[Clang][NFC] Refactor "Designators" to be more similar

[void]

Summary

This makes the two interfaces for designators more similar so that it's
easier to merge them together in a future refactoring.

[void]

Rebase.

[shafik]

I guess this is prep work for tackling unifying them later on as you attempted in https://reviews.llvm.org/D140584

I knew this is not exactly the same change but can you add the test case identified in https://github.com/llvm/llvm-project/issues/61118 and https://github.com/llvm/llvm-project/issues/46132 as possible regression tests to insure that during this refactor process we don't run into the same issue as before.

Thank you

[shafik]

I guess I should have waited till I saw: https://reviews.llvm.org/D147673

[void]

In D147580#4250232, @shafik wrote:

I guess I should have waited till I saw: https://reviews.llvm.org/D147673

Yeah, sorry about that. I realized that I still needed to add the testcase before continuing. :-)

clang/include/clang/AST/Expr.h

DesignatedInitExpr(const ASTContext &C, QualType Ty,
                      SourceLocation EqualOrColonLoc, bool GNUSyntax,
                      ArrayRef<Expr *> IndexExprs, Expr *Init);
 
   explicit DesignatedInitExpr(unsigned NumSubExprs)
     : Expr(DesignatedInitExprClass, EmptyShell()),
       NumDesignators(0), NumSubExprs(NumSubExprs), Designators(nullptr) { }
 
 public:
+  /// Represents a single C99 designator.
+  ///
+  /// @todo This class is infuriatingly similar to clang::Designator,
+  /// but minor differences (storing indices vs. storing pointers)
+  /// keep us from reusing it. Try harder, later, to rectify these
+  /// differences.
+  class Designator {
     /// A field designator, e.g., ".x".
-  struct FieldDesignator {
+    struct FieldDesignatorInfo {
       /// Refers to the field that is being initialized. The low bit
       /// of this field determines whether this is actually a pointer
       /// to an IdentifierInfo (if 1) or a FieldDecl (if 0). When
       /// initially constructed, a field designator will store an
       /// IdentifierInfo*. After semantic analysis has resolved that
       /// name, the field designator will instead store a FieldDecl*.
       uintptr_t NameOrField;
 
       /// The location of the '.' in the designated initializer.
       SourceLocation DotLoc;
 
       /// The location of the field name in the designated initializer.
       SourceLocation FieldLoc;
+
+      FieldDesignatorInfo(const IdentifierInfo *II, SourceLocation DotLoc,
+                          SourceLocation FieldLoc)
+          : NameOrField(reinterpret_cast<uintptr_t>(II) | 0x1), DotLoc(DotLoc),
+            FieldLoc(FieldLoc) {}
     };
 
-  /// An array or GNU array-range designator, e.g., "[9]" or "[10..15]".
-  struct ArrayOrRangeDesignator {
+    /// An array or GNU array-range designator, e.g., "[9]" or "[10...15]".
+    struct ArrayOrRangeDesignatorInfo {
       /// Location of the first index expression within the designated
       /// initializer expression's list of subexpressions.
       unsigned Index;
+
       /// The location of the '[' starting the array range designator.
       SourceLocation LBracketLoc;
+
       /// The location of the ellipsis separating the start and end
       /// indices. Only valid for GNU array-range designators.
       SourceLocation EllipsisLoc;
+
       /// The location of the ']' terminating the array range designator.
       SourceLocation RBracketLoc;
+
+      ArrayOrRangeDesignatorInfo(unsigned Index, SourceLocation LBracketLoc,
+                                 SourceLocation RBracketLoc)
+          : Index(Index), LBracketLoc(LBracketLoc), RBracketLoc(RBracketLoc) {}
+
+      ArrayOrRangeDesignatorInfo(unsigned Index,
+                                 SourceLocation LBracketLoc,
+                                 SourceLocation EllipsisLoc,
+                                 SourceLocation RBracketLoc)
+          : Index(Index), LBracketLoc(LBracketLoc), EllipsisLoc(EllipsisLoc),
+            RBracketLoc(RBracketLoc) {}
     };
 
-  /// Represents a single C99 designator.
-  ///
-  /// @todo This class is infuriatingly similar to clang::Designator,
-  /// but minor differences (storing indices vs. storing pointers)
-  /// keep us from reusing it. Try harder, later, to rectify these
-  /// differences.
-  class Designator {
     /// The kind of designator this describes.
-    enum {
+    enum DesignatorKind {
       FieldDesignator,
       ArrayDesignator,
       ArrayRangeDesignator
-    } Kind;
+    };
+
+    DesignatorKind Kind;
 
     union {
       /// A field designator, e.g., ".x".
-      struct FieldDesignator Field;
+      struct FieldDesignatorInfo FieldInfo;
+
       /// An array or GNU array-range designator, e.g., "[9]" or "[10..15]".
-      struct ArrayOrRangeDesignator ArrayOrRange;
+      struct ArrayOrRangeDesignatorInfo ArrayOrRangeInfo;
     };
-    friend class DesignatedInitExpr;
+
+    Designator(DesignatorKind Kind) : Kind(Kind) {}
 
   public:
     Designator() {}
 
-    /// Initializes a field designator.
-    Designator(const IdentifierInfo *FieldName, SourceLocation DotLoc,
-               SourceLocation FieldLoc)
-      : Kind(FieldDesignator) {
-      new (&Field) DesignatedInitExpr::FieldDesignator;
-      Field.NameOrField = reinterpret_cast<uintptr_t>(FieldName) | 0x01;
-      Field.DotLoc = DotLoc;
-      Field.FieldLoc = FieldLoc;
-    }
-
-    /// Initializes an array designator.
-    Designator(unsigned Index, SourceLocation LBracketLoc,
-               SourceLocation RBracketLoc)
-      : Kind(ArrayDesignator) {
-      new (&ArrayOrRange) DesignatedInitExpr::ArrayOrRangeDesignator;
-      ArrayOrRange.Index = Index;
-      ArrayOrRange.LBracketLoc = LBracketLoc;
-      ArrayOrRange.EllipsisLoc = SourceLocation();
-      ArrayOrRange.RBracketLoc = RBracketLoc;
-    }
-
-    /// Initializes a GNU array-range designator.
-    Designator(unsigned Index, SourceLocation LBracketLoc,
-               SourceLocation EllipsisLoc, SourceLocation RBracketLoc)
-      : Kind(ArrayRangeDesignator) {
-      new (&ArrayOrRange) DesignatedInitExpr::ArrayOrRangeDesignator;
-      ArrayOrRange.Index = Index;
-      ArrayOrRange.LBracketLoc = LBracketLoc;
-      ArrayOrRange.EllipsisLoc = EllipsisLoc;
-      ArrayOrRange.RBracketLoc = RBracketLoc;
-    }
-
     bool isFieldDesignator() const { return Kind == FieldDesignator; }
     bool isArrayDesignator() const { return Kind == ArrayDesignator; }
     bool isArrayRangeDesignator() const { return Kind == ArrayRangeDesignator; }
 
