Add typeName() to all types.

Fixes some possible empty error messages (from
vec<unsupported type> at least). Also, will be useful
in the future to describe types.

Bug: 34807779
Test: manual
Change-Id: I52898f854e5747a65a4ca0c7a6ada0277feca761
diff --git a/Scope.cpp b/Scope.cpp
index b12cec8..13a6f28 100644
--- a/Scope.cpp
+++ b/Scope.cpp
@@ -185,6 +185,14 @@
     });
 }
 
+RootScope::RootScope(const char* localName, const Location& location, Scope* parent)
+    : Scope(localName, location, parent) {}
+RootScope::~RootScope() {}
+
+std::string RootScope::typeName() const {
+    return "(root scope)";
+}
+
 LocalIdentifier::LocalIdentifier(){}
 LocalIdentifier::~LocalIdentifier(){}