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| 1 | +// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT |
| 2 | +// file at the top-level directory of this distribution and at |
| 3 | +// http://rust-lang.org/COPYRIGHT. |
| 4 | +// |
| 5 | +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| 6 | +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| 7 | +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| 8 | +// option. This file may not be copied, modified, or distributed |
| 9 | +// except according to those terms. |
| 10 | + |
| 11 | +//! Error Reporting for Anonymous Region Lifetime Errors |
| 12 | +//! where both the regions are anonymous. |
| 13 | +use hir; |
| 14 | +use infer::InferCtxt; |
| 15 | +use ty::{self, Region}; |
| 16 | +use infer::region_inference::RegionResolutionError::*; |
| 17 | +use infer::region_inference::RegionResolutionError; |
| 18 | +use hir::map as hir_map; |
| 19 | +use middle::resolve_lifetime as rl; |
| 20 | +use hir::intravisit::{self, Visitor, NestedVisitorMap}; |
| 21 | + |
| 22 | +impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> { |
| 23 | + // This method prints the error message for lifetime errors when both the concerned regions |
| 24 | + // are anonymous. |
| 25 | + // Consider a case where we have |
| 26 | + // fn foo(x: &mut Vec<&u8>, y: &u8) |
| 27 | + // { x.push(y); }. |
| 28 | + // The example gives |
| 29 | + // fn foo(x: &mut Vec<&u8>, y: &u8) { |
| 30 | + // --- --- these references must have the same lifetime |
| 31 | + // x.push(y); |
| 32 | + // ^ data from `y` flows into `x` here |
| 33 | + // It will later be extended to trait objects and structs. |
| 34 | + pub fn try_report_anon_anon_conflict(&self, error: &RegionResolutionError<'tcx>) -> bool { |
| 35 | + |
| 36 | + let (span, sub, sup) = match *error { |
| 37 | + ConcreteFailure(ref origin, sub, sup) => (origin.span(), sub, sup), |
| 38 | + _ => return false, // inapplicable |
| 39 | + }; |
| 40 | + |
| 41 | + // Determine whether the sub and sup consist of both anonymous (elided) regions. |
| 42 | + let (ty1, ty2) = if self.is_suitable_anonymous_region(sup).is_some() && |
| 43 | + self.is_suitable_anonymous_region(sub).is_some() { |
| 44 | + if let (Some(anon_reg1), Some(anon_reg2)) = |
| 45 | + (self.is_suitable_anonymous_region(sup), self.is_suitable_anonymous_region(sub)) { |
| 46 | + let ((_, br1), (_, br2)) = (anon_reg1, anon_reg2); |
| 47 | + if self.find_anon_type(sup, &br1).is_some() && |
| 48 | + self.find_anon_type(sub, &br2).is_some() { |
| 49 | + (self.find_anon_type(sup, &br1).unwrap(), |
| 50 | + self.find_anon_type(sub, &br2).unwrap()) |
| 51 | + } else { |
| 52 | + return false; |
| 53 | + } |
| 54 | + } else { |
| 55 | + return false; |
| 56 | + } |
| 57 | + } else { |
| 58 | + return false; // inapplicable |
| 59 | + }; |
| 60 | + |
| 61 | + if let (Some(sup_arg), Some(sub_arg)) = |
| 62 | + (self.find_arg_with_anonymous_region(sup, sup), |
| 63 | + self.find_arg_with_anonymous_region(sub, sub)) { |
| 64 | + let ((anon_arg1, _, _, _), (anon_arg2, _, _, _)) = (sup_arg, sub_arg); |
| 65 | + |
| 66 | + let span_label_var1 = if let Some(simple_name) = anon_arg1.pat.simple_name() { |
| 67 | + format!(" from `{}` ", simple_name) |
| 68 | + } else { |
| 69 | + format!(" ") |
| 70 | + }; |
| 71 | + |
| 72 | + let span_label_var2 = if let Some(simple_name) = anon_arg2.pat.simple_name() { |
| 73 | + format!(" into `{}` ", simple_name) |
| 74 | + } else { |
| 75 | + format!(" ") |
| 76 | + }; |
| 77 | + |
| 78 | + struct_span_err!(self.tcx.sess, span, E0623, "lifetime mismatch") |
| 79 | + .span_label(ty1.span, |
| 80 | + format!("these references must have the same lifetime")) |
| 81 | + .span_label(ty2.span, format!("")) |
| 82 | + .span_label(span, |
| 83 | + format!("data{}flows{}here", span_label_var1, span_label_var2)) |
| 84 | + .emit(); |
| 85 | + } else { |
| 86 | + return false; |
| 87 | + } |
| 88 | + |
| 89 | + return true; |
| 90 | + } |
| 91 | + |
| 92 | + /// This function calls the `visit_ty` method for the parameters |
| 93 | + /// corresponding to the anonymous regions. The `nested_visitor.found_type` |
| 94 | + /// contains the anonymous type. |
| 95 | + /// |
| 96 | + /// # Arguments |
| 97 | + /// |
| 98 | + /// region - the anonymous region corresponding to the anon_anon conflict |
