[PATCH] D117295: [clang][sema] Allow unnamed decls in C++20 module export{} blocks

[Timm Bäder via Phabricator via cfe-commits]

tbaeder updated this revision to Diff 402813.
tbaeder added a comment.

Limited the change to c++2b


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D117295/new/

https://reviews.llvm.org/D117295

Files:
  clang/lib/Sema/SemaModule.cpp
  clang/test/CXX/module/module.interface/p3.cpp
  clang/test/Modules/cxx20-export.cpp


Index: clang/test/Modules/cxx20-export.cpp
===================================================================
--- /dev/null
+++ clang/test/Modules/cxx20-export.cpp
@@ -0,0 +1,23 @@
+
+// RUN: %clang_cc1 -std=c++2b -verify %s
+export module testmodule;
+
+export static_assert(true); // expected-error {{static_assert declaration cannot be exported}}
+export;                     // expected-error {{empty declaration cannot be exported}}
+
+namespace A {};
+
+export {
+#define STR(x) constexpr char x[] = #x;
+  STR(foo);
+#undef STR
+
+  static_assert(true);
+
+  template <typename T> struct X { T t; };
+  template <typename T> X(T) -> X<T>;
+
+  ; // Empty declaration
+
+  using namespace A;
+}
Index: clang/test/CXX/module/module.interface/p3.cpp
===================================================================
--- clang/test/CXX/module/module.interface/p3.cpp
+++ clang/test/CXX/module/module.interface/p3.cpp
@@ -9,12 +9,6 @@
 export static_assert(true); // expected-error {{static_assert declaration cannot be exported}}
 export using namespace A; // expected-error {{ISO C++20 does not permit using directive to be exported}}
 
-export { // expected-note 3{{export block begins here}}
-  ; // expected-error {{ISO C++20 does not permit an empty declaration to appear in an export block}}
-  static_assert(true); // expected-error {{ISO C++20 does not permit a static_assert declaration to appear in an export block}}
-  using namespace A; // expected-error {{ISO C++20 does not permit using directive to be exported}}
-}
-
 export struct {}; // expected-error {{must be class member}} expected-error {{GNU extension}} expected-error {{does not declare anything}}
 export struct {} struct_;
 export union {}; // expected-error {{must be declared 'static'}} expected-error {{does not declare anything}}
Index: clang/lib/Sema/SemaModule.cpp
===================================================================
--- clang/lib/Sema/SemaModule.cpp
+++ clang/lib/Sema/SemaModule.cpp
@@ -615,12 +615,10 @@
   return llvm::None;
 }
 
-unsigned getUnnamedDeclDiag(UnnamedDeclKind UDK, bool InBlock) {
+static unsigned getUnnamedDeclDiag(UnnamedDeclKind UDK, bool InBlock) {
   switch (UDK) {
   case UnnamedDeclKind::Empty:
   case UnnamedDeclKind::StaticAssert:
-    // Allow empty-declarations and static_asserts in an export block as an
-    // extension.
     return InBlock ? diag::ext_export_no_name_block : diag::err_export_no_name;
 
   case UnnamedDeclKind::UsingDirective:
@@ -648,10 +646,16 @@
 
 /// Check that it's valid to export \p D.
 static bool checkExportedDecl(Sema &S, Decl *D, SourceLocation BlockStart) {
-  // C++2a [module.interface]p3:
-  //   An exported declaration shall declare at least one name
-  if (auto UDK = getUnnamedDeclKind(D))
-    diagExportedUnnamedDecl(S, *UDK, D, BlockStart);
+  if (auto UDK = getUnnamedDeclKind(D)) {
+    if (S.getLangOpts().CPlusPlus2b) {
+      if (BlockStart.isInvalid())
+        diagExportedUnnamedDecl(S, *UDK, D, BlockStart);
+    } else {
+      // C++2a [module.interface]p3:
+      //   An exported declaration shall declare at least one name
+      diagExportedUnnamedDecl(S, *UDK, D, BlockStart);
+    }
+  }
 
   //   [...] shall not declare a name with internal linkage.
   if (auto *ND = dyn_cast<NamedDecl>(D)) {


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