Remove IfConfigDecl from the AST

The swift-syntax tree retains information about the parsed #if
regions. Drop it from the semantic AST.

Author: DougGregor

include/swift/AST/Decl.h

@@ -151,7 +151,6 @@ enum class DescriptiveDeclKind : uint8_t {
   Extension,
   EnumCase,
   TopLevelCode,
-  IfConfig,
   PoundDiagnostic,
   PatternBinding,
   Var,
@@ -819,11 +818,6 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
     HasLazyConformances : 1
   );
 
-  SWIFT_INLINE_BITFIELD(IfConfigDecl, Decl, 1,
-    /// Whether this decl is missing its closing '#endif'.
-    HadMissingEnd : 1
-  );
-
   SWIFT_INLINE_BITFIELD(PoundDiagnosticDecl, Decl, 1+1,
     /// `true` if the diagnostic is an error, `false` if it's a warning.
     IsError : 1,
@@ -2658,51 +2652,6 @@ class SerializedTopLevelCodeDeclContext : public DeclContext {
   }
 };
 
-/// IfConfigDecl - This class represents #if/#else/#endif blocks.
-/// Active and inactive block members are stored separately, with the intention
-/// being that active members will be handed back to the enclosing context.
-class IfConfigDecl : public Decl {
-  /// An array of clauses controlling each of the #if/#elseif/#else conditions.
-  /// The array is ASTContext allocated.
-  ArrayRef<IfConfigClause> Clauses;
-  SourceLoc EndLoc;
-  SourceLoc getLocFromSource() const { return Clauses[0].Loc; }
-  friend class Decl;
-public:
-  
-  IfConfigDecl(DeclContext *Parent, ArrayRef<IfConfigClause> Clauses,
-               SourceLoc EndLoc, bool HadMissingEnd)
-    : Decl(DeclKind::IfConfig, Parent), Clauses(Clauses), EndLoc(EndLoc)
-  {
-    Bits.IfConfigDecl.HadMissingEnd = HadMissingEnd;
-  }
-
-  ArrayRef<IfConfigClause> getClauses() const { return Clauses; }
-
-  /// Return the active clause, or null if there is no active one.
-  const IfConfigClause *getActiveClause() const {
-    for (auto &Clause : Clauses)
-      if (Clause.isActive) return &Clause;
-    return nullptr;
-  }
-
-  const ArrayRef<ASTNode> getActiveClauseElements() const {
-    if (auto *Clause = getActiveClause())
-      return Clause->Elements;
-    return {};
-  }
-  
-  SourceLoc getEndLoc() const { return EndLoc; }
-
-  bool hadMissingEnd() const { return Bits.IfConfigDecl.HadMissingEnd; }
-  
-  SourceRange getSourceRange() const;
-  
-  static bool classof(const Decl *D) {
-    return D->getKind() == DeclKind::IfConfig;
-  }
-};
-
 class StringLiteralExpr;
 
 class PoundDiagnosticDecl : public Decl {

include/swift/AST/DeclExportabilityVisitor.h

@@ -170,7 +170,6 @@ class DeclExportabilityVisitor
 #define UNINTERESTING(KIND)                                                    \
   bool visit##KIND##Decl(const KIND##Decl *D) { return true; }
   UNINTERESTING(TopLevelCode);
-  UNINTERESTING(IfConfig);
   UNINTERESTING(Import);
   UNINTERESTING(PoundDiagnostic);
   UNINTERESTING(PrecedenceGroup);

include/swift/AST/DeclNodes.def

@@ -185,7 +185,6 @@ ABSTRACT_DECL(Value, Decl)
 ITERABLE_GENERIC_DECL(Extension, Decl)
 CONTEXT_DECL(TopLevelCode, Decl)
 DECL(Import, Decl)
-DECL(IfConfig, Decl)
 DECL(PoundDiagnostic, Decl)
 DECL(PrecedenceGroup, Decl)
 DECL(Missing, Decl)

include/swift/AST/TypeMemberVisitor.h

@@ -42,12 +42,6 @@ class TypeMemberVisitor : public DeclVisitor<ImplClass, RetTy> {
   BAD_MEMBER(PrecedenceGroup)
   BAD_MEMBER(Macro)
 
