Fix SYSLIB1045 code fixer generating duplicate MyRegex names across partial class declarations by danmoseley · Pull Request #124698 · dotnet/runtime

danmoseley · 2026-02-21T04:37:17Z

Problem

When the SYSLIB1045 BatchFixer applies multiple code fixes concurrently to separate partial class declarations, each fix independently checks existing members via the semantic model. Since all fixers see the original compilation (before any fix is applied), they all conclude MyRegex is available and generate duplicate property names, causing CS0756.

Fix

In UpgradeToGeneratedRegexCodeFixer.CreateGeneratedRegexProperty, after finding the first available name via the semantic model, the new CountPrecedingRegexCallSites helper scans all DeclaringSyntaxReferences of the containing type for Regex constructor/static-method call sites that would also generate new property names. These are sorted deterministically (by file path, then span position). The current node's index in that sorted list determines how many names to skip, giving each concurrent fixer a unique name.

Test

Added CodeFixerGeneratesUniqueNamesAcrossPartialClassDeclarations — two new Regex(...) calls in separate partial class declarations of the same type, verifying MyRegex and MyRegex1 are generated. Verified the test fails without the fix (both declarations produce MyRegex).

Copilot

Pull request overview

This PR fixes issue #77409 where the SYSLIB1045 code fixer (which converts Regex constructor calls to GeneratedRegex) generates duplicate property names when applied to multiple partial class declarations via batch fixing. The root cause is that concurrent batch fixers all see the original compilation state before any fixes are applied, causing them to independently conclude that the same name (e.g., "MyRegex") is available.

The PR also includes two unrelated changes: a performance optimization using SetSearchValues for the regex interpreter, and a regression test for character class encoding validation.

Changes:

Adds CountPrecedingRegexCallSites helper to deterministically order all Regex call sites across partial declarations by file path and position, allowing each concurrent fixer to offset its name generation
Implements SetSearchValues optimization in the regex interpreter for vectorized character class matching
Adds validation for character class encoding before calling GetSetChars to prevent IndexOutOfRangeException on malformed input

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs	Adds CountPrecedingRegexCallSites helper and name offset logic to prevent duplicate names in batch fixing
src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/UpgradeToGeneratedRegexAnalyzerTests.cs	Adds test validating unique name generation across partial class declarations
src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexInterpreterCode.cs	Adds SetSearchValues precomputation and character class encoding validation (unrelated optimization)
src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexInterpreter.cs	Uses SetSearchValues for vectorized Set opcode matching (unrelated optimization)
src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/Regex.Match.Tests.cs	Adds regression test for Multi literal resembling character class encoding (unrelated)

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs

...System.Text.RegularExpressions/tests/FunctionalTests/UpgradeToGeneratedRegexAnalyzerTests.cs

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs

...es/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexInterpreterCode.cs

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs

...System.Text.RegularExpressions/tests/FunctionalTests/UpgradeToGeneratedRegexAnalyzerTests.cs

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs

...System.Text.RegularExpressions/tests/FunctionalTests/UpgradeToGeneratedRegexAnalyzerTests.cs

…artial class declarations When the BatchFixer applies multiple fixes concurrently, each fix sees the original compilation and independently picks the same first-available name. This causes CS0756 when two partial declarations of the same class both contain Regex calls that need fixing. The fix scans all partial declarations of the containing type for Regex call sites that would generate new property names, orders them deterministically (by file path, then position), and offsets the generated name by the current node's index in that list. Fixes dotnet#77409 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs

Extract fixable method names into shared FixableMethodNames set on the analyzer, referenced by both the analyzer and the fixer. Add test verifying Regex.Escape calls don't inflate the generated name offset. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexAnalyzer.cs

danmoseley · 2026-03-19T04:22:00Z

Feedback addressed.

danmoseley · 2026-03-19T21:54:29Z

/ba-g unrelated infra issues

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs

Field and property initializer call sites are fixed via ConvertFieldToGeneratedRegexProperty / ConvertPropertyToGeneratedRegexProperty, which keep the original member name and don't compete for MyRegex* names. Counting them inflated the name offset for method-body fixes (e.g., producing MyRegex1 when MyRegex was available). Updated AnayzerSupportsMultipleDiagnostics test to include a field initializer between two method-body calls to cover this scenario. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

danmoseley · 2026-04-01T19:12:31Z

@eiriktsarpalis I reviewed yours to the regex source gen. Do you want to do this one? It's much simpler.

danmoseley · 2026-04-02T16:41:40Z

/ba-g unrelated

danmoseley · 2026-04-08T19:07:02Z

@stephentoub you looked at this a while back -- could you sign off?

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexAnalyzer.cs

src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs

- Rename FixableMethodNames to s_fixableMethodNames (naming convention) - Simplify name generation loop to avoid throwaway strings - Extract shared IsFixableRegexOperation to eliminate duplication between analyzer and fixer - Refactor analyzer to use IsFixableRegexOperation, removing AnalyzeInvocation/AnalyzeObjectCreation/GetMethodSymbolHash Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…pleDiagnostics Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR fixes a SYSLIB1045 code-fix naming collision that can occur when Roslyn’s BatchFixer applies fixes concurrently across multiple partial declarations of the same type, leading to duplicate generated member names (e.g., multiple MyRegex properties).

Changes:

Update the code fixer’s generated-member naming logic to derive a deterministic per-callsite suffix across all partial declarations of the containing type.
Refactor analyzer/fixer shared “fixable Regex call” logic into UpgradeToGeneratedRegexAnalyzer.IsFixableRegexOperation (and make ValidateParameters reusable).
Add/extend functional tests to validate unique naming across partial declarations (same file and separate files) and relevant edge cases.

Show a summary per file

File	Description
src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/UpgradeToGeneratedRegexAnalyzerTests.cs	Adds/updates tests validating unique generated names across partial declarations and related naming edge cases.
src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexCodeFixer.cs	Implements deterministic unique naming via `CountPrecedingRegexCallSites` and adjusts member insertion formatting.
src/libraries/System.Text.RegularExpressions/gen/UpgradeToGeneratedRegexAnalyzer.cs	Centralizes “fixable Regex operation” logic for reuse by the code fixer and analyzer.

Copilot's findings

Files reviewed: 3/3 changed files
Comments generated: 0 new

danmoseley · 2026-04-10T02:36:56Z

/ba-g unrelated wasm

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XHarness package install failure on iOS due to devicectl NSPOSIXErrorDomain error 49 #123796

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osx builds failing with CMake error #125757

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Cannot find 'arm64-v8a' device dotnet/dnceng#2284

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System.IO.Tests.Directory_Delete_MountVolume.RunTest failure #125295

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Fix typo: AnayzerSupportsMultipleDiagnostics -> AnalyzerSupportsMulti…

6badc10

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danmoseley merged commit 063c8ea into dotnet:main Apr 10, 2026
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danmoseley deleted the fix/77409-codefixer-duplicate-namesc branch April 10, 2026 02:37

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[main] Source code updates from dotnet/runtime dotnet/dotnet#5969

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