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 ty::{self, BoundRegion, Region, Ty, TyCtxt};
  13 use std::borrow::Cow;
  14 use std::fmt;
  15 use rustc_target::spec::abi;
  16 use syntax::ast;
  17 use errors::{Applicability, DiagnosticBuilder};
  18 use syntax_pos::Span;
  19
  20 use hir;
  21
  22 #[derive(Clone, Copy, Debug)]
  23 pub struct ExpectedFound<T> {
  24     pub expected: T,
  25     pub found: T,
  26 }
  27
  28 // Data structures used in type unification
  29 #[derive(Clone, Debug)]
  30 pub enum TypeError<'tcx> {
  31     Mismatch,
  32     UnsafetyMismatch(ExpectedFound<hir::Unsafety>),
  33     AbiMismatch(ExpectedFound<abi::Abi>),
  34     Mutability,
  35     TupleSize(ExpectedFound<usize>),
  36     FixedArraySize(ExpectedFound<u64>),
  37     ArgCount,
  38
  39     RegionsDoesNotOutlive(Region<'tcx>, Region<'tcx>),
  40     RegionsInsufficientlyPolymorphic(BoundRegion, Region<'tcx>),
  41     RegionsOverlyPolymorphic(BoundRegion, Region<'tcx>),
  42
  43     Sorts(ExpectedFound<Ty<'tcx>>),
  44     IntMismatch(ExpectedFound<ty::IntVarValue>),
  45     FloatMismatch(ExpectedFound<ast::FloatTy>),
  46     Traits(ExpectedFound<DefId>),
  47     VariadicMismatch(ExpectedFound<bool>),
  48
  49     /// Instantiating a type variable with the given type would have
  50     /// created a cycle (because it appears somewhere within that
  51     /// type).
  52     CyclicTy(Ty<'tcx>),
  53     ProjectionMismatched(ExpectedFound<DefId>),
  54     ProjectionBoundsLength(ExpectedFound<usize>),
  55     ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>),
  56 }
  57
  58 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  59 pub enum UnconstrainedNumeric {
  60     UnconstrainedFloat,
  61     UnconstrainedInt,
  62     Neither,
  63 }
  64
  65 /// Explains the source of a type err in a short, human readable way. This is meant to be placed
  66 /// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()`
  67 /// afterwards to present additional details, particularly when it comes to lifetime-related
  68 /// errors.
  69 impl<'tcx> fmt::Display for TypeError<'tcx> {
  70     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  71         use self::TypeError::*;
  72         fn report_maybe_different(f: &mut fmt::Formatter<'_>,
  73                                   expected: &str, found: &str) -> fmt::Result {
  74             // A naive approach to making sure that we're not reporting silly errors such as:
  75             // (expected closure, found closure).
  76             if expected == found {
  77                 write!(f, "expected {}, found a different {}", expected, found)
  78             } else {
  79                 write!(f, "expected {}, found {}", expected, found)
  80             }
  81         }
  82
  83         match *self {
  84             CyclicTy(_) => write!(f, "cyclic type of infinite size"),
  85             Mismatch => write!(f, "types differ"),
  86             UnsafetyMismatch(values) => {
  87                 write!(f, "expected {} fn, found {} fn",
  88                        values.expected,
  89                        values.found)
  90             }
  91             AbiMismatch(values) => {
  92                 write!(f, "expected {} fn, found {} fn",
  93                        values.expected,
  94                        values.found)
  95             }
  96             Mutability => write!(f, "types differ in mutability"),
  97             FixedArraySize(values) => {
  98                 write!(f, "expected an array with a fixed size of {} elements, \
  99                            found one with {} elements",
 100                        values.expected,
 101                        values.found)
 102             }
 103             TupleSize(values) => {
 104                 write!(f, "expected a tuple with {} elements, \
 105                            found one with {} elements",
 106                        values.expected,
 107                        values.found)
 108             }
 109             ArgCount => {
 110                 write!(f, "incorrect number of function parameters")
 111             }
 112             RegionsDoesNotOutlive(..) => {
 113                 write!(f, "lifetime mismatch")
 114             }
 115             RegionsInsufficientlyPolymorphic(br, _) => {
 116                 write!(f,
 117                        "expected bound lifetime parameter{}{}, found concrete lifetime",
 118                        if br.is_named() { " " } else { "" },
 119                        br)
 120             }
 121             RegionsOverlyPolymorphic(br, _) => {
 122                 write!(f,
 123                        "expected concrete lifetime, found bound lifetime parameter{}{}",
 124                        if br.is_named() { " " } else { "" },
 125                        br)
 126             }
 127             Sorts(values) => ty::tls::with(|tcx| {
 128                 report_maybe_different(f, &values.expected.sort_string(tcx),
 129                                        &values.found.sort_string(tcx))
 130             }),
 131             Traits(values) => ty::tls::with(|tcx| {
 132                 report_maybe_different(f,
 133                                        &format!("trait `{}`",
 134                                                 tcx.item_path_str(values.expected)),
 135                                        &format!("trait `{}`",
 136                                                 tcx.item_path_str(values.found)))
 137             }),
 138             IntMismatch(ref values) => {
 139                 write!(f, "expected `{:?}`, found `{:?}`",
 140                        values.expected,
 141                        values.found)
 142             }
 143             FloatMismatch(ref values) => {
 144                 write!(f, "expected `{:?}`, found `{:?}`",
 145                        values.expected,
 146                        values.found)
 147             }
 148             VariadicMismatch(ref values) => {
 149                 write!(f, "expected {} fn, found {} function",
 150                        if values.expected { "variadic" } else { "non-variadic" },
 151                        if values.found { "variadic" } else { "non-variadic" })
 152             }