-    IdentifierInfo *getFieldName() const;
+    //===------------------------------------------------------------------===//
+    // FieldDesignatorInfo
+
+    /// Initializes a field designator.
+    static Designator CreateFieldDesignator(const IdentifierInfo *FieldName,
+                                            SourceLocation DotLoc,
+                                            SourceLocation FieldLoc) {
+      Designator D(FieldDesignator);
+      new (&D.FieldInfo) FieldDesignatorInfo(FieldName, DotLoc, FieldLoc);
+      return D;
+    }
+
+    const IdentifierInfo *getFieldName() const;
 
     FieldDecl *getField() const {
-      assert(Kind == FieldDesignator && "Only valid on a field designator");
-      if (Field.NameOrField & 0x01)
+      assert(isFieldDesignator() && "Only valid on a field designator");
+      if (FieldInfo.NameOrField & 0x01)
         return nullptr;
       else
-        return reinterpret_cast<FieldDecl *>(Field.NameOrField);
+        return reinterpret_cast<FieldDecl *>(FieldInfo.NameOrField);
     }
 
     void setField(FieldDecl *FD) {
-      assert(Kind == FieldDesignator && "Only valid on a field designator");
-      Field.NameOrField = reinterpret_cast<uintptr_t>(FD);
+      assert(isFieldDesignator() && "Only valid on a field designator");
+      FieldInfo.NameOrField = reinterpret_cast<uintptr_t>(FD);
     }
 
     SourceLocation getDotLoc() const {
-      assert(Kind == FieldDesignator && "Only valid on a field designator");
-      return Field.DotLoc;
+      assert(isFieldDesignator() && "Only valid on a field designator");
+      return FieldInfo.DotLoc;
     }
 
     SourceLocation getFieldLoc() const {
-      assert(Kind == FieldDesignator && "Only valid on a field designator");
-      return Field.FieldLoc;
+      assert(isFieldDesignator() && "Only valid on a field designator");
+      return FieldInfo.FieldLoc;
     }
 
-    SourceLocation getLBracketLoc() const {
-      assert((Kind == ArrayDesignator || Kind == ArrayRangeDesignator) &&
+    //===------------------------------------------------------------------===//
+    // ArrayOrRangeDesignator
+
+    /// Initializes an array designator.
+    static Designator CreateArrayDesignator(unsigned Index,
+                                            SourceLocation LBracketLoc,
+                                            SourceLocation RBracketLoc) {
+      Designator D(ArrayDesignator);
+      new (&D.ArrayOrRangeInfo) ArrayOrRangeDesignatorInfo(Index, LBracketLoc,
+                                                           RBracketLoc);
+      return D;
+    }
+
+    /// Initializes a GNU array-range designator.
+    static Designator CreateArrayRangeDesignator(unsigned Index,
+                                                 SourceLocation LBracketLoc,
+                                                 SourceLocation EllipsisLoc,
+                                                 SourceLocation RBracketLoc) {
+      Designator D(ArrayRangeDesignator);
+      new (&D.ArrayOrRangeInfo) ArrayOrRangeDesignatorInfo(Index, LBracketLoc,
+                                                           EllipsisLoc,
+                                                           RBracketLoc);
+      return D;
+    }
+
+    unsigned getArrayIndex() const {
+      assert((isArrayDesignator() || isArrayRangeDesignator()) &&
              "Only valid on an array or array-range designator");
-      return ArrayOrRange.LBracketLoc;
+      return ArrayOrRangeInfo.Index;
     }
 
-    SourceLocation getRBracketLoc() const {
-      assert((Kind == ArrayDesignator || Kind == ArrayRangeDesignator) &&
+    SourceLocation getLBracketLoc() const {
+      assert((isArrayDesignator() || isArrayRangeDesignator()) &&
              "Only valid on an array or array-range designator");
-      return ArrayOrRange.RBracketLoc;
+      return ArrayOrRangeInfo.LBracketLoc;
     }
 
     SourceLocation getEllipsisLoc() const {
-      assert(Kind == ArrayRangeDesignator &&
+      assert(isArrayRangeDesignator() &&
              "Only valid on an array-range designator");
-      return ArrayOrRange.EllipsisLoc;
+      return ArrayOrRangeInfo.EllipsisLoc;
     }
 
-    unsigned getFirstExprIndex() const {
-      assert((Kind == ArrayDesignator || Kind == ArrayRangeDesignator) &&
+    SourceLocation getRBracketLoc() const {
+      assert((isArrayDesignator() || isArrayRangeDesignator()) &&
+             "Only valid on an array or array-range designator");
+      return ArrayOrRangeInfo.RBracketLoc;
+    }
+
+    unsigned xgetFirstExprIndex() const {
+      assert((isArrayDesignator() || isArrayRangeDesignator()) &&
              "Only valid on an array or array-range designator");
-      return ArrayOrRange.Index;
+      return ArrayOrRangeInfo.Index;
     }
 
