Diagnostic groups

Overview

Diagnostic groups collect some number of diagnostics together under a common group name. This allows for extra documentation to help explain relevant language concepts, as well as the ability to control the behavior of warnings in a more precise manner (when that group contains warnings):

• -Werror <group> - upgrades warnings in the specified group to errors

• -Wwarning <group> - indicates that warnings in the specified group should remain warnings, even if they were previously upgraded to errors

As a concrete example, to upgrade deprecated declaration warnings to errors:

-Werror DeprecatedDeclaration

Or upgrade all warnings except deprecated declaration to errors:

-warnings-as-errors -Wwarning DeprecatedDeclaration

Groups with warnings

• Add @preconcurrency import (AddPreconcurrencyImport)

• Always enabled availability domains (AlwaysAvailableDomain)

• Argument matching for trailing closures (TrailingClosureMatching)

• Compilation caching (CompilationCaching)

• Conforming to `StringInterpolationProtocol` (StringInterpolationConformance)

• Deprecated declaration warnings (DeprecatedDeclaration)

• Deprecated implementation-only imports (ImplementationOnlyDeprecated)

• Dynamic exclusivity (DynamicExclusivity)

• Embedded Swift language restrictions (EmbeddedRestrictions)

• Existential Types and Performance (ExistentialType)

• Explicit `Sendable` annotations on public type declarations (ExplicitSendable)

• Extraneous @preconcurrency imports (PreconcurrencyImport)

• Foreign reference types (ForeignReferenceType)

• Implicit Copy On Return (ReturnTypeImplicitCopy)

• Implicit strong captures of weak capture list items (ImplicitStrongCapture)

• Imported Clang declaration warnings (ClangDeclarationImport)

• Inconsistent import access level (InconsistentImportAccess)

• Isolated conformances (IsolatedConformances)

• Language mode and tools version (ErrorInFutureSwiftVersion)

• Migrating away from experimental suppressed associated types (OldSuppressedAssociatedTypes)

• Missing module for canImport (CanImportMissingModule)

• Missing module version (ModuleVersionMissing)

• Module self-import (ModuleSelfImport)

• OSLog module (OSLog)

• Option obsoleted by module selectors (OptionObsoletedByModuleSelectors)

• Public imports of project-internal modules (PublicImportOfProjectInternalModule)

• Result builder methods (ResultBuilderMethods)

• SPI import ignored (SPIImportIgnored)

• Semantic copies (SemanticCopies)

• Strict language feature enablement (StrictLanguageFeatures)

• Strict memory safety (StrictMemorySafety)

• Unavailable Sendable conformance (UnavailableSendableConformance)

• Unknown warning group (UnknownWarningGroup)

• Unnecessary effect markers (UnnecessaryEffectMarker)

• Unnecessary unsafe (UnnecessaryUnsafe)

• Unsupported scoped import (UnsupportedScopedImport)

• Untyped throws (UntypedThrows)

• Unused import access level (UnusedImportAccess)

• Unused throwing unstructured task creation (NoUseUnstructuredThrowingTask)

• Unused values (NoUsage)

• Use anyAppleOS availability (UseAnyAppleOSAvailability)

• Useless availability check (UselessAvailabilityCheck)

• Useless conditional statement (UselessConditionalStatement)

Topics

• @dynamicCallable implementation requirements (DynamicCallable)
• Add @preconcurrency import (AddPreconcurrencyImport)
• Always enabled availability domains (AlwaysAvailableDomain)
• Argument matching for trailing closures (TrailingClosureMatching)
• Calling a mutating async actor-isolated method (ActorIsolatedMutatingAsync)
• Calling an actor-isolated method from a synchronous nonisolated context (ActorIsolatedCall)
• Captures in a `@Sendable` closure (SendableClosureCaptures)
• Compilation caching (CompilationCaching)
• Conforming to `StringInterpolationProtocol` (StringInterpolationConformance)
• Conversion from `@isolated(any)` function type to synchronous function type (ConversionFromIsolatedAnyToSynchronous)
• Cross-isolation data race (RegionIsolationCrossIsolationDataRace)
• Deprecated declaration warnings (DeprecatedDeclaration)
• Deprecated implementation-only imports (ImplementationOnlyDeprecated)
• Dynamic exclusivity (DynamicExclusivity)
• Embedded Swift language restrictions (EmbeddedRestrictions)
• Existential Types and Performance (ExistentialType)
• Explicit `Sendable` annotations on public type declarations (ExplicitSendable)
• Extraneous @preconcurrency imports (PreconcurrencyImport)
• Foreign reference types (ForeignReferenceType)
• Implicit Copy On Return (ReturnTypeImplicitCopy)
• Implicit strong captures of weak capture list items (ImplicitStrongCapture)
• Imported Clang declaration warnings (ClangDeclarationImport)
• Inconsistent import access level (InconsistentImportAccess)
• Isolated conformances (IsolatedConformances)
• Language mode and tools version (ErrorInFutureSwiftVersion)
• Migrating away from experimental suppressed associated types (OldSuppressedAssociatedTypes)
• Missing module for canImport (CanImportMissingModule)
• Missing module on known path from a dependency (MissingModuleOnKnownPaths)
• Missing module version (ModuleVersionMissing)
• Module not testable (ModuleNotTestable)
• Module self-import (ModuleSelfImport)
• Multiple inheritance (MultipleInheritance)
• Nominal types (NominalTypes)
• OSLog module (OSLog)
• Option obsoleted by module selectors (OptionObsoletedByModuleSelectors)
• Overlapping accesses, but operation requires exclusive access (ExclusivityViolation)
• Performance Hints (PerformanceHints)
• Property wrapper implementation requirements (PropertyWrappers)
• Protocol conformances crossing into actor-isolated code (ConformanceIsolation)
• Protocol types cannot conform to protocols (ProtocolTypeNonConformance)
• Public imports of project-internal modules (PublicImportOfProjectInternalModule)
• Result builder methods (ResultBuilderMethods)
• SPI import ignored (SPIImportIgnored)
• Semantic copies (SemanticCopies)
• Sendable metatypes (SendableMetatypes)
• Sending closure risks causing data races (SendingClosureRisksDataRace)
• Sending value risks causing data races (SendingRisksDataRace)
• Strict language feature enablement (StrictLanguageFeatures)
• Strict memory safety (StrictMemorySafety)
• Temporary pointers (TemporaryPointers)
• Unavailable Sendable conformance (UnavailableSendableConformance)
• Underlying type inference for opaque result types (OpaqueTypeInference)
• Unknown region isolation pattern (RegionIsolationUnknownPattern)
• Unknown warning group (UnknownWarningGroup)
• Unnecessary effect markers (UnnecessaryEffectMarker)
• Unnecessary unsafe (UnnecessaryUnsafe)
• Unrecognized availability platforms (AvailabilityUnrecognizedName)
• Unsafe mutable global and static variables (MutableGlobalVariable)
• Unsupported scoped import (UnsupportedScopedImport)
• Untyped throws (UntypedThrows)
• Unused import access level (UnusedImportAccess)
• Unused throwing unstructured task creation (NoUseUnstructuredThrowingTask)
• Unused values (NoUsage)
• Use anyAppleOS availability (UseAnyAppleOSAvailability)
• Useless availability check (UselessAvailabilityCheck)
• Useless conditional statement (UselessConditionalStatement)
• Using protocol members with references to `Self` or `Self`-rooted associated types (ExistentialMemberAccess)

See Also

• Upcoming language features