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fuchsia / third_party / rust / bdb3f532d7a393b1da512dbc1bed65c9eb63846e / . / src / librustc_typeck / astconv.rs
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// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Conversion from AST representation of types to the ty.rs
//! representation. The main routine here is `ast_ty_to_ty()`: each use
//! is parameterized by an instance of `AstConv`.
use smallvec::SmallVec;
use hir::{self, GenericArg, GenericArgs};
use hir::def::Def;
use hir::def_id::DefId;
use hir::HirVec;
use middle::resolve_lifetime as rl;
use namespace::Namespace;
use rustc::ty::subst::{Kind, Subst, Substs};
use rustc::traits;
use rustc::ty::{self, Ty, TyCtxt, ToPredicate, TypeFoldable};
use rustc::ty::{GenericParamDef, GenericParamDefKind};
use rustc::ty::wf::object_region_bounds;
use rustc_target::spec::abi;
use std::collections::BTreeSet;
use std::slice;
use require_c_abi_if_variadic;
use util::common::ErrorReported;
use util::nodemap::FxHashMap;
use errors::{Applicability, FatalError, DiagnosticId};
use lint;
use std::iter;
use syntax::ast;
use syntax::ptr::P;
use syntax::feature_gate::{GateIssue, emit_feature_err};
use syntax_pos::{Span, MultiSpan};
pub trait AstConv<'gcx, 'tcx> {
fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
/// Returns the set of bounds in scope for the type parameter with
/// the given id.
fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
-> ty::GenericPredicates<'tcx>;
/// What lifetime should we use when a lifetime is omitted (and not elided)?
fn re_infer(&self, span: Span, _def: Option<&ty::GenericParamDef>)
-> Option<ty::Region<'tcx>>;
/// What type should we use when a type is omitted?
fn ty_infer(&self, span: Span) -> Ty<'tcx>;
/// Same as ty_infer, but with a known type parameter definition.
fn ty_infer_for_def(&self,
_def: &ty::GenericParamDef,
span: Span) -> Ty<'tcx> {
self.ty_infer(span)
}
/// Projecting an associated type from a (potentially)
/// higher-ranked trait reference is more complicated, because of
/// the possibility of late-bound regions appearing in the
/// associated type binding. This is not legal in function
/// signatures for that reason. In a function body, we can always
/// handle it because we can use inference variables to remove the
/// late-bound regions.
fn projected_ty_from_poly_trait_ref(&self,
span: Span,
item_def_id: DefId,
poly_trait_ref: ty::PolyTraitRef<'tcx>)
-> Ty<'tcx>;
/// Normalize an associated type coming from the user.
fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
/// Invoked when we encounter an error from some prior pass
/// (e.g. resolve) that is translated into a ty-error. This is
/// used to help suppress derived errors typeck might otherwise
/// report.
fn set_tainted_by_errors(&self);
fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
}
struct ConvertedBinding<'tcx> {
item_name: ast::Ident,
ty: Ty<'tcx>,
span: Span,
}
#[derive(PartialEq)]
enum GenericArgPosition {
Type,
Value, // e.g. functions
MethodCall,
}
/// Dummy type used for the `Self` of a `TraitRef` created for converting
/// a trait object, and which gets removed in `ExistentialTraitRef`.
/// This type must not appear anywhere in other converted types.
const TRAIT_OBJECT_DUMMY_SELF: ty::TyKind<'static> = ty::Infer(ty::FreshTy(0));
impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx>+'o {
pub fn ast_region_to_region(&self,
lifetime: &hir::Lifetime,
def: Option<&ty::GenericParamDef>)
-> ty::Region<'tcx>
{
let tcx = self.tcx();
let lifetime_name = |def_id| {
tcx.hir.name(tcx.hir.as_local_node_id(def_id).unwrap()).as_interned_str()
};
let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
let r = match tcx.named_region(hir_id) {
Some(rl::Region::Static) => {
tcx.types.re_static
}
Some(rl::Region::LateBound(debruijn, id, _)) => {
let name = lifetime_name(id);
tcx.mk_region(ty::ReLateBound(debruijn,
ty::BrNamed(id, name)))
}
Some(rl::Region::LateBoundAnon(debruijn, index)) => {
tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
}
Some(rl::Region::EarlyBound(index, id, _)) => {
let name = lifetime_name(id);
tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
def_id: id,
index,
name,
}))
}
Some(rl::Region::Free(scope, id)) => {
let name = lifetime_name(id);
tcx.mk_region(ty::ReFree(ty::FreeRegion {
scope,
bound_region: ty::BrNamed(id, name)
}))
// (*) -- not late-bound, won't change
}
None => {
self.re_infer(lifetime.span, def)
.unwrap_or_else(|| {
// This indicates an illegal lifetime
// elision. `resolve_lifetime` should have
// reported an error in this case -- but if
// not, let's error out.
