[libTooling] Restore defaults for matchers in makeRule.

[ymandel]

Summary

This patch restores the default traversal for Transformer's makeRule to
TK_AsIs. The implicit mode has proven problematic.

clang/lib/Tooling/Transformer/RewriteRule.cpp

for (int I = 0, N = Cases.size(); I < N; ++I) {
     assert(hasValidKind(Cases[I].Matcher) &&
            "Matcher must be non-(Qual)Type node matcher");
     Buckets[Cases[I].Matcher.getSupportedKind()].emplace_back(I, Cases[I]);
   }
 
   // Each anyOf explicitly controls the traversal kind. The anyOf itself is set
   // to `TK_AsIs` to ensure no nodes are skipped, thereby deferring to the kind
   // of the branches. Then, each branch is either left as is, if the kind is
-  // already set, or explicitly set to `TK_IgnoreUnlessSpelledInSource`. We
-  // choose this setting, because we think it is the one most friendly to
-  // beginners, who are (largely) the target audience of Transformer.
+  // already set, or explicitly set to `TK_AsIs`. We choose this setting because
+  // it is the default interpretation of matchers.
   std::vector<DynTypedMatcher> Matchers;
   for (const auto &Bucket : Buckets) {
     DynTypedMatcher M = DynTypedMatcher::constructVariadic(
         DynTypedMatcher::VO_AnyOf, Bucket.first,
-        taggedMatchers("Tag", Bucket.second, TK_IgnoreUnlessSpelledInSource));
+        taggedMatchers("Tag", Bucket.second, TK_AsIs));
     M.setAllowBind(true);
     // `tryBind` is guaranteed to succeed, because `AllowBind` was set to true.
     Matchers.push_back(M.tryBind(RootID)->withTraversalKind(TK_AsIs));
   }
   return Matchers;
 }
 
 DynTypedMatcher transformer::detail::buildMatcher(const RewriteRule &Rule) {

clang/unittests/Tooling/TransformerTest.cpp

RewriteRule DeclRule = makeRule(functionDecl(hasName("f2")).bind("fun"),
                                   changeTo(name("fun"), cat("DECL_RULE")));
 
   RewriteRule Rule = applyFirst({ReplaceF1, DeclRule, ReplaceF1OrF2});
   EXPECT_EQ(transformer::detail::buildMatchers(Rule).size(), 2UL);
   testRule(Rule, Input, Expected);
 }
 
 // Verifies that a rule with a top-level matcher for an implicit node (like
-// `implicitCastExpr`) does not change the code, when the AST traversal skips
-// implicit nodes. In this test, only the rule with the explicit-node matcher
-// will fire.
-TEST_F(TransformerTest, OrderedRuleImplicitIgnored) {
+// `implicitCastExpr`) works correctly -- the implicit nodes are not skipped.
+TEST_F(TransformerTest, OrderedRuleImplicitMatched) {
   std::string Input = R"cc(
     void f1();
     int f2();
     void call_f1() { f1(); }
     float call_f2() { return f2(); }
   )cc";
   std::string Expected = R"cc(
     void f1();
     int f2();
     void call_f1() { REPLACE_F1; }
-    float call_f2() { return f2(); }
+    float call_f2() { return REPLACE_F2; }
   )cc";
 
   RewriteRule ReplaceF1 =
       makeRule(callExpr(callee(functionDecl(hasName("f1")))),
                changeTo(cat("REPLACE_F1")));
   RewriteRule ReplaceF2 =
       makeRule(implicitCastExpr(hasSourceExpression(callExpr())),
                changeTo(cat("REPLACE_F2")));
   testRule(applyFirst({ReplaceF1, ReplaceF2}), Input, Expected);
 }
 
-// Verifies that explicitly setting the traversal kind fixes the problem in the
-// previous test.
-TEST_F(TransformerTest, OrderedRuleImplicitMatched) {
-  std::string Input = R"cc(
-    void f1();
-    int f2();
-    void call_f1() { f1(); }
-    float call_f2() { return f2(); }
-  )cc";
-  std::string Expected = R"cc(
-    void f1();
-    int f2();
-    void call_f1() { REPLACE_F1; }
-    float call_f2() { return REPLACE_F2; }
-  )cc";
-
-  RewriteRule ReplaceF1 = makeRule(
-      traverse(clang::TK_AsIs, callExpr(callee(functionDecl(hasName("f1"))))),
-      changeTo(cat("REPLACE_F1")));
-  RewriteRule ReplaceF2 =
-      makeRule(traverse(clang::TK_AsIs,
-                        implicitCastExpr(hasSourceExpression(callExpr()))),
-               changeTo(cat("REPLACE_F2")));
-  testRule(applyFirst({ReplaceF1, ReplaceF2}), Input, Expected);
-}
-
 //
 // Negative tests (where we expect no transformation to occur).
 //
 
 // Tests for a conflict in edits from a single match for a rule.
 TEST_F(TransformerTest, TextGeneratorFailure) {
   std::string Input = "int conflictOneRule() { return 3 + 7; }";
   // Try to change the whole binary-operator expression AND one its operands: