cl--loop-let is a compiled Lisp function in `cl-macs.el'.

(cl--loop-let SPECS BODY PAR)

Build an expression equivalent to (let SPECS BODY).
SPECS can include bindings using `cl-loop's destructuring (not to be
confused with the patterns of `cl-destructuring-bind').
If PAR is nil, do the bindings step by step, like `let*'.
If BODY is `setq', then use SPECS for assignments rather than for bindings.