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     ConstError(ConstError<'tcx>),
  49 }
  50
  51 // Data structure used in const unification
  52 #[derive(Clone, Debug)]
  53 pub enum ConstError<'tcx> {
  54     Mismatch(ExpectedFound<&'tcx ty::LazyConst<'tcx>>),
  55 }
  56
  57 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  58 pub enum UnconstrainedNumeric {
  59     UnconstrainedFloat,
  60     UnconstrainedInt,
  61     Neither,
  62 }
  63
  64 /// Explains the source of a type err in a short, human readable way. This is meant to be placed
  65 /// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()`
  66 /// afterwards to present additional details, particularly when it comes to lifetime-related
  67 /// errors.
  68 impl<'tcx> fmt::Display for TypeError<'tcx> {
  69     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  70         use self::TypeError::*;
  71         fn report_maybe_different(f: &mut fmt::Formatter<'_>,
  72                                   expected: &str, found: &str) -> fmt::Result {
  73             // A naive approach to making sure that we're not reporting silly errors such as:
  74             // (expected closure, found closure).
  75             if expected == found {
  76                 write!(f, "expected {}, found a different {}", expected, found)
  77             } else {
  78                 write!(f, "expected {}, found {}", expected, found)
  79             }
  80         }
  81
  82         let br_string = |br: ty::BoundRegion| {
  83             match br {
  84                 ty::BrNamed(_, name) => format!(" {}", name),
  85                 _ => String::new(),
  86             }
  87         };
  88
  89         match *self {
  90             CyclicTy(_) => write!(f, "cyclic type of infinite size"),
  91             Mismatch => write!(f, "types differ"),
  92             UnsafetyMismatch(values) => {
  93                 write!(f, "expected {} fn, found {} fn",
  94                        values.expected,
  95                        values.found)
  96             }
  97             AbiMismatch(values) => {
  98                 write!(f, "expected {} fn, found {} fn",
  99                        values.expected,
 100                        values.found)
 101             }
 102             Mutability => write!(f, "types differ in mutability"),
 103             FixedArraySize(values) => {
 104                 write!(f, "expected an array with a fixed size of {} elements, \
 105                            found one with {} elements",
 106                        values.expected,
 107                        values.found)
 108             }
 109             TupleSize(values) => {
 110                 write!(f, "expected a tuple with {} elements, \
 111                            found one with {} elements",
 112                        values.expected,
 113                        values.found)
 114             }
 115             ArgCount => {
 116                 write!(f, "incorrect number of function parameters")
 117             }
 118             RegionsDoesNotOutlive(..) => {
 119                 write!(f, "lifetime mismatch")
 120             }
 121             RegionsInsufficientlyPolymorphic(br, _) => {
 122                 write!(f,
 123                        "expected bound lifetime parameter{}, found concrete lifetime",
 124                        br_string(br))
 125             }
 126             RegionsOverlyPolymorphic(br, _) => {
 127                 write!(f,
 128                        "expected concrete lifetime, found bound lifetime parameter{}",
 129                        br_string(br))
 130             }
 131             RegionsPlaceholderMismatch => {
 132                 write!(f, "one type is more general than the other")
 133             }
 134             Sorts(values) => ty::tls::with(|tcx| {
 135                 report_maybe_different(f, &values.expected.sort_string(tcx),
 136                                        &values.found.sort_string(tcx))
 137             }),
 138             Traits(values) => ty::tls::with(|tcx| {
 139                 report_maybe_different(f,
 140                                        &format!("trait `{}`",
 141                                                 tcx.def_path_str(values.expected)),
 142                                        &format!("trait `{}`",
 143                                                 tcx.def_path_str(values.found)))
 144             }),
 145             IntMismatch(ref values) => {
 146                 write!(f, "expected `{:?}`, found `{:?}`",
 147                        values.expected,
 148                        values.found)
 149             }
 150             FloatMismatch(ref values) => {
 151                 write!(f, "expected `{:?}`, found `{:?}`",
 152                        values.expected,
 153                        values.found)
 154             }
 155             VariadicMismatch(ref values) => {
 156                 write!(f, "expected {} fn, found {} function",
 157                        if values.expected { "variadic" } else { "non-variadic" },
 158                        if values.found { "variadic" } else { "non-variadic" })
 159             }
 160             ProjectionMismatched(ref values) => ty::tls::with(|tcx| {
 161                 write!(f, "expected {}, found {}",
 162                        tcx.def_path_str(values.expected),
 163                        tcx.def_path_str(values.found))
 164             }),
 165             ProjectionBoundsLength(ref values) => {
 166                 write!(f, "expected {} associated type bindings, found {}",
 167                        values.expected,
 168                        values.found)
 169             },
 170             ExistentialMismatch(ref values) => {
 171                 report_maybe_different(f, &format!("trait `{}`", values.expected),
 172                                        &format!("trait `{}`", values.found))
 173             }
 174             ConstError(ref err) => {
 175                 write!(f, "{}", err)
 176             }
