src/librustc/ty/error.rs

   1 // Copyright 2012-2015 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 use hir::def_id::DefId;
  12 use infer::type_variable;
  13 use ty::{self, BoundRegion, DefIdTree, Region, Ty, TyCtxt};
  14
  15 use std::fmt;
  16 use syntax::abi;
  17 use syntax::ast;
  18 use errors::DiagnosticBuilder;
  19 use syntax_pos::Span;
  20
  21 use hir;
  22
  23 #[derive(Clone, Copy, Debug)]
  24 pub struct ExpectedFound<T> {
  25     pub expected: T,
  26     pub found: T,
  27 }
  28
  29 // Data structures used in type unification
  30 #[derive(Clone, Debug)]
  31 pub enum TypeError<'tcx> {
  32     Mismatch,
  33     UnsafetyMismatch(ExpectedFound<hir::Unsafety>),
  34     AbiMismatch(ExpectedFound<abi::Abi>),
  35     Mutability,
  36     TupleSize(ExpectedFound<usize>),
  37     FixedArraySize(ExpectedFound<usize>),
  38     ArgCount,
  39     RegionsDoesNotOutlive(Region<'tcx>, Region<'tcx>),
  40     RegionsNotSame(Region<'tcx>, Region<'tcx>),
  41     RegionsNoOverlap(Region<'tcx>, Region<'tcx>),
  42     RegionsInsufficientlyPolymorphic(BoundRegion, Region<'tcx>),
  43     RegionsOverlyPolymorphic(BoundRegion, Region<'tcx>),
  44     Sorts(ExpectedFound<Ty<'tcx>>),
  45     IntMismatch(ExpectedFound<ty::IntVarValue>),
  46     FloatMismatch(ExpectedFound<ast::FloatTy>),
  47     Traits(ExpectedFound<DefId>),
  48     VariadicMismatch(ExpectedFound<bool>),
  49     CyclicTy,
  50     ProjectionMismatched(ExpectedFound<DefId>),
  51     ProjectionBoundsLength(ExpectedFound<usize>),
  52     TyParamDefaultMismatch(ExpectedFound<type_variable::Default<'tcx>>),
  53     ExistentialMismatch(ExpectedFound<&'tcx ty::Slice<ty::ExistentialPredicate<'tcx>>>),
  54 }
  55
  56 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  57 pub enum UnconstrainedNumeric {
  58     UnconstrainedFloat,
  59     UnconstrainedInt,
  60     Neither,
  61 }
  62
  63 /// Explains the source of a type err in a short, human readable way. This is meant to be placed
  64 /// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()`
  65 /// afterwards to present additional details, particularly when it comes to lifetime-related
  66 /// errors.
  67 impl<'tcx> fmt::Display for TypeError<'tcx> {
  68     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  69         use self::TypeError::*;
  70         fn report_maybe_different(f: &mut fmt::Formatter,
  71                                   expected: String, found: String) -> fmt::Result {
  72             // A naive approach to making sure that we're not reporting silly errors such as:
  73             // (expected closure, found closure).
  74             if expected == found {
  75                 write!(f, "expected {}, found a different {}", expected, found)
  76             } else {
  77                 write!(f, "expected {}, found {}", expected, found)
  78             }
  79         }
  80
  81         match *self {
  82             CyclicTy => write!(f, "cyclic type of infinite size"),
  83             Mismatch => write!(f, "types differ"),
  84             UnsafetyMismatch(values) => {
  85                 write!(f, "expected {} fn, found {} fn",
  86                        values.expected,
  87                        values.found)
  88             }
  89             AbiMismatch(values) => {
  90                 write!(f, "expected {} fn, found {} fn",
  91                        values.expected,
  92                        values.found)
  93             }
  94             Mutability => write!(f, "types differ in mutability"),
  95             FixedArraySize(values) => {
  96                 write!(f, "expected an array with a fixed size of {} elements, \
  97                            found one with {} elements",
  98                        values.expected,
  99                        values.found)
 100             }
 101             TupleSize(values) => {
 102                 write!(f, "expected a tuple with {} elements, \
 103                            found one with {} elements",
 104                        values.expected,
 105                        values.found)
 106             }
 107             ArgCount => {
 108                 write!(f, "incorrect number of function parameters")
 109             }
 110             RegionsDoesNotOutlive(..) => {
 111                 write!(f, "lifetime mismatch")
 112             }
 113             RegionsNotSame(..) => {
 114                 write!(f, "lifetimes are not the same")
 115             }
 116             RegionsNoOverlap(..) => {
 117                 write!(f, "lifetimes do not intersect")
 118             }
 119             RegionsInsufficientlyPolymorphic(br, _) => {
 120                 write!(f,
 121                        "expected bound lifetime parameter{}{}, found concrete lifetime",
 122                        if br.is_named() { " " } else { "" },
 123                        br)
 124             }
 125             RegionsOverlyPolymorphic(br, _) => {
 126                 write!(f,
 127                        "expected concrete lifetime, found bound lifetime parameter{}{}",