     SourceLocation getBeginLoc() const LLVM_READONLY {
-      if (Kind == FieldDesignator)
-        return getDotLoc().isInvalid()? getFieldLoc() : getDotLoc();
-      else
-        return getLBracketLoc();
+      if (isFieldDesignator())
+        return getDotLoc().isInvalid() ? getFieldLoc() : getDotLoc();
     }
+
     SourceLocation getEndLoc() const LLVM_READONLY {
-      return Kind == FieldDesignator ? getFieldLoc() : getRBracketLoc();
+      return isFieldDesignator() ? getFieldLoc() : getRBracketLoc();
     }
+
     SourceRange getSourceRange() const LLVM_READONLY {
       return SourceRange(getBeginLoc(), getEndLoc());
     }
   };
 
   static DesignatedInitExpr *Create(const ASTContext &C,
                                     llvm::ArrayRef<Designator> Designators,
                                     ArrayRef<Expr*> IndexExprs,

clang/include/clang/Sema/Designator.h

 
 class Expr;
 class IdentifierInfo;
 class Sema;
 
 /// Designator - A designator in a C99 designated initializer.
 ///
 /// This class is a discriminated union which holds the various
-/// different sorts of designators possible.  A Designation is an array of
+/// different sorts of designators possible. A Designation is an array of
 /// these.  An example of a designator are things like this:
-///     [8] .field [47]        // C99 designation: 3 designators
-///     [8 ... 47]  field:     // GNU extensions: 2 designators
+///
+///      [8] .field [47]        // C99 designation: 3 designators
+///      [8 ... 47]  field:     // GNU extensions: 2 designators
+///
 /// These occur in initializers, e.g.:
-///  int a[10] = {2, 4, [8]=9, 10};
+///
+///      int a[10] = {2, 4, [8]=9, 10};
 ///
 class Designator {
-public:
-  enum DesignatorKind {
-    FieldDesignator, ArrayDesignator, ArrayRangeDesignator
-  };
-private:
-  Designator() {};
-
-  DesignatorKind Kind;
-
+  /// A field designator, e.g., ".x = 42".
   struct FieldDesignatorInfo {
+    /// Refers to the field being initialized.
     const IdentifierInfo *II;
+
+    /// The location of the '.' in the designated initializer.
     SourceLocation DotLoc;
+
+    /// The location of the field name in the designated initializer.
     SourceLocation NameLoc;
+
+    FieldDesignatorInfo(const IdentifierInfo *II, SourceLocation DotLoc,
+                        SourceLocation NameLoc)
+        : II(II), DotLoc(DotLoc), NameLoc(NameLoc) {}
   };
+
+  /// An array designator, e.g., "[42] = 0".
   struct ArrayDesignatorInfo {
     Expr *Index;
+
+    // The location of the '[' in the designated initializer.
     SourceLocation LBracketLoc;
+
+    // The location of the ']' in the designated initializer.
     mutable SourceLocation RBracketLoc;
+
+    ArrayDesignatorInfo(Expr *Index, SourceLocation LBracketLoc)
+        : Index(Index), LBracketLoc(LBracketLoc) {}
   };
+
+  /// An array range designator, e.g. "[42 ... 50] = 1".
   struct ArrayRangeDesignatorInfo {
-    Expr *Start, *End;
-    SourceLocation LBracketLoc, EllipsisLoc;
+    Expr *Start;
+    Expr *End;
+
+    // The location of the '[' in the designated initializer.
+    SourceLocation LBracketLoc;
+
+    // The location of the '...' in the designated initializer.
+    SourceLocation EllipsisLoc;
+
+    // The location of the ']' in the designated initializer.
     mutable SourceLocation RBracketLoc;
+
+    ArrayRangeDesignatorInfo(Expr *Start, Expr *End, SourceLocation LBracketLoc,
+                             SourceLocation EllipsisLoc)
+        : Start(Start), End(End), LBracketLoc(LBracketLoc),
+          EllipsisLoc(EllipsisLoc) {}
+  };
+
+  /// The kind of designator this describes.
+  enum DesignatorKind {
+    FieldDesignator,
+    ArrayDesignator,
+    ArrayRangeDesignator
   };
 
+  DesignatorKind Kind;
+
   union {
     FieldDesignatorInfo FieldInfo;
     ArrayDesignatorInfo ArrayInfo;
     ArrayRangeDesignatorInfo ArrayRangeInfo;
   };
 
-public:
+  Designator(DesignatorKind Kind) : Kind(Kind) {}
 
-  DesignatorKind getKind() const { return Kind; }
+public:
   bool isFieldDesignator() const { return Kind == FieldDesignator; }
   bool isArrayDesignator() const { return Kind == ArrayDesignator; }
   bool isArrayRangeDesignator() const { return Kind == ArrayRangeDesignator; }
 
+  //===--------------------------------------------------------------------===//
+  // FieldDesignatorInfo
+
+  static Designator CreateFieldDesignator(const IdentifierInfo *II,
+                                          SourceLocation DotLoc,
+                                          SourceLocation NameLoc) {
+    Designator D(FieldDesignator);
+    new (&D.FieldInfo) FieldDesignatorInfo(II, DotLoc, NameLoc);
+    return D;
+  }
+
   const IdentifierInfo *getField() const {
     assert(isFieldDesignator() && "Invalid accessor");
     return FieldInfo.II;
   }
 
   SourceLocation getDotLoc() const {
     assert(isFieldDesignator() && "Invalid accessor");
     return FieldInfo.DotLoc;
   }
 
   SourceLocation getFieldLoc() const {
     assert(isFieldDesignator() && "Invalid accessor");
     return FieldInfo.NameLoc;
   }
 
+  //===--------------------------------------------------------------------===//
+  // ArrayDesignatorInfo:
+
+  static Designator CreateArrayDesignator(Expr *Index,
+                                          SourceLocation LBracketLoc) {
+    Designator D(ArrayDesignator);
+    new (&D.ArrayInfo) ArrayDesignatorInfo(Index, LBracketLoc);
+    return D;
+  }
+
   Expr *getArrayIndex() const {
     assert(isArrayDesignator() && "Invalid accessor");
     return ArrayInfo.Index;
   }
 
