Ensure that freestanding macros get consistent discriminators

Due to the duality between the expression and declaration forms of
freestanding macros, we could end up assigning two different discriminators
to what is effectively the same freestanding macro expansion. Across
different source files, this could lead to inconsistent discriminators in
different translation units. Unify the storage of the discriminator to
avoid this issue.

Fixes rdar://116259748

Author: DougGregor

include/swift/AST/Decl.h

@@ -792,10 +792,6 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
     NumberOfVTableEntries : 2
   );
 
-  SWIFT_INLINE_BITFIELD(MacroExpansionDecl, Decl, 16,
-    Discriminator : 16
-  );
-
   } Bits;
   // Turn back on clang-format now that we have defined our inline bitfields.
   // clang-format on
@@ -9008,8 +9004,6 @@ class MacroDecl : public GenericContext, public ValueDecl {
 class MacroExpansionDecl : public Decl, public FreestandingMacroExpansion {
 
 public:
-  enum : unsigned { InvalidDiscriminator = 0xFFFF };
-
   MacroExpansionDecl(DeclContext *dc, MacroExpansionInfo *info);
 
   static MacroExpansionDecl *create(DeclContext *dc, SourceLoc poundLoc,
@@ -9029,24 +9023,6 @@ class MacroExpansionDecl : public Decl, public FreestandingMacroExpansion {
   /// Enumerate the nodes produced by expanding this macro expansion.
   void forEachExpandedNode(llvm::function_ref<void(ASTNode)> callback) const;
 
-  /// Returns a discriminator which determines this macro expansion's index
-  /// in the sequence of macro expansions within the current function.
-  unsigned getDiscriminator() const;
-
-  /// Retrieve the raw discriminator, which may not have been computed yet.
-  ///
-  /// Only use this for queries that are checking for (e.g.) reentrancy or
-  /// intentionally do not want to initiate verification.
-  unsigned getRawDiscriminator() const {
-    return Bits.MacroExpansionDecl.Discriminator;
-  }
-
-  void setDiscriminator(unsigned discriminator) {
-    assert(getRawDiscriminator() == InvalidDiscriminator);
-    assert(discriminator != InvalidDiscriminator);
-    Bits.MacroExpansionDecl.Discriminator = discriminator;
-  }
-
   static bool classof(const Decl *D) {
     return D->getKind() == DeclKind::MacroExpansion;
   }

include/swift/AST/Expr.h

@@ -369,11 +369,6 @@ class alignas(8) Expr : public ASTAllocated<Expr> {
     NumElements : 32
   );
 
-  SWIFT_INLINE_BITFIELD(MacroExpansionExpr, Expr, (16-NumExprBits)+16,
-    : 16 - NumExprBits, // Align and leave room for subclasses
-    Discriminator : 16
-  );
-
   } Bits;
   // clang-format on
 
@@ -6309,7 +6304,6 @@ class MacroExpansionExpr final : public Expr,
       : Expr(ExprKind::MacroExpansion, isImplicit, ty),
         FreestandingMacroExpansion(FreestandingMacroKind::Expr, info), DC(dc),
         Rewritten(nullptr), Roles(roles), SubstituteDecl(nullptr) {
-    Bits.MacroExpansionExpr.Discriminator = InvalidDiscriminator;
   }
 
   static MacroExpansionExpr *
@@ -6333,24 +6327,6 @@ class MacroExpansionExpr final : public Expr,
   DeclContext *getDeclContext() const { return DC; }
   void setDeclContext(DeclContext *dc) { DC = dc; }
 
