Odd "operator does not exist" message

Stumbled across this and it just seemed unusual - though by no means
cryptic.

SELECT 'text' || AS label

ERROR:  operator does not exist: unknown ||

The lack of a second type to the right of the operator symbol caught my
attention.

SELECT 1 + AS label

ERROR: syntax error at or near "AS"

Was seemingly what I had been expecting...

David J.