Transform the Module class into ModuleDecl.

Modules occupy a weird space in the AST now: they can be treated like
types (Swift.Int), which is captured by ModuleType. They can be
treated like values for disambiguation (Swift.print), which is
captured by ModuleExpr. And we jump through hoops in various places to
store "either a module or a decl".

Start cleaning this up by transforming Module into ModuleDecl, a
TypeDecl that's implicitly created to describe a module. Subsequent
changes will start folding away the special cases (ModuleExpr ->
DeclRefExpr, name lookup results stop having a separate Module case,
etc.).

Note that the Module -> ModuleDecl typedef is there to limit the
changes needed. Much of this patch is actually dealing with the fact
that Module used to have Ctx and Name public members that now need to
be accessed via getASTContext() and getName(), respectively.

Swift SVN r28284

Author: DougGregor

include/swift/AST/ASTContext.h

@@ -63,7 +63,7 @@ namespace swift {
   class FunctionType;
   class ArchetypeType;
   class Identifier;
-  class Module;
+  class ModuleDecl;
   class ModuleLoader;
   class NominalTypeDecl;
   class TupleTypeElt;
@@ -174,13 +174,13 @@ class ASTContext {
   DiagnosticEngine &Diags;
 
   /// The set of top-level modules we have loaded.
-  llvm::DenseMap<Identifier, Module*> LoadedModules;
+  llvm::DenseMap<Identifier, ModuleDecl*> LoadedModules;
 
   /// The builtin module.
-  Module * const TheBuiltinModule;
+  ModuleDecl * const TheBuiltinModule;
 
   /// The standard library module.
-  mutable Module *TheStdlibModule = nullptr;
+  mutable ModuleDecl *TheStdlibModule = nullptr;
 
   /// The name of the standard library module "Swift".
   Identifier StdlibModuleName;
@@ -220,7 +220,7 @@ class ASTContext {
   llvm::StringMap<Type> RemappedTypes;
 
   /// Cache for generic mangling signatures.
-  llvm::DenseMap<std::pair<GenericSignature*, Module*>,
+  llvm::DenseMap<std::pair<GenericSignature*, ModuleDecl*>,
                  CanGenericSignature> ManglingSignatures;
 
 private:
@@ -599,28 +599,28 @@ class ASTContext {
 
   /// \returns a module with a given name that was already loaded.  If the
   /// module was not loaded, returns nullptr.
-  Module *getLoadedModule(
+  ModuleDecl *getLoadedModule(
       ArrayRef<std::pair<Identifier, SourceLoc>> ModulePath) const;
 
-  Module *getLoadedModule(Identifier ModuleName) const;
+  ModuleDecl *getLoadedModule(Identifier ModuleName) const;
 
   /// \brief Attempts to load a module into this ASTContext.
   ///
   /// If a module by this name has already been loaded, the existing module will
   /// be returned.
   ///
   /// \returns The requested module, or NULL if the module cannot be found.
-  Module *getModule(ArrayRef<std::pair<Identifier, SourceLoc>> ModulePath);
+  ModuleDecl *getModule(ArrayRef<std::pair<Identifier, SourceLoc>> ModulePath);
 
-  Module *getModuleByName(StringRef ModuleName);
+  ModuleDecl *getModuleByName(StringRef ModuleName);
 
   /// Returns the standard library module, or null if the library isn't present.
   ///
   /// If \p loadIfAbsent is true, the ASTContext will attempt to load the module
   /// if it hasn't been set yet.
-  Module *getStdlibModule(bool loadIfAbsent = false);
+  ModuleDecl *getStdlibModule(bool loadIfAbsent = false);
 
-  Module *getStdlibModule() const {
+  ModuleDecl *getStdlibModule() const {
     return const_cast<ASTContext *>(this)->getStdlibModule(false);
   }
 
@@ -697,7 +697,7 @@ class ASTContext {
                              DeclContext *gpContext) const;
 
   /// Record compiler-known protocol information in the AST.
-  void recordKnownProtocols(Module *Stdlib);
+  void recordKnownProtocols(ModuleDecl *Stdlib);
 
