1 files changed, 17 insertions, 1 deletions
diff --git a/tools/diagtool/FindDiagnosticID.cpp b/tools/diagtool/FindDiagnosticID.cpp
index 167b9925eedc..db6fe5e472a9 100644
--- a/tools/diagtool/FindDiagnosticID.cpp
+++ b/tools/diagtool/FindDiagnosticID.cpp
@@ -18,6 +18,15 @@ DEF_DIAGTOOL("find-diagnostic-id", "Print the id of the given diagnostic",
 using namespace clang;
 using namespace diagtool;
 
+static StringRef getNameFromID(StringRef Name) {
+  int DiagID;
+  if(!Name.getAsInteger(0, DiagID)) {
+    const DiagnosticRecord &Diag = getDiagnosticForID(DiagID);
+    return Diag.getName();
+  }
+  return StringRef();
+}
+
 static Optional<DiagnosticRecord>
 findDiagnostic(ArrayRef<DiagnosticRecord> Diagnostics, StringRef Name) {
   for (const auto &Diag : Diagnostics) {
@@ -38,7 +47,7 @@ int FindDiagnosticID::run(unsigned int argc, char **argv,
       llvm::cl::Required, llvm::cl::cat(FindDiagnosticIDOptions));
 
   std::vector<const char *> Args;
-  Args.push_back("find-diagnostic-id");
+  Args.push_back("diagtool find-diagnostic-id");
   for (const char *A : llvm::makeArrayRef(argv, argc))
     Args.push_back(A);
 
@@ -50,6 +59,13 @@ int FindDiagnosticID::run(unsigned int argc, char **argv,
   Optional<DiagnosticRecord> Diag =
       findDiagnostic(AllDiagnostics, DiagnosticName);
   if (!Diag) {
+    // Name to id failed, so try id to name.
+    auto Name = getNameFromID(DiagnosticName);
+    if (!Name.empty()) {
+      OS << Name << '\n';
+      return 0;
+    }
+
     llvm::errs() << "error: invalid diagnostic '" << DiagnosticName << "'\n";
     return 1;
   }