From f53be7187486feeff8398ee9569df72077d1e7db Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alexis=20Laferri=C3=A8re?= <alaf@apple.com>
Date: Tue, 11 Jun 2024 16:32:45 -0700
Subject: [PATCH] ModuleInterface: Print imports shadowed by a cross-import
 overlay

In some cases this import may be superfluous as it's also
`@_exported` imported by the overlay. However, when the overlay
is hidden and the import not printed, the import can go entierly
missing.
---
 lib/Frontend/ModuleInterfaceSupport.cpp       |  3 +-
 test/CrossImport/module-interface.swift       |  3 +-
 .../with-implementation-only.swift            | 71 +++++++++++++++++++
 3 files changed, 74 insertions(+), 3 deletions(-)
 create mode 100644 test/CrossImport/with-implementation-only.swift

diff --git a/lib/Frontend/ModuleInterfaceSupport.cpp b/lib/Frontend/ModuleInterfaceSupport.cpp
index 491baa89e67..83db1e19b75 100644
--- a/lib/Frontend/ModuleInterfaceSupport.cpp
+++ b/lib/Frontend/ModuleInterfaceSupport.cpp
@@ -240,7 +240,8 @@ static void printImports(raw_ostream &out,
   // it's not obvious what higher-level optimization would be factored out here.
   ModuleDecl::ImportFilter allImportFilter = {
       ModuleDecl::ImportFilterKind::Exported,
-      ModuleDecl::ImportFilterKind::Default};
+      ModuleDecl::ImportFilterKind::Default,
+      ModuleDecl::ImportFilterKind::ShadowedByCrossImportOverlay};
 
   // With -experimental-spi-imports:
   // When printing the private or package swiftinterface file, print implementation-only
diff --git a/test/CrossImport/module-interface.swift b/test/CrossImport/module-interface.swift
index 991e1e52f3c..2b0d52b7012 100644
--- a/test/CrossImport/module-interface.swift
+++ b/test/CrossImport/module-interface.swift
@@ -10,7 +10,6 @@
 // RUN: %target-swift-emit-module-interface(%t.swiftinterface) %s -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
 // RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
 // RUN: %FileCheck %s < %t.swiftinterface
-// RUN: %FileCheck -check-prefix NEGATIVE %s < %t.swiftinterface
 
 //
 // Should fail with -disable-cross-import-overlays
@@ -38,9 +37,9 @@ public func shadow(_: DeclaringLibrary.ShadowTy, _: ShadowTy) {}
 // CHECK: // swift-module-flags: {{.*}} -module-name ClientLibrary
 
 // CHECK-DAG: import Swift
+// CHECK-DAG: import DeclaringLibrary
 // CHECK-DAG: import BystandingLibrary
 // CHECK-DAG: import _OverlayLibrary
-// NEGATIVE-NOT: import DeclaringLibrary
 
 // CHECK-DAG: public func fn(_: DeclaringLibrary.DeclaringLibraryTy, _: BystandingLibrary.BystandingLibraryTy, _: _OverlayLibrary.OverlayLibraryTy)
 // CHECK-DAG: public func alias(_: _OverlayLibrary.OverlayLibraryTy)
diff --git a/test/CrossImport/with-implementation-only.swift b/test/CrossImport/with-implementation-only.swift
new file mode 100644
index 00000000000..a78c9d540be
--- /dev/null
+++ b/test/CrossImport/with-implementation-only.swift
@@ -0,0 +1,71 @@
+/// Check cross-import overlays with @_implementationOnly imports.
+
+// RUN: %empty-directory(%t)
+// RUN: cp -r %S/Inputs/lib-templates/* %t/
+// RUN: split-file --leading-lines %s %t
+
+//--- BothPublic.swift
+// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %t/BothPublic.swift -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
+// RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
+// RUN: %FileCheck %t/BothPublic.swift < %t.swiftinterface
+
+import DeclaringLibrary
+import BystandingLibrary
+
+// CHECK: // swift-interface-format-version
+// CHECK: // swift-module-flags: {{.*}} -module-name ClientLibrary
+// CHECK-DAG: import Swift
+// CHECK-DAG: import DeclaringLibrary
+// CHECK-DAG: import BystandingLibrary
+// CHECK-DAG: import _OverlayLibrary
+
+
+//--- BothHidden.swift
+// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %t/BothHidden.swift -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
+// RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
+// RUN: %FileCheck %t/BothHidden.swift < %t.swiftinterface
+// RUN: %FileCheck -check-prefix NEGATIVE %t/BothHidden.swift < %t.swiftinterface
+
+@_implementationOnly import DeclaringLibrary
+@_implementationOnly import BystandingLibrary
+
+// CHECK: // swift-interface-format-version
+// CHECK: // swift-module-flags: {{.*}} -module-name ClientLibrary
+// CHECK-DAG: import Swift
+// NEGATIVE-NOT: import DeclaringLibrary
+// NEGATIVE-NOT: import BystandingLibrary
+// NEGATIVE-NOT: import _OverlayLibrary
+
+
+//--- FirstHidden.swift
+// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %t/FirstHidden.swift -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
+// RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
+// RUN: %FileCheck %t/FirstHidden.swift < %t.swiftinterface
+// RUN: %FileCheck -check-prefix NEGATIVE %t/FirstHidden.swift < %t.swiftinterface
+
+@_implementationOnly import DeclaringLibrary
+import BystandingLibrary
+
+// CHECK: // swift-interface-format-version
+// CHECK: // swift-module-flags: {{.*}} -module-name ClientLibrary
+// CHECK-DAG: import Swift
+// CHECK-DAG: import BystandingLibrary
+// NEGATIVE-NOT: import DeclaringLibrary
+// NEGATIVE-NOT: import _OverlayLibrary
+
+
+//--- SecondHidden.swift
+// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %t/SecondHidden.swift -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
+// RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -enable-cross-import-overlays -I %t/lib/swift -module-name ClientLibrary
+// RUN: %FileCheck %t/SecondHidden.swift < %t.swiftinterface
+// RUN: %FileCheck -check-prefix NEGATIVE %t/SecondHidden.swift < %t.swiftinterface
+
+import DeclaringLibrary
+@_implementationOnly import BystandingLibrary
+
+// CHECK: // swift-interface-format-version
+// CHECK: // swift-module-flags: {{.*}} -module-name ClientLibrary
+// CHECK-DAG: import Swift
+// CHECK-DAG: import DeclaringLibrary
+// NEGATIVE-NOT: import BystandingLibrary
+// NEGATIVE-NOT: import _OverlayLibrary