how to get file/line of a function's caller? cf in D: void fun(string file=__FILE__)

[timotheecour]

how to get file/line of a function's caller?

in D this works:

void fun(string file=__FILE__, int line=__LINE__){import std.stdio; writeln(file, ":", line);}
fun(); // main.d:2
fun(); // main.d:3

in D we can get the file/line of a function caller using __FILE__, __LINE__ (__MODULE__, etc)

how would we do that in nim proc's ?

proc fun(line:int = instantiationInfo(-1, true).line): auto=
    echo $("fun:line", line) # this is -1
    return
fun() # expecting:2
fun() # expecting:3

NOTE: this also doesn't work:

template currentSourceLine*: int = instantiationInfo(-1, true).line
proc fun(line:int = currentSourceLine):auto=
  echo $("fun:line", line) # this is 2
  return
fun() # expecting:5
fun() # expecting:6

NOTE: looking for a solution that works with proc (eg, no template bloat)

[cooldome]

check instantiationInfo(-2) and callsite

[timotheecour]

sorry could you please post a working test case?

proc fun1():auto=
    echo instantiationInfo(-2)
fun1() #(filename: "???", line: -1)

proc fun2():auto=
    let e = callsite() #Error: 'callsite' can only be used in compile-time context
    echo e
fun2()

[zah]

instantiationInfo is available only in macros and templates because different code needs to be expanded on each call-site. You can introduce a helper template that will forward the filename and line to a regular proc:

type
  FileInfo = tuple[filename: string, line: int]

proc fooImpl(callerInfo: FileInfo) =
  echo callerInfo.filename, ":", callerInfo.line

template foo(): untyped =
  fooImpl(instantiationInfo())

foo()
foo()

Since my particular file is called "test.nim", the output is the following:

test.nim:10
test.nim:11

[timotheecour]

thanks, so it confirms what I was afraid of which is that this isnt' possible without introducing template bloat.

Could nim implement this feature just like it's done in D? in D, optional arguments (eg __FILE__, __LINE__, __MODULE__, __FUNC__ etc) get instantiated at caller-site, not callee site, and it works with regular functions (no need for templates).

otherwise, what are (objectively) the downsides of using template instead of proc (so that instantiationInfo() works) ?

[Araq]

There is no template bloat.