 128                        if br.is_named() { " " } else { "" },
 129                        br)
 130             }
 131             Sorts(values) => ty::tls::with(|tcx| {
 132                 report_maybe_different(f, values.expected.sort_string(tcx),
 133                                        values.found.sort_string(tcx))
 134             }),
 135             Traits(values) => ty::tls::with(|tcx| {
 136                 report_maybe_different(f,
 137                                        format!("trait `{}`",
 138                                                tcx.item_path_str(values.expected)),
 139                                        format!("trait `{}`",
 140                                                tcx.item_path_str(values.found)))
 141             }),
 142             IntMismatch(ref values) => {
 143                 write!(f, "expected `{:?}`, found `{:?}`",
 144                        values.expected,
 145                        values.found)
 146             }
 147             FloatMismatch(ref values) => {
 148                 write!(f, "expected `{:?}`, found `{:?}`",
 149                        values.expected,
 150                        values.found)
 151             }
 152             VariadicMismatch(ref values) => {
 153                 write!(f, "expected {} fn, found {} function",
 154                        if values.expected { "variadic" } else { "non-variadic" },
 155                        if values.found { "variadic" } else { "non-variadic" })
 156             }
 157             ProjectionMismatched(ref values) => ty::tls::with(|tcx| {
 158                 write!(f, "expected {}, found {}",
 159                        tcx.item_path_str(values.expected),
 160                        tcx.item_path_str(values.found))
 161             }),
 162             ProjectionBoundsLength(ref values) => {
 163                 write!(f, "expected {} associated type bindings, found {}",
 164                        values.expected,
 165                        values.found)
 166             },
 167             TyParamDefaultMismatch(ref values) => {
 168                 write!(f, "conflicting type parameter defaults `{}` and `{}`",
 169                        values.expected.ty,
 170                        values.found.ty)
 171             }
 172             ExistentialMismatch(ref values) => {
 173                 report_maybe_different(f, format!("trait `{}`", values.expected),
 174                                        format!("trait `{}`", values.found))
 175             }
 176         }
 177     }
 178 }
 179
 180 impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
 181     pub fn sort_string(&self, tcx: TyCtxt<'a, 'gcx, 'lcx>) -> String {
 182         match self.sty {
 183             ty::TyBool | ty::TyChar | ty::TyInt(_) |
 184             ty::TyUint(_) | ty::TyFloat(_) | ty::TyStr | ty::TyNever => self.to_string(),
 185             ty::TyTuple(ref tys, _) if tys.is_empty() => self.to_string(),
 186
 187             ty::TyAdt(def, _) => format!("{} `{}`", def.descr(), tcx.item_path_str(def.did)),
 188             ty::TyArray(_, n) => format!("array of {} elements", n),
 189             ty::TySlice(_) => "slice".to_string(),
 190             ty::TyRawPtr(_) => "*-ptr".to_string(),
 191             ty::TyRef(region, tymut) => {
 192                 let tymut_string = tymut.to_string();
 193                 if tymut_string == "_" ||         //unknown type name,
 194                    tymut_string.len() > 10 ||     //name longer than saying "reference",
 195                    region.to_string() != ""       //... or a complex type
 196                 {
 197                     match tymut {
 198                         ty::TypeAndMut{mutbl, ..} => {
 199                             format!("{}reference", match mutbl {
 200                                 hir::Mutability::MutMutable => "mutable ",
 201                                 _ => ""
 202                             })
 203                         }
 204                     }
 205                 } else {
 206                     format!("&{}", tymut_string)
 207                 }
 208             }
 209             ty::TyFnDef(..) => format!("fn item"),
 210             ty::TyFnPtr(_) => "fn pointer".to_string(),
 211             ty::TyDynamic(ref inner, ..) => {
 212                 inner.principal().map_or_else(|| "trait".to_string(),
 213                     |p| format!("trait {}", tcx.item_path_str(p.def_id())))
 214             }
 215             ty::TyClosure(..) => "closure".to_string(),
 216             ty::TyTuple(..) => "tuple".to_string(),
 217             ty::TyInfer(ty::TyVar(_)) => "inferred type".to_string(),
 218             ty::TyInfer(ty::IntVar(_)) => "integral variable".to_string(),
 219             ty::TyInfer(ty::FloatVar(_)) => "floating-point variable".to_string(),
 220             ty::TyInfer(ty::FreshTy(_)) => "skolemized type".to_string(),
 221             ty::TyInfer(ty::FreshIntTy(_)) => "skolemized integral type".to_string(),
