Introduce the virtual method Decl::getPrimaryDecl().

When a Decl subclass can have multiple re-declarations in the same declaration context (like FunctionDecl),
getPrimaryDecl() will return a particular Decl that all of them will point to as the "primary" declaration.

llvm-svn: 74800

clang/include/clang/AST/Decl.h

@@ -413,6 +413,8 @@ public:
     PreviousDeclaration = PrevDecl;
   }
 
+  virtual Decl *getPrimaryDecl() const;
+
   /// hasLocalStorage - Returns true if a variable with function scope
   ///  is a non-static local variable.
   bool hasLocalStorage() const {
@@ -811,6 +813,8 @@ public:
 
   void setPreviousDeclaration(FunctionDecl * PrevDecl);
 
+  virtual Decl *getPrimaryDecl() const;
+
   unsigned getBuiltinID(ASTContext &Context) const;
 
   unsigned getNumParmVarDeclsFromType() const;

clang/include/clang/AST/DeclBase.h

@@ -311,6 +311,13 @@ public:
   // be defined inside or outside a function etc).
   bool isDefinedOutsideFunctionOrMethod() const;
 
+  /// \brief When there are multiple re-declarations (e.g. for functions),
+  /// this will return the primary one which all of them point to.
+  virtual Decl *getPrimaryDecl() const { return const_cast<Decl*>(this); }
+
+  /// \brief Whether this particular Decl is a primary one.
+  bool isPrimaryDecl() const { return getPrimaryDecl() == this; }
+
   /// getBody - If this Decl represents a declaration for a body of code,
   ///  such as a function or method definition, this method returns the
   ///  top-level Stmt* of that body.  Otherwise this method returns null.

clang/lib/AST/Decl.cpp

@@ -358,6 +358,14 @@ const Expr *VarDecl::getDefinition(const VarDecl *&Def) const {
   return Def? Def->getInit() : 0;
 }
 
+Decl *VarDecl::getPrimaryDecl() const {
+  const VarDecl *Prim = this;
+  while (Prim->getPreviousDeclaration())
+    Prim = Prim->getPreviousDeclaration();
+
+  return const_cast<VarDecl *>(Prim);
+}
+
 //===----------------------------------------------------------------------===//
 // FunctionDecl Implementation
 //===----------------------------------------------------------------------===//
@@ -569,6 +577,14 @@ FunctionDecl::setPreviousDeclaration(FunctionDecl *PrevDecl) {
   }
 }
 
+Decl *FunctionDecl::getPrimaryDecl() const {
+  const FunctionDecl *Prim = this;
+  while (Prim->getPreviousDeclaration())
+    Prim = Prim->getPreviousDeclaration();
+
+  return const_cast<FunctionDecl *>(Prim);
+}
+
 /// getOverloadedOperator - Which C++ overloaded operator this
 /// function represents, if any.
 OverloadedOperatorKind FunctionDecl::getOverloadedOperator() const {