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
  49 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Hash, Debug, Copy)]
  50 pub enum UnconstrainedNumeric {
  51     UnconstrainedFloat,
  52     UnconstrainedInt,
  53     Neither,
  54 }
  55
  56 /// Explains the source of a type err in a short, human readable way. This is meant to be placed
  57 /// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()`
  58 /// afterwards to present additional details, particularly when it comes to lifetime-related
  59 /// errors.
  60 impl<'tcx> fmt::Display for TypeError<'tcx> {
  61     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  62         use self::TypeError::*;
  63         fn report_maybe_different(f: &mut fmt::Formatter<'_>,
  64                                   expected: &str, found: &str) -> fmt::Result {
  65             // A naive approach to making sure that we're not reporting silly errors such as:
  66             // (expected closure, found closure).
  67             if expected == found {
  68                 write!(f, "expected {}, found a different {}", expected, found)
  69             } else {
  70                 write!(f, "expected {}, found {}", expected, found)
  71             }
  72         }
  73
  74         match *self {
  75             CyclicTy(_) => write!(f, "cyclic type of infinite size"),
  76             Mismatch => write!(f, "types differ"),
  77             UnsafetyMismatch(values) => {
  78                 write!(f, "expected {} fn, found {} fn",
  79                        values.expected,
  80                        values.found)
  81             }
  82             AbiMismatch(values) => {
  83                 write!(f, "expected {} fn, found {} fn",
  84                        values.expected,
  85                        values.found)
  86             }
  87             Mutability => write!(f, "types differ in mutability"),
  88             FixedArraySize(values) => {
  89                 write!(f, "expected an array with a fixed size of {} elements, \
  90                            found one with {} elements",
  91                        values.expected,
  92                        values.found)
  93             }
  94             TupleSize(values) => {
  95                 write!(f, "expected a tuple with {} elements, \
  96                            found one with {} elements",
  97                        values.expected,
  98                        values.found)
  99             }
 100             ArgCount => {
 101                 write!(f, "incorrect number of function parameters")
 102             }
 103             RegionsDoesNotOutlive(..) => {
 104                 write!(f, "lifetime mismatch")
 105             }
 106             RegionsInsufficientlyPolymorphic(br, _) => {
 107                 write!(f,
 108                        "expected bound lifetime parameter{}{}, found concrete lifetime",
 109                        if br.is_named() { " " } else { "" },
 110                        br)
 111             }
 112             RegionsOverlyPolymorphic(br, _) => {
 113                 write!(f,
 114                        "expected concrete lifetime, found bound lifetime parameter{}{}",
 115                        if br.is_named() { " " } else { "" },
 116                        br)
 117             }
 118             RegionsPlaceholderMismatch => {
 119                 write!(f, "one type is more general than the other")
 120             }
 121             Sorts(values) => ty::tls::with(|tcx| {
 122                 report_maybe_different(f, &values.expected.sort_string(tcx),
 123                                        &values.found.sort_string(tcx))
 124             }),
 125             Traits(values) => ty::tls::with(|tcx| {
 126                 report_maybe_different(f,
 127                                        &format!("trait `{}`",
 128                                                 tcx.item_path_str(values.expected)),
 129                                        &format!("trait `{}`",
 130                                                 tcx.item_path_str(values.found)))
 131             }),
 132             IntMismatch(ref values) => {
 133                 write!(f, "expected `{:?}`, found `{:?}`",
 134                        values.expected,
 135                        values.found)
 136             }
 137             FloatMismatch(ref values) => {
 138                 write!(f, "expected `{:?}`, found `{:?}`",
 139                        values.expected,
 140                        values.found)
 141             }
 142             VariadicMismatch(ref values) => {
 143                 write!(f, "expected {} fn, found {} function",
 144                        if values.expected { "variadic" } else { "non-variadic" },
 145                        if values.found { "variadic" } else { "non-variadic" })
 146             }
 147             ProjectionMismatched(ref values) => ty::tls::with(|tcx| {
 148                 write!(f, "expected {}, found {}",
 149                        tcx.item_path_str(values.expected),
 150                        tcx.item_path_str(values.found))
 151             }),
 152             ProjectionBoundsLength(ref values) => {
 153                 write!(f, "expected {} associated type bindings, found {}",
 154                        values.expected,
 155                        values.found)
 156             },
 157             ExistentialMismatch(ref values) => {
 158                 report_maybe_different(f, &format!("trait `{}`", values.expected),
 159                                        &format!("trait `{}`", values.found))
 160             }
 161         }
 162     }
 163 }
 164
 165 impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
 166     pub fn sort_string(&self, tcx: TyCtxt<'a, 'gcx, 'lcx>) -> Cow<'static, str> {
 167         match self.sty {
 168             ty::Bool | ty::Char | ty::Int(_) |
 169             ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => self.to_string().into(),
 170             ty::Tuple(ref tys) if tys.is_empty() => self.to_string().into(),
 171
 172             ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.item_path_str(def.did)).into(),
 173             ty::Foreign(def_id) => format!("extern type `{}`", tcx.item_path_str(def_id)).into(),
 174             ty::Array(_, n) => match n {
 175                 ty::LazyConst::Evaluated(n) => match n.assert_usize(tcx) {
 176                     Some(n) => format!("array of {} elements", n).into(),
 177                     None => "array".into(),
 178                 },
 179                 ty::LazyConst::Unevaluated(..) => "array".into(),
 180             }
 181             ty::Slice(_) => "slice".into(),
 182             ty::RawPtr(_) => "*-ptr".into(),
 183             ty::Ref(region, ty, mutbl) => {
 184                 let tymut = ty::TypeAndMut { ty, mutbl };
 185                 let tymut_string = tymut.to_string();
 186                 if tymut_string == "_" ||         //unknown type name,
 187                    tymut_string.len() > 10 ||     //name longer than saying "reference",
 188                    region.to_string() != ""       //... or a complex type
 189                 {
 190                     format!("{}reference", match mutbl {
 191                         hir::Mutability::MutMutable => "mutable ",
 192                         _ => ""
 193                     }).into()
 194                 } else {
 195                     format!("&{}", tymut_string).into()
 196                 }
 197             }
 198             ty::FnDef(..) => "fn item".into(),
 199             ty::FnPtr(_) => "fn pointer".into(),
 200             ty::Dynamic(ref inner, ..) => {
 201                 if let Some(principal) = inner.principal() {
 202                     format!("trait {}", tcx.item_path_str(principal.def_id())).into()
 203                 } else {
 204                     "trait".into()
 205                 }
 206             }
 207             ty::Closure(..) => "closure".into(),
 208             ty::Generator(..) => "generator".into(),
 209             ty::GeneratorWitness(..) => "generator witness".into(),
 210             ty::Tuple(..) => "tuple".into(),
 211             ty::Infer(ty::TyVar(_)) => "inferred type".into(),
 212             ty::Infer(ty::IntVar(_)) => "integer".into(),
 213             ty::Infer(ty::FloatVar(_)) => "floating-point number".into(),
 214             ty::Placeholder(..) => "placeholder type".into(),
 215             ty::Bound(..) => "bound type".into(),
 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(
 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 }