[Sema] Restrict reexported SPIs to modules with an export_as relationship

@_exported exports SPIs only when the exported module defines export_as
pointing to the exporter module. Other reexports do not reexport SPIs.
This is to prevent SPI reexporting to get out of hands with the wide
reexports of the Objective-C world.

rdar://102335473

Author: xymus

lib/AST/Module.cpp

@@ -2861,7 +2861,8 @@ void SourceFile::lookupImportedSPIGroups(
   for (auto &import : *Imports) {
     if (import.options.contains(ImportFlags::SPIAccessControl) &&
         (importedModule == import.module.importedModule ||
-         imports.isImportedBy(importedModule, import.module.importedModule))) {
+         (imports.isImportedBy(importedModule, import.module.importedModule) &&
+          importedModule->isExportedAs(import.module.importedModule)))) {
       spiGroups.insert(import.spiGroups.begin(), import.spiGroups.end());
     }
   }

lib/Serialization/SerializedModuleLoader.cpp

@@ -1494,7 +1494,8 @@ void SerializedASTFile::lookupImportedSPIGroups(
       continue;
 
     if (dep.Import->importedModule == importedModule ||
-        imports.isImportedBy(importedModule, dep.Import->importedModule)) {
+        (imports.isImportedBy(importedModule, dep.Import->importedModule) &&
+         importedModule->isExportedAs(dep.Import->importedModule))) {
       spiGroups.insert(dep.spiGroups.begin(), dep.spiGroups.end());
     }
   }

test/SPI/reexported-spi-groups.swift

@@ -3,13 +3,13 @@
 
 /// Build lib defining SPIs
 // RUN: %target-swift-frontend -emit-module %t/Exported.swift \
-// RUN:   -module-name Exported -swift-version 5 \
+// RUN:   -module-name Exported -swift-version 5 -I %t \
 // RUN:   -enable-library-evolution \
 // RUN:   -emit-module-path %t/Exported.swiftmodule \
 // RUN:   -emit-module-interface-path %t/Exported.swiftinterface \
 // RUN:   -emit-private-module-interface-path %t/Exported.private.swiftinterface
-// RUN: %target-swift-typecheck-module-from-interface(%t/Exported.swiftinterface)
-// RUN: %target-swift-typecheck-module-from-interface(%t/Exported.private.swiftinterface) -module-name Exported
+// RUN: %target-swift-typecheck-module-from-interface(%t/Exported.swiftinterface) -I %t
+// RUN: %target-swift-typecheck-module-from-interface(%t/Exported.private.swiftinterface) -module-name Exported -I %t
 
 /// Build lib reexporting SPIs
 // RUN: %target-swift-frontend -emit-module %t/Exporter.swift \
@@ -21,6 +21,15 @@
 // RUN: %target-swift-typecheck-module-from-interface(%t/Exporter.swiftinterface) -I %t
 // RUN: %target-swift-typecheck-module-from-interface(%t/Exporter.private.swiftinterface) -module-name Exporter -I %t
 
+// RUN: %target-swift-frontend -emit-module %t/NonExportedAs.swift \
+// RUN:   -module-name NonExportedAs -swift-version 5 -I %t \
+// RUN:   -enable-library-evolution \
+// RUN:   -emit-module-path %t/NonExportedAs.swiftmodule \
+// RUN:   -emit-module-interface-path %t/NonExportedAs.swiftinterface \
+// RUN:   -emit-private-module-interface-path %t/NonExportedAs.private.swiftinterface
+// RUN: %target-swift-typecheck-module-from-interface(%t/NonExportedAs.swiftinterface) -I %t
+// RUN: %target-swift-typecheck-module-from-interface(%t/NonExportedAs.private.swiftinterface) -module-name NonExportedAs -I %t
+
 /// Build lib not reexporting SPIs (a normal import)
 // RUN: %target-swift-frontend -emit-module %t/NonExporter.swift \
 // RUN:   -module-name NonExporter -swift-version 5 -I %t \
@@ -46,6 +55,11 @@
 // RUN:   %t/Client_FileA.swift %t/Client_FileB.swift\
 // RUN:   -swift-version 5 -I %t -verify
 
+/// Test that SPIs aren't avaible from a reexport without export_as
+// RUN: %target-swift-frontend -typecheck \
+// RUN:   %t/NonExportedAsClient.swift \
+// RUN:   -swift-version 5 -I %t -verify
+
 /// Test that SPIs don't leak when not reexported
 // RUN: %target-swift-frontend -typecheck \
 // RUN:   %t/NonExporterClient.swift \
@@ -63,9 +77,15 @@
 // RUN:   %t/PublicClient.swift \
 // RUN:   -swift-version 5 -I %t -verify
 
+//--- module.modulemap
+module Exported {
+    export_as Exporter
+}
 
 //--- Exported.swift
 
+@_exported import Exported
+
 public func exportedPublicFunc() {}
 
 @_spi(X) public func exportedSpiFunc() {}
@@ -78,6 +98,12 @@ public func exportedPublicFunc() {}
 
 @_spi(X) public func exporterSpiFunc() {}
 
+//--- NonExportedAs.swift
+
+@_exported import Exported
+
+@_spi(X) public func exporterSpiFunc() {}
+
 //--- NonExporter.swift
 
 @_spi(X) import Exported
@@ -127,6 +153,16 @@ public func clientB() {
     exporterSpiFunc() // expected-error {{cannot find 'exporterSpiFunc' in scope}}
 }
 
+//--- NonExportedAsClient.swift
+
+@_spi(X) import NonExportedAs
+
+public func client() {
+    exportedPublicFunc()
+    exportedSpiFunc() // expected-error {{cannot find 'exportedSpiFunc' in scope}}
+    exporterSpiFunc()
+}
+
 //--- NonExporterClient.swift
 
 @_spi(X) import NonExporter