tcx.sess.delay_span_bug(lifetime.span, "unelided lifetime in signature");
// Supply some dummy value. We don't have an
// `re_error`, annoyingly, so use `'static`.
tcx.types.re_static
})
}
};
debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
lifetime,
r);
r
}
/// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
/// returns an appropriate set of substitutions for this particular reference to `I`.
pub fn ast_path_substs_for_ty(&self,
span: Span,
def_id: DefId,
item_segment: &hir::PathSegment)
-> &'tcx Substs<'tcx>
{
let (substs, assoc_bindings) = item_segment.with_generic_args(|generic_args| {
self.create_substs_for_ast_path(
span,
def_id,
generic_args,
item_segment.infer_types,
None,
)
});
assoc_bindings.first().map(|b| Self::prohibit_assoc_ty_binding(self.tcx(), b.span));
substs
}
/// Report error if there is an explicit type parameter when using `impl Trait`.
fn check_impl_trait(
tcx: TyCtxt,
span: Span,
seg: &hir::PathSegment,
generics: &ty::Generics,
) -> bool {
let explicit = !seg.infer_types;
let impl_trait = generics.params.iter().any(|param| match param.kind {
ty::GenericParamDefKind::Type {
synthetic: Some(hir::SyntheticTyParamKind::ImplTrait), ..
} => true,
_ => false,
});
if explicit && impl_trait {
let mut err = struct_span_err! {
tcx.sess,
span,
E0632,
"cannot provide explicit type parameters when `impl Trait` is \
used in argument position."
};
err.emit();
}
impl_trait
}
/// Check that the correct number of generic arguments have been provided.
/// Used specifically for function calls.
pub fn check_generic_arg_count_for_call(
tcx: TyCtxt,
span: Span,
def: &ty::Generics,
seg: &hir::PathSegment,
is_method_call: bool,
) -> bool {
let empty_args = P(hir::GenericArgs {
args: HirVec::new(), bindings: HirVec::new(), parenthesized: false,
});
let suppress_mismatch = Self::check_impl_trait(tcx, span, seg, &def);
Self::check_generic_arg_count(
tcx,
span,
def,
if let Some(ref args) = seg.args {
args
} else {
&empty_args
},
if is_method_call {
GenericArgPosition::MethodCall
} else {
GenericArgPosition::Value
},
def.parent.is_none() && def.has_self, // `has_self`
seg.infer_types || suppress_mismatch, // `infer_types`
)
}
/// Check that the correct number of generic arguments have been provided.
/// This is used both for datatypes and function calls.
fn check_generic_arg_count(
tcx: TyCtxt,
span: Span,
def: &ty::Generics,
args: &hir::GenericArgs,
position: GenericArgPosition,
has_self: bool,
infer_types: bool,
) -> bool {
// At this stage we are guaranteed that the generic arguments are in the correct order, e.g.
// that lifetimes will proceed types. So it suffices to check the number of each generic
// arguments in order to validate them with respect to the generic parameters.
let param_counts = def.own_counts();
let arg_counts = args.own_counts();
let infer_lifetimes = position != GenericArgPosition::Type && arg_counts.lifetimes == 0;
let mut defaults: ty::GenericParamCount = Default::default();
for param in &def.params {
match param.kind {
GenericParamDefKind::Lifetime => {}
GenericParamDefKind::Type { has_default, .. } => {
defaults.types += has_default as usize
}
};
}
if position != GenericArgPosition::Type && !args.bindings.is_empty() {
AstConv::prohibit_assoc_ty_binding(tcx, args.bindings[0].span);
}
// Prohibit explicit lifetime arguments if late-bound lifetime parameters are present.
