| use crate::hir; |
| use crate::hir::def_id::DefId; |
| use crate::ty::{self, BoundRegion, Region, Ty, TyCtxt}; |
| |
| use errors::{Applicability, DiagnosticBuilder}; |
| use rustc_target::spec::abi; |
| use syntax::ast; |
| use syntax::errors::pluralize; |
| use syntax_pos::Span; |
| |
| use std::borrow::Cow; |
| use std::fmt; |
| |
| #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable)] |
| pub struct ExpectedFound<T> { |
| pub expected: T, |
| pub found: T, |
| } |
| |
| // Data structures used in type unification |
| #[derive(Clone, Debug, TypeFoldable)] |
| pub enum TypeError<'tcx> { |
| Mismatch, |
| UnsafetyMismatch(ExpectedFound<hir::Unsafety>), |
| AbiMismatch(ExpectedFound<abi::Abi>), |
| Mutability, |
| TupleSize(ExpectedFound<usize>), |
| FixedArraySize(ExpectedFound<u64>), |
| ArgCount, |
| |
| RegionsDoesNotOutlive(Region<'tcx>, Region<'tcx>), |
| RegionsInsufficientlyPolymorphic(BoundRegion, Region<'tcx>), |
| RegionsOverlyPolymorphic(BoundRegion, Region<'tcx>), |
| RegionsPlaceholderMismatch, |
| |
| Sorts(ExpectedFound<Ty<'tcx>>), |
| IntMismatch(ExpectedFound<ty::IntVarValue>), |
| FloatMismatch(ExpectedFound<ast::FloatTy>), |
| Traits(ExpectedFound<DefId>), |
| VariadicMismatch(ExpectedFound<bool>), |
| |
| /// Instantiating a type variable with the given type would have |
| /// created a cycle (because it appears somewhere within that |
| /// type). |
| CyclicTy(Ty<'tcx>), |
| ProjectionMismatched(ExpectedFound<DefId>), |
| ProjectionBoundsLength(ExpectedFound<usize>), |
| ExistentialMismatch(ExpectedFound<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>), |
| ObjectUnsafeCoercion(DefId), |
| ConstMismatch(ExpectedFound<&'tcx ty::Const<'tcx>>), |
| |
| IntrinsicCast, |
| } |
| |
| pub enum UnconstrainedNumeric { |
| UnconstrainedFloat, |
| UnconstrainedInt, |
| Neither, |
| } |
| |
| /// Explains the source of a type err in a short, human readable way. This is meant to be placed |
| /// in parentheses after some larger message. You should also invoke `note_and_explain_type_err()` |
| /// afterwards to present additional details, particularly when it comes to lifetime-related |
| /// errors. |
| impl<'tcx> fmt::Display for TypeError<'tcx> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| use self::TypeError::*; |
| fn report_maybe_different( |
| f: &mut fmt::Formatter<'_>, |
| expected: &str, |
| found: &str, |
| ) -> fmt::Result { |
| // A naive approach to making sure that we're not reporting silly errors such as: |
| // (expected closure, found closure). |
| if expected == found { |
| write!(f, "expected {}, found a different {}", expected, found) |
| } else { |
| write!(f, "expected {}, found {}", expected, found) |
| } |
| } |
| |
| let br_string = |br: ty::BoundRegion| { |
| match br { |
| ty::BrNamed(_, name) => format!(" {}", name), |
| _ => String::new(), |
| } |
| }; |
| |
| match *self { |
| CyclicTy(_) => write!(f, "cyclic type of infinite size"), |
| Mismatch => write!(f, "types differ"), |
| UnsafetyMismatch(values) => { |
| write!(f, "expected {} fn, found {} fn", |
| values.expected, |
| values.found) |
| } |
| AbiMismatch(values) => { |
| write!(f, "expected {} fn, found {} fn", |
| values.expected, |
| values.found) |
| } |
| Mutability => write!(f, "types differ in mutability"), |
| TupleSize(values) => { |
| write!(f, "expected a tuple with {} element{}, \ |
| found one with {} element{}", |
| values.expected, |
| pluralize!(values.expected), |
| values.found, |
| pluralize!(values.found)) |
| } |
| FixedArraySize(values) => { |
| write!(f, "expected an array with a fixed size of {} element{}, \ |
| found one with {} element{}", |
| values.expected, |
| pluralize!(values.expected), |
| values.found, |
| pluralize!(values.found)) |
| } |
| ArgCount => { |
| write!(f, "incorrect number of function parameters") |
| } |
| RegionsDoesNotOutlive(..) => { |
| write!(f, "lifetime mismatch") |
| } |
| RegionsInsufficientlyPolymorphic(br, _) => { |
| write!(f, |