   /// \brief Retrieve the substitutions for a bound generic type, if known.
   Optional<ArrayRef<Substitution>>

include/swift/AST/ASTVisitor.h

@@ -20,6 +20,7 @@
 
 #include "swift/AST/Decl.h"
 #include "swift/AST/Expr.h"
+#include "swift/AST/Module.h"
 #include "swift/AST/Pattern.h"
 #include "swift/AST/Stmt.h"
 #include "swift/AST/TypeRepr.h"

include/swift/AST/ASTWalker.h

@@ -20,7 +20,7 @@ namespace swift {
 
 class Decl;
 class Expr;
-class Module;
+class ModuleDecl;
 class Stmt;
 class Pattern;
 class TypeRepr;
@@ -37,7 +37,7 @@ class ASTWalker {
     void *Ptr = nullptr;
 
   public:
-    ParentTy(Module *Mod) : Kind(ParentKind::Module), Ptr(Mod) {}
+    ParentTy(ModuleDecl *Mod) : Kind(ParentKind::Module), Ptr(Mod) {}
     ParentTy(Decl *D) : Kind(ParentKind::Decl), Ptr(D) {}
     ParentTy(Stmt *S) : Kind(ParentKind::Stmt), Ptr(S) {}
     ParentTy(Expr *E) : Kind(ParentKind::Expr), Ptr(E) {}
@@ -51,8 +51,9 @@ class ASTWalker {
       return Kind;
     }
 
-    Module *getAsModule() const {
-      return Kind == ParentKind::Module ? static_cast<Module*>(Ptr) : nullptr;
+    ModuleDecl *getAsModule() const {
+      return Kind == ParentKind::Module ? static_cast<ModuleDecl*>(Ptr)
+                                        : nullptr;
     }
     Decl *getAsDecl() const {
       return Kind == ParentKind::Decl ? static_cast<Decl*>(Ptr) : nullptr;

include/swift/AST/ArchetypeBuilder.h

@@ -43,7 +43,7 @@ class GenericSignature;
 class GenericTypeParamDecl;
 class GenericTypeParamType;
 class LazyResolver;
-class Module;
+class ModuleDecl;
 class Pattern;
 class ProtocolConformance;
 class ProtocolDecl;
@@ -114,7 +114,7 @@ class ArchetypeBuilder {
   class InferRequirementsWalker;
   friend class InferRequirementsWalker;
 
-  Module &Mod;
+  ModuleDecl &Mod;
   ASTContext &Context;
   DiagnosticEngine &Diags;
   LazyResolver *Resolver = nullptr;
@@ -157,7 +157,7 @@ class ArchetypeBuilder {
   void visitPotentialArchetypes(F f);
 
 public:
-  ArchetypeBuilder(Module &mod, DiagnosticEngine &diags);
+  ArchetypeBuilder(ModuleDecl &mod, DiagnosticEngine &diags);
 
   /// The type of a callback used to retrieve the superclass and
   /// protocol requirements placed on
@@ -180,11 +180,12 @@ class ArchetypeBuilder {
   /// to which the given type parameter conforms. The produces the final
   /// results of AbstractTypeParamDecl::getProtocols() for an associated type.
   ArchetypeBuilder(
-    Module &mod, DiagnosticEngine &diags, LazyResolver *resolver,
+    ModuleDecl &mod, DiagnosticEngine &diags, LazyResolver *resolver,
     std::function<ArrayRef<ProtocolDecl *>(ProtocolDecl *)>
       getInheritedProtocols,
     GetConformsToCallback getConformsTo,
-    std::function<ProtocolConformance * (Module &M, Type T, ProtocolDecl* P)>
+    std::function<ProtocolConformance * (ModuleDecl &M, Type T,
+                                         ProtocolDecl* P)>
       conformsToProtocol);
   ArchetypeBuilder(ArchetypeBuilder &&);
   ~ArchetypeBuilder();
@@ -193,7 +194,7 @@ class ArchetypeBuilder {
   ASTContext &getASTContext() const { return Context; }
 
   /// Retrieve the module.
-  Module &getModule() const { return Mod; }
+  ModuleDecl &getModule() const { return Mod; }
 
   /// Retrieve the lazy resolver, if there is one.
   LazyResolver *getLazyResolver() const { return Resolver; }
@@ -345,7 +346,7 @@ class ArchetypeBuilder {
   void dump(llvm::raw_ostream &out);
 
   /// FIXME: Share the guts of our mapTypeIntoContext implementation with
-  static Type mapTypeIntoContext(Module *M,
+  static Type mapTypeIntoContext(ModuleDecl *M,
                                  GenericParamList *genericParams,
                                  Type type,
                                  LazyResolver *resolver = nullptr);

include/swift/AST/Attr.h

@@ -437,6 +437,7 @@ class DeclAttribute : public AttributeBase {
     OnGenericTypeParam = 1 << 28,
     OnAssociatedType   = 1 << 29,
     OnParam            = 1 << 30,
+    OnModule           = 1 << 31,
 
