add a cursive-based screen to view tree results

[nikomatsakis]

Perhaps a good starting point for #2:

• Take the existing --tree-callees output and make it into a cursive-based tree view
  • with ability to open/close leaves on the tree
  • and ability to tune percentage, perhaps?
    • probably a command to "open everything up till a specific threshold or depth"
      • corresponds to --tree-min-percent and --tree-max-depth, respectively

[nikomatsakis]

Example of cursive tree view:

https://github.com/BonsaiDen/cursive_tree_view

[nikomatsakis]

Example of tree view as it is today (with some kinda' dirty data, hence lots of "unknown" frames):

lunch-box. perf focus --tree-callees --relative '{mir_validated}' --tree-min-percent 20
Matcher    : {mir_validated}
Matches    : 1096
Not Matches: 8993
Percentage : 100%

Tree
| matched `{mir_validated}` (100% total, 0% self)
: | [unknown] (84% total, 0% self)
: : | [unknown] (84% total, 0% self)
: : : | [unknown] (84% total, 0% self)
: : : : | [unknown] (84% total, 0% self)
: : : : : | [unknown] (84% total, 0% self)
: : : : : : | [unknown] (84% total, 0% self)
: : : : : : : | [unknown] (84% total, 0% self)
: : : : : : : : | [unknown] (84% total, 0% self)
: : : : : : : : : | rustc_mir::transform::mir_const (84% total, 0% self)
: : : : : : : : : : | rustc_mir::transform::mir_const::_$u7b$$u7b$closure$u7d$$u7d$::h87d8243f26931557 (68% total, 0% self)
: : : : : : : : : : : | <rustc_mir::borrow_check::nll::type_check::TypeckMir as rustc_mir::transform::MirPass>::run_pass (65% total, 0% self)
: : : : : : : : : : : : | rustc::ty::context::GlobalCtxt::enter_local (65% total, 0% self)
: : : : : : : : : : : : : | <std::thread::local::LocalKey<T>>::with (65% total, 0% self)
: : : : : : : : : : : : : : | rustc_mir::borrow_check::nll::type_check::type_check_internal (64% total, 0% self)
: : : : : : : : : : : : : : : | <rustc_mir::borrow_check::nll::type_check::TypeVerifier<'a, 'b, 'gcx, 'tcx> as rustc::mir::visit::Visitor<'tcx>>::visit_mir (32% total, 0% self)
: : : : : : : : : : : : : : : : | <rustc_mir::borrow_check::nll::type_check::TypeVerifier<'a, 'b, 'gcx, 'tcx> as rustc::mir::visit::Visitor<'tcx>>::visit_constant (28% total, 0% self)
: : : : : : : : : : : : : : : | rustc_mir::borrow_check::nll::type_check::TypeChecker::typeck_mir (31% total, 0% self)

[nikomatsakis]

Probably a starting point would be to work through the cursive tutorials:

https://github.com/gyscos/Cursive#tutorials