| 99 | + /// br - the bound region corresponding to the above region which is of type `BrAnon(_)` |
| 100 | + /// |
| 101 | + /// # Example |
| 102 | + /// ``` |
| 103 | + /// fn foo(x: &mut Vec<&u8>, y: &u8) |
| 104 | + /// { x.push(y); } |
| 105 | + /// ``` |
| 106 | + /// The function returns the nested type corresponding to the anonymous region |
| 107 | + /// for e.g. `&u8` and Vec<`&u8`. |
| 108 | + fn find_anon_type(&self, region: Region<'tcx>, br: &ty::BoundRegion) -> Option<&hir::Ty> { |
| 109 | + if let Some(anon_reg) = self.is_suitable_anonymous_region(region) { |
| 110 | + let (def_id, _) = anon_reg; |
| 111 | + if let Some(node_id) = self.tcx.hir.as_local_node_id(def_id) { |
| 112 | + let ret_ty = self.tcx.type_of(def_id); |
| 113 | + if let ty::TyFnDef(_, _) = ret_ty.sty { |
| 114 | + if let hir_map::NodeItem(it) = self.tcx.hir.get(node_id) { |
| 115 | + if let hir::ItemFn(ref fndecl, _, _, _, _, _) = it.node { |
| 116 | + return fndecl |
| 117 | + .inputs |
| 118 | + .iter() |
| 119 | + .filter_map(|arg| { |
| 120 | + let mut nested_visitor = FindNestedTypeVisitor { |
| 121 | + infcx: &self, |
| 122 | + hir_map: &self.tcx.hir, |
| 123 | + bound_region: *br, |
| 124 | + found_type: None, |
| 125 | + }; |
| 126 | + nested_visitor.visit_ty(&**arg); |
| 127 | + if nested_visitor.found_type.is_some() { |
| 128 | + nested_visitor.found_type |
| 129 | + } else { |
| 130 | + None |
| 131 | + } |
| 132 | + }) |
| 133 | + .next(); |
| 134 | + } |
| 135 | + } |
| 136 | + } |
| 137 | + } |
| 138 | + } |
| 139 | + None |
| 140 | + } |
| 141 | +} |
| 142 | + |
| 143 | +// The FindNestedTypeVisitor captures the corresponding `hir::Ty` of the |
| 144 | +// anonymous region. The example above would lead to a conflict between |
| 145 | +// the two anonymous lifetimes for &u8 in x and y respectively. This visitor |
| 146 | +// would be invoked twice, once for each lifetime, and would |
| 147 | +// walk the types like &mut Vec<&u8> and &u8 looking for the HIR |
| 148 | +// where that lifetime appears. This allows us to highlight the |
| 149 | +// specific part of the type in the error message. |
| 150 | +struct FindNestedTypeVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> { |
| 151 | + infcx: &'a InferCtxt<'a, 'gcx, 'tcx>, |
| 152 | + hir_map: &'a hir::map::Map<'gcx>, |
| 153 | + // The bound_region corresponding to the Refree(freeregion) |
| 154 | + // associated with the anonymous region we are looking for. |
| 155 | + bound_region: ty::BoundRegion, |
| 156 | + // The type where the anonymous lifetime appears |
| 157 | + // for e.g. Vec<`&u8`> and <`&u8`> |
| 158 | + found_type: Option<&'gcx hir::Ty>, |
| 159 | +} |
| 160 | + |
| 161 | +impl<'a, 'gcx, 'tcx> Visitor<'gcx> for FindNestedTypeVisitor<'a, 'gcx, 'tcx> { |
| 162 | + fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'gcx> { |
| 163 | + NestedVisitorMap::OnlyBodies(&self.hir_map) |
| 164 | + } |
| 165 | + |
| 166 | + fn visit_ty(&mut self, arg: &'gcx hir::Ty) { |
| 167 | + // Find the index of the anonymous region that was part of the |
| 168 | + // error. We will then search the function parameters for a bound |
| 169 | + // region at the right depth with the same index. |
| 170 | + let br_index = match self.bound_region { |
| 171 | + ty::BrAnon(index) => index, |
| 172 | + _ => return, |
| 173 | + }; |
| 174 | + |
| 175 | + match arg.node { |
| 176 | + hir::TyRptr(ref lifetime, _) => { |
| 177 | + match self.infcx.tcx.named_region_map.defs.get(&lifetime.id) { |
| 178 | + // the lifetime of the TyRptr |
| 179 | + Some(&rl::Region::LateBoundAnon(debuijn_index, anon_index)) => { |
| 180 | + if debuijn_index.depth == 1 && anon_index == br_index { |
| 181 | + self.found_type = Some(arg); |
| 182 | + return; // we can stop visiting now |
| 183 | + } |
| 184 | + } |
| 185 | + Some(&rl::Region::Static) | |
| 186 | + Some(&rl::Region::EarlyBound(_, _)) | |
| 187 | + Some(&rl::Region::LateBound(_, _)) | |
| 188 | + Some(&rl::Region::Free(_, _)) | |
| 189 | + None => { |
| 190 | + debug!("no arg found"); |
| 191 | + } |
| 192 | + } |
| 193 | + } |
| 194 | + _ => {} |
| 195 | + } |
| 196 | + // walk the embedded contents: e.g., if we are visiting `Vec<&Foo>`, |
| 197 | + // go on to visit `&Foo` |
| 198 | + intravisit::walk_ty(self, arg); |
| 199 | + } |
| 200 | +} |
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