 222             ty::TyInfer(ty::FreshFloatTy(_)) => "skolemized floating-point type".to_string(),
 223             ty::TyProjection(_) => "associated type".to_string(),
 224             ty::TyParam(ref p) => {
 225                 if p.is_self() {
 226                     "Self".to_string()
 227                 } else {
 228                     "type parameter".to_string()
 229                 }
 230             }
 231             ty::TyAnon(..) => "anonymized type".to_string(),
 232             ty::TyError => "type error".to_string(),
 233         }
 234     }
 235 }
 236
 237 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 238     pub fn note_and_explain_type_err(self,
 239                                      db: &mut DiagnosticBuilder,
 240                                      err: &TypeError<'tcx>,
 241                                      sp: Span) {
 242         use self::TypeError::*;
 243
 244         match err.clone() {
 245             RegionsDoesNotOutlive(subregion, superregion) => {
 246                 self.note_and_explain_region(db, "", subregion, "...");
 247                 self.note_and_explain_region(db, "...does not necessarily outlive ",
 248                                            superregion, "");
 249             }
 250             RegionsNotSame(region1, region2) => {
 251                 self.note_and_explain_region(db, "", region1, "...");
 252                 self.note_and_explain_region(db, "...is not the same lifetime as ",
 253                                            region2, "");
 254             }
 255             RegionsNoOverlap(region1, region2) => {
 256                 self.note_and_explain_region(db, "", region1, "...");
 257                 self.note_and_explain_region(db, "...does not overlap ",
 258                                            region2, "");
 259             }
 260             RegionsInsufficientlyPolymorphic(_, conc_region) => {
 261                 self.note_and_explain_region(db, "concrete lifetime that was found is ",
 262                                            conc_region, "");
 263             }
 264             RegionsOverlyPolymorphic(_, &ty::ReVar(_)) => {
 265                 // don't bother to print out the message below for
 266                 // inference variables, it's not very illuminating.
 267             }
 268             RegionsOverlyPolymorphic(_, conc_region) => {
 269                 self.note_and_explain_region(db, "expected concrete lifetime is ",
 270                                            conc_region, "");
 271             }
 272             Sorts(values) => {
 273                 let expected_str = values.expected.sort_string(self);
 274                 let found_str = values.found.sort_string(self);
 275                 if expected_str == found_str && expected_str == "closure" {
 276                     db.span_note(sp,
 277                         "no two closures, even if identical, have the same type");
 278                     db.span_help(sp,
 279                         "consider boxing your closure and/or using it as a trait object");
 280                 }
 281             },
 282             TyParamDefaultMismatch(values) => {
 283                 let expected = values.expected;
 284                 let found = values.found;
 285                 db.span_note(sp, &format!("conflicting type parameter defaults `{}` and `{}`",
 286                                           expected.ty,
 287                                           found.ty));
 288
 289                 match self.hir.span_if_local(expected.def_id) {
 290                     Some(span) => {
 291                         db.span_note(span, "a default was defined here...");
 292                     }
 293                     None => {
 294                         let item_def_id = self.parent(expected.def_id).unwrap();
 295                         db.note(&format!("a default is defined on `{}`",
 296                                          self.item_path_str(item_def_id)));
 297                     }
 298                 }
 299
 300                 db.span_note(
 301                     expected.origin_span,
 302                     "...that was applied to an unconstrained type variable here");
 303
 304                 match self.hir.span_if_local(found.def_id) {
 305                     Some(span) => {
 306                         db.span_note(span, "a second default was defined here...");
 307                     }
 308                     None => {
 309                         let item_def_id = self.parent(found.def_id).unwrap();
 310                         db.note(&format!("a second default is defined on `{}`",
 311                                          self.item_path_str(item_def_id)));
 312                     }
 313                 }
 314
 315                 db.span_note(found.origin_span,
 316                              "...that also applies to the same type variable here");
 317             }
 318             _ => {}
 319         }
 320     }
 321 }