Rather, it is now a struct where properties like opts are accessed
directly, and the error-reporting methods are part of a static impl
(with the same name as the type).
This makes it possible to omit the semicolon after the block, and will
cause the pretty-printer to properly print such calls (if
pretty-printing of blocks wasn't so broken). Block calls (with the
block outside of the parentheses) can now only occur at statement
level, and their value can not be used. When calling a block-style
function that returns a useful value, the block must be put insde the
parentheses.
Issue #1054