| "expected bound lifetime parameter{}, found concrete lifetime", |
| br_string(br)) |
| } |
| RegionsOverlyPolymorphic(br, _) => { |
| write!(f, |
| "expected concrete lifetime, found bound lifetime parameter{}", |
| br_string(br)) |
| } |
| RegionsPlaceholderMismatch => { |
| write!(f, "one type is more general than the other") |
| } |
| Sorts(values) => ty::tls::with(|tcx| { |
| report_maybe_different(f, &values.expected.sort_string(tcx), |
| &values.found.sort_string(tcx)) |
| }), |
| Traits(values) => ty::tls::with(|tcx| { |
| report_maybe_different(f, |
| &format!("trait `{}`", |
| tcx.def_path_str(values.expected)), |
| &format!("trait `{}`", |
| tcx.def_path_str(values.found))) |
| }), |
| IntMismatch(ref values) => { |
| write!(f, "expected `{:?}`, found `{:?}`", |
| values.expected, |
| values.found) |
| } |
| FloatMismatch(ref values) => { |
| write!(f, "expected `{:?}`, found `{:?}`", |
| values.expected, |
| values.found) |
| } |
| VariadicMismatch(ref values) => { |
| write!(f, "expected {} fn, found {} function", |
| if values.expected { "variadic" } else { "non-variadic" }, |
| if values.found { "variadic" } else { "non-variadic" }) |
| } |
| ProjectionMismatched(ref values) => ty::tls::with(|tcx| { |
| write!(f, "expected {}, found {}", |
| tcx.def_path_str(values.expected), |
| tcx.def_path_str(values.found)) |
| }), |
| ProjectionBoundsLength(ref values) => { |
| write!(f, "expected {} associated type binding{}, found {}", |
| values.expected, |
| pluralize!(values.expected), |
| values.found) |
| }, |
| ExistentialMismatch(ref values) => { |
| report_maybe_different(f, &format!("trait `{}`", values.expected), |
| &format!("trait `{}`", values.found)) |
| } |
| ConstMismatch(ref values) => { |
| write!(f, "expected `{}`, found `{}`", values.expected, values.found) |
| } |
| IntrinsicCast => { |
| write!(f, "cannot coerce intrinsics to function pointers") |
| } |
| ObjectUnsafeCoercion(_) => write!(f, "coercion to object-unsafe trait object"), |
| } |
| } |
| } |
| |
| impl<'tcx> TypeError<'tcx> { |
| pub fn must_include_note(&self) -> bool { |
| use self::TypeError::*; |
| match self { |
| CyclicTy(_) | |
| UnsafetyMismatch(_) | |
| Mismatch | |
| AbiMismatch(_) | |
| FixedArraySize(_) | |
| Sorts(_) | |
| IntMismatch(_) | |
| FloatMismatch(_) | |
| VariadicMismatch(_) => false, |
| |
| Mutability | |
| TupleSize(_) | |
| ArgCount | |
| RegionsDoesNotOutlive(..) | |
| RegionsInsufficientlyPolymorphic(..) | |
| RegionsOverlyPolymorphic(..) | |
| RegionsPlaceholderMismatch | |
| Traits(_) | |
| ProjectionMismatched(_) | |
| ProjectionBoundsLength(_) | |
| ExistentialMismatch(_) | |
| ConstMismatch(_) | |
| IntrinsicCast | |
| ObjectUnsafeCoercion(_) => true, |
| } |
| } |
| } |
| |
| impl<'tcx> ty::TyS<'tcx> { |
| pub fn sort_string(&self, tcx: TyCtxt<'_>) -> Cow<'static, str> { |
| match self.kind { |
| ty::Bool | ty::Char | ty::Int(_) | |
| ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => format!("`{}`", self).into(), |
| ty::Tuple(ref tys) if tys.is_empty() => format!("`{}`", self).into(), |
| |
| ty::Adt(def, _) => format!("{} `{}`", def.descr(), tcx.def_path_str(def.did)).into(), |
| ty::Foreign(def_id) => format!("extern type `{}`", tcx.def_path_str(def_id)).into(), |
| ty::Array(t, n) => { |
| let n = tcx.lift(&n).unwrap(); |
| match n.try_eval_usize(tcx, ty::ParamEnv::empty()) { |
| _ if t.is_simple_ty() => format!("array `{}`", self).into(), |
| Some(n) => format!("array of {} element{} ", n, pluralize!(n)).into(), |
| None => "array".into(), |
| } |
| } |
| ty::Slice(ty) if ty.is_simple_ty() => format!("slice `{}`", self).into(), |
| ty::Slice(_) => "slice".into(), |
| ty::RawPtr(_) => "*-ptr".into(), |
| ty::Ref(_, ty, mutbl) => { |
| let tymut = ty::TypeAndMut { ty, mutbl }; |
| let tymut_string = tymut.to_string(); |
| if tymut_string != "_" && ( |
| ty.is_simple_text() || tymut_string.len() < "mutable reference".len() |
| ) { |
| format!("`&{}`", tymut_string).into() |