     // More coarse-grained aggregations for use in Attr.def.
     OnOperator = OnInfixOperator|OnPrefixOperator|OnPostfixOperator,

include/swift/AST/ClangModuleLoader.h

@@ -34,7 +34,7 @@ class ClangModuleLoader : public ModuleLoader {
 
   /// Returns the module that contains imports and declarations from all loaded
   /// Objective-C header files.
-  virtual Module *getImportedHeaderModule() const = 0;
+  virtual ModuleDecl *getImportedHeaderModule() const = 0;
 
   /// Adds a new search path to the Clang CompilerInstance, as if specified with
   /// -I or -F.

include/swift/AST/Decl.h

@@ -71,7 +71,7 @@ namespace swift {
   class GenericSignature;
   class GenericTypeParamDecl;
   class GenericTypeParamType;
-  class Module;
+  class ModuleDecl;
   class NameAliasType;
   class EnumCaseDecl;
   class EnumElementDecl;
@@ -191,6 +191,7 @@ enum class DescriptiveDeclKind : uint8_t {
   WillSet,
   DidSet,
   EnumElement,
+  Module,
 };
 
 /// Keeps track of stage of circularity checking for the given protocol.
@@ -636,14 +637,15 @@ class alignas(1 << DeclAlignInBits) Decl {
   friend class MemberLookupTable;
 
 private:
-  DeclContext *Context;
+  llvm::PointerUnion<DeclContext *, ASTContext *> Context;
 
   Decl(const Decl&) = delete;
   void operator=(const Decl&) = delete;
 
 protected:
 
-  Decl(DeclKind kind, DeclContext *DC) : OpaqueBits(0), Context(DC) {
+  Decl(DeclKind kind, llvm::PointerUnion<DeclContext *, ASTContext *> context)
+    : OpaqueBits(0), Context(context) {
     DeclBits.Kind = unsigned(kind);
     DeclBits.Invalid = false;
     DeclBits.Implicit = false;
@@ -694,7 +696,9 @@ class alignas(1 << DeclAlignInBits) Decl {
   /// for instance, self.
   bool isUserAccessible() const;
 
-  DeclContext *getDeclContext() const { return Context; }
+  DeclContext *getDeclContext() const {
+    return Context.dyn_cast<DeclContext *>();
+  }
   void setDeclContext(DeclContext *DC);
 
   /// Retrieve the innermost declaration context corresponding to this
@@ -703,12 +707,14 @@ class alignas(1 << DeclAlignInBits) Decl {
   DeclContext *getInnermostDeclContext();
 
   /// \brief Retrieve the module in which this declaration resides.
-  Module *getModuleContext() const;
+  ModuleDecl *getModuleContext() const;
 
   /// getASTContext - Return the ASTContext that this decl lives in.
   ASTContext &getASTContext() const {
-    assert(Context && "Decl doesn't have an assigned context");
-    return Context->getASTContext();
+    if (auto dc = Context.dyn_cast<DeclContext *>())
+      return dc->getASTContext();
+
+    return *Context.get<ASTContext *>();
   }
 
   const DeclAttributes &getAttrs() const {
@@ -836,7 +842,7 @@ class alignas(1 << DeclAlignInBits) Decl {
   bool isPrivateStdlibDecl(bool whitelistProtocols=true) const;
 
   /// Whether this declaration is weak-imported.
-  bool isWeakImported(Module *fromModule) const;
+  bool isWeakImported(ModuleDecl *fromModule) const;
 
   // Make vanilla new/delete illegal for Decls.
   void *operator new(size_t Bytes) = delete;
@@ -1504,7 +1510,7 @@ class ImportDecl : public Decl {
   unsigned NumPathElements;
 
   /// The resolved module.
-  Module *Mod = nullptr;
+  ModuleDecl *Mod = nullptr;
   /// The resolved decls if this is a decl import.
   ArrayRef<ValueDecl *> Decls;
 
@@ -1562,8 +1568,8 @@ class ImportDecl : public Decl {
     return getAttrs().hasAttribute<ExportedAttr>();
   }
 
-  Module *getModule() const { return Mod; }
-  void setModule(Module *M) { Mod = M; }
+  ModuleDecl *getModule() const { return Mod; }
+  void setModule(ModuleDecl *M) { Mod = M; }
 
