diff --git a/src/indexer.cc b/src/indexer.cc
index 8929762d..954597d0 100644
--- a/src/indexer.cc
+++ b/src/indexer.cc
@@ -163,9 +163,6 @@ StorageClass GetStorageClass(CX_StorageClass storage) {
       return StorageClass::Auto;
     case CX_SC_Register:
       return StorageClass::Register;
-    default:
-      assert(0);
-      return StorageClass::Invalid;
   }
 }
 
diff --git a/src/ipc.cc b/src/ipc.cc
index 01029af8..ba7cee11 100644
--- a/src/ipc.cc
+++ b/src/ipc.cc
@@ -96,11 +96,9 @@ const char* IpcIdToString(IpcId id) {
       return "$cquery/indexFile";
     case IpcId::CqueryWait:
       return "$cquery/wait";
-
-    default:
-      assert(false && "missing IpcId string name");
-      exit(1);
   }
+
+  CQUERY_UNREACHABLE("missing IpcId string name");
 }
 
 BaseIpcMessage::BaseIpcMessage(IpcId method_id) : method_id(method_id) {}
diff --git a/src/messages/text_document_definition.cc b/src/messages/text_document_definition.cc
index fdeeefb2..0fd0ab5a 100644
--- a/src/messages/text_document_definition.cc
+++ b/src/messages/text_document_definition.cc
@@ -126,6 +126,7 @@ struct TextDocumentDefinitionHandler
           lsLocation result;
           result.uri = lsDocumentUri::FromPath(include.resolved_path);
           out.result.push_back(result);
+          has_symbol = true;
           break;
         }
       }
@@ -135,6 +136,9 @@ struct TextDocumentDefinitionHandler
         const std::string& buffer = working_file->buffer_content;
         std::string query = LexWordAroundPos(position, buffer);
 
+        // For symbols whose detailed names contain |query| as a substring,
+        // we use the tuple <length difference, not in the same file, line
+        // distance> to find the best match.
         std::tuple<int, bool, int> best_score = {INT_MAX, true, 0};
         int best_i = -1;
         for (int i = 0; i < (int)db->symbols.size(); ++i) {
diff --git a/src/port.cc b/src/port.cc
new file mode 100644
index 00000000..7f5d5be2
--- /dev/null
+++ b/src/port.cc
@@ -0,0 +1,10 @@
+#include "port.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+
+void cquery_unreachable_internal(const char* msg, const char* file, int line) {
+  fprintf(stderr, "unreachable %s:%d %s\n", file, line, msg);
+  CQUERY_BUILTIN_UNREACHABLE;
+  abort();
+}
diff --git a/src/port.h b/src/port.h
index d2a1db03..fbb152cc 100644
--- a/src/port.h
+++ b/src/port.h
@@ -1,7 +1,27 @@
 #pragma once
 
+#ifndef __has_builtin
+# define __has_builtin(x) 0
+#endif
+
 #if defined(__GNUC__)
 #define ATTRIBUTE_UNUSED __attribute__((unused))
 #else
 #define ATTRIBUTE_UNUSED
 #endif
+
+// TODO GCC
+#if __has_builtin(__builtin_unreachable)
+#define CQUERY_BUILTIN_UNREACHABLE __builtin_unreachable()
+#elif defined(_MSC_VER)
+#define CQUERY_BUILTIN_UNREACHABLE __assume(false)
+#else
+#define CQUERY_BUILTIN_UNREACHABLE
+#endif
+
+void cquery_unreachable_internal(const char* msg, const char* file, int line);
+#ifndef NDEBUG
+#define CQUERY_UNREACHABLE(msg) cquery_unreachable_internal(msg, __FILE__, __LINE__)
+#else
+#define CQUERY_UNREACHABLE(msg)
+#endif