1 files changed, 38 insertions, 5 deletions

diff --git a/flang/lib/Parser/message.cpp b/flang/lib/Parser/message.cpp
index 2a8101dd0b81..cfcd08b0861e 100644
--- a/flang/lib/Parser/message.cpp
+++ b/flang/lib/Parser/message.cpp
@@ -21,6 +21,10 @@
 
 namespace Fortran::parser {
 
+// The nextCh parser emits this, and Message::GetProvenanceRange() looks for it.
+const MessageFixedText MessageFixedText::endOfFileMessage{
+    "end of file"_err_en_US};
+
 llvm::raw_ostream &operator<<(llvm::raw_ostream &o, const MessageFixedText &t) {
   std::size_t n{t.text().size()};
   for (std::size_t j{0}; j < n; ++j) {
@@ -232,7 +236,20 @@ std::optional<ProvenanceRange> Message::GetProvenanceRange(
     const AllCookedSources &allCooked) const {
   return common::visit(
       common::visitors{
-          [&](CharBlock cb) { return allCooked.GetProvenanceRange(cb); },
+          [&](CharBlock cb) -> std::optional<ProvenanceRange> {
+            if (auto pr{allCooked.GetProvenanceRange(cb)}) {
+              return pr;
+            } else if (const auto *fixed{std::get_if<MessageFixedText>(&text_)};
+                fixed &&
+                fixed->text() == MessageFixedText::endOfFileMessage.text() &&
+                cb.begin() && cb.size() == 1) {
+              // Failure from "nextCh" due to reaching EOF.  Back up one byte
+              // to the terminal newline so that the output looks better.
+              return allCooked.GetProvenanceRange(CharBlock{cb.begin() - 1, 1});
+            } else {
+              return std::nullopt;
+            }
+          },
           [](const ProvenanceRange &pr) { return std::make_optional(pr); },
       },
       location_);
@@ -460,15 +477,31 @@ void Messages::Emit(llvm::raw_ostream &o, const AllCookedSources &allCooked,
   }
   std::stable_sort(sorted.begin(), sorted.end(),
       [](const Message *x, const Message *y) { return x->SortBefore(*y); });
-  const Message *lastMsg{nullptr};
+  std::vector<const Message *> msgsWithLastLocation;
   std::size_t errorsEmitted{0};
   for (const Message *msg : sorted) {
-    if (lastMsg && *msg == *lastMsg) {
-      // Don't emit two identical messages for the same location
+    bool shouldSkipMsg{false};
+    // Don't emit two identical messages for the same location.
+    // At the same location, messages are sorted by the order they were
+    // added to the Messages buffer, which is a decent proxy for the
+    // causality of the messages.
+    if (!msgsWithLastLocation.empty()) {
+      if (msgsWithLastLocation[0]->AtSameLocation(*msg)) {
+        for (const Message *msgAtThisLocation : msgsWithLastLocation) {
+          if (*msg == *msgAtThisLocation) {
+            shouldSkipMsg = true; // continue loop over sorted messages
+            break;
+          }
+        }
+      } else {
+        msgsWithLastLocation.clear();
+      }
+    }
+    if (shouldSkipMsg) {
       continue;
     }
+    msgsWithLastLocation.push_back(msg);
     msg->Emit(o, allCooked, echoSourceLines, hintFlagPtr);
-    lastMsg = msg;
     if (warningsAreErrors || msg->IsFatal()) {
       ++errorsEmitted;
     }