Add MA0201 for zero-valued enum flag checks#1163
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Add a new warning rule to detect constant enum flag checks when the checked flag value is 0, including ==, !=, is, is not, HasFlag, and HasFlags patterns. Also update MA0192 to skip zero-valued flags and refresh tests/documentation/config entries. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Resolve System.Enum.HasFlag during compilation start and report invocation diagnostics only for that method symbol. Custom extension methods such as HasFlags are no longer considered. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Resolve Enum.HasFlag with DocumentationCommentId directly in the CompilationStart callback and remove the extra lookup helper. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Move zero-valued enum flag diagnostics into the MA0192 analyzer class, remove the standalone MA0201 analyzer file, and keep both diagnostics in one analyzer class with dedicated tests and source documentation updates. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Consolidate zero-valued flag rule tests into UseHasFlagMethodAnalyzerTests and use explicit {|ruleid:code|} markers for expected diagnostics.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Drop MA0192_SeverityAndDefault and MA0201_SeverityAndDefault from UseHasFlagMethodAnalyzerTests per review feedback. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This was referenced May 19, 2026
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This was referenced May 22, 2026
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Zero-valued enum members (
None = 0) make flag checks constant, but we did not have a dedicated rule to catch this. This adds a warning rule for these cases so users are alerted when the condition is always true or always false.What changed
MA0201(DoNotUseZeroValuedEnumFlagsInFlagChecks) as aUsagerule, warning severity, enabled by default.(value & flag) == ...(value & flag) != ...(value & flag) is ...(value & flag) is not ...value.HasFlag(...)when the checked flag value is zero.
System.Enum.HasFlagduring compilation start and reports diagnostics only for that exact method symbol. Custom extension methods are intentionally not analyzed.MA0192(UseHasFlagMethodAnalyzer) so it no longer reports zero-valued flag checks, avoiding conflicting guidance.MA0192interaction.docs/Rules/MA0201.mdRuleIdentifiers.editorconfigfilesREADME.mdanddocs/README.mdentries.