alembic: literal_column() in ExcludeConstraint are autogenerated as column(), failing in the migration

Describe the bug

If you add a literal_column in a ExcludeConstraint (e.g. a literal_column("int8range(col_from, col_to)")), this is rendered as column("int8range(col_from, col_to)") in the autogenerated migration and the migration will fail as such a column does not exist in the table.

Expected behavior

literal_columns are passed through in the rendered migration

To Reproduce

from sqlalchemy.dialects.postgresql import JSONB, ExcludeConstraint
from sqlalchemy.sql.expression import column, literal_column
from sqlalchemy import Column, Table
from sqlalchemy.orm import declarative_base
from sqlalchemy.sql.schema import MetaData
from sqlalchemy.sql.sqltypes import *

Base2 = declarative_base()
whatever2 = Table(
    "whatever2",
    Base2.metadata,
    Column("id", BigInteger(), nullable=False, primary_key=True),
    ExcludeConstraint(
        ("id", "="),
        (literal_column("id + 2"), "="),
        name=f"whatever_id_int8range_excl",
    ),
)

Error

The migration code after alembic revision --autogenerate -m "test2"looks like this:

def upgrade() -> None:
    # ### commands auto generated by Alembic - please adjust! ###
    op.create_table('whatever2',
    sa.Column('id', sa.BigInteger(), nullable=False),
    postgresql.ExcludeConstraint((sa.column('id'), '='), (sa.column('id + 2'), '='), using='gist', name='whatever_id_int8range_excl'),
    sa.PrimaryKeyConstraint('id')
    )

running this migration via alembic upgrade head results in:

psycopg2.errors.UndefinedColumn: column "id + 2" named in key does not exist


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/bin/alembic", line 8, in <module>
    sys.exit(main())
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/config.py", line 591, in main
    CommandLine(prog=prog).main(argv=argv)
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/config.py", line 585, in main
    self.run_cmd(cfg, options)
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/config.py", line 562, in run_cmd
    fn(
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/command.py", line 378, in upgrade
    script.run_env()
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/script/base.py", line 569, in run_env
    util.load_python_file(self.dir, "env.py")
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/util/pyfiles.py", line 94, in load_python_file
    module = load_module_py(module_id, path)
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/util/pyfiles.py", line 110, in load_module_py
    spec.loader.exec_module(module)  # type: ignore
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/Users/jankatins/projects/50hz/mds-elt-service/alembic/env.py", line 115, in <module>
    run_migrations_online()
  File "/Users/jankatins/projects/50hz/mds-elt-service/alembic/env.py", line 109, in run_migrations_online
    context.run_migrations()
  File "<string>", line 8, in run_migrations
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/runtime/environment.py", line 867, in run_migrations
    self.get_context().run_migrations(**kw)
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/runtime/migration.py", line 624, in run_migrations
    step.migration_fn(**kw)
  File "/Users/jankatins/projects/50hz/mds-elt-service/alembic/versions/f7aae215babc_test2.py", line 30, in upgrade
    op.create_table('whatever2',
  File "<string>", line 8, in create_table
  File "<string>", line 3, in create_table
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/operations/ops.py", line 1260, in create_table
    return operations.invoke(op)
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/operations/base.py", line 401, in invoke
    return fn(self, operation)
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/operations/toimpl.py", line 114, in create_table
    operations.impl.create_table(table)
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/ddl/impl.py", line 354, in create_table
    self._exec(schema.CreateTable(table))
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/alembic/ddl/impl.py", line 193, in _exec
    return conn.execute(  # type: ignore[call-overload]
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/sqlalchemy/engine/base.py", line 1380, in execute
    return meth(self, multiparams, params, _EMPTY_EXECUTION_OPTS)
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/sqlalchemy/sql/ddl.py", line 80, in _execute_on_connection
    return connection._execute_ddl(
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/sqlalchemy/engine/base.py", line 1472, in _execute_ddl
    ret = self._execute_context(
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/sqlalchemy/engine/base.py", line 1943, in _execute_context
    self._handle_dbapi_exception(
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/sqlalchemy/engine/base.py", line 2124, in _handle_dbapi_exception
    util.raise_(
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/sqlalchemy/util/compat.py", line 211, in raise_
    raise exception
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/sqlalchemy/engine/base.py", line 1900, in _execute_context
    self.dialect.do_execute(
  File "/Users/jankatins/Library/Caches/pypoetry/virtualenvs/mds-elt-service-JeB-l5pZ-py3.10/lib/python3.10/site-packages/sqlalchemy/engine/default.py", line 736, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.ProgrammingError: (psycopg2.errors.UndefinedColumn) column "id + 2" named in key does not exist

[SQL:
CREATE TABLE whatever2 (
        id BIGSERIAL NOT NULL,
        PRIMARY KEY (id),
        CONSTRAINT whatever_id_int8range_excl EXCLUDE USING gist (id WITH =, "id + 2" WITH =)
)

]
(Background on this error at: https://sqlalche.me/e/14/f405)

Versions.

• OS: Macosx latest
• Python: 3.10
• Alembic: alembic==1.9.4
• SQLAlchemy: SQLAlchemy==1.4.46
• Database: postgresql 14
• DBAPI: psycopg2-binary==2.9.5