-  Expr *getArrayRangeStart() const {
-    assert(isArrayRangeDesignator() && "Invalid accessor");
-    return ArrayRangeInfo.Start;
-  }
-  Expr *getArrayRangeEnd() const {
-    assert(isArrayRangeDesignator() && "Invalid accessor");
-    return ArrayRangeInfo.End;
-  }
-
   SourceLocation getLBracketLoc() const {
     assert((isArrayDesignator() || isArrayRangeDesignator()) &&
            "Invalid accessor");
-    if (isArrayDesignator())
-      return ArrayInfo.LBracketLoc;
-    else
-      return ArrayRangeInfo.LBracketLoc;
+    return isArrayDesignator() ? ArrayInfo.LBracketLoc
+                               : ArrayRangeInfo.LBracketLoc;
   }
 
   SourceLocation getRBracketLoc() const {
     assert((isArrayDesignator() || isArrayRangeDesignator()) &&
            "Invalid accessor");
-    if (isArrayDesignator())
-      return ArrayInfo.RBracketLoc;
-    else
-      return ArrayRangeInfo.RBracketLoc;
+    return isArrayDesignator() ? ArrayInfo.RBracketLoc
+                               : ArrayRangeInfo.RBracketLoc;
   }
 
-  SourceLocation getEllipsisLoc() const {
-    assert(isArrayRangeDesignator() && "Invalid accessor");
-    return ArrayRangeInfo.EllipsisLoc;
-  }
+  //===--------------------------------------------------------------------===//
+  // ArrayRangeDesignatorInfo:
 
-  static Designator getField(const IdentifierInfo *II, SourceLocation DotLoc,
-                             SourceLocation NameLoc) {
-    Designator D;
-    D.Kind = FieldDesignator;
-    new (&D.FieldInfo) FieldDesignatorInfo;
-    D.FieldInfo.II = II;
-    D.FieldInfo.DotLoc = DotLoc;
-    D.FieldInfo.NameLoc = NameLoc;
+  static Designator CreateArrayRangeDesignator(Expr *Start, Expr *End,
+                                               SourceLocation LBracketLoc,
+                                               SourceLocation EllipsisLoc) {
+    Designator D(ArrayRangeDesignator);
+    new (&D.ArrayRangeInfo)
+        ArrayRangeDesignatorInfo(Start, End, LBracketLoc, EllipsisLoc);
     return D;
   }
 
-  static Designator getArray(Expr *Index,
-                             SourceLocation LBracketLoc) {
-    Designator D;
-    D.Kind = ArrayDesignator;
-    new (&D.ArrayInfo) ArrayDesignatorInfo;
-    D.ArrayInfo.Index = Index;
-    D.ArrayInfo.LBracketLoc = LBracketLoc;
-    D.ArrayInfo.RBracketLoc = SourceLocation();
-    return D;
+  Expr *getArrayRangeStart() const {
+    assert(isArrayRangeDesignator() && "Invalid accessor");
+    return ArrayRangeInfo.Start;
   }
 
-  static Designator getArrayRange(Expr *Start,
-                                  Expr *End,
-                                  SourceLocation LBracketLoc,
-                                  SourceLocation EllipsisLoc) {
-    Designator D;
-    D.Kind = ArrayRangeDesignator;
-    new (&D.ArrayRangeInfo) ArrayRangeDesignatorInfo;
-    D.ArrayRangeInfo.Start = Start;
-    D.ArrayRangeInfo.End = End;
-    D.ArrayRangeInfo.LBracketLoc = LBracketLoc;
-    D.ArrayRangeInfo.EllipsisLoc = EllipsisLoc;
-    D.ArrayRangeInfo.RBracketLoc = SourceLocation();
-    return D;
+  Expr *getArrayRangeEnd() const {
+    assert(isArrayRangeDesignator() && "Invalid accessor");
+    return ArrayRangeInfo.End;
+  }
+
+  SourceLocation getEllipsisLoc() const {
+    assert(isArrayRangeDesignator() && "Invalid accessor");
+    return ArrayRangeInfo.EllipsisLoc;
   }
 
   void setRBracketLoc(SourceLocation RBracketLoc) const {
     assert((isArrayDesignator() || isArrayRangeDesignator()) &&
            "Invalid accessor");
     if (isArrayDesignator())
       ArrayInfo.RBracketLoc = RBracketLoc;
     else
       ArrayRangeInfo.RBracketLoc = RBracketLoc;
   }
-
-  /// ClearExprs - Null out any expression references, which prevents
-  /// them from being 'delete'd later.
-  void ClearExprs(Sema &Actions) {}
-
-  /// FreeExprs - Release any unclaimed memory for the expressions in
-  /// this designator.
-  void FreeExprs(Sema &Actions) {}
 };
 
-
 /// Designation - Represent a full designation, which is a sequence of
 /// designators.  This class is mostly a helper for InitListDesignations.
 class Designation {
   /// Designators - The actual designators for this initializer.
   SmallVector<Designator, 2> Designators;
 
 public:
   /// AddDesignator - Add a designator to the end of this list.
-  void AddDesignator(Designator D) {
-    Designators.push_back(D);
-  }
+  void AddDesignator(Designator D) { Designators.push_back(D); }
 
   bool empty() const { return Designators.empty(); }
 
   unsigned getNumDesignators() const { return Designators.size(); }
   const Designator &getDesignator(unsigned Idx) const {
     assert(Idx < Designators.size());
     return Designators[Idx];
   }
-
-  /// ClearExprs - Null out any expression references, which prevents them from
-  /// being 'delete'd later.
-  void ClearExprs(Sema &Actions) {}
-
-  /// FreeExprs - Release any unclaimed memory for the expressions in this
-  /// designation.
-  void FreeExprs(Sema &Actions) {}
 };
 
 } // end namespace clang
 
 #endif

clang/lib/AST/ASTImporter.cpp

if (D.isFieldDesignator()) {
     ExpectedSLoc ToDotLocOrErr = import(D.getDotLoc());
     if (!ToDotLocOrErr)
       return ToDotLocOrErr.takeError();
 
     ExpectedSLoc ToFieldLocOrErr = import(D.getFieldLoc());
     if (!ToFieldLocOrErr)
       return ToFieldLocOrErr.takeError();
 
