Merge pull request #60918 from xymus/spi-only-attr

[Sema] Intro the @_spiOnly attribute on import statements

Author: xymus

docs/ReferenceGuides/UnderscoredAttributes.md

@@ -451,6 +451,13 @@ This prevents types from that module being exposed in API
 (types of public functions, constraints in public extension etc.)
 and ABI (usage in `@inlinable` code).
 
+## `@_spiOnly`
+
+Marks an import to be used in SPI and implementation details only.
+The import statement will be printed in the private swiftinterface only and
+skipped in the public swiftinterface. Any use of imported types and decls in API
+will be diagnosed.
+
 ## `@_implements(ProtocolName, Requirement)`
 
 An attribute that indicates that a function with one name satisfies

include/swift/AST/Attr.def

@@ -768,6 +768,11 @@ SIMPLE_DECL_ATTR(typeWrapper, TypeWrapper,
   ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIStableToRemove,
   134)
 
+SIMPLE_DECL_ATTR(_spiOnly, SPIOnly,
+  OnImport | UserInaccessible |
+  ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIStableToRemove,
+  135)
+
 // If you're adding a new underscored attribute here, please document it in
 // docs/ReferenceGuides/UnderscoredAttributes.md.
 

include/swift/AST/DiagnosticsSema.def

@@ -1902,6 +1902,9 @@ WARNING(spi_attribute_on_import_of_public_module,none,
         "'@_spi' import of %0 will not include any SPI symbols; "
         "%0 was built from the public interface at %1",
         (DeclName, StringRef))
+ERROR(spi_only_imports_not_enabled, none,
+      "'@_spiOnly' requires setting the frontend flag '-experimental-spi-only-imports'",
+      ())
 
 // Opaque return types
 ERROR(opaque_type_invalid_constraint,none,

include/swift/AST/Import.h

@@ -88,7 +88,11 @@ enum class ImportFlags {
   WeakLinked = 0x40,
 
   /// Used for DenseMap.
-  Reserved = 0x80
+  Reserved = 0x80,
+
+  /// The imported module can only be referenced from SPI decls, or
+  /// implementation details.
+  SPIOnly = 0x100
 };
 
 /// \see ImportFlags

include/swift/AST/Module.h

@@ -696,11 +696,13 @@ class ModuleDecl
     Default = 1 << 1,
     /// Include imports declared with `@_implementationOnly`.
     ImplementationOnly = 1 << 2,
-    /// Include imports of SPIs declared with `@_spi`
+    /// Include imports of SPIs declared with `@_spi`.
     SPIAccessControl = 1 << 3,
+    /// Include imports declared with `@_spiOnly`.
+    SPIOnly = 1 << 4,
     /// Include imports shadowed by a cross-import overlay. Unshadowed imports
     /// are included whether or not this flag is specified.
-    ShadowedByCrossImportOverlay = 1 << 4
+    ShadowedByCrossImportOverlay = 1 << 5
   };
   /// \sa getImportedModules
   using ImportFilter = OptionSet<ImportFilterKind>;

include/swift/Basic/LangOptions.h

@@ -456,6 +456,9 @@ namespace swift {
     // FrontendOptions.
     bool AllowModuleWithCompilerErrors = false;
 
+    /// Enable using @_spiOnly on import decls.
+    bool EnableSPIOnlyImports = false;
+
     /// A helper enum to represent whether or not we customized the default
     /// ASTVerifier behavior via a frontend flag. By default, we do not
     /// customize.

include/swift/Option/FrontendOptions.td

@@ -1110,4 +1110,8 @@ def enable_emit_generic_class_ro_t_list :
   Flag<["-"], "enable-emit-generic-class-ro_t-list">,
   HelpText<"Enable emission of a section with references to class_ro_t of "
            "generic class patterns">;
+
+def experimental_spi_only_imports :
+  Flag<["-"], "experimental-spi-only-imports">,
+  HelpText<"Enable use of @_spiOnly imports">;
 } // end let Flags = [FrontendOption, NoDriverOption, HelpHidden]

lib/AST/ImportCache.cpp

@@ -195,6 +195,7 @@ ImportSet &ImportCache::getImportSet(const DeclContext *dc) {
     file->getImportedModules(imports,
                              {ModuleDecl::ImportFilterKind::Default,
                               ModuleDecl::ImportFilterKind::ImplementationOnly,
+                              ModuleDecl::ImportFilterKind::SPIOnly,
                               ModuleDecl::ImportFilterKind::SPIAccessControl});
   }
 
@@ -279,6 +280,7 @@ ImportCache::getAllAccessPathsNotShadowedBy(const ModuleDecl *mod,
     file->getImportedModules(stack,
                              {ModuleDecl::ImportFilterKind::Default,
                               ModuleDecl::ImportFilterKind::ImplementationOnly,
+                              ModuleDecl::ImportFilterKind::SPIOnly,
                               ModuleDecl::ImportFilterKind::SPIAccessControl});
   }
 

lib/AST/Module.cpp

@@ -1596,6 +1596,8 @@ SourceFile::getImportedModules(SmallVectorImpl<ImportedModule> &modules,
       requiredFilter |= ModuleDecl::ImportFilterKind::Exported;
     else if (desc.options.contains(ImportFlags::ImplementationOnly))
       requiredFilter |= ModuleDecl::ImportFilterKind::ImplementationOnly;
+    else if (desc.options.contains(ImportFlags::SPIOnly))
+      requiredFilter |= ModuleDecl::ImportFilterKind::SPIOnly;
     else if (desc.options.contains(ImportFlags::SPIAccessControl))
       requiredFilter |= ModuleDecl::ImportFilterKind::SPIAccessControl;
     else
@@ -1904,6 +1906,7 @@ SourceFile::collectLinkLibraries(ModuleDecl::LinkLibraryCallback callback) const
 
   ModuleDecl::ImportFilter topLevelFilter = filter;
   topLevelFilter |= ModuleDecl::ImportFilterKind::ImplementationOnly;
+  topLevelFilter |= ModuleDecl::ImportFilterKind::SPIOnly;
   topLevel->getImportedModules(stack, topLevelFilter);
 
   // Make sure the top-level module is first; we want pre-order-ish traversal.
@@ -2600,6 +2603,7 @@ canBeUsedForCrossModuleOptimization(DeclContext *ctxt) const {
   // @_implementationOnly or @_spi.
   ModuleDecl::ImportFilter filter = {
     ModuleDecl::ImportFilterKind::ImplementationOnly,
+    ModuleDecl::ImportFilterKind::SPIOnly,
     ModuleDecl::ImportFilterKind::SPIAccessControl
   };
   SmallVector<ImportedModule, 4> results;

lib/Frontend/CompilerInvocation.cpp

@@ -721,6 +721,8 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     }
   }
 
+  Opts.EnableSPIOnlyImports = Args.hasArg(OPT_experimental_spi_only_imports);
+
   if (Opts.EnableSwift3ObjCInference) {
     if (const Arg *A = Args.getLastArg(
                                    OPT_warn_swift3_objc_inference_minimal,