Make the ExprMutationAnalyzer explicit about how it traverses the AST

[steveire]

Update

[aaron.ballman]

LGTM, assuming that this causes existing tests cover the changes so we don't need new tests.

clang/lib/Analysis/ExprMutationAnalyzer.cpp

const Stmt *ExprMutationAnalyzer::findDirectMutation(const Expr *Exp) {
   // If we're returning 'Exp' directly then it's returned as non-const-ref.
   // For returning by value there will be an ImplicitCastExpr <LValueToRValue>.
   // For returning by const-ref there will be an ImplicitCastExpr <NoOp> (for
   // adding const.)
   const auto AsNonConstRefReturn = returnStmt(hasReturnValue(
                                                 maybeEvalCommaExpr(equalsNode(Exp))));
 
   const auto Matches =
-      match(findAll(stmt(anyOf(AsAssignmentLhs, AsIncDecOperand, AsNonConstThis,
+      match(traverse(ast_type_traits::TK_AsIs,
+        findAll(stmt(anyOf(AsAssignmentLhs, AsIncDecOperand, AsNonConstThis,
                                AsAmpersandOperand, AsPointerFromArrayDecay,
                                AsOperatorArrowThis, AsNonConstRefArg,
                                AsLambdaRefCaptureInit, AsNonConstRefReturn))
-                        .bind("stmt")),
+                        .bind("stmt"))),
             Stm, Context);
   return selectFirst<Stmt>("stmt", Matches);
 }
 
 const Stmt *ExprMutationAnalyzer::findMemberMutation(const Expr *Exp) {
   // Check whether any member of 'Exp' is mutated.
   const auto MemberExprs =
       match(findAll(expr(anyOf(memberExpr(hasObjectExpression(equalsNode(Exp))),

 }
 
 const Stmt *ExprMutationAnalyzer::findFunctionArgMutation(const Expr *Exp) {
   const auto NonConstRefParam = forEachArgumentWithParam(
       equalsNode(Exp),
       parmVarDecl(hasType(nonConstReferenceType())).bind("parm"));
   const auto IsInstantiated = hasDeclaration(isInstantiated());
   const auto FuncDecl = hasDeclaration(functionDecl().bind("func"));
-  const auto Matches = match(
+  const auto Matches = match(traverse(ast_type_traits::TK_AsIs,
       findAll(expr(anyOf(callExpr(NonConstRefParam, IsInstantiated, FuncDecl,
                                   unless(callee(namedDecl(hasAnyName(
                                       "::std::move", "::std::forward"))))),
                          cxxConstructExpr(NonConstRefParam, IsInstantiated,
                                           FuncDecl)))
-                  .bind(NodeID<Expr>::value)),
+                  .bind(NodeID<Expr>::value))),
       Stm, Context);
   for (const auto &Nodes : Matches) {
     const auto *Exp = Nodes.getNodeAs<Expr>(NodeID<Expr>::value);
     const auto *Func = Nodes.getNodeAs<FunctionDecl>("func");
     if (!Func->getBody() || !Func->getPrimaryTemplate())
       return Exp;
 
     const auto *Parm = Nodes.getNodeAs<ParmVarDecl>("parm");