| } else { // Unknown type name, it's long or has type arguments |
| match mutbl { |
| hir::Mutability::Mutable => "mutable reference", |
| _ => "reference", |
| }.into() |
| } |
| } |
| ty::FnDef(..) => "fn item".into(), |
| ty::FnPtr(_) => "fn pointer".into(), |
| ty::Dynamic(ref inner, ..) => { |
| if let Some(principal) = inner.principal() { |
| format!("trait `{}`", tcx.def_path_str(principal.def_id())).into() |
| } else { |
| "trait".into() |
| } |
| } |
| ty::Closure(..) => "closure".into(), |
| ty::Generator(..) => "generator".into(), |
| ty::GeneratorWitness(..) => "generator witness".into(), |
| ty::Tuple(..) => "tuple".into(), |
| ty::Infer(ty::TyVar(_)) => "inferred type".into(), |
| ty::Infer(ty::IntVar(_)) => "integer".into(), |
| ty::Infer(ty::FloatVar(_)) => "floating-point number".into(), |
| ty::Placeholder(..) => "placeholder type".into(), |
| ty::Bound(..) => "bound type".into(), |
| ty::Infer(ty::FreshTy(_)) => "fresh type".into(), |
| ty::Infer(ty::FreshIntTy(_)) => "fresh integral type".into(), |
| ty::Infer(ty::FreshFloatTy(_)) => "fresh floating-point type".into(), |
| ty::Projection(_) => "associated type".into(), |
| ty::UnnormalizedProjection(_) => "non-normalized associated type".into(), |
| ty::Param(p) => format!("type parameter `{}`", p).into(), |
| ty::Opaque(..) => "opaque type".into(), |
| ty::Error => "type error".into(), |
| } |
| } |
| |
| pub fn prefix_string(&self) -> Cow<'static, str> { |
| match self.kind { |
| ty::Infer(_) | ty::Error | ty::Bool | ty::Char | ty::Int(_) | |
| ty::Uint(_) | ty::Float(_) | ty::Str | ty::Never => "type".into(), |
| ty::Tuple(ref tys) if tys.is_empty() => "unit type".into(), |
| ty::Adt(def, _) => def.descr().into(), |
| ty::Foreign(_) => "extern type".into(), |
| ty::Array(..) => "array".into(), |
| ty::Slice(_) => "slice".into(), |
| ty::RawPtr(_) => "raw pointer".into(), |
| ty::Ref(.., mutbl) => match mutbl { |
| hir::Mutability::Mutable => "mutable reference", |
| _ => "reference" |
| }.into(), |
| ty::FnDef(..) => "fn item".into(), |
| ty::FnPtr(_) => "fn pointer".into(), |
| ty::Dynamic(..) => "trait object".into(), |
| ty::Closure(..) => "closure".into(), |
| ty::Generator(..) => "generator".into(), |
| ty::GeneratorWitness(..) => "generator witness".into(), |
| ty::Tuple(..) => "tuple".into(), |
| ty::Placeholder(..) => "higher-ranked type".into(), |
| ty::Bound(..) => "bound type variable".into(), |
| ty::Projection(_) => "associated type".into(), |
| ty::UnnormalizedProjection(_) => "associated type".into(), |
| ty::Param(_) => "type parameter".into(), |
| ty::Opaque(..) => "opaque type".into(), |
| } |
| } |
| } |
| |
| impl<'tcx> TyCtxt<'tcx> { |
| pub fn note_and_explain_type_err( |
| self, |
| db: &mut DiagnosticBuilder<'_>, |
| err: &TypeError<'tcx>, |
| sp: Span, |
| body_owner_def_id: DefId, |
| ) { |
| use self::TypeError::*; |
| |
| match err { |
| Sorts(values) => { |
| let expected_str = values.expected.sort_string(self); |
| let found_str = values.found.sort_string(self); |
| if expected_str == found_str && expected_str == "closure" { |
| db.note("no two closures, even if identical, have the same type"); |
| db.help("consider boxing your closure and/or using it as a trait object"); |
| } |
| if expected_str == found_str && expected_str == "opaque type" { // Issue #63167 |
| db.note("distinct uses of `impl Trait` result in different opaque types"); |
| let e_str = values.expected.to_string(); |
| let f_str = values.found.to_string(); |
| if &e_str == &f_str && &e_str == "impl std::future::Future" { |
| // FIXME: use non-string based check. |
| db.help("if both `Future`s have the same `Output` type, consider \ |
| `.await`ing on both of them"); |
| } |
| } |
| match (&values.expected.kind, &values.found.kind) { |
| (ty::Float(_), ty::Infer(ty::IntVar(_))) => if let Ok( // Issue #53280 |
| snippet, |
| ) = self.sess.source_map().span_to_snippet(sp) { |
| if snippet.chars().all(|c| c.is_digit(10) || c == '-' || c == '_') { |
