swift234

Use the pretty-printer to render imported declarations for diagnostics.

Note: this is an experiment.

When we're asked to render a diagnostic for a declaration that does
not have source information, pretty-print the declaration into a
buffer and synthesize a location pointing into that buffer. This gives
the illusion of Clang-style diagnostics where we have all of the
source headers, but without actually requiring that source location
information. It may prove useful or infuriating, but at the very least
it might help us understand how the importer works. Example:

cfuncs_diags.swift:14:7: error: no candidates found for call
  exit(5)
  ~~~~^~~
cfuncs_diags.swift:6:6: note: found this candidate
func exit(_ : Float) {}
     ^
cfuncs.exit:1:6: note: found this candidate
func exit(_ : CInt)
     ^



Swift SVN r3434