-  /// Returns a discriminator which determines this macro expansion's index
-  /// in the sequence of macro expansions within the current function.
-  unsigned getDiscriminator() const;
-
-  /// Retrieve the raw discriminator, which may not have been computed yet.
-  ///
-  /// Only use this for queries that are checking for (e.g.) reentrancy or
-  /// intentionally do not want to initiate verification.
-  unsigned getRawDiscriminator() const {
-    return Bits.MacroExpansionExpr.Discriminator;
-  }
-
-  void setDiscriminator(unsigned discriminator) {
-    assert(getRawDiscriminator() == InvalidDiscriminator);
-    assert(discriminator != InvalidDiscriminator);
-    Bits.MacroExpansionExpr.Discriminator = discriminator;
-  }
-
   SourceRange getSourceRange() const {
     return getExpansionInfo()->getSourceRange();
   }

include/swift/AST/FreestandingMacroExpansion.h

@@ -45,6 +45,10 @@ struct MacroExpansionInfo : ASTAllocated<MacroExpansionInfo> {
   /// The referenced macro.
   ConcreteDeclRef macroRef;
 
+  enum : unsigned { InvalidDiscriminator = 0xFFFF };
+
+  unsigned Discriminator = InvalidDiscriminator;
+
   MacroExpansionInfo(SourceLoc sigilLoc, DeclNameRef moduleName,
                      DeclNameLoc moduleNameLoc, DeclNameRef macroName,
                      DeclNameLoc macroNameLoc, SourceLoc leftAngleLoc,
@@ -71,12 +75,12 @@ enum class FreestandingMacroKind {
 /// A base class of either 'MacroExpansionExpr' or 'MacroExpansionDecl'.
 class FreestandingMacroExpansion {
   llvm::PointerIntPair<MacroExpansionInfo *, 1, FreestandingMacroKind>
-      infoAndKind;
+    infoAndKind;
 
 protected:
   FreestandingMacroExpansion(FreestandingMacroKind kind,
                              MacroExpansionInfo *info)
-      : infoAndKind(info, kind) {}
+  : infoAndKind(info, kind) {}
 
 public:
   MacroExpansionInfo *getExpansionInfo() const {
@@ -114,7 +118,13 @@ class FreestandingMacroExpansion {
 
   DeclContext *getDeclContext() const;
   SourceRange getSourceRange() const;
+
+  /// Returns a discriminator which determines this macro expansion's index
+  /// in the sequence of macro expansions within the current context.
   unsigned getDiscriminator() const;
+
+  /// Returns the raw discriminator, for debugging purposes only.
+  unsigned getRawDiscriminator() const;
 };
 
 } // namespace swift

lib/AST/Decl.cpp

@@ -11680,7 +11680,6 @@ MacroExpansionDecl::MacroExpansionDecl(DeclContext *dc,
                                        MacroExpansionInfo *info)
     : Decl(DeclKind::MacroExpansion, dc),
       FreestandingMacroExpansion(FreestandingMacroKind::Decl, info) {
-  Bits.MacroExpansionDecl.Discriminator = InvalidDiscriminator;
 }
 
 MacroExpansionDecl *
@@ -11704,23 +11703,6 @@ MacroExpansionDecl::create(
   return new (ctx) MacroExpansionDecl(dc, info);
 }
 
-unsigned MacroExpansionDecl::getDiscriminator() const {
-  if (getRawDiscriminator() != InvalidDiscriminator)
-    return getRawDiscriminator();
-
-  auto mutableThis = const_cast<MacroExpansionDecl *>(this);
-  auto dc = getDeclContext();
-  ASTContext &ctx = dc->getASTContext();
-  auto discriminatorContext =
-      MacroDiscriminatorContext::getParentOf(mutableThis);
-  mutableThis->setDiscriminator(
-      ctx.getNextMacroDiscriminator(
-          discriminatorContext, getMacroName().getBaseName()));
-
-  assert(getRawDiscriminator() != InvalidDiscriminator);
-  return getRawDiscriminator();
-}
-
 void MacroExpansionDecl::forEachExpandedNode(
     llvm::function_ref<void(ASTNode)> callback
 ) const {

lib/AST/Expr.cpp

@@ -2786,23 +2786,6 @@ MacroExpansionExpr *MacroExpansionExpr::create(
   return new (ctx) MacroExpansionExpr(dc, info, roles, isImplicit, ty);
 }
 
