revert to just type name

because we can't safely print full types, because they GC

src/gc-heap-snapshot.cpp

@@ -210,16 +210,16 @@ void record_node_to_gc_snapshot(jl_value_t *a) JL_GC_DISABLED {
             name = jl_symbol_name((jl_sym_t*)a);
             self_size = name.length();
         } else if (jl_is_datatype(type)) {
-            ios_t str_;
-            ios_mem(&str_, 1024);
-            JL_STREAM* str = (JL_STREAM*)&str_;
-
-            jl_static_show(str, (jl_value_t*)type);
-
-            name = string((const char*)str_.buf, str_.size);
-            ios_close(&str_);
-
             self_size = (size_t)jl_datatype_size(type);
+            // TODO: get the entire type, including type parameters
+            // - option 1: jl_static_show it here:
+            //   crashes because it might do GC, and we are already inside GC.
+            //
+            // - option 2: put type jl_datatype_t* directly in the Node struct:
+            //   bad because the jl_datatype_t might be freed before we serialize
+            //   the snapshot. Maybe we should allocate some gc-rooted object
+            //   and attach all the jl_datatype_t*'s we need to it?
+            name = jl_symbol_name(type->name->name);
         }
     }