ruby - How does module_eval / class_eval / instance_eval counts the line numbers -

i have found line_number passed class_eval, module_eval , instance_eval doesn't match line numbers reported error. behaviour not explained ruby-doc says: (use instance_eval example)

the optional second , third parameters supply filename , starting line number used when reporting compilation errors.

all these 3 methods class_eval, module_eval , instance_eval accepts 2 additional params specify filename , lineno parameters set text error messages.

this question has practical demo behavior.

however, have found calculation of line numbers more complex explanation. here demo

class thing   def add_method     = %{       non_exist     }     instance_eval(a, 'dummy', 12)   end end  # error raise 15 instead of 12 specified  puts thing.new.add_method 

the code above proves line_no param passed instance_eval not line numbers reported error related line_no.

i wondering exact behavior of params?

as snippet of documentation states, lineno specifies starting line number of pseudo-file. string eval contains 3 lines, second line contains non_exist (%{} preserves line breaks).

when execute code, error in line 14, not 15 receive. have expected 13, seems ruby parser "notice" error on next line, possibly looking method arguments or else make sense of non_exists (i not sure on that). if insert blank line (that contains no indentation) after non_exists, expected 13.

any lines inserted after %{ before non_exists increment line number in error one, should expected.