-    return Designator(ToFieldName, *ToDotLocOrErr, *ToFieldLocOrErr);
+    return DesignatedInitExpr::Designator::CreateFieldDesignator(
+        ToFieldName, *ToDotLocOrErr, *ToFieldLocOrErr);
   }
 
   ExpectedSLoc ToLBracketLocOrErr = import(D.getLBracketLoc());
   if (!ToLBracketLocOrErr)
     return ToLBracketLocOrErr.takeError();
 
   ExpectedSLoc ToRBracketLocOrErr = import(D.getRBracketLoc());
   if (!ToRBracketLocOrErr)
     return ToRBracketLocOrErr.takeError();
 
   if (D.isArrayDesignator())
-    return Designator(D.getFirstExprIndex(),
-                      *ToLBracketLocOrErr, *ToRBracketLocOrErr);
+    return Designator::CreateArrayDesignator(D.getArrayIndex(),
+                                             *ToLBracketLocOrErr,
+                                             *ToRBracketLocOrErr);
 
   ExpectedSLoc ToEllipsisLocOrErr = import(D.getEllipsisLoc());
   if (!ToEllipsisLocOrErr)
     return ToEllipsisLocOrErr.takeError();
 
   assert(D.isArrayRangeDesignator());
-  return Designator(
-      D.getFirstExprIndex(), *ToLBracketLocOrErr, *ToEllipsisLocOrErr,
+  return Designator::CreateArrayRangeDesignator(
+      D.getArrayIndex(), *ToLBracketLocOrErr, *ToEllipsisLocOrErr,
       *ToRBracketLocOrErr);
 }
 
 template <>
 Expected<LambdaCapture> ASTNodeImporter::import(const LambdaCapture &From) {
   ValueDecl *Var = nullptr;
   if (From.capturesVariable()) {
     if (auto VarOrErr = import(From.getCapturedVar()))

clang/lib/AST/Expr.cpp

void *Mem = Context.Allocate(
       alignof(GenericSelectionExpr));
   return new (Mem) GenericSelectionExpr(EmptyShell(), NumAssocs);
 }
 
 //===----------------------------------------------------------------------===//
 //  DesignatedInitExpr
 //===----------------------------------------------------------------------===//
 
-IdentifierInfo *DesignatedInitExpr::Designator::getFieldName() const {
-  assert(Kind == FieldDesignator && "Only valid on a field designator");
-  if (Field.NameOrField & 0x01)
-    return reinterpret_cast<IdentifierInfo *>(Field.NameOrField & ~0x01);
+const IdentifierInfo *DesignatedInitExpr::Designator::getFieldName() const {
+  assert(isFieldDesignator() && "Only valid on a field designator");
+  if (FieldInfo.NameOrField & 0x01)
+    return reinterpret_cast<IdentifierInfo *>(FieldInfo.NameOrField & ~0x01);
   return getField()->getIdentifier();
 }
 
 DesignatedInitExpr::DesignatedInitExpr(const ASTContext &C, QualType Ty,
                                        llvm::ArrayRef<Designator> Designators,
                                        SourceLocation EqualOrColonLoc,
                                        bool GNUSyntax,
                                        ArrayRef<Expr *> IndexExprs, Expr *Init)
SourceRange DesignatedInitExpr::getDesignatorsSourceRange() const {
   DesignatedInitExpr *DIE = const_cast<DesignatedInitExpr*>(this);
   if (size() == 1)
     return DIE->getDesignator(0)->getSourceRange();
   return SourceRange(DIE->getDesignator(0)->getBeginLoc(),
                      DIE->getDesignator(size() - 1)->getEndLoc());
 }
 
 SourceLocation DesignatedInitExpr::getBeginLoc() const {
-  SourceLocation StartLoc;
   auto *DIE = const_cast<DesignatedInitExpr *>(this);
   Designator &First = *DIE->getDesignator(0);
   if (First.isFieldDesignator())
-    StartLoc = GNUSyntax ? First.Field.FieldLoc : First.Field.DotLoc;
-  else
-    StartLoc = First.ArrayOrRange.LBracketLoc;
-  return StartLoc;
+    return GNUSyntax ? First.getFieldLoc() : First.getDotLoc();
+  return First.getLBracketLoc();
 }
 
 SourceLocation DesignatedInitExpr::getEndLoc() const {
   return getInit()->getEndLoc();
 }
 
 Expr *DesignatedInitExpr::getArrayIndex(const Designator& D) const {
-  assert(D.Kind == Designator::ArrayDesignator && "Requires array designator");
-  return getSubExpr(D.ArrayOrRange.Index + 1);
+  assert(D.isArrayDesignator() && "Requires array designator");
+  return getSubExpr(D.getArrayIndex() + 1);
 }
 
 Expr *DesignatedInitExpr::getArrayRangeStart(const Designator &D) const {
-  assert(D.Kind == Designator::ArrayRangeDesignator &&
-         "Requires array range designator");
-  return getSubExpr(D.ArrayOrRange.Index + 1);
+  assert(D.isArrayRangeDesignator() && "Requires array range designator");
+  return getSubExpr(D.getArrayIndex() + 1);
 }
 
 Expr *DesignatedInitExpr::getArrayRangeEnd(const Designator &D) const {
-  assert(D.Kind == Designator::ArrayRangeDesignator &&
-         "Requires array range designator");
-  return getSubExpr(D.ArrayOrRange.Index + 2);
+  assert(D.isArrayRangeDesignator() && "Requires array range designator");
+  return getSubExpr(D.getArrayIndex() + 2);
 }
 
