Report entity name to SDT function

[onokonem]

$§ wil be replaces by the name of the entity on preparing SDT call

[shivansh]

This looks great! Please address the comments below.

[shivansh]

I'm not sure but are the variables holding compiled regular expressions required to be global ?

[onokonem]

of course it is not required to be global

in the same time it might be compiled once on package init and used everywhere later

[shivansh]

I think a small comment here explaining the functionality of SDTVal() would be helpful in future. Something along the lines of -

// SDTVal converts a handwritten action expression into an equivalent expression
// usable by gocc during runtime.
// For e.g. the expression `<< $0.(int64) + $2.(int64), nil >>` is converted to
// `X[0].(int64) + X[2].(int64), nil`. `X` usually represents a slice of
// attributes in the code generated by gocc.

[onokonem]

there was no such explanation in the original code, so I do did not add it :)

are you sure any explanation is required here? this code is completely self-explaining FMPOV