Parser returns incorrect locations

[ajor]

After #2624, the parser appears to return incorrect locations for some AST nodes.

e.g.:

# bpftrace -e 'fn f($a : int64): str_t[16] { return $a; }'
stdin:1:33-42: ERROR: Function f is of type string[16], cannot return int64
fn f($a : int64): str_t[16] { return $a; }
                                ~~~~~~~~~
# bpftrace -e 'BEGIN { for ($v : @a) print(1) }'                        
stdin:1:24-29: ERROR: syntax error, unexpected call, expecting {
BEGIN { for ($v : @a) print(1) }
                       ~~~~~

[ajor]

cc @lenticularis39

[ajor]

It seems to be the "AFTER_COLON" state which is causing the problem:

bpftrace/src/lexer.l

Line 100 in 26e310f

yy_push_state(AFTER_COLON, yyscanner);

[lenticularis39]

Oops my lexer hacks are a bit broken.. hopefully just a little :D I'll have a look at it

[ajor]

I've got a possible fix here: ajor@113ffab. Not very familiar with flex though. Feel free to take this on if you fancy it, otherwise I'll continue some time next week.

All the tests I added today for error locations (#3064, #3065, #3066) have revealed some older problems too, which weren't caused by the user-defined functions PR, e.g.:
ajor@113ffab#diff-9537c973c4937d6eee4a927120e27d86a4f347f6d81caa5ca40e52745eb39f8aR297-R304

I'm wondering they're all related to us not restoring the location after calling unput().