[flang] Avoid a std::move() when emplacing new messages.

Original-commit: flang-compiler/f18@39c0e1fdba
Reviewed-on: https://github.com/flang-compiler/f18/pull/59
Tree-same-pre-rewrite: false

flang/lib/parser/message.h

@@ -12,6 +12,7 @@
 #include <optional>
 #include <ostream>
 #include <string>
+#include <utility>
 
 namespace Fortran {
 namespace parser {
@@ -179,24 +180,18 @@ public:
     }
   }
 
-  Message &Put(Message &&m) {
-    CHECK(IsValidLocation(m));
-    if (messages_.empty()) {
-      messages_.emplace_front(std::move(m));
-      last_ = messages_.begin();
-    } else {
-      last_ = messages_.emplace_after(last_, std::move(m));
-    }
-    return *last_;
+  void Put(Message &&m) {
+//    CHECK(IsValidLocation(m));
+    last_ = messages_.emplace_after(last_, std::move(m));
+  }
+
+  template<typename... A> void Say(A &&... args) {
+    last_ = messages_.emplace_after(last_, std::forward<A>(args)...);
   }
 
   void Annex(Messages &that) {
     if (!that.messages_.empty()) {
-      if (messages_.empty()) {
-        messages_ = std::move(that.messages_);
-      } else {
-        messages_.splice_after(last_, that.messages_);
-      }
+      messages_.splice_after(last_, that.messages_);
       last_ = that.last_;
     }
   }
@@ -209,7 +204,7 @@ public:
 private:
   const CookedSource &cooked_;
   listType messages_;
-  iterator last_;  // valid iff messages_ nonempty
+  iterator last_{messages_.before_begin()};
 };
 }  // namespace parser
 }  // namespace Fortran

flang/lib/parser/parse-state.h

@@ -126,13 +126,13 @@ public:
   void Say(MessageExpectedText &&t) { return Say(p_, std::move(t)); }
 
   void Say(const char *at, MessageFixedText t) {
-    messages_.Put(Message{at, t, context_.get()});
+    messages_.Say(at, t, context_.get());
   }
   void Say(const char *at, MessageFormattedText &&t) {
-    messages_.Put(Message{at, std::move(t), context_.get()});
+    messages_.Say(at, std::move(t), context_.get());
   }
   void Say(const char *at, MessageExpectedText &&t) {
-    messages_.Put(Message{at, std::move(t), context_.get()});
+    messages_.Say(at, std::move(t), context_.get());
   }
 
   bool IsAtEnd() const { return p_ >= limit_; }

flang/lib/parser/reference-counted.h

@@ -29,15 +29,16 @@ public:
   CountedReference(const CountedReference &c) : p_{c.p_} { Take(); }
   CountedReference(CountedReference &&c) : p_{c.p_} { c.p_ = nullptr; }
   CountedReference &operator=(const CountedReference &c) {
+    c.Take();
     Drop();
     p_ = c.p_;
-    Take();
     return *this;
   }
   CountedReference &operator=(CountedReference &&c) {
-    Drop();
-    p_ = c.p_;
+    A *p{c.p_};
     c.p_ = nullptr;
+    Drop();
+    p_ = p;
     return *this;
   }
   ~CountedReference() { Drop(); }
@@ -47,7 +48,7 @@ public:
   type *operator->() const { return p_; }
 
 private:
-  void Take() {
+  void Take() const {
     if (p_) {
       p_->TakeReference();
     }