Add isFirstDecl to DecBase too and use it instead of getPreviousDecl() == 0.

Redeclarable already had a isFirstDecl, but it was missing from DeclBase.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193027 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/AST/Decl.h b/include/clang/AST/Decl.h
index c9b8656..a7e41ea 100644
--- a/include/clang/AST/Decl.h
+++ b/include/clang/AST/Decl.h
@@ -368,6 +368,7 @@
   using redeclarable_base::redecls_end;
   using redeclarable_base::getPreviousDecl;
   using redeclarable_base::getMostRecentDecl;
+  using redeclarable_base::isFirstDecl;
 
   /// \brief Returns true if this is an anonymous namespace declaration.
   ///
@@ -775,6 +776,7 @@
   using redeclarable_base::redecls_end;
   using redeclarable_base::getPreviousDecl;
   using redeclarable_base::getMostRecentDecl;
+  using redeclarable_base::isFirstDecl;
 
   static VarDecl *Create(ASTContext &C, DeclContext *DC,
                          SourceLocation StartLoc, SourceLocation IdLoc,
@@ -1563,6 +1565,7 @@
   using redeclarable_base::redecls_end;
   using redeclarable_base::getPreviousDecl;
   using redeclarable_base::getMostRecentDecl;
+  using redeclarable_base::isFirstDecl;
 
   static FunctionDecl *Create(ASTContext &C, DeclContext *DC,
                               SourceLocation StartLoc, SourceLocation NLoc,
@@ -2390,6 +2393,7 @@
   using redeclarable_base::redecls_end;
   using redeclarable_base::getPreviousDecl;
   using redeclarable_base::getMostRecentDecl;
+  using redeclarable_base::isFirstDecl;
 
   bool isModed() const { return MaybeModedTInfo.is<ModedTInfo*>(); }
 
@@ -2574,6 +2578,7 @@
   using redeclarable_base::redecls_end;
   using redeclarable_base::getPreviousDecl;
   using redeclarable_base::getMostRecentDecl;
+  using redeclarable_base::isFirstDecl;
 
   SourceLocation getRBraceLoc() const { return RBraceLoc; }
   void setRBraceLoc(SourceLocation L) { RBraceLoc = L; }
diff --git a/include/clang/AST/DeclBase.h b/include/clang/AST/DeclBase.h
index 1fdb857..9fbff6e 100644
--- a/include/clang/AST/DeclBase.h
+++ b/include/clang/AST/DeclBase.h
@@ -785,7 +785,12 @@
   const Decl *getPreviousDecl() const { 
     return const_cast<Decl *>(this)->getPreviousDeclImpl();
   }
-  
+
+  /// \brief Returns true if this is the first declaration.
+  bool isFirstDecl() const {
+    return getPreviousDecl() == 0;
+  }
+
   /// \brief Retrieve the most recent declaration that declares the same entity
   /// as this declaration (which may be this declaration).
   Decl *getMostRecentDecl() { return getMostRecentDeclImpl(); }
diff --git a/include/clang/AST/DeclObjC.h b/include/clang/AST/DeclObjC.h
index ee204a6..d924ddd 100644
--- a/include/clang/AST/DeclObjC.h
+++ b/include/clang/AST/DeclObjC.h
@@ -1201,6 +1201,7 @@
   using redeclarable_base::redecls_end;
   using redeclarable_base::getPreviousDecl;
   using redeclarable_base::getMostRecentDecl;
+  using redeclarable_base::isFirstDecl;
 
   /// Retrieves the canonical declaration of this Objective-C class.
   ObjCInterfaceDecl *getCanonicalDecl() { return getFirstDecl(); }
@@ -1503,6 +1504,7 @@
   using redeclarable_base::redecls_end;
   using redeclarable_base::getPreviousDecl;
   using redeclarable_base::getMostRecentDecl;
+  using redeclarable_base::isFirstDecl;
 