if !infer_lifetimes {
if let Some(span_late) = def.has_late_bound_regions {
let msg = "cannot specify lifetime arguments explicitly \
if late bound lifetime parameters are present";
let note = "the late bound lifetime parameter is introduced here";
let span = args.args[0].span();
if position == GenericArgPosition::Value
&& arg_counts.lifetimes != param_counts.lifetimes {
let mut err = tcx.sess.struct_span_err(span, msg);
err.span_note(span_late, note);
err.emit();
return true;
} else {
let mut multispan = MultiSpan::from_span(span);
multispan.push_span_label(span_late, note.to_string());
tcx.lint_node(lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS,
args.args[0].id(), multispan, msg);
return false;
}
}
}
let check_kind_count = |kind,
required,
permitted,
provided,
offset| {
// We enforce the following: `required` <= `provided` <= `permitted`.
// For kinds without defaults (i.e. lifetimes), `required == permitted`.
// For other kinds (i.e. types), `permitted` may be greater than `required`.
if required <= provided && provided <= permitted {
return false;
}
// Unfortunately lifetime and type parameter mismatches are typically styled
// differently in diagnostics, which means we have a few cases to consider here.
let (bound, quantifier) = if required != permitted {
if provided < required {
(required, "at least ")
} else { // provided > permitted
(permitted, "at most ")
}
} else {
(required, "")
};
let mut span = span;
let label = if required == permitted && provided > permitted {
let diff = provided - permitted;
if diff == 1 {
// In the case when the user has provided too many arguments,
// we want to point to the first unexpected argument.
let first_superfluous_arg: &GenericArg = &args.args[offset + permitted];
span = first_superfluous_arg.span();
}
format!(
"{}unexpected {} argument{}",
if diff != 1 { format!("{} ", diff) } else { String::new() },
kind,
if diff != 1 { "s" } else { "" },
)
} else {
format!(
"expected {}{} {} argument{}",
quantifier,
bound,
kind,
if bound != 1 { "s" } else { "" },
)
};
tcx.sess.struct_span_err_with_code(
span,
&format!(
"wrong number of {} arguments: expected {}{}, found {}",
kind,
quantifier,
bound,
provided,
),
DiagnosticId::Error("E0107".into())
).span_label(span, label).emit();
provided > required // `suppress_error`
};
if !infer_lifetimes || arg_counts.lifetimes > param_counts.lifetimes {
check_kind_count(
"lifetime",
param_counts.lifetimes,
param_counts.lifetimes,
arg_counts.lifetimes,
0,
);
}
if !infer_types
|| arg_counts.types > param_counts.types - defaults.types - has_self as usize {
check_kind_count(
"type",
param_counts.types - defaults.types - has_self as usize,
param_counts.types - has_self as usize,
arg_counts.types,
arg_counts.lifetimes,
)
} else {
false
}
}
/// Creates the relevant generic argument substitutions
/// corresponding to a set of generic parameters. This is a
/// rather complex little function. Let me try to explain the
/// role of each of its parameters:
///
/// To start, we are given the `def_id` of the thing we are
/// creating the substitutions for, and a partial set of
/// substitutions `parent_substs`. In general, the substitutions
/// for an item begin with substitutions for all the "parents" of
/// that item -- so e.g. for a method it might include the
/// parameters from the impl.
///
/// Therefore, the method begins by walking down these parents,
/// starting with the outermost parent and proceed inwards until
/// it reaches `def_id`. For each parent P, it will check `parent_substs`
/// first to see if the parent's substitutions are listed in there. If so,
/// we can append those and move on. Otherwise, it invokes the
/// three callback functions:
///
/// - `args_for_def_id`: given the def-id P, supplies back the
/// generic arguments that were given to that parent from within
/// the path; so e.g. if you have `<T as Foo>::Bar`, the def-id
/// might refer to the trait `Foo`, and the arguments might be
/// `[T]`. The boolean value indicates whether to infer values
/// for arguments whose values were not explicitly provided.