 /// Replaces the designator at index @p Idx with the series
 /// of designators in [First, Last).
 void DesignatedInitExpr::ExpandDesignator(const ASTContext &C, unsigned Idx,
                                           const Designator *First,
                                           const Designator *Last) {
   unsigned NumNewDesignators = Last - First;

clang/lib/AST/StmtPrinter.cpp

void StmtPrinter::VisitParenListExpr(ParenListExpr* Node) {
   OS << ")";
 }
 
 void StmtPrinter::VisitDesignatedInitExpr(DesignatedInitExpr *Node) {
   bool NeedsEquals = true;
   for (const DesignatedInitExpr::Designator &D : Node->designators()) {
     if (D.isFieldDesignator()) {
       if (D.getDotLoc().isInvalid()) {
-        if (IdentifierInfo *II = D.getFieldName()) {
+        if (const IdentifierInfo *II = D.getFieldName()) {
           OS << II->getName() << ":";
           NeedsEquals = false;
         }
       } else {
         OS << "." << D.getFieldName()->getName();
       }
     } else {
       OS << "[";

clang/lib/AST/StmtProfile.cpp

for (const DesignatedInitExpr::Designator &D : S->designators()) {
     }
 
     if (D.isArrayDesignator()) {
       ID.AddInteger(1);
     } else {
       assert(D.isArrayRangeDesignator());
       ID.AddInteger(2);
     }
-    ID.AddInteger(D.getFirstExprIndex());
+    ID.AddInteger(D.getArrayIndex());
   }
 }
 
 // Seems that if VisitInitListExpr() only works on the syntactic form of an
 // InitListExpr, then a DesignatedInitUpdateExpr is not encountered.
 void StmtProfiler::VisitDesignatedInitUpdateExpr(
     const DesignatedInitUpdateExpr *S) {
   llvm_unreachable("Unexpected DesignatedInitUpdateExpr in syntactic form of "

clang/lib/Parse/ParseInit.cpp

if (Tok.is(tok::identifier)) {
     assert(Tok.is(tok::colon) && "MayBeDesignationStart not working properly!");
     SourceLocation ColonLoc = ConsumeToken();
 
     Diag(NameLoc, diag::ext_gnu_old_style_field_designator)
       << FixItHint::CreateReplacement(SourceRange(NameLoc, ColonLoc),
                                       NewSyntax);
 
     Designation D;
-    D.AddDesignator(Designator::getField(FieldName, SourceLocation(), NameLoc));
+    D.AddDesignator(Designator::CreateFieldDesignator(
+        FieldName, SourceLocation(), NameLoc));
     PreferredType.enterDesignatedInitializer(
         Tok.getLocation(), DesignatorCompletion.PreferredBaseType, D);
     return Actions.ActOnDesignatedInitializer(D, ColonLoc, true,
                                               ParseInitializer());
   }
 
   // Desig - This is initialized when we see our first designator.  We may have
   // an objc message send with no designator, so we don't want to create this
if (Tok.is(tok::period)) {
                                        DesignatorCompletion.InitExprs, Desig);
         return ExprError();
       }
       if (Tok.isNot(tok::identifier)) {
         Diag(Tok.getLocation(), diag::err_expected_field_designator);
         return ExprError();
       }
 
-      Desig.AddDesignator(Designator::getField(Tok.getIdentifierInfo(), DotLoc,
-                                               Tok.getLocation()));
+      Desig.AddDesignator(Designator::CreateFieldDesignator(
+          Tok.getIdentifierInfo(), DotLoc, Tok.getLocation()));
       ConsumeToken(); // Eat the identifier.
       continue;
     }
 
     // We must have either an array designator now or an objc message send.
     assert(Tok.is(tok::l_square) && "Unexpected token!");
 
     // Handle the two forms of array designator:
if (getLangOpts().ObjC && Tok.isNot(tok::ellipsis) &&
         Tok.isNot(tok::r_square)) {
       CheckArrayDesignatorSyntax(*this, Tok.getLocation(), Desig);
       return ParseAssignmentExprWithObjCMessageExprStart(
           StartLoc, SourceLocation(), nullptr, Idx.get());
     }
 
     // If this is a normal array designator, remember it.
     if (Tok.isNot(tok::ellipsis)) {
-      Desig.AddDesignator(Designator::getArray(Idx.get(), StartLoc));
+      Desig.AddDesignator(Designator::CreateArrayDesignator(Idx.get(),
+                                                            StartLoc));
     } else {
       // Handle the gnu array range extension.
       Diag(Tok, diag::ext_gnu_array_range);
       SourceLocation EllipsisLoc = ConsumeToken();
 
       ExprResult RHS(ParseConstantExpression());
       if (RHS.isInvalid()) {
         SkipUntil(tok::r_square, StopAtSemi);
         return RHS;
       }
-      Desig.AddDesignator(Designator::getArrayRange(Idx.get(),
-                                                    RHS.get(),
-                                                    StartLoc, EllipsisLoc));
+      Desig.AddDesignator(Designator::CreateArrayRangeDesignator(
+          Idx.get(), RHS.get(), StartLoc, EllipsisLoc));
     }
 
     T.consumeClose();
     Desig.getDesignator(Desig.getNumDesignators() - 1).setRBracketLoc(
                                                         T.getCloseLocation());
   }
 
   // Okay, we're done with the designator sequence.  We know that there must be

clang/lib/Sema/SemaCodeComplete.cpp

 static std::optional<unsigned>
 getNextAggregateIndexAfterDesignatedInit(const ResultCandidate &Aggregate,
                                          ArrayRef<Expr *> Args) {
   static constexpr unsigned Invalid = std::numeric_limits<unsigned>::max();
   assert(Aggregate.getKind() == ResultCandidate::CK_Aggregate);
 
   // Look for designated initializers.
   // They're in their syntactic form, not yet resolved to fields.
-  IdentifierInfo *DesignatedFieldName = nullptr;
+  const IdentifierInfo *DesignatedFieldName = nullptr;
   unsigned ArgsAfterDesignator = 0;
   for (const Expr *Arg : Args) {
     if (const auto *DIE = dyn_cast<DesignatedInitExpr>(Arg)) {
       if (DIE->size() == 1 && DIE->getDesignator(0)->isFieldDesignator()) {
         DesignatedFieldName = DIE->getDesignator(0)->getFieldName();
         ArgsAfterDesignator = 0;
       } else {
         return Invalid; // Complicated designator.

clang/lib/Sema/SemaInit.cpp

static void ExpandAnonymousFieldDesignator(Sema &SemaRef,
                                            IndirectFieldDecl *IndirectField) {
   typedef DesignatedInitExpr::Designator Designator;
 
