This is a tracking issue for the RFC "Implicit caller location" (rust-lang/rfcs#2091).

Steps:

• Implement the RFC (cc @rust-lang/compiler -- can anyone write up mentoring instructions?)
• Adjust documentation (see instructions on forge)
• Stabilization PR (see instructions on forge)

Unresolved questions:

• If we want to support adding #[track_caller] to trait methods, the redirection
  pass/query/whatever should be placed after monomorphization, not before. Currently the RFC
  simply prohibits applying #[track_caller] to trait methods as a future-proofing measure.

• Diverging functions should be supported.

• The closure foo::{{closure}} should inherit most attributes applied to the function foo, in
  particular #[inline], #[cold], #[naked] and also the ABI. Currently a procedural macro
  won't see any of these, nor would there be anyway to apply these attributes to a closure.
  Therefore, #[rustc_implicit_caller_location] currently will reject #[naked] and ABI, and
  leaving #[inline] and #[cold] mean no-op. There is no semantic reason why these cannot be
  used though.