rubocop-ast.wasm

matches a literal symbol

matches a literal integer

matches a literal nil

matches (send ...)

matches (send)

matches (send ...)

matches (send ...) or (class ...)

matches (send) or (class)

matches (send (const ...))

matches (send <anything> :new)

as above, but whatever matches the $_ is captured

you can use as many captures as you want

! negates the next part of the pattern

arbitrary matching can be performed on a capture

wildcards can be named (for readability)

you can specifically match against the last child (this only works for the very last)

capture all the children as an array

capture all children but the last as an array

unification is performed on named wildcards

unification is performed on named wildcards (like Prolog variables...) (#== is used to see if values unify)

words which end with a ? are predicate methods, are are called on the target to see if it matches any Ruby method which the matched object supports can be used if a truthy value is returned, the match succeeds

[] contains multiple patterns, ALL of which must match in that position in other words, while {} is pattern union (logical OR), [] is intersection (logical AND)

each ^ ascends one level in the AST so this matches against the grandparent node

we call this a 'funcall'; it calls a method in the context where a pattern-matching method is defined if that returns a truthy value, the match succeeds

predicates can be given 1 or more extra args

funcalls can also be given 1 or more extra args