   // Build the replacement designators.
   SmallVector<Designator, 4> Replacements;
   for (IndirectFieldDecl::chain_iterator PI = IndirectField->chain_begin(),
        PE = IndirectField->chain_end(); PI != PE; ++PI) {
     if (PI + 1 == PE)
-      Replacements.push_back(Designator((IdentifierInfo *)nullptr,
-                                    DIE->getDesignator(DesigIdx)->getDotLoc(),
-                                DIE->getDesignator(DesigIdx)->getFieldLoc()));
+      Replacements.push_back(Designator::CreateFieldDesignator(
+          (IdentifierInfo *)nullptr, DIE->getDesignator(DesigIdx)->getDotLoc(),
     else
-      Replacements.push_back(Designator((IdentifierInfo *)nullptr,
-                                        SourceLocation(), SourceLocation()));
+      Replacements.push_back(Designator::CreateFieldDesignator(
+          (IdentifierInfo *)nullptr, SourceLocation(), SourceLocation()));
     assert(isa<FieldDecl>(*PI));
     Replacements.back().setField(cast<FieldDecl>(*PI));
   }
 
   // Expand the current designator into the set of replacement
   // designators, so we have a full subobject path down to where the
   // member of the anonymous struct/union is actually stored.
   DIE->ExpandDesignator(SemaRef.Context, DesigIdx, &Replacements[0],
if (!RT) {
         SemaRef.Diag(Loc, diag::err_field_designator_non_aggr)
           << SemaRef.getLangOpts().CPlusPlus << CurrentObjectType;
       ++Index;
       return true;
     }
 
     FieldDecl *KnownField = D->getField();
     if (!KnownField) {
-      IdentifierInfo *FieldName = D->getFieldName();
+      const IdentifierInfo *FieldName = D->getFieldName();
       DeclContext::lookup_result Lookup = RT->getDecl()->lookup(FieldName);
       for (NamedDecl *ND : Lookup) {
         if (auto *FD = dyn_cast<FieldDecl>(ND)) {
           KnownField = FD;
           break;
         }
         if (auto *IFD = dyn_cast<IndirectFieldDecl>(ND)) {
           // In verify mode, don't modify the original.
ExprResult Sema::ActOnDesignatedInitializer(Designation &Desig,
 
   bool Invalid = false;
   SmallVector<ASTDesignator, 32> Designators;
   SmallVector<Expr *, 32> InitExpressions;
 
   // Build designators and check array designator expressions.
   for (unsigned Idx = 0; Idx < Desig.getNumDesignators(); ++Idx) {
     const Designator &D = Desig.getDesignator(Idx);
-    switch (D.getKind()) {
-    case Designator::FieldDesignator:
-      Designators.push_back(ASTDesignator(D.getField(), D.getDotLoc(),
-                                          D.getFieldLoc()));
-      break;
 
-    case Designator::ArrayDesignator: {
+    if (D.isFieldDesignator()) {
+      Designators.push_back(ASTDesignator::CreateFieldDesignator(
+          D.getField(), D.getDotLoc(), D.getFieldLoc()));
+    } else if (D.isArrayDesignator()) {
       Expr *Index = static_cast<Expr *>(D.getArrayIndex());
       llvm::APSInt IndexValue;
       if (!Index->isTypeDependent() && !Index->isValueDependent())
         Index = CheckArrayDesignatorExpr(*this, Index, IndexValue).get();
       if (!Index)
         Invalid = true;
       else {
-        Designators.push_back(ASTDesignator(InitExpressions.size(),
-                                            D.getLBracketLoc(),
-                                            D.getRBracketLoc()));
+        Designators.push_back(ASTDesignator::CreateArrayDesignator(
+            InitExpressions.size(), D.getLBracketLoc(), D.getRBracketLoc()));
         InitExpressions.push_back(Index);
       }
-      break;
-    }
-
-    case Designator::ArrayRangeDesignator: {
+    } else if (D.isArrayRangeDesignator()) {
       Expr *StartIndex = static_cast<Expr *>(D.getArrayRangeStart());
       Expr *EndIndex = static_cast<Expr *>(D.getArrayRangeEnd());
       llvm::APSInt StartValue;
       llvm::APSInt EndValue;
       bool StartDependent = StartIndex->isTypeDependent() ||
                             StartIndex->isValueDependent();
       bool EndDependent = EndIndex->isTypeDependent() ||
                           EndIndex->isValueDependent();
if (D.isFieldDesignator()) {
           StartValue = StartValue.extend(EndValue.getBitWidth());
 
         if (!StartDependent && !EndDependent && EndValue < StartValue) {
           Diag(D.getEllipsisLoc(), diag::err_array_designator_empty_range)
             << toString(StartValue, 10) << toString(EndValue, 10)
             << StartIndex->getSourceRange() << EndIndex->getSourceRange();
           Invalid = true;
         } else {
-          Designators.push_back(ASTDesignator(InitExpressions.size(),
-                                              D.getLBracketLoc(),
-                                              D.getEllipsisLoc(),
-                                              D.getRBracketLoc()));
+          Designators.push_back(ASTDesignator::CreateArrayRangeDesignator(
+              InitExpressions.size(), D.getLBracketLoc(), D.getEllipsisLoc(),
           InitExpressions.push_back(StartIndex);
           InitExpressions.push_back(EndIndex);
         }
       }
-      break;
-    }
     }
   }
 
   if (Invalid || Init.isInvalid())
     return ExprError();
 
-  // Clear out the expressions within the designation.
-  Desig.ClearExprs(*this);
-
   return DesignatedInitExpr::Create(Context, Designators, InitExpressions,
                                     EqualOrColonLoc, GNUSyntax,
                                     Init.getAs<Expr>());
 }
 
 //===----------------------------------------------------------------------===//
 // Initialization entity
 //===----------------------------------------------------------------------===//

clang/lib/Sema/TreeTransform.h

TreeTransform<Derived>::TransformDesignatedInitExpr(DesignatedInitExpr *E) {
   if (Init.isInvalid())
     return ExprError();
 
