[AST] Make RecursiveASTVisitor visit TemplateDecls in source order

Summary:
This causes template arguments to be traversed before the templated
declaration, which is useful for clients that expect the nodes in
the same order as they are in the source code. Additionally, there
seems to be no good reason not to do so.

This was moved here from LexicallyOrderedRecursiveASTVisitor. The tests
still reside in LexicallyOrderedRecursiveASTVisitorTest.cpp under
VisitTemplateDecls.

Reviewers: arphaman, rsmith, klimek

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D37662

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@312911 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/LexicallyOrderedRecursiveASTVisitor.h

@@ -111,8 +111,6 @@ class LexicallyOrderedRecursiveASTVisitor
     return true;
   }
 
-  bool shouldTraverseTemplateArgumentsBeforeDecl() const { return true; }
-
   Stmt::child_range getStmtChildren(Stmt *S) { return S->children(); }
 
   SmallVector<Stmt *, 8> getStmtChildren(CXXOperatorCallExpr *CE) {

include/clang/AST/RecursiveASTVisitor.h

@@ -537,7 +537,6 @@ template <typename Derived> class RecursiveASTVisitor {
 
   bool dataTraverseNode(Stmt *S, DataRecursionQueue *Queue);
   bool PostVisitStmt(Stmt *S);
-  bool shouldTraverseTemplateArgumentsBeforeDecl() const { return false; }
 };
 
 template <typename Derived>
@@ -1691,13 +1690,8 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateInstantiations(
 // template declarations.
 #define DEF_TRAVERSE_TMPL_DECL(TMPLDECLKIND)                                   \
   DEF_TRAVERSE_DECL(TMPLDECLKIND##TemplateDecl, {                              \
-    if (getDerived().shouldTraverseTemplateArgumentsBeforeDecl()) {            \
-      TRY_TO(TraverseTemplateParameterListHelper(D->getTemplateParameters())); \
-      TRY_TO(TraverseDecl(D->getTemplatedDecl()));                             \
-    } else {                                                                   \
-      TRY_TO(TraverseDecl(D->getTemplatedDecl()));                             \
-      TRY_TO(TraverseTemplateParameterListHelper(D->getTemplateParameters())); \
-    }                                                                          \
+    TRY_TO(TraverseTemplateParameterListHelper(D->getTemplateParameters()));   \
+    TRY_TO(TraverseDecl(D->getTemplatedDecl()));                               \
                                                                                \
     /* By default, we do not traverse the instantiations of                    \
        class templates since they do not appear in the user code. The          \