[C++20][Modules][3/8] Initial handling for module partitions.

This implements the parsing and recognition of module partition CMIs
and removes the FIXMEs in the parser.

Module partitions are recognised in the base computation of visibility,
however additional amendments to visibility follow in subsequent patches.

Differential Revision: https://reviews.llvm.org/D118586

1 files changed, 119 insertions, 47 deletions

diff --git a/clang/lib/Sema/SemaModule.cpp b/clang/lib/Sema/SemaModule.cpp
index bd5b900..125dbef 100644
--- a/clang/lib/Sema/SemaModule.cpp
+++ b/clang/lib/Sema/SemaModule.cpp
@@ -54,6 +54,23 @@ static void checkModuleImportContext(Sema &S, Module *M,
   }
 }
 
+// We represent the primary and partition names as 'Paths' which are sections
+// of the hierarchical access path for a clang module.  However for C++20
+// the periods in a name are just another character, and we will need to
+// flatten them into a string.
+static std::string stringFromPath(ModuleIdPath Path) {
+  std::string Name;
+  if (Path.empty())
+    return Name;
+
+  for (auto &Piece : Path) {
+    if (!Name.empty())
+      Name += ".";
+    Name += Piece.first->getName();
+  }
+  return Name;
+}
+
 Sema::DeclGroupPtrTy
 Sema::ActOnGlobalModuleFragmentDecl(SourceLocation ModuleLoc) {
   if (!ModuleScopes.empty() &&
@@ -80,11 +97,10 @@ Sema::ActOnGlobalModuleFragmentDecl(SourceLocation ModuleLoc) {
   return nullptr;
 }
 
-Sema::DeclGroupPtrTy Sema::ActOnModuleDecl(SourceLocation StartLoc,
-                                           SourceLocation ModuleLoc,
-                                           ModuleDeclKind MDK,
-                                           ModuleIdPath Path,
-                                           ModuleImportState &ImportState) {
+Sema::DeclGroupPtrTy
+Sema::ActOnModuleDecl(SourceLocation StartLoc, SourceLocation ModuleLoc,
+                      ModuleDeclKind MDK, ModuleIdPath Path,
+                      ModuleIdPath Partition, ModuleImportState &ImportState) {
   assert((getLangOpts().ModulesTS || getLangOpts().CPlusPlusModules) &&
          "should only have module decl in Modules TS or C++20");
 
@@ -163,19 +179,20 @@ Sema::DeclGroupPtrTy Sema::ActOnModuleDecl(SourceLocation StartLoc,
   // Flatten the dots in a module name. Unlike Clang's hierarchical module map
   // modules, the dots here are just another character that can appear in a
   // module name.
-  std::string ModuleName;
-  for (auto &Piece : Path) {
-    if (!ModuleName.empty())
-      ModuleName += ".";
-    ModuleName += Piece.first->getName();
+  std::string ModuleName = stringFromPath(Path);
+  bool IsPartition = !Partition.empty();
+  if (IsPartition) {
+    ModuleName += ":";
+    ModuleName += stringFromPath(Partition);
   }
-
   // If a module name was explicitly specified on the command line, it must be
   // correct.
   if (!getLangOpts().CurrentModule.empty() &&
       getLangOpts().CurrentModule != ModuleName) {
     Diag(Path.front().second, diag::err_current_module_name_mismatch)
-        << SourceRange(Path.front().second, Path.back().second)
+        << SourceRange(Path.front().second, IsPartition
+                                                ? Partition.back().second
+                                                : Path.back().second)
         << getLangOpts().CurrentModule;
     return nullptr;
   }
@@ -202,6 +219,8 @@ Sema::DeclGroupPtrTy Sema::ActOnModuleDecl(SourceLocation StartLoc,
     // Create a Module for the module that we're defining.
     Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
                                            GlobalModuleFragment);
+    if (IsPartition)
+      Mod->Kind = Module::ModulePartitionInterface;
     assert(Mod && "module creation should not fail");
     break;
   }
@@ -209,14 +228,26 @@ Sema::DeclGroupPtrTy Sema::ActOnModuleDecl(SourceLocation StartLoc,
   case ModuleDeclKind::Implementation:
     std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc(
         PP.getIdentifierInfo(ModuleName), Path[0].second);
-    Mod = getModuleLoader().loadModule(ModuleLoc, {ModuleNameLoc},
-                                       Module::AllVisible,
-                                       /*IsInclusionDirective=*/false);
-    if (!Mod) {
-      Diag(ModuleLoc, diag::err_module_not_defined) << ModuleName;
-      // Create an empty module interface unit for error recovery.
+    if (IsPartition) {
+      // Create an interface, but note that it is an implementation
+      // unit.
       Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
                                              GlobalModuleFragment);
+      Mod->Kind = Module::ModulePartitionImplementation;
+    } else {
+      // C++20 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.
+      Mod = getModuleLoader().loadModule(ModuleLoc, {ModuleNameLoc},
+                                         Module::AllVisible,
+                                         /*IsInclusionDirective=*/false);
+      if (!Mod) {
+        Diag(ModuleLoc, diag::err_module_not_defined) << ModuleName;
+        // Create an empty module interface unit for error recovery.
+        Mod = Map.createModuleForInterfaceUnit(ModuleLoc, ModuleName,
+                                               GlobalModuleFragment);
+      }
     }
     break;
   }
@@ -233,7 +264,9 @@ Sema::DeclGroupPtrTy Sema::ActOnModuleDecl(SourceLocation StartLoc,
   // Switch from the global module fragment (if any) to the named module.
   ModuleScopes.back().BeginLoc = StartLoc;
   ModuleScopes.back().Module = Mod;
-  ModuleScopes.back().ModuleInterface = MDK != ModuleDeclKind::Implementation;
+  ModuleScopes.back().ModuleInterface =
+      (MDK != ModuleDeclKind::Implementation || IsPartition);
+  ModuleScopes.back().IsPartition = IsPartition;
   VisibleModules.setVisible(Mod, ModuleLoc);
 
