3 files changed, 78 insertions, 12 deletions

diff --git a/clang/include/clang/Tooling/Refactoring/Transformer.h b/clang/include/clang/Tooling/Refactoring/Transformer.h
index 587edb9d02c..0971cc3e667 100644
--- a/clang/include/clang/Tooling/Refactoring/Transformer.h
+++ b/clang/include/clang/Tooling/Refactoring/Transformer.h
@@ -251,6 +251,12 @@ ast_matchers::internal::DynTypedMatcher buildMatcher(const RewriteRule &Rule);
 std::vector<ast_matchers::internal::DynTypedMatcher>
 buildMatchers(const RewriteRule &Rule);
 
+/// Gets the beginning location of the source matched by a rewrite rule. If the
+/// match occurs within a macro expansion, returns the beginning of the
+/// expansion point. `Result` must come from the matching of a rewrite rule.
+SourceLocation
+getRuleMatchLoc(const ast_matchers::MatchFinder::MatchResult &Result);
+
 /// Returns the \c Case of \c Rule that was selected in the match result.
 /// Assumes a matcher built with \c buildMatcher.
 const RewriteRule::Case &
diff --git a/clang/lib/Tooling/Refactoring/Transformer.cpp b/clang/lib/Tooling/Refactoring/Transformer.cpp
index c27739c5962..905d5944449 100644
--- a/clang/lib/Tooling/Refactoring/Transformer.cpp
+++ b/clang/lib/Tooling/Refactoring/Transformer.cpp
@@ -150,6 +150,21 @@ DynTypedMatcher tooling::detail::buildMatcher(const RewriteRule &Rule) {
   return Ms[0];
 }
 
+SourceLocation tooling::detail::getRuleMatchLoc(const MatchResult &Result) {
+  auto &NodesMap = Result.Nodes.getMap();
+  auto Root = NodesMap.find(RewriteRule::RootID);
+  assert(Root != NodesMap.end() && "Transformation failed: missing root node.");
+  llvm::Optional<CharSourceRange> RootRange = getRangeForEdit(
+      CharSourceRange::getTokenRange(Root->second.getSourceRange()),
+      *Result.Context);
+  if (RootRange)
+    return RootRange->getBegin();
+  // The match doesn't have a coherent range, so fall back to the expansion
+  // location as the "beginning" of the match.
+  return Result.SourceManager->getExpansionLoc(
+      Root->second.getSourceRange().getBegin());
+}
+
 // Finds the case that was "selected" -- that is, whose matcher triggered the
 // `MatchResult`.
 const RewriteRule::Case &
@@ -178,14 +193,6 @@ void Transformer::run(const MatchResult &Result) {
   if (Result.Context->getDiagnostics().hasErrorOccurred())
     return;
 
-  // Verify the existence and validity of the AST node that roots this rule.
-  auto &NodesMap = Result.Nodes.getMap();
-  auto Root = NodesMap.find(RewriteRule::RootID);
-  assert(Root != NodesMap.end() && "Transformation failed: missing root node.");
-  SourceLocation RootLoc = Result.SourceManager->getExpansionLoc(
-      Root->second.getSourceRange().getBegin());
-  assert(RootLoc.isValid() && "Invalid location for Root node of match.");
-
   RewriteRule::Case Case = tooling::detail::findSelectedCase(Result, Rule);
   auto Transformations = tooling::detail::translateEdits(Result, Case.Edits);
   if (!Transformations) {
@@ -195,14 +202,16 @@ void Transformer::run(const MatchResult &Result) {
 
   if (Transformations->empty()) {
     // No rewrite applied (but no error encountered either).
-    RootLoc.print(llvm::errs() << "note: skipping match at loc ",
-                  *Result.SourceManager);
+    detail::getRuleMatchLoc(Result).print(
+        llvm::errs() << "note: skipping match at loc ", *Result.SourceManager);
     llvm::errs() << "\n";
     return;
   }
 
-  // Record the results in the AtomicChange.
-  AtomicChange AC(*Result.SourceManager, RootLoc);
+  // Record the results in the AtomicChange, anchored at the location of the
+  // first change.
+  AtomicChange AC(*Result.SourceManager,
+                  (*Transformations)[0].Range.getBegin());
   for (const auto &T : *Transformations) {
     if (auto Err = AC.replace(*Result.SourceManager, T.Range, T.Replacement)) {
       Consumer(std::move(Err));
diff --git a/clang/unittests/Tooling/TransformerTest.cpp b/clang/unittests/Tooling/TransformerTest.cpp
index 554e586c3c4..5d55182f827 100644
--- a/clang/unittests/Tooling/TransformerTest.cpp
+++ b/clang/unittests/Tooling/TransformerTest.cpp
@@ -710,6 +710,57 @@ TEST_F(TransformerTest, IdentityMacro) {
   testRule(ruleStrlenSize(), Input, Expected);
 }
 
+// Tests that two changes in a single macro expansion do not lead to conflicts
+// in applying the changes.
+TEST_F(TransformerTest, TwoChangesInOneMacroExpansion) {
+  std::string Input = R"cc(
+#define PLUS(a,b) (a) + (b)
+    int f() { return PLUS(3, 4); }
+  )cc";
+  std::string Expected = R"cc(
+#define PLUS(a,b) (a) + (b)
+    int f() { return PLUS(LIT, LIT); }
+  )cc";
+
+  testRule(makeRule(integerLiteral(), change(text("LIT"))), Input, Expected);
+}
+
+// Tests case where the rule's match spans both source from the macro and its
+// arg, with the begin location (the "anchor") being the arg.
+TEST_F(TransformerTest, MatchSpansMacroTextButChangeDoesNot) {
+  std::string Input = R"cc(
+#define PLUS_ONE(a) a + 1
+    int f() { return PLUS_ONE(3); }
+  )cc";
+  std::string Expected = R"cc(
+#define PLUS_ONE(a) a + 1
+    int f() { return PLUS_ONE(LIT); }
+  )cc";
+
+  StringRef E = "expr";
+  testRule(makeRule(binaryOperator(hasLHS(expr().bind(E))),
+                    change(node(E), text("LIT"))),
+           Input, Expected);
+}
+
+// Tests case where the rule's match spans both source from the macro and its
+// arg, with the begin location (the "anchor") being inside the macro.
+TEST_F(TransformerTest, MatchSpansMacroTextButChangeDoesNotAnchoredInMacro) {
+  std::string Input = R"cc(
+#define PLUS_ONE(a) 1 + a
+    int f() { return PLUS_ONE(3); }
+  )cc";
+  std::string Expected = R"cc(
+#define PLUS_ONE(a) 1 + a
+    int f() { return PLUS_ONE(LIT); }
+  )cc";
+
+  StringRef E = "expr";
+  testRule(makeRule(binaryOperator(hasRHS(expr().bind(E))),
+                    change(node(E), text("LIT"))),
+           Input, Expected);
+}
+
 // No rewrite is applied when the changed text does not encompass the entirety
 // of the expanded text. That is, the edit would have to be applied to the
 // macro's definition to succeed and editing the expansion point would not