[Sema] Allow the use of SPI in API for SPI modules

When the whole module has an SPI distribution, SPI declarations can be
used in API.

rdar://75335462

Author: xymus

lib/Frontend/CompilerInvocation.cpp

@@ -331,6 +331,13 @@ static void ParseModuleInterfaceArgs(ModuleInterfaceOptions &Opts,
     Args.hasArg(OPT_experimental_spi_imports);
   Opts.DebugPrintInvalidSyntax |=
     Args.hasArg(OPT_debug_emit_invalid_swiftinterface_syntax);
+
+  if (const Arg *A = Args.getLastArg(OPT_library_level)) {
+    StringRef contents = A->getValue();
+    if (contents == "spi") {
+      Opts.PrintSPIs = true;
+    }
+  }
 }
 
 /// Save a copy of any flags marked as ModuleInterfaceOption, if running

lib/FrontendTool/FrontendTool.cpp

@@ -862,7 +862,7 @@ static bool emitAnyWholeModulePostTypeCheckSupplementaryOutputs(
   }
 
   if (opts.InputsAndOutputs.hasPrivateModuleInterfaceOutputPath()) {
-    // Copy the settings from the module interface
+    // Copy the settings from the module interface to add SPI printing.
     ModuleInterfaceOptions privOpts = Invocation.getModuleInterfaceOptions();
     privOpts.PrintSPIs = true;
 

lib/Sema/TypeCheckAvailability.cpp

@@ -179,7 +179,7 @@ ExportContext ExportContext::forDeclSignature(Decl *D) {
       (Ctx.LangOpts.DisableAvailabilityChecking
        ? AvailabilityContext::alwaysAvailable()
        : TypeChecker::overApproximateAvailabilityAtLocation(D->getEndLoc(), DC));
-  bool spi = false;
+  bool spi = Ctx.LangOpts.LibraryLevel == LibraryLevel::SPI;
   bool implicit = false;
   bool deprecated = false;
   Optional<PlatformKind> unavailablePlatformKind;
@@ -208,7 +208,7 @@ ExportContext ExportContext::forFunctionBody(DeclContext *DC, SourceLoc loc) {
        ? AvailabilityContext::alwaysAvailable()
        : TypeChecker::overApproximateAvailabilityAtLocation(loc, DC));
 
-  bool spi = false;
+  bool spi = Ctx.LangOpts.LibraryLevel == LibraryLevel::SPI;
   bool implicit = false;
   bool deprecated = false;
   Optional<PlatformKind> unavailablePlatformKind;

test/SPI/export_spi_from_spi_module.swift

@@ -0,0 +1,27 @@
+/// Check that SPI declarations can be exported from an SPI module.
+
+// RUN: %empty-directory(%t)
+// RUN: %target-typecheck-verify-swift -I %t -verify-ignore-unknown -enable-library-evolution -swift-version 5 -library-level spi
+
+@_spi(S) public func spiFunc() {}
+@_spi(S) public class SPIClass {
+  public init() {}
+}
+@_spi(S) public class SPIStruct {
+  public init() {}
+}
+@_spi(S) public protocol SPIProtocol {}
+
+public func useOfSPITypeOk(_ p0: SPIProtocol, p1: SPIClass) -> SPIClass { fatalError() }
+
+@inlinable
+func inlinable() -> SPIClass {
+  spiFunc()
+  _ = SPIClass()
+}
+
+@frozen public struct FrozenStruct {
+  public var spiInFrozen = SPIStruct()
+  var spiTypeInFrozen = SPIStruct()
+  private var spiTypeInFrozen1: SPIClass
+}

test/SPI/private_swiftinterface.swift

@@ -42,6 +42,14 @@
 // RUN: %target-swift-frontend -typecheck-module-from-interface -I %t %t/Merged.swiftinterface
 // RUN: %target-swift-frontend -typecheck-module-from-interface -I %t %t/Merged.private.swiftinterface -module-name Merged
 
+/// Both the public and private textual interfaces should have
+/// SPI information with `-library-level spi`.
+// RUN: %target-swift-frontend -typecheck %s -emit-module-interface-path %t/SPIModule.swiftinterface -emit-private-module-interface-path %t/SPIModule.private.swiftinterface -enable-library-evolution -swift-version 5 -I %t -module-name SPIModule -library-level spi
+// RUN: %FileCheck -check-prefix=CHECK-PRIVATE %s < %t/SPIModule.swiftinterface
+// RUN: %FileCheck -check-prefix=CHECK-PRIVATE %s < %t/SPIModule.private.swiftinterface
+// RUN: %target-swift-frontend -typecheck-module-from-interface -I %t %t/SPIModule.swiftinterface
+// RUN: %target-swift-frontend -typecheck-module-from-interface -I %t %t/SPIModule.private.swiftinterface -module-name SPIModule
+
 @_spi(HelperSPI) @_spi(OtherSPI) @_spi(OtherSPI) import SPIHelper
 // CHECK-PUBLIC: import SPIHelper
 // CHECK-PRIVATE: @_spi(OtherSPI) @_spi(HelperSPI) import SPIHelper

test/SPI/public_client.swift

@@ -12,9 +12,10 @@
 // RUN: rm %t/SPIHelper.swiftmodule
 // RUN: %target-typecheck-verify-swift -I %t -verify-ignore-unknown
 
-/// Reading from .swiftinterface should still produce the same failures
+/// Reading from the public .swiftinterface should raise errors on missing
+/// declarations.
 // RUN: rm %t/SPIHelper.private.swiftinterface
-// RUN: not %target-swift-frontend -typecheck -I %t
+// RUN: not %target-swift-frontend -typecheck -I %t %s
 
 import SPIHelper