ProofBlockDelimiterSourceA goal is simple if it nor depends on nor impacts on any other goal. This function is used to detect, dynamically, if a proof block leaks, i.e. if skipping it could impact other goals (like not instantiating their type). `Simple carries the list of focused goals.
val crawl :
Stm.document_view ->
?init:Stm.document_node option ->
('a -> Stm.document_node -> 'a until) ->
'a ->
Stm.static_block_declaration option