# Buggy code
def _canonicalize(
    self,
    schema: s_schema.Schema,
    context: CommandContext,
    scls: so.Object,
) -> Sequence[Command]:
    mcls = self.get_schema_metaclass()
    commands = []

    for refdict in mcls.get_refdicts():
        all_refs = set(scls.get_field_value(schema, refdict.attr).objects(schema))

        ref: so.Object
        for ref in all_refs:
            ref_name = ref.get_name(schema)
            quals = list(sn.quals_from_fullname(ref_name))
            assert isinstance(self.new_name, sn.QualName)
            quals[0] = str(self.new_name)
            shortname = sn.shortname_from_fullname(ref_name)
            new_ref_name = sn.QualName(
                name=sn.get_specialized_name(shortname, *quals),
                module=self.new_name.module,
            )

            commands.append(
                self._canonicalize_ref_rename(
                    ref, ref_name, new_ref_name, schema, context, scls
                )
            )

    # Record the fact that RenameObject._canonicalize
    # was called on this object to guard against possible
    # duplicate calls.
    context.store_value(("renamecanon", self), True)

    return commands


# Traceback (AttributeError)
ERROR: InternalServerError: 'UnionType' object has no attribute 'get_name'
Hint: This is most likely a bug in EdgeDB. Please consider opening an issue ticket at https://github.com/edgedb/edgedb/issues/new?template=bug_report.md
Server traceback:
Traceback (most recent call last):
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/server/procpool/worker.py", line 75, in worker
res = await meth(*args)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/server/compiler/compiler.py", line 1808, in compile_eql_tokens
return self._compile(ctx=ctx, tokens=eql_tokens)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/server/compiler/compiler.py", line 1442, in _compile
comp: dbstate.BaseQuery = self._compile_dispatch_ql(ctx, stmt)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/server/compiler/compiler.py", line 1365, in _compile_dispatch_ql
return self._compile_ql_migration(ctx, ql)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/server/compiler/compiler.py", line 794, in _compile_ql_migration
target_schema = s_ddl.apply_sdl(
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/schema/ddl.py", line 371, in apply_sdl
ddl_stmts = s_decl.sdl_to_ddl(current_schema, documents)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/edgeql/declarative.py", line 230, in sdl_to_ddl
trace_dependencies(decl_ast, ctx=ctx)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/functools.py", line 875, in wrapper
return dispatch(args[0].__class__)(*args, **kw)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/edgeql/declarative.py", line 499, in trace_default
_register_item(node, ctx=ctx)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/edgeql/declarative.py", line 623, in _register_item
trace_dependencies(cmd, ctx=ctx)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/functools.py", line 875, in wrapper
return dispatch(args[0].__class__)(*args, **kw)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/edgeql/declarative.py", line 443, in trace_ConcretePointer
_register_item(
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/edgeql/declarative.py", line 638, in _register_item
tdeps = qltracer.trace_refs(
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/edgeql/tracer.py", line 162, in trace_refs
trace(qltree, ctx=ctx)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/functools.py", line 875, in wrapper
return dispatch(args[0].__class__)(*args, **kw)
File "/usr/lib/x86_64-linux-gnu/edgedb-server-1-alpha6/lib/python3.8/site-packages/edb/edgeql/tracer.py", line 653, in trace_Select
ctx.path_prefix = tip.get_name(ctx.schema)
AttributeError: 'UnionType' object has no attribute 'get_name'

# Fixed code
def _canonicalize(
    self,
    schema: s_schema.Schema,
    context: CommandContext,
    scls: so.Object,
) -> None:
    mcls = self.get_schema_metaclass()

    for refdict in mcls.get_refdicts():
        all_refs = set(scls.get_field_value(schema, refdict.attr).objects(schema))

        ref: so.Object
        for ref in all_refs:
            ref_name = ref.get_name(schema)
            quals = list(sn.quals_from_fullname(ref_name))
            assert isinstance(self.new_name, sn.QualName)
            quals[0] = str(self.new_name)
            shortname = sn.shortname_from_fullname(ref_name)
            new_ref_name = sn.QualName(
                name=sn.get_specialized_name(shortname, *quals),
                module=self.new_name.module,
            )
            self.add(
                self.init_rename_branch(
                    ref,
                    new_ref_name,
                    schema=schema,
                    context=context,
                )
            )