   // From now on, we have an owning module for all declarations we see.
@@ -317,17 +350,40 @@ Sema::ActOnPrivateModuleFragmentDecl(SourceLocation ModuleLoc,
 
 DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
                                    SourceLocation ExportLoc,
-                                   SourceLocation ImportLoc,
-                                   ModuleIdPath Path) {
-  // Flatten the module path for a C++20 or Modules TS module name.
+                                   SourceLocation ImportLoc, ModuleIdPath Path,
+                                   ModuleIdPath Partition) {
+
+  bool IsPartition = !Partition.empty();
+  bool Cxx20Mode = getLangOpts().CPlusPlusModules || getLangOpts().ModulesTS;
+  assert((!IsPartition || Cxx20Mode) && "partition seen in non-C++20 code?");
+  assert((!IsPartition || Path.empty()) &&
+         "trying to import a partition with its named module specified?");
+
+  // For a C++20 module name, flatten into a single identifier with the source
+  // location of the first component.
   std::pair<IdentifierInfo *, SourceLocation> ModuleNameLoc;
+
   std::string ModuleName;
-  if (getLangOpts().CPlusPlusModules || getLangOpts().ModulesTS) {
-    for (auto &Piece : Path) {
-      if (!ModuleName.empty())
-        ModuleName += ".";
-      ModuleName += Piece.first->getName();
+  if (IsPartition) {
+    // We already checked that we are in a module purview in the parser.
+    assert(!ModuleScopes.empty() && "in a module purview, but no module?");
+    Module *NamedMod = ModuleScopes.back().Module;
+    if (ModuleScopes.back().IsPartition) {
+      // We're importing a partition into a partition, find the name of the
+      // owning named module.
+      size_t P = NamedMod->Name.find_first_of(":");
+      ModuleName = NamedMod->Name.substr(0, P + 1);
+    } else {
+      // We're importing a partition into the named module itself (either the
+      // interface or an implementation TU).
+      ModuleName = NamedMod->Name;
+      ModuleName += ":";
     }
+    ModuleName += stringFromPath(Partition);
+    ModuleNameLoc = {PP.getIdentifierInfo(ModuleName), Partition[0].second};
+    Partition = ModuleIdPath(ModuleNameLoc);
+  } else if (Cxx20Mode) {
+    ModuleName = stringFromPath(Path);
     ModuleNameLoc = {PP.getIdentifierInfo(ModuleName), Path[0].second};
     Path = ModuleIdPath(ModuleNameLoc);
   }
@@ -340,13 +396,14 @@ DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
     return true;
   }
 
-  Module *Mod =
-      getModuleLoader().loadModule(ImportLoc, Path, Module::AllVisible,
-                                   /*IsInclusionDirective=*/false);
+  Module *Mod = getModuleLoader().loadModule(
+      ImportLoc, IsPartition ? Partition : Path, Module::AllVisible,
+      /*IsInclusionDirective=*/false);
   if (!Mod)
     return true;
 
