[clang] a29f8db - [C++20][Modules][8/8] Amend module visibility rules for partitions.

[Iain Sandoe via cfe-commits]

Author: Iain Sandoe
Date: 2022-03-01T08:29:05Z
New Revision: a29f8dbb7f3e816344a7be75996eea3ab5a0b5a3

URL: https://github.com/llvm/llvm-project/commit/a29f8dbb7f3e816344a7be75996eea3ab5a0b5a3
DIFF: https://github.com/llvm/llvm-project/commit/a29f8dbb7f3e816344a7be75996eea3ab5a0b5a3.diff

LOG: [C++20][Modules][8/8] Amend module visibility rules for partitions.

Implementation partitions bring two extra cases where we have
visibility of module-private data.

1) When we import a module implementation partition.
2) When a partition implementation imports the primary module intertace.

We maintain a record of direct imports into the current module since
partition decls from direct imports (but not trasitive ones) are visible.

The rules on decl-reachability are much more relaxed (with the standard
giving permission for an implementation to load dependent modules and for
the decls there to be reachable, but not visible).

Differential Revision: https://reviews.llvm.org/D118599

Added: 
    

Modified: 
    clang/lib/Sema/SemaLookup.cpp
    clang/test/Modules/cxx20-10-1-ex2.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 13320497c4b4b..65f5112afee3e 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -1687,8 +1687,8 @@ bool LookupResult::isVisibleSlow(Sema &SemaRef, NamedDecl *D) {
   Module *DeclModule = SemaRef.getOwningModule(D);
   assert(DeclModule && "hidden decl has no owning module");
 
-  // If the owning module is visible, the decl is visible.
   if (SemaRef.isModuleVisible(DeclModule, D->isModulePrivate()))
+    // If the owning module is visible, the decl is visible.
     return true;
 
   // Determine whether a decl context is a file context for the purpose of
@@ -1762,6 +1762,22 @@ bool Sema::isModuleVisible(const Module *M, bool ModulePrivate) {
   if (ModulePrivate) {
     if (isInCurrentModule(M, getLangOpts()))
       return true;
+    else if (M->Kind == Module::ModuleKind::ModulePartitionImplementation &&
+             isModuleDirectlyImported(M))
+      // Unless a partition implementation is directly imported it is not
+      // counted as visible for lookup, although the contained decls might
+      // still be reachable.  It's a partition, so it must be part of the
+      // current module to be a valid import.
+      return true;
+    else if (getLangOpts().CPlusPlusModules && !ModuleScopes.empty() &&
+             ModuleScopes[0].Module->Kind ==
+                 Module::ModuleKind::ModulePartitionImplementation &&
+             ModuleScopes[0].Module->getPrimaryModuleInterfaceName() ==
+                 M->Name &&
+             isModuleDirectlyImported(M))
+      // We are building a module implementation partition and the TU imports
+      // the primary module interface unit.
+      return true;
   } else {
     if (VisibleModules.isVisible(M))
       return true;

diff  --git a/clang/test/Modules/cxx20-10-1-ex2.cpp b/clang/test/Modules/cxx20-10-1-ex2.cpp
index 66323fc9d6460..6b47fb0f41eec 100644
--- a/clang/test/Modules/cxx20-10-1-ex2.cpp
+++ b/clang/test/Modules/cxx20-10-1-ex2.cpp
@@ -12,9 +12,8 @@
 // RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/std10-1-ex2-tu3.cpp \
 // RUN:   -o %t/B_X1.pcm -verify
 
-// Not expected to work yet.
-//  %clang_cc1 -std=c++20 -emit-module-interface %t/std10-1-ex2-tu4.cpp \
-//   -fmodule-file=%t/B.pcm  -o %t/B_X2.pcm
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/std10-1-ex2-tu4.cpp \
+// RUN:-fmodule-file=%t/B.pcm  -o %t/B_X2.pcm
 
 // RUN: %clang_cc1 -std=c++20 -emit-obj %t/std10-1-ex2-tu5.cpp \
 // RUN:  -fmodule-file=%t/B.pcm  -o %t/b_tu5.o
@@ -22,9 +21,8 @@
 // RUN: %clang_cc1 -std=c++20 -S %t/std10-1-ex2-tu6.cpp \
 // RUN:  -fmodule-file=%t/B.pcm  -o %t/b_tu6.s -verify
 
-// Not expected to work yet.
-//  %clang_cc1 -std=c++20 -emit-module-interface %t/std10-1-ex2-tu7.cpp \
-//   -fmodule-file=%t/B_X2.pcm  -o %t/B_X3.pcm -verify
+// RUN: %clang_cc1 -std=c++20 -emit-module-interface %t/std10-1-ex2-tu7.cpp \
+// RUN: -fmodule-file=%t/B_X2.pcm  -o %t/B_X3.pcm -verify
 
 //--- std10-1-ex2-tu1.cpp
 module B:Y;