of some possible complicated control flow, the compiler thinks these variables are not deterministically initialized.
This repros back to .NET 7 when the source generator was first introduced. It's just a really rare set of constructs that triggers this and so we haven't seen it come up before.