Teach PackExpansionExpr to keep track of the number of pack expansions

it will expand to, if known. Propagate this information throughout Sema.

llvm-svn: 123470

clang/include/clang/AST/ExprCXX.h

@@ -2612,16 +2612,27 @@ public:
 /// or more function arguments to the function object \c f.
 class PackExpansionExpr : public Expr {
   SourceLocation EllipsisLoc;
+  
+  /// \brief The number of expansions that will be produced by this pack
+  /// expansion expression, if known.
+  ///
+  /// When zero, the number of expansions is not known. Otherwise, this value
+  /// is the number of expansions + 1.
+  unsigned NumExpansions;
+  
   Stmt *Pattern;
   
   friend class ASTStmtReader;
+  friend class ASTStmtWriter;
   
 public:
-  PackExpansionExpr(QualType T, Expr *Pattern, SourceLocation EllipsisLoc)
+  PackExpansionExpr(QualType T, Expr *Pattern, SourceLocation EllipsisLoc,
+                    llvm::Optional<unsigned> NumExpansions)
     : Expr(PackExpansionExprClass, T, Pattern->getValueKind(), 
            Pattern->getObjectKind(), /*TypeDependent=*/true, 
            /*ValueDependent=*/true, /*ContainsUnexpandedParameterPack=*/false),
       EllipsisLoc(EllipsisLoc),
+      NumExpansions(NumExpansions? *NumExpansions + 1 : 0),
       Pattern(Pattern) { }
 
   PackExpansionExpr(EmptyShell Empty) : Expr(PackExpansionExprClass, Empty) { }
@@ -2636,6 +2647,15 @@ public:
   /// expansion.
   SourceLocation getEllipsisLoc() const { return EllipsisLoc; }
   
+  /// \brief Determine the number of expansions that will be produced when 
+  /// this pack expansion is instantiated, if already known.
+  llvm::Optional<unsigned> getNumExpansions() const {
+    if (NumExpansions)
+      return NumExpansions - 1;
+    
+    return llvm::Optional<unsigned>();
+  }
+  
   virtual SourceRange getSourceRange() const;
 
   static bool classof(const Stmt *T) {

clang/include/clang/Sema/Sema.h

@@ -3348,7 +3348,17 @@ public:
   ///
   /// \param EllipsisLoc The location of the ellipsis.
   ExprResult ActOnPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc);
-  
+
+  /// \brief Invoked when parsing an expression followed by an ellipsis, which
+  /// creates a pack expansion.
+  ///
+  /// \param Pattern The expression preceding the ellipsis, which will become
+  /// the pattern of the pack expansion.
+  ///
+  /// \param EllipsisLoc The location of the ellipsis.
+  ExprResult CheckPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc,
+                                llvm::Optional<unsigned> NumExpansions);
+
   /// \brief Determine whether we could expand a pack expansion with the
   /// given set of parameter packs into separate arguments by repeatedly
   /// transforming the pattern.

clang/lib/AST/DeclTemplate.cpp

@@ -332,7 +332,8 @@ ClassTemplateDecl::getInjectedClassNameSpecialization() {
 
       if (NTTP->isParameterPack())
         E = new (Context) PackExpansionExpr(Context.DependentTy, E,
-                                            NTTP->getLocation());
+                                            NTTP->getLocation(),
+                                            llvm::Optional<unsigned>());
       Arg = TemplateArgument(E);
     } else {
       TemplateTemplateParmDecl *TTP = cast<TemplateTemplateParmDecl>(*Param);

clang/lib/AST/TemplateBase.cpp

@@ -384,7 +384,7 @@ TemplateArgumentLoc::getPackExpansionPattern(SourceLocation &Ellipsis,
       = cast<PackExpansionExpr>(Argument.getAsExpr());
     Expr *Pattern = Expansion->getPattern();
     Ellipsis = Expansion->getEllipsisLoc();
-    // FIXME: Variadic templates num expansions
+    NumExpansions = Expansion->getNumExpansions();
     return TemplateArgumentLoc(Pattern, Pattern);
   }
 

clang/lib/Sema/SemaTemplateDeduction.cpp

@@ -1463,9 +1463,6 @@ DeduceTemplateArguments(Sema &S,
   unsigned ArgIdx = 0, ParamIdx = 0;
   for (; hasTemplateArgumentForDeduction(Params, ParamIdx, NumParams); 
        ++ParamIdx) {
-    // FIXME: Variadic templates.
-    // What do we do if the argument is a pack expansion?
-    
     if (!Params[ParamIdx].isPackExpansion()) {
       // The simple case: deduce template arguments by matching Pi and Ai.
       

