compiler/rustc_typeck/src/check/gather_locals.rs

   1 use crate::check::{FnCtxt, LocalTy, UserType};
   2 use rustc_hir as hir;
   3 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
   4 use rustc_hir::PatKind;
   5 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
   6 use rustc_middle::ty::Ty;
   7 use rustc_span::Span;
   8 use rustc_trait_selection::traits;
   9 use std::mem;
  10
  11 pub(super) struct GatherLocalsVisitor<'a, 'tcx> {
  12     fcx: &'a FnCtxt<'a, 'tcx>,
  13     parent_id: hir::HirId,
  14     // parameters are special cases of patterns, but we want to handle them as
  15     // *distinct* cases. so track when we are hitting a pattern *within* an fn
  16     // parameter.
  17     outermost_fn_param_pat: bool,
  18 }
  19
  20 impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
  21     pub(super) fn new(fcx: &'a FnCtxt<'a, 'tcx>, parent_id: hir::HirId) -> Self {
  22         Self { fcx, parent_id, outermost_fn_param_pat: false }
  23     }
  24
  25     fn assign(&mut self, span: Span, nid: hir::HirId, ty_opt: Option<LocalTy<'tcx>>) -> Ty<'tcx> {
  26         match ty_opt {
  27             None => {
  28                 // Infer the variable's type.
  29                 let var_ty = self.fcx.next_ty_var(TypeVariableOrigin {
  30                     kind: TypeVariableOriginKind::TypeInference,
  31                     span,
  32                 });
  33                 self.fcx
  34                     .locals
  35                     .borrow_mut()
  36                     .insert(nid, LocalTy { decl_ty: var_ty, revealed_ty: var_ty });
  37                 var_ty
  38             }
  39             Some(typ) => {
  40                 // Take type that the user specified.
  41                 self.fcx.locals.borrow_mut().insert(nid, typ);
  42                 typ.revealed_ty
  43             }
  44         }
  45     }
  46 }
  47
  48 impl<'a, 'tcx> Visitor<'tcx> for GatherLocalsVisitor<'a, 'tcx> {
  49     type Map = intravisit::ErasedMap<'tcx>;
  50
  51     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
  52         NestedVisitorMap::None
  53     }
  54
  55     // Add explicitly-declared locals.
  56     fn visit_local(&mut self, local: &'tcx hir::Local<'tcx>) {
  57         let local_ty = match local.ty {
  58             Some(ref ty) => {
  59                 let o_ty = self.fcx.to_ty(&ty);
  60
  61                 let revealed_ty = if self.fcx.tcx.features().impl_trait_in_bindings {
  62                     self.fcx.instantiate_opaque_types_from_value(self.parent_id, o_ty, ty.span)
  63                 } else {
  64                     o_ty
  65                 };
  66
  67                 let c_ty =
  68                     self.fcx.inh.infcx.canonicalize_user_type_annotation(UserType::Ty(revealed_ty));
  69                 debug!(
  70                     "visit_local: ty.hir_id={:?} o_ty={:?} revealed_ty={:?} c_ty={:?}",
  71                     ty.hir_id, o_ty, revealed_ty, c_ty
  72                 );
  73                 self.fcx
  74                     .typeck_results
  75                     .borrow_mut()
  76                     .user_provided_types_mut()
  77                     .insert(ty.hir_id, c_ty);
  78
  79                 Some(LocalTy { decl_ty: o_ty, revealed_ty })
  80             }
  81             None => None,
  82         };
  83         self.assign(local.span, local.hir_id, local_ty);
  84
  85         debug!(
  86             "local variable {:?} is assigned type {}",
  87             local.pat,
  88             self.fcx.ty_to_string(&*self.fcx.locals.borrow().get(&local.hir_id).unwrap().decl_ty)
  89         );
  90         intravisit::walk_local(self, local);
  91     }
  92
  93     fn visit_param(&mut self, param: &'tcx hir::Param<'tcx>) {
  94         let old_outermost_fn_param_pat = mem::replace(&mut self.outermost_fn_param_pat, true);
  95         intravisit::walk_param(self, param);
  96         self.outermost_fn_param_pat = old_outermost_fn_param_pat;
  97     }
  98
  99     // Add pattern bindings.
 100     fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
 101         if let PatKind::Binding(_, _, ident, _) = p.kind {
 102             let var_ty = self.assign(p.span, p.hir_id, None);
 103
 104             if self.outermost_fn_param_pat {
 105                 if !self.fcx.tcx.features().unsized_fn_params {
 106                     self.fcx.require_type_is_sized(
 107                         var_ty,
 108                         p.span,
 109                         traits::SizedArgumentType(Some(p.span)),
 110                     );
 111                 }
 112             } else {
 113                 if !self.fcx.tcx.features().unsized_locals {
 114                     self.fcx.require_type_is_sized(var_ty, p.span, traits::VariableType(p.hir_id));
 115                 }
 116             }
 117
 118             debug!(
 119                 "pattern binding {} is assigned to {} with type {:?}",
 120                 ident,
 121                 self.fcx.ty_to_string(&*self.fcx.locals.borrow().get(&p.hir_id).unwrap().decl_ty),
 122                 var_ty
 123             );
 124         }
 125         let old_outermost_fn_param_pat = mem::replace(&mut self.outermost_fn_param_pat, false);
 126         intravisit::walk_pat(self, p);
 127         self.outermost_fn_param_pat = old_outermost_fn_param_pat;
 128     }
 129
 130     // Don't descend into the bodies of nested closures.
 131     fn visit_fn(
 132         &mut self,
 133         _: intravisit::FnKind<'tcx>,
 134         _: &'tcx hir::FnDecl<'tcx>,
 135         _: hir::BodyId,
 136         _: Span,
 137         _: hir::HirId,
 138     ) {
 139     }
 140 }