-  return ActOnModuleImport(StartLoc, ExportLoc, ImportLoc, Mod, Path);
+  return ActOnModuleImport(StartLoc, ExportLoc, ImportLoc, Mod,
+                           IsPartition ? Partition : Path);
 }
 
 /// Determine whether \p D is lexically within an export-declaration.
@@ -359,8 +416,8 @@ static const ExportDecl *getEnclosingExportDecl(const Decl *D) {
 
 DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
                                    SourceLocation ExportLoc,
-                                   SourceLocation ImportLoc,
-                                   Module *Mod, ModuleIdPath Path) {
+                                   SourceLocation ImportLoc, Module *Mod,
+                                   ModuleIdPath Path) {
   VisibleModules.setVisible(Mod, ImportLoc);
 
   checkModuleImportContext(*this, Mod, ImportLoc, CurContext);
@@ -379,22 +436,26 @@ DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
   }
 
   SmallVector<SourceLocation, 2> IdentifierLocs;
-  Module *ModCheck = Mod;
-  for (unsigned I = 0, N = Path.size(); I != N; ++I) {
-    // If we've run out of module parents, just drop the remaining identifiers.
-    // We need the length to be consistent.
-    if (!ModCheck)
-      break;
-    ModCheck = ModCheck->Parent;
-
-    IdentifierLocs.push_back(Path[I].second);
-  }
 
-  // If this was a header import, pad out with dummy locations.
-  // FIXME: Pass in and use the location of the header-name token in this case.
   if (Path.empty()) {
-    for (; ModCheck; ModCheck = ModCheck->Parent) {
+    // If this was a header import, pad out with dummy locations.
+    // FIXME: Pass in and use the location of the header-name token in this
+    // case.
+    for (Module *ModCheck = Mod; ModCheck; ModCheck = ModCheck->Parent)
       IdentifierLocs.push_back(SourceLocation());
+  } else if (getLangOpts().CPlusPlusModules && !Mod->Parent) {
+    // A single identifier for the whole name.
+    IdentifierLocs.push_back(Path[0].second);
+  } else {
+    Module *ModCheck = Mod;
+    for (unsigned I = 0, N = Path.size(); I != N; ++I) {
+      // If we've run out of module parents, just drop the remaining
+      // identifiers.  We need the length to be consistent.
+      if (!ModCheck)
+        break;
+      ModCheck = ModCheck->Parent;
+
+      IdentifierLocs.push_back(Path[I].second);
     }
   }
 
@@ -420,6 +481,10 @@ DeclResult Sema::ActOnModuleImport(SourceLocation StartLoc,
     // An export-declaration shall inhabit a namespace scope and appear in the
     // purview of a module interface unit.
     Diag(ExportLoc, diag::err_export_not_in_module_interface) << 0;
+  } else if (getLangOpts().isCompilingModule()) {
+    Module *ThisModule = PP.getHeaderSearchInfo().lookupModule(
+        getLangOpts().CurrentModule, ExportLoc, false, false);
+    assert(ThisModule && "was expecting a module if building one");
   }
 
   return Import;
@@ -457,6 +522,12 @@ void Sema::BuildModuleInclude(SourceLocation DirectiveLoc, Module *Mod) {
 
   getModuleLoader().makeModuleVisible(Mod, Module::AllVisible, DirectiveLoc);
   VisibleModules.setVisible(Mod, DirectiveLoc);
+
+  if (getLangOpts().isCompilingModule()) {
+    Module *ThisModule = PP.getHeaderSearchInfo().lookupModule(
+        getLangOpts().CurrentModule, DirectiveLoc, false, false);
+    assert(ThisModule && "was expecting a module if building one");
+  }
 }
 
 void Sema::ActOnModuleBegin(SourceLocation DirectiveLoc, Module *Mod) {
@@ -757,8 +828,9 @@ Module *Sema::PushGlobalModuleFragment(SourceLocation BeginLoc,
   // Enter the scope of the global module.
   ModuleScopes.push_back({BeginLoc, GlobalModuleFragment,
                           /*ModuleInterface=*/false,
+                          /*IsPartition=*/false,
                           /*ImplicitGlobalModuleFragment=*/IsImplicit,
-                          /*VisibleModuleSet*/ {}});
+                          /*OuterVisibleModules=*/{}});
   VisibleModules.setVisible(GlobalModuleFragment, BeginLoc);
 
   return GlobalModuleFragment;