src/librustc_mir/borrow_check/nll/region_infer/error_reporting/var_name.rs

   1 use crate::borrow_check::nll::region_infer::RegionInferenceContext;
   2 use crate::borrow_check::nll::ToRegionVid;
   3 use crate::borrow_check::Upvar;
   4 use rustc::mir::{Local, Body};
   5 use rustc::ty::{RegionVid, TyCtxt};
   6 use rustc_index::vec::Idx;
   7 use syntax::source_map::Span;
   8 use syntax_pos::symbol::Symbol;
   9
  10 impl<'tcx> RegionInferenceContext<'tcx> {
  11     crate fn get_var_name_and_span_for_region(
  12         &self,
  13         tcx: TyCtxt<'tcx>,
  14         body: &Body<'tcx>,
  15         upvars: &[Upvar],
  16         fr: RegionVid,
  17     ) -> Option<(Option<Symbol>, Span)> {
  18         debug!("get_var_name_and_span_for_region(fr={:?})", fr);
  19         assert!(self.universal_regions.is_universal_region(fr));
  20
  21         debug!("get_var_name_and_span_for_region: attempting upvar");
  22         self.get_upvar_index_for_region(tcx, fr)
  23             .map(|index| {
  24                 let (name, span) =
  25                     self.get_upvar_name_and_span_for_region(tcx, upvars, index);
  26                 (Some(name), span)
  27             })
  28             .or_else(|| {
  29                 debug!("get_var_name_and_span_for_region: attempting argument");
  30                 self.get_argument_index_for_region(tcx, fr)
  31                     .map(|index| self.get_argument_name_and_span_for_region(body, index))
  32             })
  33     }
  34
  35     /// Search the upvars (if any) to find one that references fr. Return its index.
  36     crate fn get_upvar_index_for_region(&self, tcx: TyCtxt<'tcx>, fr: RegionVid) -> Option<usize> {
  37         let upvar_index = self
  38             .universal_regions
  39             .defining_ty
  40             .upvar_tys(tcx)
  41             .position(|upvar_ty| {
  42                 debug!("get_upvar_index_for_region: upvar_ty={:?}", upvar_ty);
  43                 tcx.any_free_region_meets(&upvar_ty, |r| {
  44                     let r = r.to_region_vid();
  45                     debug!("get_upvar_index_for_region: r={:?} fr={:?}", r, fr);
  46                     r == fr
  47                 })
  48             })?;
  49
  50         let upvar_ty = self
  51             .universal_regions
  52             .defining_ty
  53             .upvar_tys(tcx)
  54             .nth(upvar_index);
  55
  56         debug!(
  57             "get_upvar_index_for_region: found {:?} in upvar {} which has type {:?}",
  58             fr, upvar_index, upvar_ty,
  59         );
  60
  61         Some(upvar_index)
  62     }
  63
  64     /// Given the index of an upvar, finds its name and the span from where it was
  65     /// declared.
  66     crate fn get_upvar_name_and_span_for_region(
  67         &self,
  68         tcx: TyCtxt<'tcx>,
  69         upvars: &[Upvar],
  70         upvar_index: usize,
  71     ) -> (Symbol, Span) {
  72         let upvar_hir_id = upvars[upvar_index].var_hir_id;
  73         debug!("get_upvar_name_and_span_for_region: upvar_hir_id={:?}", upvar_hir_id);
  74
  75         let upvar_name = tcx.hir().name(upvar_hir_id);
  76         let upvar_span = tcx.hir().span(upvar_hir_id);
  77         debug!("get_upvar_name_and_span_for_region: upvar_name={:?} upvar_span={:?}",
  78                upvar_name, upvar_span);
  79
  80         (upvar_name, upvar_span)
  81     }
  82
  83     /// Search the argument types for one that references fr (which should be a free region).
  84     /// Returns Some(_) with the index of the input if one is found.
  85     ///
  86     /// N.B., in the case of a closure, the index is indexing into the signature as seen by the
  87     /// user - in particular, index 0 is not the implicit self parameter.
  88     crate fn get_argument_index_for_region(
  89         &self,
  90         tcx: TyCtxt<'tcx>,
  91         fr: RegionVid,
  92     ) -> Option<usize> {
  93         let implicit_inputs = self.universal_regions.defining_ty.implicit_inputs();
  94         let argument_index = self
  95             .universal_regions
  96             .unnormalized_input_tys
  97             .iter()
  98             .skip(implicit_inputs)
  99             .position(|arg_ty| {
 100                 debug!(
 101                     "get_argument_index_for_region: arg_ty = {:?}",
 102                     arg_ty
 103                 );
 104                 tcx.any_free_region_meets(arg_ty, |r| r.to_region_vid() == fr)
 105             })?;
 106
 107         debug!(
 108             "get_argument_index_for_region: found {:?} in argument {} which has type {:?}",
 109             fr, argument_index, self.universal_regions.unnormalized_input_tys[argument_index],
 110         );
 111
 112         Some(argument_index)
 113     }
 114
 115     /// Given the index of an argument, finds its name (if any) and the span from where it was
 116     /// declared.
 117     crate fn get_argument_name_and_span_for_region(
 118         &self,
 119         body: &Body<'tcx>,
 120         argument_index: usize,
 121     ) -> (Option<Symbol>, Span) {
 122         let implicit_inputs = self.universal_regions.defining_ty.implicit_inputs();
 123         let argument_local = Local::new(implicit_inputs + argument_index + 1);
 124         debug!("get_argument_name_and_span_for_region: argument_local={:?}", argument_local);
 125
 126         let argument_name = body.local_decls[argument_local].name;
 127         let argument_span = body.local_decls[argument_local].source_info.span;
 128         debug!("get_argument_name_and_span_for_region: argument_name={:?} argument_span={:?}",
 129                argument_name, argument_span);
 130
 131         (argument_name, argument_span)
 132     }
 133 }