   /// Retrieves the canonical declaration of this Objective-C protocol.
   ObjCProtocolDecl *getCanonicalDecl() { return getFirstDecl(); }
diff --git a/include/clang/AST/DeclTemplate.h b/include/clang/AST/DeclTemplate.h
index a663823..38b0799 100644
--- a/include/clang/AST/DeclTemplate.h
+++ b/include/clang/AST/DeclTemplate.h
@@ -715,6 +715,7 @@
   using redeclarable_base::redecls_end;
   using redeclarable_base::getPreviousDecl;
   using redeclarable_base::getMostRecentDecl;
+  using redeclarable_base::isFirstDecl;
 
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 1774b80..88e1d04 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -2922,13 +2922,11 @@
          "Template type parameter types are always available.");
 
   if (const RecordDecl *Record = dyn_cast<RecordDecl>(Decl)) {
-    assert(!Record->getPreviousDecl() &&
-           "struct/union has previous declaration");
+    assert(Record->isFirstDecl() && "struct/union has previous declaration");
     assert(!NeedsInjectedClassNameType(Record));
     return getRecordType(Record);
   } else if (const EnumDecl *Enum = dyn_cast<EnumDecl>(Decl)) {
-    assert(!Enum->getPreviousDecl() &&
-           "enum has previous declaration");
+    assert(Enum->isFirstDecl() && "enum has previous declaration");
     return getEnumType(Enum);
   } else if (const UnresolvedUsingTypenameDecl *Using =
                dyn_cast<UnresolvedUsingTypenameDecl>(Decl)) {
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 632cc19..2b48de4 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -5388,7 +5388,7 @@
 
   // If this is the first declaration of an extern C variable, update
   // the map of such variables.
-  if (!NewVD->getPreviousDecl() && !NewVD->isInvalidDecl() &&
+  if (NewVD->isFirstDecl() && !NewVD->isInvalidDecl() &&
       isIncompleteDeclExternC(*this, NewVD))
     RegisterLocallyScopedExternCDecl(NewVD, S);
 
@@ -7205,7 +7205,7 @@
 
   // If this is the first declaration of an extern C variable, update
   // the map of such variables.
-  if (!NewFD->getPreviousDecl() && !NewFD->isInvalidDecl() &&
+  if (NewFD->isFirstDecl() && !NewFD->isInvalidDecl() &&
       isIncompleteDeclExternC(*this, NewFD))
     RegisterLocallyScopedExternCDecl(NewFD, S);
 
@@ -8520,7 +8520,7 @@
           // is accepted by gcc. Hence here we issue a warning instead of
           // an error and we do not invalidate the static declaration.
           // NOTE: to avoid multiple warnings, only check the first declaration.
-          if (Var->getPreviousDecl() == 0)
+          if (Var->isFirstDecl())
             RequireCompleteType(Var->getLocation(), Type,
                                 diag::ext_typecheck_decl_incomplete_type);
         }
@@ -9619,7 +9619,7 @@
     // The only way to be included in UndefinedButUsed is if there is an
     // ODR use before the definition. Avoid the expensive map lookup if this
     // is the first declaration.
-    if (FD->getPreviousDecl() != 0 && FD->getPreviousDecl()->isUsed()) {
+    if (!FD->isFirstDecl() && FD->getPreviousDecl()->isUsed()) {
       if (!FD->isExternallyVisible())
         UndefinedButUsed.erase(FD);
       else if (FD->isInlined() &&
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index d232670..3ee9830 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -3531,7 +3531,7 @@
 
   for (unsigned I = 0, N = Redeclarations.size(); I != N; ++I) {
     Decl *First = Redeclarations[I];
-    assert(First->getPreviousDecl() == 0 && "Not the first declaration?");
+    assert(First->isFirstDecl() && "Not the first declaration?");
     
     Decl *MostRecent = First->getMostRecentDecl();