[clang] Turn 'counted_by' into a type attribute and parse it into 'CountAttributedType' (PR #78000)

[Yeoul Na via cfe-commits]

================
@@ -2917,6 +2942,133 @@ class PointerType : public Type, public llvm::FoldingSetNode {
   static bool classof(const Type *T) { return T->getTypeClass() == Pointer; }
 };
 
+/// [BoundsSafety] Represents information of declarations referenced by the
+/// arguments of the `counted_by` attribute and the likes.
+class TypeCoupledDeclRefInfo {
+public:
+  using BaseTy = llvm::PointerIntPair<ValueDecl *, 1, unsigned>;
+
+private:
+  enum {
+    DerefShift = 0,
+    DerefMask = 1,
+  };
+  BaseTy Data;
+
+public:
+  /// \p D is to a declaration referenced by the argument of attribute. \p Deref
+  /// indicates whether \p D is referenced as a dereferenced form, e.g., \p
+  /// Deref is true for `*n` in `int *__counted_by(*n)`.
+  TypeCoupledDeclRefInfo(ValueDecl *D = nullptr, bool Deref = false);
+
+  bool isDeref() const;
+  ValueDecl *getDecl() const;
+  unsigned getInt() const;
+  void *getOpaqueValue() const;
+  bool operator==(const TypeCoupledDeclRefInfo &Other) const;
+  void setFromOpaqueValue(void *V);
+};
+
+/// [BoundsSafety] Represents a parent type class for CountAttributedType and
+/// similar sugar types that will be introduced to represent a type with a
+/// bounds attribute.
+///
+/// Provides a common interface to navigate declarations referred to by the
+/// bounds expression.
+
+class BoundsAttributedType : public Type, public llvm::FoldingSetNode {
+  QualType WrappedTy;
+
+protected:
+  ArrayRef<TypeCoupledDeclRefInfo> Decls; // stored in trailing objects
+
+  BoundsAttributedType(TypeClass TC, QualType Wrapped, QualType Canon);
+
+public:
+  bool isSugared() const { return true; }
+  QualType desugar() const { return WrappedTy; }
+
+  using decl_iterator = const TypeCoupledDeclRefInfo *;
+  using decl_range = llvm::iterator_range<decl_iterator>;
+
+  decl_iterator dependent_decl_begin() const { return Decls.begin(); }
+  decl_iterator dependent_decl_end() const { return Decls.end(); }
+
+  unsigned getNumCoupledDecls() const { return Decls.size(); }
+
+  decl_range dependent_decls() const {
+    return decl_range(dependent_decl_begin(), dependent_decl_end());
+  }
+
+  ArrayRef<TypeCoupledDeclRefInfo> getCoupledDecls() const {
+    return {dependent_decl_begin(), dependent_decl_end()};
+  }
+
+  bool referencesFieldDecls() const;
+
+  static bool classof(const Type *T) {
+    switch (T->getTypeClass()) {
----------------
rapidsna wrote:

@bwendling I wrote this way as we will extend it to support other bounds attribute as well. I'll add a comment there.

https://github.com/llvm/llvm-project/pull/78000