-  // The children of these are automatically inserted into the
-  // surrounding context.
-  RetTy visitIfConfigDecl(IfConfigDecl *D) {
-    return RetTy();
-  }
-
   // These decls are disregarded.
   RetTy visitPoundDiagnosticDecl(PoundDiagnosticDecl *D) {
     return RetTy();

include/swift/Parse/Parser.h

@@ -1023,7 +1023,7 @@ class Parser {
       llvm::function_ref<void(bool)> parseElements);
 
   /// Parse an #if ... #endif containing only attributes.
-  ParserStatus parseIfConfigDeclAttributes(
+  ParserStatus parseIfConfigAttributes(
     DeclAttributes &attributes, bool ifConfigsAreDeclAttrs,
     PatternBindingInitializer *initContext);
 

include/swift/SIL/SILWitnessVisitor.h

@@ -172,11 +172,6 @@ template <class T> class SILWitnessVisitor : public ASTVisitor<T> {
     // We only care about the contained VarDecls.
   }
 
-  void visitIfConfigDecl(IfConfigDecl *icd) {
-    // We only care about the active members, which were already subsumed by the
-    // enclosing type.
-  }
-
   void visitPoundDiagnosticDecl(PoundDiagnosticDecl *pdd) {
     // We don't care about diagnostics at this stage.
   }

lib/APIDigester/ModuleAnalyzerNodes.cpp

@@ -1943,8 +1943,6 @@ SwiftDeclCollector::addMembersToRoot(SDKNode *Root, IterableDeclContext *Context
       // All containing variables should have been handled.
     } else if (isa<EnumCaseDecl>(Member)) {
       // All containing variables should have been handled.
-    } else if (isa<IfConfigDecl>(Member)) {
-      // All containing members should have been handled.
     } else if (isa<PoundDiagnosticDecl>(Member)) {
       // All containing members should have been handled.
     } else if (isa<DestructorDecl>(Member)) {

lib/AST/ASTDumper.cpp

@@ -1634,12 +1634,6 @@ namespace {
       printFoot();
     }
 
-    void visitIfConfigDecl(IfConfigDecl *ICD, StringRef label) {
-      printCommon(ICD, "if_config_decl", label);
-      printRecRange(ICD->getClauses(), &ICD->getASTContext(), "clauses");
-      printFoot();
-    }
-
     void visitPoundDiagnosticDecl(PoundDiagnosticDecl *PDD, StringRef label) {
       printCommon(PDD, "pound_diagnostic_decl", label);
       printField(PDD->isError() ? "error" : "warning", "kind");

lib/AST/ASTMangler.cpp

@@ -4871,7 +4871,6 @@ ASTMangler::BaseEntitySignature::BaseEntitySignature(const Decl *decl)
     case DeclKind::Extension:
     case DeclKind::TopLevelCode:
     case DeclKind::Import:
-    case DeclKind::IfConfig:
     case DeclKind::PoundDiagnostic:
     case DeclKind::PrecedenceGroup:
     case DeclKind::Missing:

lib/AST/ASTPrinter.cpp

@@ -2284,10 +2284,6 @@ bool ShouldPrintChecker::shouldPrint(const Decl *D,
     return false;
   }
 
-  if (isa<IfConfigDecl>(D)) {
-    return false;
-  }
-
   return true;
 }
 
@@ -3373,10 +3369,6 @@ void PrintAST::visitTopLevelCodeDecl(TopLevelCodeDecl *decl) {
   printASTNodes(decl->getBody()->getElements(), /*NeedIndent=*/false);
 }
 
-void PrintAST::visitIfConfigDecl(IfConfigDecl *ICD) {
-  // Never printed
-}
-
 void PrintAST::visitPoundDiagnosticDecl(PoundDiagnosticDecl *PDD) {
   /// TODO: Should we even print #error/#warning?
   if (PDD->isError()) {
@@ -5533,8 +5525,6 @@ void PrintAST::visitSwitchStmt(SwitchStmt *stmt) {
   for (auto N : stmt->getRawCases()) {
     if (N.is<Stmt*>())
       visit(cast<CaseStmt>(N.get<Stmt*>()));
-    else
-      visit(cast<IfConfigDecl>(N.get<Decl*>()));
     Printer.printNewline();
   }
   indent();
@@ -5633,10 +5623,6 @@ bool Decl::shouldPrintInContext(const PrintOptions &PO) const {
     }
   }
 
-  if (isa<IfConfigDecl>(this)) {
-    return false;
-  }
-
   // Print everything else.
   return true;
 }