   // transform the designators.
   SmallVector<Expr*, 4> ArrayExprs;
   bool ExprChanged = false;
   for (const DesignatedInitExpr::Designator &D : E->designators()) {
     if (D.isFieldDesignator()) {
-      Desig.AddDesignator(Designator::getField(D.getFieldName(),
-                                               D.getDotLoc(),
-                                               D.getFieldLoc()));
+      Desig.AddDesignator(Designator::CreateFieldDesignator(
+          D.getFieldName(), D.getDotLoc(), D.getFieldLoc()));
       if (D.getField()) {
         FieldDecl *Field = cast_or_null<FieldDecl>(
             getDerived().TransformDecl(D.getFieldLoc(), D.getField()));
         if (Field != D.getField())
           // Rebuild the expression when the transformed FieldDecl is
           // different to the already assigned FieldDecl.
           ExprChanged = true;
       } else {
         // Ensure that the designator expression is rebuilt when there isn't
         // a resolved FieldDecl in the designator as we don't want to assign
         // a FieldDecl to a pattern designator that will be instantiated again.
         ExprChanged = true;
       }
       continue;
     }
 
     if (D.isArrayDesignator()) {
       ExprResult Index = getDerived().TransformExpr(E->getArrayIndex(D));
       if (Index.isInvalid())
         return ExprError();
 
       Desig.AddDesignator(
-          Designator::getArray(Index.get(), D.getLBracketLoc()));
+          Designator::CreateArrayDesignator(Index.get(), D.getLBracketLoc()));
 
       ExprChanged = ExprChanged || Init.get() != E->getArrayIndex(D);
       ArrayExprs.push_back(Index.get());
       continue;
     }
 
     assert(D.isArrayRangeDesignator() && "New kind of designator?");
     ExprResult Start
       = getDerived().TransformExpr(E->getArrayRangeStart(D));
     if (Start.isInvalid())
       return ExprError();
 
     ExprResult End = getDerived().TransformExpr(E->getArrayRangeEnd(D));
     if (End.isInvalid())
       return ExprError();
 
-    Desig.AddDesignator(Designator::getArrayRange(Start.get(),
-                                                  End.get(),
-                                                  D.getLBracketLoc(),
-                                                  D.getEllipsisLoc()));
+    Desig.AddDesignator(Designator::CreateArrayRangeDesignator(
+        Start.get(), End.get(), D.getLBracketLoc(), D.getEllipsisLoc()));
 
     ExprChanged = ExprChanged || Start.get() != E->getArrayRangeStart(D) ||
                   End.get() != E->getArrayRangeEnd(D);
 
     ArrayExprs.push_back(Start.get());
     ArrayExprs.push_back(End.get());
   }
 

clang/lib/Serialization/ASTReaderStmt.cpp

void ASTStmtReader::VisitDesignatedInitExpr(DesignatedInitExpr *E) {
 
   SmallVector<Designator, 4> Designators;
   while (Record.getIdx() < Record.size()) {
     switch ((DesignatorTypes)Record.readInt()) {
     case DESIG_FIELD_DECL: {
       auto *Field = readDeclAs<FieldDecl>();
       SourceLocation DotLoc = readSourceLocation();
       SourceLocation FieldLoc = readSourceLocation();
-      Designators.push_back(Designator(Field->getIdentifier(), DotLoc,
-                                       FieldLoc));
+      Designators.push_back(Designator::CreateFieldDesignator(
+          Field->getIdentifier(), DotLoc, FieldLoc));
       Designators.back().setField(Field);
       break;
     }
 
     case DESIG_FIELD_NAME: {
       const IdentifierInfo *Name = Record.readIdentifier();
       SourceLocation DotLoc = readSourceLocation();
       SourceLocation FieldLoc = readSourceLocation();
-      Designators.push_back(Designator(Name, DotLoc, FieldLoc));
+      Designators.push_back(Designator::CreateFieldDesignator(Name, DotLoc,
+                                                              FieldLoc));
       break;
     }
 
     case DESIG_ARRAY: {
       unsigned Index = Record.readInt();
       SourceLocation LBracketLoc = readSourceLocation();
       SourceLocation RBracketLoc = readSourceLocation();
-      Designators.push_back(Designator(Index, LBracketLoc, RBracketLoc));
+      Designators.push_back(Designator::CreateArrayDesignator(Index,
+                                                              LBracketLoc,
+                                                              RBracketLoc));
       break;
     }
 
     case DESIG_ARRAY_RANGE: {
       unsigned Index = Record.readInt();
       SourceLocation LBracketLoc = readSourceLocation();
       SourceLocation EllipsisLoc = readSourceLocation();
       SourceLocation RBracketLoc = readSourceLocation();
-      Designators.push_back(Designator(Index, LBracketLoc, EllipsisLoc,
-                                       RBracketLoc));
+      Designators.push_back(Designator::CreateArrayRangeDesignator(
+          Index, LBracketLoc, EllipsisLoc, RBracketLoc));
       break;
     }
     }
   }
   E->setDesignators(Record.getContext(),
                     Designators.data(), Designators.size());
 }
 

clang/lib/Serialization/ASTWriterStmt.cpp

if (D.isFieldDesignator()) {
       } else {
         Record.push_back(serialization::DESIG_FIELD_NAME);
         Record.AddIdentifierRef(D.getFieldName());
       }
       Record.AddSourceLocation(D.getDotLoc());
       Record.AddSourceLocation(D.getFieldLoc());
     } else if (D.isArrayDesignator()) {
       Record.push_back(serialization::DESIG_ARRAY);
-      Record.push_back(D.getFirstExprIndex());
+      Record.push_back(D.getArrayIndex());
       Record.AddSourceLocation(D.getLBracketLoc());
       Record.AddSourceLocation(D.getRBracketLoc());
     } else {
       assert(D.isArrayRangeDesignator() && "Unknown designator");
       Record.push_back(serialization::DESIG_ARRAY_RANGE);
-      Record.push_back(D.getFirstExprIndex());
+      Record.push_back(D.getArrayIndex());
       Record.AddSourceLocation(D.getLBracketLoc());
       Record.AddSourceLocation(D.getEllipsisLoc());
       Record.AddSourceLocation(D.getRBracketLoc());
     }
   }
   Code = serialization::EXPR_DESIGNATED_INIT;
 }