all: add support for @LOCATION, for more convenient logging/tracing, without needing to combine @FILE, @LINE at runtime

[spytheman]

// abc
// def

fn abc() {
	eprintln(@LOCATION)
}

struct MyStruct {
}

fn MyStruct.new() MyStruct {
	eprintln(@LOCATION)
	return MyStruct{}
}

fn (s MyStruct) mymethod() {
	eprintln(@LOCATION)
}

eprintln(@LOCATION)
abc()
MyStruct.new().mymethod()
eprintln(@LOCATION)

produces:

/Users/delyanangelov/code/misc/2023_10_01__19/loc.v:20, main.main
/Users/delyanangelov/code/misc/2023_10_01__19/loc.v:5, main.abc
/Users/delyanangelov/code/misc/2023_10_01__19/loc.v:12, main.MyStruct.new (static)
/Users/delyanangelov/code/misc/2023_10_01__19/loc.v:17, main.MyStruct{}.mymethod
/Users/delyanangelov/code/misc/2023_10_01__19/loc.v:23, main.main

[spytheman]

This PR, also fixes dump(@FILE), dump(@LINE) etc, which printed the expanded version twice before, instead of showing the source name @FILE, @LINE etc, once, and then the expanded value, i.e.

0[20:19:46]@m1: (feature/at_location_pseudo_variable) ~/code/v $ v run l.v ## master
[l.v:3] 3: 3
0[20:19:52]@m1: (feature/at_location_pseudo_variable) ~/code/v $ ./v run l.v ## this PR
[l.v:3] @LINE: 3

[Larpon]

This is a huge time saver when used with return error(@LOCATION + 'message') or similar for locating where an error originally comes from

[spytheman]

This is a huge time saver when used with return error(@LOCATION + 'message') or similar for locating where an error originally comes from

Should I add a space at the end of @LOCATION, to ease that (it currently does not have one)?

[lmptg]

This is a huge time saver when used with return error(@LOCATION + 'message') or similar for locating where an error originally comes from

Should I add a space at the end of @LOCATION, to ease that (it currently does not have one)?

Late to the party,

I do not think that it is necessary at this point in time - I can think of use-cases where you'd maybe not want an automatic white space. I can imagine that some errors might not need an extra message with simply error(@LOCATION) - and having error automatically strip white space from messages seems like a weird side effect. Also adding format to a comptime var feels odd

All good for now IMO 👍

[JalonSolov]

Agreed... don't add a space at the end of @LOCATION - that's not the location any longer if you do.