Only inherit C++ modules when C++ interop enabled

Imports of modules marked `requires: cplusplus` should only be inherited
when C++ interop is enabled. Similarly, imports of modules marked
`requires: !cplusplus` should only be inherited when C++ interop is
disabled.

Author: hnrklssn

lib/ClangImporter/ClangImporter.cpp

@@ -2848,13 +2848,19 @@ ClangModuleUnit *ClangImporter::Implementation::getWrapperForModule(
     for (auto UI : implicitImportInfo.AdditionalUnloadedImports)
       Imported.insert(UI.module.getImportPath());
     assert(implicitImportInfo.AdditionalImports.empty());
+    const bool cxx = SwiftContext.LangOpts.EnableCXXInterop;
 
-    auto addImplicitImport = [&implicitImportInfo, &Imported,
+    auto addImplicitImport = [&implicitImportInfo, &Imported, cxx,
                               this](const clang::Module *M,
                                     bool guaranteedUnique) {
-      const bool cannotBeImported = llvm::any_of(M->Requirements, [](auto &Req) {
-        return !Req.RequiredState && Req.FeatureName == "swift";
-      });
+      const bool cannotBeImported =
+          llvm::any_of(M->Requirements, [cxx](auto &Req) {
+            if (Req.FeatureName == "swift")
+              return !Req.RequiredState;
+            if (Req.FeatureName == "cplusplus")
+              return Req.RequiredState != cxx;
+            return false;
+          });
       if (cannotBeImported) {
         return;
       }

