Add 'EscapedFromIfConfig' bit to Decl

This is a temporary stop-gap for getting round-trip parsing
off the ground. The real fix, not re-injecting declarations
into an if-config's declaration context, is a deep dive and
is still ongoing.

Author: bitjammer

include/swift/AST/Decl.h

@@ -237,8 +237,12 @@ class alignas(1 << DeclAlignInBits) Decl {
 
     /// \brief Whether this declaration is currently being validated.
     unsigned BeingValidated : 1;
+
+    /// \brief Whether this declaration was added to the surrounding
+    /// DeclContext of an active #if config clause.
+    unsigned EscapedFromIfConfig : 1;
   };
-  enum { NumDeclBits = 11 };
+  enum { NumDeclBits = 12 };
   static_assert(NumDeclBits <= 32, "fits in an unsigned");
 
   class PatternBindingDeclBitfields {
@@ -649,6 +653,7 @@ class alignas(1 << DeclAlignInBits) Decl {
     DeclBits.FromClang = false;
     DeclBits.EarlyAttrValidation = false;
     DeclBits.BeingValidated = false;
+    DeclBits.EscapedFromIfConfig = false;
   }
 
   ClangNode getClangNodeImpl() const {
@@ -804,6 +809,14 @@ class alignas(1 << DeclAlignInBits) Decl {
     DeclBits.BeingValidated = ibv;
   }
 
+  bool escapedFromIfConfig() const {
+    return DeclBits.EscapedFromIfConfig;
+  }
+
+  void setEscapedFromIfConfig(bool Escaped) {
+    DeclBits.EscapedFromIfConfig = Escaped;
+  }
+
   /// \returns the unparsed comment attached to this declaration.
   RawComment getRawComment() const;
 

lib/Parse/ParseStmt.cpp

@@ -345,6 +345,9 @@ ParserStatus Parser::parseBraceItems(SmallVectorImpl<ASTNode> &Entries,
       IfConfigStmt *ICS = cast<IfConfigStmt>(Result.get<Stmt*>());
       for (auto &Entry : ICS->getActiveClauseElements()) {
         Entries.push_back(Entry);
+        if (Entry.is<Decl*>()) {
+          Entry.get<Decl*>()->setEscapedFromIfConfig(true);
+        }
       }
     } else if (Tok.is(tok::pound_line)) {
       ParserStatus Status = parseLineDirective(true);