# Buggy code
def _alter_begin(
    self,
    schema: s_schema.Schema,
    context: CommandContext,
) -> s_schema.Schema:
    self._validate_legal_command(schema, context)

    for op in self.get_prerequisites():
        schema = op.apply(schema, context)

    if not context.canonical:
        schema = self.populate_ddl_identity(schema, context)
        schema = self.canonicalize_attributes(schema, context)
        computed_status = self._get_computed_status_of_fields(schema, context)
        self._update_computed_fields(schema, context, computed_status)
        self.validate_alter(schema, context)

    props = self.get_resolved_attributes(schema, context)
    schema = self.scls.update(schema, props)
    return schema


# 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 _alter_begin(
    self,
    schema: s_schema.Schema,
    context: CommandContext,
) -> s_schema.Schema:
    scls = self.scls
    context.renames[self.classname] = self.new_name
    context.renamed_objs.add(scls)

    vn = scls.get_verbosename(schema)
    schema = self._propagate_if_expr_refs(
        schema,
        context,
        action=f"rename {vn}",
        fixer=self._fix_referencing_expr,
    )

    if not context.canonical:
        self.set_attribute_value(
            "name",
            value=self.new_name,
            orig_value=self.classname,
        )

    return super()._alter_begin(schema, context)