clang/lib/Sema/SemaTemplateVariadic.cpp

@@ -415,6 +415,11 @@ QualType Sema::CheckPackExpansion(QualType Pattern,
 }
 
 ExprResult Sema::ActOnPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc) {
+  return CheckPackExpansion(Pattern, EllipsisLoc, llvm::Optional<unsigned>());
+}
+
+ExprResult Sema::CheckPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc,
+                                    llvm::Optional<unsigned> NumExpansions) {
   if (!Pattern)
     return ExprError();
   
@@ -430,7 +435,7 @@ ExprResult Sema::ActOnPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc) {
   
   // Create the pack expansion expression and source-location information.
   return Owned(new (Context) PackExpansionExpr(Context.DependentTy, Pattern,
-                                               EllipsisLoc));
+                                               EllipsisLoc, NumExpansions));
 }
 
 /// \brief Retrieve the depth and index of a parameter pack.
@@ -459,10 +464,6 @@ bool Sema::CheckParameterPacksForExpansion(SourceLocation EllipsisLoc,
   std::pair<IdentifierInfo *, SourceLocation> FirstPack;
   bool HaveFirstPack = false;
   
-  // FIXME: Variadic templates. Even if we don't expand, we'd still like to
-  // return the number of expansions back to the caller, perhaps as an 
-  // llvm::Optional, so that it can be embedded in the pack expansion. This
-  // is important for the multi-level substitution case.
   for (unsigned I = 0; I != NumUnexpanded; ++I) {
     // Compute the depth and index for this parameter pack.
     unsigned Depth;

clang/lib/Sema/TreeTransform.h

@@ -2176,8 +2176,8 @@ public:
     switch (Pattern.getArgument().getKind()) {
     case TemplateArgument::Expression: {
       ExprResult Result
-        = getSema().ActOnPackExpansion(Pattern.getSourceExpression(),
-                                       EllipsisLoc);
+        = getSema().CheckPackExpansion(Pattern.getSourceExpression(),
+                                       EllipsisLoc, NumExpansions);
       if (Result.isInvalid())
         return TemplateArgumentLoc();
           
@@ -2217,8 +2217,9 @@ public:
   /// By default, performs semantic analysis to build a new pack expansion
   /// for an expression. Subclasses may override this routine to provide 
   /// different behavior.
-  ExprResult RebuildPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc) {
-    return getSema().ActOnPackExpansion(Pattern, EllipsisLoc);
+  ExprResult RebuildPackExpansion(Expr *Pattern, SourceLocation EllipsisLoc,
+                                  llvm::Optional<unsigned> NumExpansions) {
+    return getSema().CheckPackExpansion(Pattern, EllipsisLoc, NumExpansions);
   }
   
 private:
@@ -2308,7 +2309,9 @@ bool TreeTransform<Derived>::TransformExprs(Expr **Inputs,
       // be expanded.
       bool Expand = true;
       bool RetainExpansion = false;
-      llvm::Optional<unsigned> NumExpansions;
+      llvm::Optional<unsigned> OrigNumExpansions
+        = Expansion->getNumExpansions();
+      llvm::Optional<unsigned> NumExpansions = OrigNumExpansions;
       if (getDerived().TryExpandParameterPacks(Expansion->getEllipsisLoc(),
                                                Pattern->getSourceRange(),
                                                Unexpanded.data(),
@@ -2326,9 +2329,9 @@ bool TreeTransform<Derived>::TransformExprs(Expr **Inputs,
         if (OutPattern.isInvalid())
           return true;
         
