calcite does not support type implicit cast

[宋之白(之白)]

Hi
    for current calcite master repo does not support implicit type cast in 
validation,  for example 
        insert into emp values (1, 'nom', 'job', 0, timestamp '1970-01-01 
00:00:00', 1, 1,  1, false)
    is OK for validator

    but 
        insert into emp values (1, 'nom', 'job', 0, '1970-01-01 00:00:00', 1, 
1,  1, false)
    is not OK for validator