   ArrayRef<ValueDecl *> getDecls() const { return Decls; }
   void setDecls(ArrayRef<ValueDecl *> Ds) { Decls = Ds; }
@@ -2111,8 +2117,10 @@ class ValueDecl : public Decl {
   llvm::PointerIntPair<Type, 2, OptionalEnum<Accessibility>> TypeAndAccess;
 
 protected:
-  ValueDecl(DeclKind K, DeclContext *DC, DeclName name, SourceLoc NameLoc)
-    : Decl(K, DC), Name(name), NameLoc(NameLoc) {
+  ValueDecl(DeclKind K,
+            llvm::PointerUnion<DeclContext *, ASTContext *> context,
+            DeclName name, SourceLoc NameLoc)
+    : Decl(K, context), Name(name), NameLoc(NameLoc) {
     ValueDeclBits.AlreadyInLookupTable = false;
     ValueDeclBits.CheckedRedeclaration = false;
   }
@@ -2324,18 +2332,18 @@ class ValueDecl : public Decl {
   static bool classof(const Decl *D) {
     return D->getKind() >= DeclKind::First_ValueDecl &&
            D->getKind() <= DeclKind::Last_ValueDecl;
-  }
-  
+  }  
 };
 
 /// This is a common base class for declarations which declare a type.
 class TypeDecl : public ValueDecl {
   MutableArrayRef<TypeLoc> Inherited;
 
 protected:
-  TypeDecl(DeclKind K, DeclContext *DC, Identifier name, SourceLoc NameLoc,
+  TypeDecl(DeclKind K, llvm::PointerUnion<DeclContext *, ASTContext *> context,
+           Identifier name, SourceLoc NameLoc,
            MutableArrayRef<TypeLoc> inherited) :
-    ValueDecl(K, DC, name, NameLoc), Inherited(inherited)
+    ValueDecl(K, context, name, NameLoc), Inherited(inherited)
   {
     TypeDeclBits.CheckedInheritanceClause = false;
     TypeDeclBits.ProtocolsSet = false;
@@ -2774,7 +2782,7 @@ class GenericSignature : public llvm::FoldingSetNode {
   /// TODO: This is what getCanonicalSignature() ought to do, but currently
   /// cannot due to implementation dependencies on 'getAllDependentTypes'
   /// order matching 'getAllArchetypes' order of a generic param list.
-  CanGenericSignature getCanonicalManglingSignature(Module &M) const;
+  CanGenericSignature getCanonicalManglingSignature(ModuleDecl &M) const;
 
   /// Uniquing for the ASTContext.
   void Profile(llvm::FoldingSetNodeID &ID) {
@@ -3109,7 +3117,7 @@ class NominalTypeDecl : public TypeDecl, public DeclContext,
   ///
   /// \returns true if any conformances were found. 
   bool lookupConformance(
-         Module *module, ProtocolDecl *protocol,
+         ModuleDecl *module, ProtocolDecl *protocol,
          SmallVectorImpl<ProtocolConformance *> &conformances) const;
 
   /// Retrieve all of the protocols that this nominal type conforms to.

include/swift/AST/DeclContext.h

@@ -50,7 +50,7 @@ namespace swift {
   class Requirement;
   class SourceFile;
   class Type;
-  class Module;
+  class ModuleDecl;
   class NominalTypeDecl;
   class ProtocolConformance;
   class ValueDecl;
@@ -336,7 +336,7 @@ class alignas(1 << DeclContextAlignInBits) DeclContext {
   }
 
   /// Returns the module context that contains this context.
-  Module *getParentModule() const;
+  ModuleDecl *getParentModule() const;
 
   /// Returns the module scope context that contains this context.
   ///

include/swift/AST/DeclNodes.def

@@ -84,7 +84,8 @@ ABSTRACT_DECL(Value, Decl)
       NOMINAL_TYPE_DECL(Class, NominalTypeDecl)
       NOMINAL_TYPE_DECL(Protocol, NominalTypeDecl)
       DECL_RANGE(NominalType, Enum, Protocol)
-    DECL_RANGE(Type, TypeAlias, Protocol)
+    VALUE_DECL(Module, TypeDecl)
+    DECL_RANGE(Type, TypeAlias, Module)
   ABSTRACT_DECL(AbstractStorage, ValueDecl)
     VALUE_DECL(Var, AbstractStorageDecl)
       VALUE_DECL(Param, VarDecl)

include/swift/AST/Mangle.h

@@ -93,7 +93,7 @@ class Mangler {
     : Buffer(buffer), DWARFMangling(DWARFMangling), UsePunycode(usePunycode) {}
   void mangleContextOf(const ValueDecl *decl, BindGenerics shouldBind);
   void mangleContext(const DeclContext *ctx, BindGenerics shouldBind);
-  void mangleModule(const Module *module);
+  void mangleModule(const ModuleDecl *module);
   void mangleDeclName(const ValueDecl *decl);
   void mangleDeclType(const ValueDecl *decl, ResilienceExpansion expansion,
                       unsigned uncurryingLevel);