[C++20][Modules] Introduce an implementation module.

We need to be able to distinguish individual TUs from the same module in cases
where TU-local entities either need to be hidden (or, for some cases of ADL in
template instantiation, need to be detected as exposures).

This creates a module type for the implementation which implicitly imports its
primary module interface per C++20:
[module.unit/8] 'A module-declaration that contains neither an export-keyword
nor a module-partition implicitly imports the primary module interface unit of
the module as if by a module-import-declaration.

Implementation modules are never serialized (-emit-module-interface for an
implementation unit is diagnosed and rejected).

Differential Revision: https://reviews.llvm.org/D126959

1 files changed, 34 insertions, 8 deletions

diff --git a/clang/lib/Lex/ModuleMap.cpp b/clang/lib/Lex/ModuleMap.cpp
index 8dead93..f2b2d0b 100644
--- a/clang/lib/Lex/ModuleMap.cpp
+++ b/clang/lib/Lex/ModuleMap.cpp
@@ -888,23 +888,30 @@ ModuleMap::createPrivateModuleFragmentForInterfaceUnit(Module *Parent,
   return Result;
 }
 
-Module *ModuleMap::createModuleForInterfaceUnit(SourceLocation Loc,
-                                                StringRef Name) {
-  assert(LangOpts.CurrentModule == Name && "module name mismatch");
-  assert(!Modules[Name] && "redefining existing module");
-
+Module *ModuleMap::createModuleUnitWithKind(SourceLocation Loc, StringRef Name,
+                                            Module::ModuleKind Kind) {
   auto *Result =
       new Module(Name, Loc, nullptr, /*IsFramework*/ false,
                  /*IsExplicit*/ false, NumCreatedModules++);
-  Result->Kind = Module::ModuleInterfaceUnit;
-  Modules[Name] = SourceModule = Result;
+  Result->Kind = Kind;
 
-  // Reparent the current global module fragment as a submodule of this module.
+  // Reparent any current global module fragment as a submodule of this module.
   for (auto &Submodule : PendingSubmodules) {
     Submodule->setParent(Result);
     Submodule.release(); // now owned by parent
   }
   PendingSubmodules.clear();
+  return Result;
+}
+
+Module *ModuleMap::createModuleForInterfaceUnit(SourceLocation Loc,
+                                                StringRef Name) {
+  assert(LangOpts.CurrentModule == Name && "module name mismatch");
+  assert(!Modules[Name] && "redefining existing module");
+
+  auto *Result =
+      createModuleUnitWithKind(Loc, Name, Module::ModuleInterfaceUnit);
+  Modules[Name] = SourceModule = Result;
 
   // Mark the main source file as being within the newly-created module so that
   // declarations and macros are properly visibility-restricted to it.
@@ -915,6 +922,25 @@ Module *ModuleMap::createModuleForInterfaceUnit(SourceLocation Loc,
   return Result;
 }
 
+Module *ModuleMap::createModuleForImplementationUnit(SourceLocation Loc,
+                                                     StringRef Name) {
+  assert(LangOpts.CurrentModule == Name && "module name mismatch");
+  // The interface for this implementation must exist and be loaded.
+  assert(Modules[Name] && Modules[Name]->Kind == Module::ModuleInterfaceUnit &&
+         "creating implementation module without an interface");
+
+  auto *Result =
+      createModuleUnitWithKind(Loc, Name, Module::ModuleImplementationUnit);
+  SourceModule = Result;
+
+  // Mark the main source file as being within the newly-created module so that
+  // declarations and macros are properly visibility-restricted to it.
+  auto *MainFile = SourceMgr.getFileEntryForID(SourceMgr.getMainFileID());
+  assert(MainFile && "no input file for module implementation");
+
+  return Result;
+}
+
 Module *ModuleMap::createHeaderUnit(SourceLocation Loc, StringRef Name,
                                     Module::Header H) {
   assert(LangOpts.CurrentModule == Name && "module name mismatch");