body is evaluated as an implicit progn, but its forms are treated as "error situation" forms. Currently that means that the compiler does not generate code coverage inside body or for the
(error-situation-forms ...) form itself, unless force was supplied non-nil to generate-code-coverage or with-code-coverage-generation.
For code coverage,
error-situation-forms differs from without-code-coverage in that it does not generate a counter for the
(error-situation-forms ...) form itself, and therefore is more convenient to use.
LispWorks User Guide and Reference Manual - 13 Feb 2015