[ASTPrinter] Fix decl/structure nested callbacks

For now, just force any pending callbacks before doing the structure
callbacks.  This should be fine, since we are always about to print
*something* that isn't whitespace, so there is no change in location.

Author: benlangmuir

include/swift/AST/ASTPrinter.h

@@ -126,6 +126,8 @@ class ASTPrinter {
                                              const NominalTypeDecl *NTD) {}
 
   /// Called before printing a structured entity.
+  ///
+  /// Callers should use callPrintStructurePre().
   virtual void printStructurePre(PrintStructureKind Kind,
                                  const Decl *D = nullptr) {}
   /// Called after printing a structured entity.
@@ -236,6 +238,16 @@ class ASTPrinter {
     PendingNamePreCallback = Context;
   }
 
+  /// Make a callback to printStructurePre(), performing any necessary
+  /// bookkeeping.
+  void callPrintStructurePre(PrintStructureKind Kind, const Decl *D = nullptr) {
+    // FIXME: As a hack, print an empty string to force the pending callbacks.
+    // The real fix is to incorporate the structure kinds into the pending
+    // callbacks, interleaved with the decls.
+    printTextImpl("");
+    printStructurePre(Kind, D);
+  }
+
   /// To sanitize a malformed utf8 string to a well-formed one.
   static std::string sanitizeUtf8(StringRef Text);
   static bool printTypeInterface(Type Ty, DeclContext *DC, std::string &Result);

lib/AST/ASTPrinter.cpp

@@ -1042,7 +1042,7 @@ void PrintAST::printGenericParams(GenericParamList *Params) {
       }
       auto NM = Arg->getAnyNominal();
       assert(NM && "Cannot get nominal type.");
-      Printer.printStructurePre(PrintStructureKind::GenericParameter, NM);
+      Printer.callPrintStructurePre(PrintStructureKind::GenericParameter, NM);
       Printer << NM->getNameStr(); // FIXME: PrintNameContext::GenericParameter
       Printer.printStructurePost(PrintStructureKind::GenericParameter, NM);
     }
@@ -1053,7 +1053,7 @@ void PrintAST::printGenericParams(GenericParamList *Params) {
       } else {
         Printer << ", ";
       }
-      Printer.printStructurePre(PrintStructureKind::GenericParameter, GP);
+      Printer.callPrintStructurePre(PrintStructureKind::GenericParameter, GP);
       Printer.printName(GP->getName(), PrintNameContext::GenericParameter);
       printInherited(GP);
       Printer.printStructurePost(PrintStructureKind::GenericParameter, GP);
@@ -1101,7 +1101,7 @@ void PrintAST::printWhereClause(ArrayRef<RequirementRepr> requirements) {
         } else {
           Printer << ", ";
         }
-        Printer.printStructurePre(PrintStructureKind::GenericRequirement);
+        Printer.callPrintStructurePre(PrintStructureKind::GenericRequirement);
         Printer << std::get<0>(E);
         Printer << (RequirementReprKind::SameType == std::get<2>(E) ? " == " :
                                                                       " : ");
@@ -1123,7 +1123,7 @@ void PrintAST::printWhereClause(ArrayRef<RequirementRepr> requirements) {
       Printer << ", ";
     }
 
-    Printer.printStructurePre(PrintStructureKind::GenericRequirement);
+    Printer.callPrintStructurePre(PrintStructureKind::GenericRequirement);
     defer {
       Printer.printStructurePost(PrintStructureKind::GenericRequirement);
     };
@@ -2056,7 +2056,7 @@ void PrintAST::visitParamDecl(ParamDecl *decl) {
 
 void PrintAST::printOneParameter(const ParamDecl *param, bool Curried,
                                  bool ArgNameIsAPIByDefault) {
-  Printer.printStructurePre(PrintStructureKind::FunctionParameter, param);
+  Printer.callPrintStructurePre(PrintStructureKind::FunctionParameter, param);
   defer {
     Printer.printStructurePost(PrintStructureKind::FunctionParameter, param);
   };