test/Interop/Cxx/swiftify-import/clang-includes-no-cxx.swift

@@ -0,0 +1,148 @@
+// REQUIRES: swift_feature_SafeInteropWrappers
+
+// Tests that we don't try to import modules that don't work well with C++ interop (when enabled)
+
+// RUN: %empty-directory(%t)
+// RUN: split-file --leading-lines %s %t
+
+// Case 1: a.swift calls A1.B1.foo with C++ interop
+// RUN: not %target-swift-frontend -typecheck -plugin-path %swift-plugin-dir -cxx-interoperability-mode=default -I %t%{fs-sep}Inputs -enable-experimental-feature SafeInteropWrappers %t/a.swift -dump-source-file-imports 2>&1 | %FileCheck --check-prefixes CHECK-A,CHECK-A-CXX %s
+// RUN:     %target-swift-frontend -typecheck -plugin-path %swift-plugin-dir -cxx-interoperability-mode=default -I %t%{fs-sep}Inputs -enable-experimental-feature SafeInteropWrappers %t/a.swift -verify -verify-additional-prefix cxx- -verify-additional-file %t%{fs-sep}Inputs%{fs-sep}B1.h -verify-ignore-macro-note
+
+// Case 2: a.swift calls A1.B1.foo without C++ interop
+// RUN: %target-swift-frontend -typecheck -plugin-path %swift-plugin-dir -I %t%{fs-sep}Inputs -enable-experimental-feature SafeInteropWrappers %t/a.swift -dump-source-file-imports 2>&1 | %FileCheck --check-prefixes CHECK-A,CHECK-A-C %s
+// RUN: %target-swift-frontend -typecheck -plugin-path %swift-plugin-dir -I %t%{fs-sep}Inputs -enable-experimental-feature SafeInteropWrappers %t/a.swift -verify
+
+// Case 3: b.swift calls A2.B2.foo with C++ interop
+// RUN: %target-swift-frontend -typecheck -plugin-path %swift-plugin-dir -cxx-interoperability-mode=default -I %t%{fs-sep}Inputs -enable-experimental-feature SafeInteropWrappers %t/b.swift -dump-source-file-imports 2>&1 | %FileCheck --check-prefixes CHECK-B,CHECK-B-CXX %s
+// RUN: %target-swift-frontend -typecheck -plugin-path %swift-plugin-dir -cxx-interoperability-mode=default -I %t%{fs-sep}Inputs -enable-experimental-feature SafeInteropWrappers %t/b.swift -verify
+
+// Case 4: b.swift calls A2.B2.foo without C++ interop
+// RUN: not %target-swift-frontend -typecheck -plugin-path %swift-plugin-dir -I %t%{fs-sep}Inputs -enable-experimental-feature SafeInteropWrappers %t/b.swift -dump-source-file-imports 2>&1 | %FileCheck --check-prefix CHECK-B %s
+// RUN:     %target-swift-frontend -typecheck -plugin-path %swift-plugin-dir -I %t%{fs-sep}Inputs -enable-experimental-feature SafeInteropWrappers %t/b.swift -verify -verify-additional-prefix c- -verify-additional-file %t%{fs-sep}Inputs%{fs-sep}B2.h -verify-ignore-macro-note
+
+// CHECK-A:      imports for {{.*}}a.swift:
+// CHECK-A-NEXT: 	Swift
+// CHECK-A-CXX-NEXT: 	CxxShim
+// CHECK-A-CXX-NEXT: 	Cxx
+// CHECK-A-NEXT: 	_StringProcessing
+// CHECK-A-NEXT: 	_SwiftConcurrencyShims
+// CHECK-A-NEXT: 	_Concurrency
+// CHECK-A-NEXT: 	B1
+// CHECK-A-NEXT: 	A1
+// CHECK-A-NEXT: imports for A1.foo:
+
+// CHECK-A-NEXT: imports for @__swiftmacro{{.*}}foo{{.*}}_SwiftifyImport{{.*}}.swift:
+// CHECK-A-NEXT: Swift
+// CHECK-A-C-NEXT: C1
+// CHECK-A-NEXT: B1
+// CHECK-A-CXX-NEXT: CxxShim
+// CHECK-A-CXX-NEXT: Cxx
+// CHECK-A-NEXT: _StringProcessing
+// CHECK-A-NEXT: _SwiftConcurrencyShims
+// CHECK-A-NEXT: _Concurrency
+
+// CHECK-B:      imports for {{.*}}b.swift:
+// CHECK-B-NEXT: 	Swift
+// CHECK-B-CXX-NEXT: 	CxxShim
+// CHECK-B-CXX-NEXT: 	Cxx
+// CHECK-B-NEXT: 	_StringProcessing
+// CHECK-B-NEXT: 	_SwiftConcurrencyShims
+// CHECK-B-NEXT: 	_Concurrency
+// CHECK-B-NEXT: 	B2
+// CHECK-B-NEXT: 	A2
+// CHECK-B-NEXT: imports for A2.bar:
+
+// CHECK-B-NEXT: imports for @__swiftmacro{{.*}}bar{{.*}}_SwiftifyImport{{.*}}.swift:
+// CHECK-B-NEXT: Swift
+// CHECK-B-CXX-NEXT: C2
+// CHECK-B-NEXT: B2
+// CHECK-B-CXX-NEXT: CxxShim
+// CHECK-B-CXX-NEXT: Cxx
+// CHECK-B-NEXT: _StringProcessing
+// CHECK-B-NEXT: _SwiftConcurrencyShims
+// CHECK-B-NEXT: _Concurrency
+
+
+//--- Inputs/module.modulemap
+  module A1 {
+    explicit module B1 {
+      header "B1.h"
+      explicit module C1 {
+        header "C1.h"
+        requires !cplusplus
+      }
+    }
+  }
+  module A2 {
+    explicit module B2 {
+      header "B2.h"
+      explicit module C2 {
+        header "C2.h"
+        requires cplusplus
+      }
+    }
+  }
+
+//--- Inputs/B1.h
+  #pragma once
+  
+  #include "C1.h"
+  #define __sized_by(s) __attribute__((__sized_by__(s)))
+  
+  // foo causes an error with cxx-interop
+  c1_t foo(void * _Nonnull __sized_by(size), int size);
+  /*
+  expected-cxx-note@-2{{'foo' declared here}}
+  expected-cxx-expansion@-3:54{{
+    expected-cxx-error@2:110{{cannot find type 'c1_t' in scope}}
+  }}
+  */
+
+//--- Inputs/B2.h
+  #pragma once
+  
+  #include "C2.h"
+  #define __sized_by(s) __attribute__((__sized_by__(s)))
+  
+  // bar causes an error without cxx-interop
+  c2_t bar(void * _Nonnull __sized_by(size), int size);
+  /*
+  expected-c-note@-2{{'bar' declared here}}
+  expected-c-expansion@-3:54{{
+    expected-c-error@2:110{{cannot find type 'c2_t' in scope}}
+  }}
+  */
+
+//--- Inputs/C1.h
+  #pragma once
+  
+  typedef int c1_t;
+
+//--- Inputs/C2.h
+  #pragma once
+  
+  typedef int c2_t;
+
+//--- a.swift
+  import A1.B1
+  
+  public func callUnsafe(_ p: UnsafeMutableRawPointer) {
+    let _ = foo(p, 13)
+  }
+  public func callSafe(_ p: UnsafeMutableRawBufferPointer) {
+    let _ = foo(p) // expected-cxx-error{{cannot convert value of type 'UnsafeMutableRawBufferPointer' to expected argument type 'UnsafeMutableRawPointer'}}
+                   // expected-cxx-error@-1{{missing argument}}
+  }
+  
+//--- b.swift
+  import A2.B2
+
+  public func callUnsafe(_ p: UnsafeMutableRawPointer) {
+    let _ = bar(p, 13)
+  }
+  public func callSafe(_ p: UnsafeMutableRawBufferPointer) {
+    let _ = bar(p) // expected-c-error{{cannot convert value of type 'UnsafeMutableRawBufferPointer' to expected argument type 'UnsafeMutableRawPointer'}}
+                   // expected-c-error@-1{{missing argument}}
+
+  }