src/librustc/ty/error.rs

   1 use crate::hir::def_id::DefId;
   2 use crate::ty::{self, BoundRegion, Region, Ty, TyCtxt};
   3 use std::borrow::Cow;
   4 use std::fmt;
   5 use rustc_target::spec::abi;
   6 use syntax::ast;
   7 use errors::{Applicability, DiagnosticBuilder};
   8 use syntax_pos::Span;
   9
  10 use crate::hir;
  11
  12 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
  13 pub struct ExpectedFound<T> {
  14     pub expected: T,
  15     pub found: T,
  16 }
  17
  18 // Data structures used in type unification
  19 #[derive(Clone, Debug)]
  20 pub enum TypeError<'tcx> {
  21     Mismatch,
  22     UnsafetyMismatch(ExpectedFound<hir::Unsafety>),
  23     AbiMismatch(ExpectedFound<abi::Abi>),
  24     Mutability,
  25     TupleSize(ExpectedFound<usize>),
  26     FixedArraySize(ExpectedFound<u64>),
  27     ArgCount,
  28
  29     RegionsDoesNotOutlive(Region<'tcx>, Region<'tcx>),
  30     RegionsInsufficientlyPolymorphic(BoundRegion, Region<'tcx>),
  31     RegionsOverlyPolymorphic(BoundRegion, Region<'tcx>),
  32     RegionsPlaceholderMismatch,
  33
  34     Sorts(ExpectedFound<Ty<'tcx>>),
  35     IntMismatch(ExpectedFound<ty::IntVarValue>),
  36     FloatMismatch(ExpectedFound<ast::FloatTy>),
  37     Traits(ExpectedFound<DefId>),
  38     VariadicMismatch(ExpectedFound<bool>),
  39
  40     /// Instantiating a type variable with the given type would have
  41     /// created a cycle (because it appears somewhere within that
  42     /// type).
  43     CyclicTy(Ty<'tcx>),
  44     ProjectionMismatched(ExpectedFound<DefId>),
  45     ProjectionBoundsLength(ExpectedFound<usize>),
  46     ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>),
  47
  48     ConstMismatch(ExpectedFound<&'tcx ty::Const<'tcx>>),
  49 }
  50
  51 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  52 pub enum UnconstrainedNumeric {
  53     UnconstrainedFloat,
  54     UnconstrainedInt,
  55     Neither,
  56 }
  57
  58 /// Explains the source of a type err in a short, human readable way. This is meant to be placed
  59 /// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()`
  60 /// afterwards to present additional details, particularly when it comes to lifetime-related
  61 /// errors.
  62 impl<'tcx> fmt::Display for TypeError<'tcx> {
  63     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  64         use self::TypeError::*;
  65         fn report_maybe_different(f: &mut fmt::Formatter<'_>,
  66                                   expected: &str, found: &str) -> fmt::Result {
  67             // A naive approach to making sure that we're not reporting silly errors such as:
  68             // (expected closure, found closure).
  69             if expected == found {
  70                 write!(f, "expected {}, found a different {}", expected, found)
  71             } else {
  72                 write!(f, "expected {}, found {}", expected, found)
  73             }
  74         }
  75
  76         let br_string = |br: ty::BoundRegion| {
  77             match br {
  78                 ty::BrNamed(_, name) => format!(" {}", name),
  79                 _ => String::new(),
  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                        br_string(br))
 119             }
 120             RegionsOverlyPolymorphic(br, _) => {
 121                 write!(f,
 122                        "expected concrete lifetime, found bound lifetime parameter{}",
 123                        br_string(br))
 124             }
 125             RegionsPlaceholderMismatch => {
 126                 write!(f, "one type is more general than the other")
 127             }
 128             Sorts(values) => ty::tls::with(|tcx| {
 129                 report_maybe_different(f, &values.expected.sort_string(tcx),
 130                                        &values.found.sort_string(tcx))
 131             }),
 132             Traits(values) => ty::tls::with(|tcx| {
 133                 report_maybe_different(f,
 134                                        &format!("trait `{}`",
 135                                                 tcx.def_path_str(values.expected)),
 136                                        &format!("trait `{}`",
 137                                                 tcx.def_path_str(values.found)))
 138             }),
 139             IntMismatch(ref values) => {
 140                 write!(f, "expected `{:?}`, found `{:?}`",
 141                        values.expected,
 142                        values.found)
 143             }
 144             FloatMismatch(ref values) => {
 145                 write!(f, "expected `{:?}`, found `{:?}`",
 146                        values.expected,
 147                        values.found)
 148             }
 149             VariadicMismatch(ref values) => {
 150                 write!(f, "expected {} fn, found {} function",
 151                        if values.expected { "variadic" } else { "non-variadic" },
 152                        if values.found { "variadic" } else { "non-variadic" })
 153             }
 154             ProjectionMismatched(ref values) => ty::tls::with(|tcx| {
 155                 write!(f, "expected {}, found {}",
 156                        tcx.def_path_str(values.expected),
 157                        tcx.def_path_str(values.found))
 158             }),
 159             ProjectionBoundsLength(ref values) => {
 160                 write!(f, "expected {} associated type bindings, found {}",
 161                        values.expected,
 162                        values.found)
 163             },
 164             ExistentialMismatch(ref values) => {
 165                 report_maybe_different(f, &format!("trait `{}`", values.expected),