 177         }
 178     }
 179 }
 180
 181 impl<'tcx> fmt::Display for ConstError<'tcx> {
 182     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 183         use self::ConstError::*;
 184
 185         match *self {
 186             Mismatch(ref values) => {
 187                 write!(f, "expected `{:?}`, found `{:?}`", values.expected, values.found)
 188             }
 189         }
 190     }
 191 }
 192
 193 impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
 194     pub fn sort_string(&self, tcx: TyCtxt<'a, 'gcx, 'lcx>) -> Cow<'static, str> {
 195         match self.sty {
 196             ty::Bool | ty::Char | ty::Int(_) |
 197             ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => self.to_string().into(),
 198             ty::Tuple(ref tys) if tys.is_empty() => self.to_string().into(),
 199
 200             ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.def_path_str(def.did)).into(),
 201             ty::Foreign(def_id) => format!("extern type `{}`", tcx.def_path_str(def_id)).into(),
 202             ty::Array(_, n) => match n.assert_usize(tcx) {
 203                 Some(n) => format!("array of {} elements", n).into(),
 204                 None => "array".into(),
 205             }
 206             ty::Slice(_) => "slice".into(),
 207             ty::RawPtr(_) => "*-ptr".into(),
 208             ty::Ref(region, ty, mutbl) => {
 209                 let tymut = ty::TypeAndMut { ty, mutbl };
 210                 let tymut_string = tymut.to_string();
 211                 if tymut_string == "_" ||         //unknown type name,
 212                    tymut_string.len() > 10 ||     //name longer than saying "reference",
 213                    region.to_string() != "'_"     //... or a complex type
 214                 {
 215                     format!("{}reference", match mutbl {
 216                         hir::Mutability::MutMutable => "mutable ",
 217                         _ => ""
 218                     }).into()
 219                 } else {
 220                     format!("&{}", tymut_string).into()
 221                 }
 222             }
 223             ty::FnDef(..) => "fn item".into(),
 224             ty::FnPtr(_) => "fn pointer".into(),
 225             ty::Dynamic(ref inner, ..) => {
 226                 if let Some(principal) = inner.principal() {
 227                     format!("trait {}", tcx.def_path_str(principal.def_id())).into()
 228                 } else {
 229                     "trait".into()
 230                 }
 231             }
 232             ty::Closure(..) => "closure".into(),
 233             ty::Generator(..) => "generator".into(),
 234             ty::GeneratorWitness(..) => "generator witness".into(),
 235             ty::Tuple(..) => "tuple".into(),
 236             ty::Infer(ty::TyVar(_)) => "inferred type".into(),
 237             ty::Infer(ty::IntVar(_)) => "integer".into(),
 238             ty::Infer(ty::FloatVar(_)) => "floating-point number".into(),
 239             ty::Placeholder(..) => "placeholder type".into(),
 240             ty::Bound(..) => "bound type".into(),
 241             ty::Infer(ty::FreshTy(_)) => "fresh type".into(),
 242             ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(),
 243             ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(),
 244             ty::Projection(_) => "associated type".into(),
 245             ty::UnnormalizedProjection(_) => "non-normalized associated type".into(),
 246             ty::Param(ref p) => {
 247                 if p.is_self() {
 248                     "Self".into()
 249                 } else {
 250                     "type parameter".into()
 251                 }
 252             }
 253             ty::Opaque(..) => "opaque type".into(),
 254             ty::Error => "type error".into(),
 255         }
 256     }
 257 }
 258
 259 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 260     pub fn note_and_explain_type_err(self,
 261                                      db: &mut DiagnosticBuilder<'_>,
 262                                      err: &TypeError<'tcx>,
 263                                      sp: Span) {
 264         use self::TypeError::*;
 265
 266         match err.clone() {
 267             Sorts(values) => {
 268                 let expected_str = values.expected.sort_string(self);
 269                 let found_str = values.found.sort_string(self);
 270                 if expected_str == found_str && expected_str == "closure" {
 271                     db.note("no two closures, even if identical, have the same type");
 272                     db.help("consider boxing your closure and/or using it as a trait object");
 273                 }
 274                 if let (ty::Infer(ty::IntVar(_)), ty::Float(_)) =
 275                        (&values.found.sty, &values.expected.sty) // Issue #53280
 276                 {
 277                     if let Ok(snippet) = self.sess.source_map().span_to_snippet(sp) {
 278                         if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') {
 279                             db.span_suggestion(
 280                                 sp,
 281                                 "use a float literal",
 282                                 format!("{}.0", snippet),
 283                                 Applicability::MachineApplicable
 284                             );
 285                         }
 286                     }
 287                 }
 288             },
 289             CyclicTy(ty) => {
 290                 // Watch out for various cases of cyclic types and try to explain.
 291                 if ty.is_closure() || ty.is_generator() {
 292                     db.note("closures cannot capture themselves or take themselves as argument;\n\
 293                              this error may be the result of a recent compiler bug-fix,\n\
 294                              see https://github.com/rust-lang/rust/issues/46062 for more details");
 295                 }
 296             }
 297             _ => {}
 298         }
 299     }
 300 }