Version 2 of using a table function instead of a view, this time no errors are thrown anywhere.

table_function_no_errors.sql

CREATE TABLE foo(
  some_id SERIAL PRIMARY KEY,
  another INT,
  stuff   VARCHAR(20)
);

CREATE OR REPLACE FUNCTION insert_crap_into_foo() RETURNS INTERVAL AS
$$
DECLARE
  counter INT := 0;
  start TIMESTAMP := timeOfDay();
  stop  TIMESTAMP;
BEGIN
  LOOP
    counter := counter + 1;
    INSERT INTO foo(another) VALUES(counter);
    EXIT WHEN counter > 2000000;
  END LOOP;
  stop := timeOfDay();
  RETURN stop - start;
END
$$
language plpgsql;

SELECT insert_crap_into_foo();

SELECT now() AS creating_view;

CREATE OR REPLACE FUNCTION create_bar_function() RETURNS INT AS
$META$
DECLARE
  columns TEXT;
  query   TEXT;
  cmd     TEXT;
BEGIN
  SELECT (select string_agg(column_name || ' ' || data_type, ', ')
      from information_schema.columns where table_name = 'foo'
      group by table_name) INTO columns;
  SELECT (select string_agg('CAST(foo.' || column_name || ' AS ' || data_type, '), ')
      from information_schema.columns where table_name = 'foo'
      group by table_name) INTO query;
  SELECT 'CREATE FUNCTION bar_function() RETURNS TABLE(' ||
         columns || ') AS $$ BEGIN' ||
         ' RETURN QUERY SELECT ' || query || ') FROM foo;' ||
         ' END $$ language plpgsql;'
         INTO cmd;
  EXECUTE 'DROP FUNCTION IF EXISTS bar_function();';
  EXECUTE cmd;
  RETURN 1;
END
$META$
language plpgsql;

SELECT create_bar_function();

SELECT * FROM bar_function() LIMIT 10;
ALTER TABLE foo ADD more_stuff NUMERIC(10,2);
ALTER TABLE foo DROP more_stuff;
ALTER TABLE foo ALTER COLUMN stuff TYPE VARCHAR(50);
ALTER TABLE foo ALTER COLUMN another TYPE BIGINT;
SELECT * FROM bar_function() LIMIT 10; --error
SELECT create_bar_function();
SELECT * FROM bar_function() LIMIT 10; --OK

DROP FUNCTION insert_crap_into_foo();
DROP FUNCTION bar_function();
DROP FUNCTION create_bar_function();
DROP TABLE foo;

By casting each column to its current type in the query inside the table function, the table can later be modified and the function doesn't stop working (it will return the old types though). The table function can be re-created at any time and it will start returning the new types.