[5.9][Macro] Attributes for freestanding macro expansion

include/swift/AST/DiagnosticsParse.def

@@ -2056,6 +2056,8 @@ ERROR(macro_expansion_expr_expected_macro_identifier,PointsToFirstBadToken,
       "expected a macro identifier for a pound literal expression", ())
 ERROR(macro_expansion_decl_expected_macro_identifier,PointsToFirstBadToken,
       "expected a macro identifier for a pound literal declaration", ())
+ERROR(extra_whitespace_macro_expansion_identifier,PointsToFirstBadToken,
+      "extraneous whitespace between '#' and macro name is not permitted", ())
 
 ERROR(macro_role_attr_expected_kind,PointsToFirstBadToken,
       "expected %select{a freestanding|an attached}0 macro role such as "

include/swift/Parse/Parser.h

@@ -900,11 +900,15 @@ class Parser {
   // Decl Parsing
 
   /// Returns true if parser is at the start of a Swift decl or decl-import.
-  bool isStartOfSwiftDecl(bool allowPoundIfAttributes = true);
+  bool isStartOfSwiftDecl(bool allowPoundIfAttributes = true,
+                          bool hadAttrsOrModifiers = false);
 
   /// Returns true if the parser is at the start of a SIL decl.
   bool isStartOfSILDecl();
 
+  /// Returns true if the parser is at a freestanding macro expansion.
+  bool isStartOfFreestandingMacroExpansion();
+
   /// Parse the top-level Swift items into the provided vector.
   ///
   /// Each item will be a declaration, statement, or expression.
@@ -1747,6 +1751,16 @@ class Parser {
   DeclNameRef parseDeclNameRef(DeclNameLoc &loc, const Diagnostic &diag,
                                DeclNameOptions flags);
 
+  /// Parse macro expansion.
+  ///
+  ///   macro-expansion:
+  ///     '#' identifier generic-arguments? expr-paren? trailing-closure?
+  ParserStatus parseFreestandingMacroExpansion(
+      SourceLoc &poundLoc, DeclNameLoc &macroNameLoc, DeclNameRef &macroNameRef,
+      SourceLoc &leftAngleLoc, SmallVectorImpl<TypeRepr *> &genericArgs,
+      SourceLoc &rightAngleLoc, ArgumentList *&argList, bool isExprBasic,
+      const Diagnostic &diag);
+
   ParserResult<Expr> parseExprIdentifier();
   Expr *parseExprEditorPlaceholder(Token PlaceholderTok,
                                    Identifier PlaceholderId);

lib/AST/ASTWalker.cpp

@@ -1482,7 +1482,7 @@ class Traversal : public ASTVisitor<Traversal, Expr*, Stmt*,
 
   bool shouldSkip(Decl *D) {
     if (!Walker.shouldWalkMacroArgumentsAndExpansion().second &&
-        D->isInMacroExpansionInContext())
+        D->isInMacroExpansionInContext() && !Walker.Parent.isNull())
       return true;
 
     if (auto *VD = dyn_cast<VarDecl>(D)) {

lib/AST/Attr.cpp

@@ -856,7 +856,7 @@ OrigDeclAttrFilter::operator()(const DeclAttribute *Attr) const {
   auto declLoc = decl->getStartLoc();
   auto *mod = decl->getModuleContext();
   auto *declFile = mod->getSourceFileContainingLocation(declLoc);
-  auto *attrFile = mod->getSourceFileContainingLocation(Attr->AtLoc);
+  auto *attrFile = mod->getSourceFileContainingLocation(Attr->getLocation());
   if (!declFile || !attrFile)
     return Attr;
 

lib/AST/Decl.cpp

@@ -17,6 +17,7 @@
 #include "swift/AST/Decl.h"
 #include "swift/AST/ASTContext.h"
 #include "swift/AST/ASTMangler.h"
+#include "swift/AST/ASTPrinter.h"
 #include "swift/AST/ASTWalker.h"
 #include "swift/AST/AccessRequests.h"
 #include "swift/AST/AccessScope.h"
@@ -10065,6 +10066,13 @@ void swift::simple_display(llvm::raw_ostream &out, const Decl *decl) {
       typeRepr->print(out);
     else
       ext->getSelfNominalTypeDecl()->dumpRef(out);
+  } else if (auto med = dyn_cast<MacroExpansionDecl>(decl)) {
+    out << '#' << med->getMacroName() << " in ";
+    printContext(out, med->getDeclContext());
+    if (med->getLoc().isValid()) {
+      out << '@';
+      med->getLoc().print(out, med->getASTContext().SourceMgr);
+    }
   } else {
     out << "(unknown decl)";
   }

lib/ASTGen/CMakeLists.txt

@@ -32,5 +32,6 @@ add_pure_swift_host_library(swiftASTGen STATIC
     SwiftSyntax::SwiftParserDiagnostics
     SwiftSyntax::SwiftSyntax
     SwiftSyntax::SwiftSyntaxMacros
+    SwiftSyntax::SwiftSyntaxMacroExpansion
     swiftLLVMJSON
 )

lib/ASTGen/Package.swift

@@ -37,10 +37,10 @@ let package = Package(
         .product(name: "SwiftOperators", package: "swift-syntax"),
         .product(name: "SwiftParser", package: "swift-syntax"),
         .product(name: "SwiftSyntaxMacros", package: "swift-syntax"),
+        .product(name: "SwiftSyntaxMacroExpansion", package: "swift-syntax"),
         "swiftLLVMJSON"
       ],
       path: "Sources/ASTGen",
-      exclude: ["CMakeLists.txt"],
       swiftSettings: swiftSetttings
     ),
     .target(