-        // FIXME: Variadic templates NumExpansions
         ExprResult Out = getDerived().RebuildPackExpansion(OutPattern.get(), 
-                                                Expansion->getEllipsisLoc());
+                                                Expansion->getEllipsisLoc(),
+                                                           NumExpansions);
         if (Out.isInvalid())
           return true;
         
@@ -2347,7 +2350,8 @@ bool TreeTransform<Derived>::TransformExprs(Expr **Inputs,
           return true;
 
         if (Out.get()->containsUnexpandedParameterPack()) {
-          Out = RebuildPackExpansion(Out.get(), Expansion->getEllipsisLoc());
+          Out = RebuildPackExpansion(Out.get(), Expansion->getEllipsisLoc(),
+                                     OrigNumExpansions);
           if (Out.isInvalid())
             return true;
         }
@@ -6818,7 +6822,8 @@ TreeTransform<Derived>::TransformPackExpansionExpr(PackExpansionExpr *E) {
   if (!getDerived().AlwaysRebuild() && Pattern.get() == E->getPattern())
     return SemaRef.Owned(E);
 
-  return getDerived().RebuildPackExpansion(Pattern.get(), E->getEllipsisLoc());
+  return getDerived().RebuildPackExpansion(Pattern.get(), E->getEllipsisLoc(),
+                                           E->getNumExpansions());
 }
 
 template<typename Derived>

clang/lib/Serialization/ASTReaderStmt.cpp

@@ -1294,6 +1294,7 @@ void ASTStmtReader::VisitCXXNoexceptExpr(CXXNoexceptExpr *E) {
 void ASTStmtReader::VisitPackExpansionExpr(PackExpansionExpr *E) {
   VisitExpr(E);
   E->EllipsisLoc = ReadSourceLocation(Record, Idx);
+  E->NumExpansions = Record[Idx++];
   E->Pattern = Reader.ReadSubExpr();  
 }
 

clang/lib/Serialization/ASTWriterStmt.cpp

@@ -1301,6 +1301,7 @@ void ASTStmtWriter::VisitCXXNoexceptExpr(CXXNoexceptExpr *E) {
 void ASTStmtWriter::VisitPackExpansionExpr(PackExpansionExpr *E) {
   VisitExpr(E);
   Writer.AddSourceLocation(E->getEllipsisLoc(), Record);
+  Record.push_back(E->NumExpansions);
   Writer.AddStmt(E->getPattern());
   Code = serialization::EXPR_PACK_EXPANSION;
 }

clang/test/CXX/temp/temp.decls/temp.variadic/multi-level-substitution.cpp

@@ -37,4 +37,33 @@ namespace PacksAtDifferentLevels {
                                         pair<int, unsigned int>,
                                         pair<long, unsigned long>>
                                        >::value == 1? 1 : -1]; 
+
+  template<unsigned ...Values> struct unsigned_tuple { };
+  template<typename ...Types>
+  struct X1 {
+    template<typename, typename> struct Inner {
+      static const unsigned value = 0;
+    };
+
+    template<typename ...YTypes>
+    struct Inner<tuple<pair<Types, YTypes>...>,
+                 unsigned_tuple<sizeof(Types) + sizeof(YTypes)...>> {
+      static const unsigned value = 1;
+    };
+  };
+
+  int check2[X1<short, int, long>::Inner<tuple<pair<short, unsigned short>,
+                                               pair<int, unsigned int>,
+                                               pair<long, unsigned long>>,
+                      unsigned_tuple<sizeof(short) + sizeof(unsigned short),
+                                     sizeof(int) + sizeof(unsigned int),
+                                     sizeof(long) + sizeof(unsigned long)>
+                                       >::value == 1? 1 : -1];
+  int check3[X1<short, int>::Inner<tuple<pair<short, unsigned short>,
+                                         pair<int, unsigned int>,
+                                         pair<long, unsigned long>>,
+                      unsigned_tuple<sizeof(short) + sizeof(unsigned short),
+                                     sizeof(int) + sizeof(unsigned int),
+                                     sizeof(long) + sizeof(unsigned long)>
+                                       >::value == 0? 1 : -1];
 }