-unsigned MacroExpansionExpr::getDiscriminator() const {
-  if (getRawDiscriminator() != InvalidDiscriminator)
-    return getRawDiscriminator();
-
-  auto mutableThis = const_cast<MacroExpansionExpr *>(this);
-  auto dc = getDeclContext();
-  ASTContext &ctx = dc->getASTContext();
-  auto discriminatorContext =
-      MacroDiscriminatorContext::getParentOf(mutableThis);
-  mutableThis->setDiscriminator(
-      ctx.getNextMacroDiscriminator(
-          discriminatorContext, getMacroName().getBaseName()));
-
-  assert(getRawDiscriminator() != InvalidDiscriminator);
-  return getRawDiscriminator();
-}
-
 MacroExpansionDecl *MacroExpansionExpr::createSubstituteDecl() {
   auto dc = DC;
   if (auto *tlcd = dyn_cast_or_null<TopLevelCodeDecl>(dc->getAsDecl()))

lib/AST/FreestandingMacroExpansion.cpp

@@ -11,8 +11,10 @@
 //===----------------------------------------------------------------------===//
 
 #include "swift/AST/FreestandingMacroExpansion.h"
+#include "swift/AST/ASTContext.h"
 #include "swift/AST/Decl.h"
 #include "swift/AST/Expr.h"
+#include "swift/AST/MacroDiscriminatorContext.h"
 
 using namespace swift;
 
@@ -43,7 +45,24 @@ SourceRange FreestandingMacroExpansion::getSourceRange() const {
   FORWARD_VARIANT(getSourceRange);
 }
 unsigned FreestandingMacroExpansion::getDiscriminator() const {
-  FORWARD_VARIANT(getDiscriminator);
+  auto info = getExpansionInfo();
+  if (info->Discriminator != MacroExpansionInfo::InvalidDiscriminator)
+    return info->Discriminator;
+
+  auto mutableThis = const_cast<FreestandingMacroExpansion *>(this);
+  auto dc = getDeclContext();
+  ASTContext &ctx = dc->getASTContext();
+  auto discriminatorContext =
+      MacroDiscriminatorContext::getParentOf(mutableThis);
+  info->Discriminator = ctx.getNextMacroDiscriminator(
+      discriminatorContext, getMacroName().getBaseName());
+
+  assert(info->Discriminator != MacroExpansionInfo::InvalidDiscriminator);
+  return info->Discriminator;
+}
+
+unsigned FreestandingMacroExpansion::getRawDiscriminator() const {
+  return getExpansionInfo()->Discriminator;
 }
 
 ASTNode FreestandingMacroExpansion::getASTNode() {

test/Macros/Inputs/AnonTypes1.swift

@@ -0,0 +1 @@
+#anonymousTypes(public: true) { "hello" }

test/Macros/Inputs/AnonTypes2.swift

@@ -0,0 +1 @@
+#anonymousTypes(public: true) { "hello" }

test/Macros/freestanding_multifile.swift

@@ -0,0 +1,14 @@
+// REQUIRES: swift_swift_parser, executable_test
+
+// RUN: %empty-directory(%t)
+// RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift
+
+@freestanding(declaration)
+macro anonymousTypes(public: Bool, _: () -> String) = #externalMacro(module: "MacroDefinition", type: "DefineAnonymousTypesMacro")
+
+// RUN: %target-swift-frontend -swift-version 5 -emit-ir -load-plugin-library %t/%target-library-name(MacroDefinition) -module-name MacroUser %S/Inputs/AnonTypes1.swift %S/Inputs/AnonTypes2.swift %s -o - -g | %FileCheck --check-prefix CHECK-IR %s
+
+// CHECK-IR: $s9MacroUser33{{.*}}14anonymousTypesfMf_4namefMu_
+// CHECK-IR-NOT: $s9MacroUser33{{.*}}14anonymousTypesfMf0_4namefMu_
+// CHECK-IR: $s9MacroUser33{{.*}}14anonymousTypesfMf_4namefMu_
+// CHECK-IR: $s9MacroUser33{{.*}}14anonymousTypesfMf0_4namefMu_