/// - `provided_kind`: given the generic parameter and the value from `args_for_def_id`,
/// instantiate a `Kind`
/// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
/// creates a suitable inference variable.
pub fn create_substs_for_generic_args<'a, 'b>(
tcx: TyCtxt<'a, 'gcx, 'tcx>,
def_id: DefId,
parent_substs: &[Kind<'tcx>],
has_self: bool,
self_ty: Option<Ty<'tcx>>,
args_for_def_id: impl Fn(DefId) -> (Option<&'b GenericArgs>, bool),
provided_kind: impl Fn(&GenericParamDef, &GenericArg) -> Kind<'tcx>,
inferred_kind: impl Fn(Option<&[Kind<'tcx>]>, &GenericParamDef, bool) -> Kind<'tcx>,
) -> &'tcx Substs<'tcx> {
// Collect the segments of the path: we need to substitute arguments
// for parameters throughout the entire path (wherever there are
// generic parameters).
let mut parent_defs = tcx.generics_of(def_id);
let count = parent_defs.count();
let mut stack = vec![(def_id, parent_defs)];
while let Some(def_id) = parent_defs.parent {
parent_defs = tcx.generics_of(def_id);
stack.push((def_id, parent_defs));
}
// We manually build up the substitution, rather than using convenience
// methods in subst.rs so that we can iterate over the arguments and
// parameters in lock-step linearly, rather than trying to match each pair.
let mut substs: SmallVec<[Kind<'tcx>; 8]> = SmallVec::with_capacity(count);
// Iterate over each segment of the path.
while let Some((def_id, defs)) = stack.pop() {
let mut params = defs.params.iter().peekable();
// If we have already computed substitutions for parents, we can use those directly.
while let Some(&param) = params.peek() {
if let Some(&kind) = parent_substs.get(param.index as usize) {
substs.push(kind);
params.next();
} else {
break;
}
}
// (Unless it's been handled in `parent_substs`) `Self` is handled first.
if has_self {
if let Some(&param) = params.peek() {
if param.index == 0 {
if let GenericParamDefKind::Type { .. } = param.kind {
substs.push(self_ty.map(|ty| ty.into())
.unwrap_or_else(|| inferred_kind(None, param, true)));
params.next();
}
}
}
}
// Check whether this segment takes generic arguments and the user has provided any.
let (generic_args, infer_types) = args_for_def_id(def_id);
let mut args = generic_args.iter().flat_map(|generic_args| generic_args.args.iter())
.peekable();
loop {
// We're going to iterate through the generic arguments that the user
// provided, matching them with the generic parameters we expect.
// Mismatches can occur as a result of elided lifetimes, or for malformed
// input. We try to handle both sensibly.
match (args.peek(), params.peek()) {
(Some(&arg), Some(&param)) => {
match (arg, &param.kind) {
(GenericArg::Lifetime(_), GenericParamDefKind::Lifetime)
| (GenericArg::Type(_), GenericParamDefKind::Type { .. }) => {
substs.push(provided_kind(param, arg));
args.next();
params.next();
}
(GenericArg::Lifetime(_), GenericParamDefKind::Type { .. }) => {
// We expected a type argument, but got a lifetime
// argument. This is an error, but we need to handle it
// gracefully so we can report sensible errors. In this
// case, we're simply going to infer this argument.
args.next();
}
(GenericArg::Type(_), GenericParamDefKind::Lifetime) => {
// We expected a lifetime argument, but got a type
// argument. That means we're inferring the lifetimes.
substs.push(inferred_kind(None, param, infer_types));
params.next();
}
}
}
(Some(_), None) => {
// We should never be able to reach this point with well-formed input.
// Getting to this point means the user supplied more arguments than
// there are parameters.
args.next();
}
(None, Some(&param)) => {
// If there are fewer arguments than parameters, it means
// we're inferring the remaining arguments.
match param.kind {
GenericParamDefKind::Lifetime | GenericParamDefKind::Type { .. } => {
let kind = inferred_kind(Some(&substs), param, infer_types);
substs.push(kind);
}
}
args.next();
params.next();
}
(None, None) => break,
}
}
}
tcx.intern_substs(&substs)
}
/// Given the type/region arguments provided to some path (along with
/// an implicit Self, if this is a trait reference) returns the complete
/// set of substitutions. This may involve applying defaulted type parameters.