 166                                        &format!("trait `{}`", values.found))
 167             }
 168             ConstMismatch(ref values) => {
 169                 write!(f, "expected `{:?}`, found `{:?}`", values.expected, values.found)
 170             }
 171         }
 172     }
 173 }
 174
 175 impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
 176     pub fn sort_string(&self, tcx: TyCtxt<'a, 'gcx, 'lcx>) -> Cow<'static, str> {
 177         match self.sty {
 178             ty::Bool | ty::Char | ty::Int(_) |
 179             ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => self.to_string().into(),
 180             ty::Tuple(ref tys) if tys.is_empty() => self.to_string().into(),
 181
 182             ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.def_path_str(def.did)).into(),
 183             ty::Foreign(def_id) => format!("extern type `{}`", tcx.def_path_str(def_id)).into(),
 184             ty::Array(_, n) => match n.assert_usize(tcx) {
 185                 Some(n) => format!("array of {} elements", n).into(),
 186                 None => "array".into(),
 187             }
 188             ty::Slice(_) => "slice".into(),
 189             ty::RawPtr(_) => "*-ptr".into(),
 190             ty::Ref(region, ty, mutbl) => {
 191                 let tymut = ty::TypeAndMut { ty, mutbl };
 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                     format!("{}reference", match mutbl {
 198                         hir::Mutability::MutMutable => "mutable ",
 199                         _ => ""
 200                     }).into()
 201                 } else {
 202                     format!("&{}", tymut_string).into()
 203                 }
 204             }
 205             ty::FnDef(..) => "fn item".into(),
 206             ty::FnPtr(_) => "fn pointer".into(),
 207             ty::Dynamic(ref inner, ..) => {
 208                 if let Some(principal) = inner.principal() {
 209                     format!("trait {}", tcx.def_path_str(principal.def_id())).into()
 210                 } else {
 211                     "trait".into()
 212                 }
 213             }
 214             ty::Closure(..) => "closure".into(),
 215             ty::Generator(..) => "generator".into(),
 216             ty::GeneratorWitness(..) => "generator witness".into(),
 217             ty::Tuple(..) => "tuple".into(),
 218             ty::Infer(ty::TyVar(_)) => "inferred type".into(),
 219             ty::Infer(ty::IntVar(_)) => "integer".into(),
 220             ty::Infer(ty::FloatVar(_)) => "floating-point number".into(),
 221             ty::Placeholder(..) => "placeholder type".into(),
 222             ty::Bound(..) => "bound type".into(),
 223             ty::Infer(ty::FreshTy(_)) => "fresh type".into(),
 224             ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
 225             ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
 226             ty::Projection(_) => "associated type".into(),
 227             ty::UnnormalizedProjection(_) => "non-normalized associated type".into(),
 228             ty::Param(ref p) => {
 229                 if p.is_self() {
 230                     "Self".into()
 231                 } else {
 232                     "type parameter".into()
 233                 }
 234             }
 235             ty::Opaque(..) => "opaque type".into(),
 236             ty::Error => "type error".into(),
 237         }
 238     }
 239 }
 240
 241 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 242     pub fn note_and_explain_type_err(self,
 243                                      db: &mut DiagnosticBuilder<'_>,
 244                                      err: &TypeError<'tcx>,
 245                                      sp: Span) {
 246         use self::TypeError::*;
 247
 248         match err.clone() {
 249             Sorts(values) => {
 250                 let expected_str = values.expected.sort_string(self);
 251                 let found_str = values.found.sort_string(self);
 252                 if expected_str == found_str && expected_str == "closure" {
 253                     db.note("no two closures, even if identical, have the same type");
 254                     db.help("consider boxing your closure and/or using it as a trait object");
 255                 }
 256                 if let (ty::Infer(ty::IntVar(_)), ty::Float(_)) =
 257                        (&values.found.sty, &values.expected.sty) // Issue #53280
 258                 {
 259                     if let Ok(snippet) = self.sess.source_map().span_to_snippet(sp) {
 260                         if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') {
 261                             db.span_suggestion(
 262                                 sp,
 263                                 "use a float literal",
 264                                 format!("{}.0", snippet),
 265                                 Applicability::MachineApplicable
 266                             );
 267                         }
 268                     }
 269                 }
 270             },
 271             CyclicTy(ty) => {
 272                 // Watch out for various cases of cyclic types and try to explain.
 273                 if ty.is_closure() || ty.is_generator() {
 274                     db.note("closures cannot capture themselves or take themselves as argument;\n\
 275                              this error may be the result of a recent compiler bug-fix,\n\
 276                              see https://github.com/rust-lang/rust/issues/46062 for more details");
 277                 }
 278             }
 279             _ => {}
 280         }
 281     }
 282 }