| db.span_suggestion( |
| sp, |
| "use a float literal", |
| format!("{}.0", snippet), |
| Applicability::MachineApplicable |
| ); |
| } |
| }, |
| (ty::Param(expected), ty::Param(found)) => { |
| let generics = self.generics_of(body_owner_def_id); |
| let e_span = self.def_span(generics.type_param(expected, self).def_id); |
| if !sp.contains(e_span) { |
| db.span_label(e_span, "expected type parameter"); |
| } |
| let f_span = self.def_span(generics.type_param(found, self).def_id); |
| if !sp.contains(f_span) { |
| db.span_label(f_span, "found type parameter"); |
| } |
| db.note("a type parameter was expected, but a different one was found; \ |
| you might be missing a type parameter or trait bound"); |
| db.note("for more information, visit \ |
| https://doc.rust-lang.org/book/ch10-02-traits.html\ |
| #traits-as-parameters"); |
| } |
| (ty::Projection(_), ty::Projection(_)) => { |
| db.note("an associated type was expected, but a different one was found"); |
| } |
| (ty::Param(_), ty::Projection(_)) | (ty::Projection(_), ty::Param(_)) => { |
| db.note("you might be missing a type parameter or trait bound"); |
| } |
| (ty::Param(p), _) | (_, ty::Param(p)) => { |
| let generics = self.generics_of(body_owner_def_id); |
| let p_span = self.def_span(generics.type_param(p, self).def_id); |
| if !sp.contains(p_span) { |
| db.span_label(p_span, "this type parameter"); |
| } |
| db.help("type parameters must be constrained to match other types"); |
| if self.sess.teach(&db.get_code().unwrap()) { |
| db.help("given a type parameter `T` and a method `foo`: |
| ``` |
| trait Trait<T> { fn foo(&self) -> T; } |
| ``` |
| the only ways to implement method `foo` are: |
| - constrain `T` with an explicit type: |
| ``` |
| impl Trait<String> for X { |
| fn foo(&self) -> String { String::new() } |
| } |
| ``` |
| - add a trait bound to `T` and call a method on that trait that returns `Self`: |
| ``` |
| impl<T: std::default::Default> Trait<T> for X { |
| fn foo(&self) -> T { <T as std::default::Default>::default() } |
| } |
| ``` |
| - change `foo` to return an argument of type `T`: |
| ``` |
| impl<T> Trait<T> for X { |
| fn foo(&self, x: T) -> T { x } |
| } |
| ```"); |
| } |
| db.note("for more information, visit \ |
| https://doc.rust-lang.org/book/ch10-02-traits.html\ |
| #traits-as-parameters"); |
| } |
| (ty::Projection(_), _) => { |
| db.note(&format!( |
| "consider constraining the associated type `{}` to `{}` or calling a \ |
| method that returns `{}`", |
| values.expected, |
| values.found, |
| values.expected, |
| )); |
| if self.sess.teach(&db.get_code().unwrap()) { |
| db.help("given an associated type `T` and a method `foo`: |
| ``` |
| trait Trait { |
| type T; |
| fn foo(&self) -> Self::T; |
| } |
| ``` |
| the only way of implementing method `foo` is to constrain `T` with an explicit associated type: |
| ``` |
| impl Trait for X { |
| type T = String; |
| fn foo(&self) -> Self::T { String::new() } |
| } |
| ```"); |
| } |
| db.note("for more information, visit \ |
| https://doc.rust-lang.org/book/ch19-03-advanced-traits.html"); |
| } |
| (_, ty::Projection(_)) => { |
| db.note(&format!( |
| "consider constraining the associated type `{}` to `{}`", |
| values.found, |
| values.expected, |
| )); |
| db.note("for more information, visit \ |
| https://doc.rust-lang.org/book/ch19-03-advanced-traits.html"); |
| } |
| _ => {} |
| } |
| debug!( |
| "note_and_explain_type_err expected={:?} ({:?}) found={:?} ({:?})", |
| values.expected, |
| values.expected.kind, |
| values.found, |
| values.found.kind, |
| ); |
| }, |
| CyclicTy(ty) => { |
| // Watch out for various cases of cyclic types and try to explain. |
| if ty.is_closure() || ty.is_generator() { |
| db.note("closures cannot capture themselves or take themselves as argument;\n\ |
| this error may be the result of a recent compiler bug-fix,\n\ |
| see https://github.com/rust-lang/rust/issues/46062 for more details"); |
| } |
| } |
| _ => {} |
| } |
| } |
| } |