///
/// Note that the type listing given here is *exactly* what the user provided.
fn create_substs_for_ast_path(&self,
span: Span,
def_id: DefId,
generic_args: &hir::GenericArgs,
infer_types: bool,
self_ty: Option<Ty<'tcx>>)
-> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
{
// If the type is parameterized by this region, then replace this
// region with the current anon region binding (in other words,
// whatever & would get replaced with).
debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
generic_args={:?})",
def_id, self_ty, generic_args);
let tcx = self.tcx();
let generic_params = tcx.generics_of(def_id);
// If a self-type was declared, one should be provided.
assert_eq!(generic_params.has_self, self_ty.is_some());
let has_self = generic_params.has_self;
Self::check_generic_arg_count(
self.tcx(),
span,
&generic_params,
&generic_args,
GenericArgPosition::Type,
has_self,
infer_types,
);
let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
let default_needs_object_self = |param: &ty::GenericParamDef| {
if let GenericParamDefKind::Type { has_default, .. } = param.kind {
if is_object && has_default {
if tcx.at(span).type_of(param.def_id).has_self_ty() {
// There is no suitable inference default for a type parameter
// that references self, in an object type.
return true;
}
}
}
false
};
let substs = Self::create_substs_for_generic_args(
self.tcx(),
def_id,
&[][..],
self_ty.is_some(),
self_ty,
// Provide the generic args, and whether types should be inferred.
|_| (Some(generic_args), infer_types),
// Provide substitutions for parameters for which (valid) arguments have been provided.
|param, arg| {
match (&param.kind, arg) {
(GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
self.ast_region_to_region(&lt, Some(param)).into()
}
(GenericParamDefKind::Type { .. }, GenericArg::Type(ty)) => {
self.ast_ty_to_ty(&ty).into()
}
_ => unreachable!(),
}
},
// Provide substitutions for parameters for which arguments are inferred.
|substs, param, infer_types| {
match param.kind {
GenericParamDefKind::Lifetime => tcx.types.re_static.into(),
GenericParamDefKind::Type { has_default, .. } => {
if !infer_types && has_default {
// No type parameter provided, but a default exists.
// If we are converting an object type, then the
// `Self` parameter is unknown. However, some of the
// other type parameters may reference `Self` in their
// defaults. This will lead to an ICE if we are not
// careful!
if default_needs_object_self(param) {
struct_span_err!(tcx.sess, span, E0393,
"the type parameter `{}` must be explicitly \
specified",
param.name)
.span_label(span,
format!("missing reference to `{}`", param.name))
.note(&format!("because of the default `Self` reference, \
type parameters must be specified on object \
types"))
.emit();
tcx.types.err.into()
} else {
// This is a default type parameter.
self.normalize_ty(
span,
tcx.at(span).type_of(param.def_id)
.subst_spanned(tcx, substs.unwrap(), Some(span))
).into()
}
} else if infer_types {
// No type parameters were provided, we can infer all.
if !default_needs_object_self(param) {
self.ty_infer_for_def(param, span).into()
} else {
self.ty_infer(span).into()
}
} else {
// We've already errored above about the mismatch.
tcx.types.err.into()
}
}
}
},
);
let assoc_bindings = generic_args.bindings.iter().map(|binding| {
ConvertedBinding {
item_name: binding.ident,
ty: self.ast_ty_to_ty(&binding.ty),
span: binding.span,
}
}).collect();
debug!("create_substs_for_ast_path(generic_params={:?}, self_ty={:?}) -> {:?}",
generic_params, self_ty, substs);
(substs, assoc_bindings)
}
/// Instantiates the path for the given trait reference, assuming that it's
/// bound to a valid trait type. Returns the def_id for the defining trait.
/// The type _cannot_ be a type other than a trait type.
///
/// If the `projections` argument is `None`, then assoc type bindings like `Foo<T=X>`
/// are disallowed. Otherwise, they are pushed onto the vector given.
pub fn instantiate_mono_trait_ref(&self,
trait_ref: &hir::TraitRef,
self_ty: Ty<'tcx>)
-> ty::TraitRef<'tcx>
{
self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
let trait_def_id = self.trait_def_id(trait_ref);
self.ast_path_to_mono_trait_ref(trait_ref.path.span,
trait_def_id,
self_ty,
trait_ref.path.segments.last().unwrap())
}
/// Get the DefId of the given trait ref. It _must_ actually be a trait.
