src/librustc_mir/borrow_check/diagnostics/var_name.rs

   1 use crate::borrow_check::{nll::ToRegionVid, region_infer::RegionInferenceContext};
   2 use crate::borrow_check::Upvar;
   3 use rustc::mir::{Local, Body};
   4 use rustc::ty::{RegionVid, TyCtxt};
   5 use rustc_index::vec::{Idx, IndexVec};
   6 use syntax::source_map::Span;
   7 use syntax_pos::symbol::Symbol;
   8
   9 impl<'tcx> RegionInferenceContext<'tcx> {
  10     crate fn get_var_name_and_span_for_region(
  11         &self,
  12         tcx: TyCtxt<'tcx>,
  13         body: &Body<'tcx>,
  14         local_names: &IndexVec<Local, Option<Symbol>>,
  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).map(|index| {
  31                     self.get_argument_name_and_span_for_region(body, local_names, index)
  32                 })
  33             })
  34     }
  35
  36     /// Search the upvars (if any) to find one that references fr. Return its index.
  37     crate fn get_upvar_index_for_region(&self, tcx: TyCtxt<'tcx>, fr: RegionVid) -> Option<usize> {
  38         let upvar_index = self
  39             .universal_regions
  40             .defining_ty
  41             .upvar_tys(tcx)
  42             .position(|upvar_ty| {
  43                 debug!("get_upvar_index_for_region: upvar_ty={:?}", upvar_ty);
  44                 tcx.any_free_region_meets(&upvar_ty, |r| {
  45                     let r = r.to_region_vid();
  46                     debug!("get_upvar_index_for_region: r={:?} fr={:?}", r, fr);
  47                     r == fr
  48                 })
  49             })?;
  50
  51         let upvar_ty = self
  52             .universal_regions
  53             .defining_ty
  54             .upvar_tys(tcx)
  55             .nth(upvar_index);
  56
  57         debug!(
  58             "get_upvar_index_for_region: found {:?} in upvar {} which has type {:?}",
  59             fr, upvar_index, upvar_ty,
  60         );
  61
  62         Some(upvar_index)
  63     }
  64
  65     /// Given the index of an upvar, finds its name and the span from where it was
  66     /// declared.
  67     crate fn get_upvar_name_and_span_for_region(
  68         &self,
  69         tcx: TyCtxt<'tcx>,
  70         upvars: &[Upvar],
  71         upvar_index: usize,
  72     ) -> (Symbol, Span) {
  73         let upvar_hir_id = upvars[upvar_index].var_hir_id;
  74         debug!("get_upvar_name_and_span_for_region: upvar_hir_id={:?}", upvar_hir_id);
  75
  76         let upvar_name = tcx.hir().name(upvar_hir_id);
  77         let upvar_span = tcx.hir().span(upvar_hir_id);
  78         debug!("get_upvar_name_and_span_for_region: upvar_name={:?} upvar_span={:?}",
  79                upvar_name, upvar_span);
  80
  81         (upvar_name, upvar_span)
  82     }
  83
  84     /// Search the argument types for one that references fr (which should be a free region).
  85     /// Returns Some(_) with the index of the input if one is found.
  86     ///
  87     /// N.B., in the case of a closure, the index is indexing into the signature as seen by the
  88     /// user - in particular, index 0 is not the implicit self parameter.
  89     crate fn get_argument_index_for_region(
  90         &self,
  91         tcx: TyCtxt<'tcx>,
  92         fr: RegionVid,
  93     ) -> Option<usize> {
  94         let implicit_inputs = self.universal_regions.defining_ty.implicit_inputs();
  95         let argument_index = self
  96             .universal_regions
  97             .unnormalized_input_tys
  98             .iter()
  99             .skip(implicit_inputs)
 100             .position(|arg_ty| {
 101                 debug!(
 102                     "get_argument_index_for_region: arg_ty = {:?}",
 103                     arg_ty
 104                 );
 105                 tcx.any_free_region_meets(arg_ty, |r| r.to_region_vid() == fr)
 106             })?;
 107
 108         debug!(
 109             "get_argument_index_for_region: found {:?} in argument {} which has type {:?}",
 110             fr, argument_index, self.universal_regions.unnormalized_input_tys[argument_index],
 111         );
 112
 113         Some(argument_index)
 114     }
 115
 116     /// Given the index of an argument, finds its name (if any) and the span from where it was
 117     /// declared.
 118     crate fn get_argument_name_and_span_for_region(
 119         &self,
 120         body: &Body<'tcx>,
 121         local_names: &IndexVec<Local, Option<Symbol>>,
 122         argument_index: usize,
 123     ) -> (Option<Symbol>, Span) {
 124         let implicit_inputs = self.universal_regions.defining_ty.implicit_inputs();
 125         let argument_local = Local::new(implicit_inputs + argument_index + 1);
 126         debug!("get_argument_name_and_span_for_region: argument_local={:?}", argument_local);
 127
 128         let argument_name = local_names[argument_local];
 129         let argument_span = body.local_decls[argument_local].source_info.span;
 130         debug!("get_argument_name_and_span_for_region: argument_name={:?} argument_span={:?}",
 131                argument_name, argument_span);
 132
 133         (argument_name, argument_span)
 134     }
 135 }