 153             ProjectionMismatched(ref values) => ty::tls::with(|tcx| {
 154                 write!(f, "expected {}, found {}",
 155                        tcx.item_path_str(values.expected),
 156                        tcx.item_path_str(values.found))
 157             }),
 158             ProjectionBoundsLength(ref values) => {
 159                 write!(f, "expected {} associated type bindings, found {}",
 160                        values.expected,
 161                        values.found)
 162             },
 163             ExistentialMismatch(ref values) => {
 164                 report_maybe_different(f, &format!("trait `{}`", values.expected),
 165                                        &format!("trait `{}`", values.found))
 166             }
 167         }
 168     }
 169 }
 170
 171 impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
 172     pub fn sort_string(&self, tcx: TyCtxt<'a, 'gcx, 'lcx>) -> Cow<'static, str> {
 173         match self.sty {
 174             ty::Bool | ty::Char | ty::Int(_) |
 175             ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => self.to_string().into(),
 176             ty::Tuple(ref tys) if tys.is_empty() => self.to_string().into(),
 177
 178             ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.item_path_str(def.did)).into(),
 179             ty::Foreign(def_id) => format!("extern type `{}`", tcx.item_path_str(def_id)).into(),
 180             ty::Array(_, n) => {
 181                 match n.assert_usize(tcx) {
 182                     Some(n) => format!("array of {} elements", n).into(),
 183                     None => "array".into(),
 184                 }
 185             }
 186             ty::Slice(_) => "slice".into(),
 187             ty::RawPtr(_) => "*-ptr".into(),
 188             ty::Ref(region, ty, mutbl) => {
 189                 let tymut = ty::TypeAndMut { ty, mutbl };
 190                 let tymut_string = tymut.to_string();
 191                 if tymut_string == "_" ||         //unknown type name,
 192                    tymut_string.len() > 10 ||     //name longer than saying "reference",
 193                    region.to_string() != ""       //... or a complex type
 194                 {
 195                     format!("{}reference", match mutbl {
 196                         hir::Mutability::MutMutable => "mutable ",
 197                         _ => ""
 198                     }).into()
 199                 } else {
 200                     format!("&{}", tymut_string).into()
 201                 }
 202             }
 203             ty::FnDef(..) => "fn item".into(),
 204             ty::FnPtr(_) => "fn pointer".into(),
 205             ty::Dynamic(ref inner, ..) => {
 206                 format!("trait {}", tcx.item_path_str(inner.principal().def_id())).into()
 207             }
 208             ty::Closure(..) => "closure".into(),
 209             ty::Generator(..) => "generator".into(),
 210             ty::GeneratorWitness(..) => "generator witness".into(),
 211             ty::Tuple(..) => "tuple".into(),
 212             ty::Infer(ty::TyVar(_)) => "inferred type".into(),
 213             ty::Infer(ty::IntVar(_)) => "integral variable".into(),
 214             ty::Infer(ty::FloatVar(_)) => "floating-point variable".into(),
 215             ty::Infer(ty::BoundTy(_)) |
 216             ty::Infer(ty::FreshTy(_)) => "fresh type".into(),
 217             ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
 218             ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
 219             ty::Projection(_) => "associated type".into(),
 220             ty::UnnormalizedProjection(_) => "non-normalized associated type".into(),
 221             ty::Param(ref p) => {
 222                 if p.is_self() {
 223                     "Self".into()
 224                 } else {
 225                     "type parameter".into()
 226                 }
 227             }
 228             ty::Opaque(..) => "opaque type".into(),
 229             ty::Error => "type error".into(),
 230         }
 231     }
 232 }
 233
 234 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 235     pub fn note_and_explain_type_err(self,
 236                                      db: &mut DiagnosticBuilder<'_>,
 237                                      err: &TypeError<'tcx>,
 238                                      sp: Span) {
 239         use self::TypeError::*;
 240
 241         match err.clone() {
 242             Sorts(values) => {
 243                 let expected_str = values.expected.sort_string(self);
 244                 let found_str = values.found.sort_string(self);
 245                 if expected_str == found_str && expected_str == "closure" {
 246                     db.note("no two closures, even if identical, have the same type");
 247                     db.help("consider boxing your closure and/or using it as a trait object");
 248                 }
 249                 if let (ty::Infer(ty::IntVar(_)), ty::Float(_)) =
 250                        (&values.found.sty, &values.expected.sty) // Issue #53280
 251                 {
 252                     if let Ok(snippet) = self.sess.source_map().span_to_snippet(sp) {
 253                         if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') {
 254                             db.span_suggestion_with_applicability(
 255                                 sp,
 256                                 "use a float literal",
 257                                 format!("{}.0", snippet),
 258                                 Applicability::MachineApplicable
 259                             );
 260                         }
 261                     }
 262                 }
 263             },
 264             CyclicTy(ty) => {
 265                 // Watch out for various cases of cyclic types and try to explain.
 266                 if ty.is_closure() || ty.is_generator() {
 267                     db.note("closures cannot capture themselves or take themselves as argument;\n\
 268                              this error may be the result of a recent compiler bug-fix,\n\
 269                              see https://github.com/rust-lang/rust/issues/46062 for more details");
 270                 }
 271             }
 272             _ => {}
 273         }
 274     }
 275 }