1 files changed, 59 insertions, 0 deletions
diff --git a/effcee/diagnostic.h b/effcee/diagnostic.h
new file mode 100644
index 0000000..b348687
--- /dev/null
+++ b/effcee/diagnostic.h
@@ -0,0 +1,59 @@
+// Copyright 2017 The Effcee Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef EFFCEE_DIAGNOSTIC_H
+#define EFFCEE_DIAGNOSTIC_H
+
+#include <sstream>
+
+#include "effcee/effcee.h"
+
+namespace effcee {
+
+// A Diagnostic contains a Result::Status value and can accumulate message
+// values via operator<<.  It is convertible to a Result object containing the
+// status and the stringified message.
+class Diagnostic {
+ public:
+  explicit Diagnostic(Result::Status status) : status_(status) {}
+
+  // Copy constructor.
+  Diagnostic(const Diagnostic& other) : status_(other.status_), message_() {
+    // We can't move an ostringstream.  As a fallback, we'd like to use the
+    // std::ostringstream(std::string init_string) constructor.  However, that
+    // initial string disappears inexplicably the first time we shift onto
+    // the |message_| member.  So fall back further and use the default
+    // constructor and later use an explicit shift.
+    message_ << other.message_.str();
+  }
+
+  // Appends the given value to the accumulated message.
+  template <typename T>
+  Diagnostic& operator<<(const T& value) {
+    message_ << value;
+    return *this;
+  }
+
+  // Converts this object to a result value containing the stored status and a
+  // stringified copy of the message.
+  operator Result() const { return Result(status_, message_.str()); }
+
+ private:
+  Result::Status status_;
+  std::ostringstream message_;
+};
+
+}  // namespace effcee
+
+#endif