fn trait_def_id(&self, trait_ref: &hir::TraitRef) -> DefId {
let path = &trait_ref.path;
match path.def {
Def::Trait(trait_def_id) => trait_def_id,
Def::TraitAlias(alias_def_id) => alias_def_id,
Def::Err => {
FatalError.raise();
}
_ => unreachable!(),
}
}
/// The given `trait_ref` must actually be trait.
pub(super) fn instantiate_poly_trait_ref_inner(&self,
trait_ref: &hir::TraitRef,
self_ty: Ty<'tcx>,
poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
speculative: bool)
-> ty::PolyTraitRef<'tcx>
{
let trait_def_id = self.trait_def_id(trait_ref);
debug!("ast_path_to_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
self.prohibit_generics(trait_ref.path.segments.split_last().unwrap().1);
let (substs, assoc_bindings) =
self.create_substs_for_ast_trait_ref(trait_ref.path.span,
trait_def_id,
self_ty,
trait_ref.path.segments.last().unwrap());
let poly_trait_ref = ty::Binder::bind(ty::TraitRef::new(trait_def_id, substs));
let mut dup_bindings = FxHashMap::default();
poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
// specify type to assert that error was already reported in Err case:
let predicate: Result<_, ErrorReported> =
self.ast_type_binding_to_poly_projection_predicate(
trait_ref.ref_id, poly_trait_ref, binding, speculative, &mut dup_bindings);
// ok to ignore Err() because ErrorReported (see above)
Some((predicate.ok()?, binding.span))
}));
debug!("ast_path_to_poly_trait_ref({:?}, projections={:?}) -> {:?}",
trait_ref, poly_projections, poly_trait_ref);
poly_trait_ref
}
pub fn instantiate_poly_trait_ref(&self,
poly_trait_ref: &hir::PolyTraitRef,
self_ty: Ty<'tcx>,
poly_projections: &mut Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>)
-> ty::PolyTraitRef<'tcx>
{
self.instantiate_poly_trait_ref_inner(&poly_trait_ref.trait_ref, self_ty,
poly_projections, false)
}
fn ast_path_to_mono_trait_ref(&self,
span: Span,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
trait_segment: &hir::PathSegment)
-> ty::TraitRef<'tcx>
{
let (substs, assoc_bindings) =
self.create_substs_for_ast_trait_ref(span,
trait_def_id,
self_ty,
trait_segment);
assoc_bindings.first().map(|b| AstConv::prohibit_assoc_ty_binding(self.tcx(), b.span));
ty::TraitRef::new(trait_def_id, substs)
}
fn create_substs_for_ast_trait_ref(&self,
span: Span,
trait_def_id: DefId,
self_ty: Ty<'tcx>,
trait_segment: &hir::PathSegment)
-> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
{
debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
trait_segment);
let trait_def = self.tcx().trait_def(trait_def_id);
if !self.tcx().features().unboxed_closures &&
trait_segment.with_generic_args(|generic_args| generic_args.parenthesized)
!= trait_def.paren_sugar {
// For now, require that parenthetical notation be used only with `Fn()` etc.
let msg = if trait_def.paren_sugar {
"the precise format of `Fn`-family traits' type parameters is subject to change. \
Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
} else {
"parenthetical notation is only stable when used with `Fn`-family traits"
};
emit_feature_err(&self.tcx().sess.parse_sess, "unboxed_closures",
span, GateIssue::Language, msg);
}
trait_segment.with_generic_args(|generic_args| {
self.create_substs_for_ast_path(span,
trait_def_id,
generic_args,
trait_segment.infer_types,
Some(self_ty))
})
}
fn trait_defines_associated_type_named(&self,
trait_def_id: DefId,
assoc_name: ast::Ident)
-> bool
{
self.tcx().associated_items(trait_def_id).any(|item| {
item.kind == ty::AssociatedKind::Type &&
self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
})
}
fn ast_type_binding_to_poly_projection_predicate(
&self,
ref_id: ast::NodeId,
trait_ref: ty::PolyTraitRef<'tcx>,
binding: &ConvertedBinding<'tcx>,
speculative: bool,
dup_bindings: &mut FxHashMap<DefId, Span>)
-> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
{
let tcx = self.tcx();
if !speculative {
// Given something like `U : SomeTrait<T=X>`, we want to produce a
// predicate like `<U as SomeTrait>::T = X`. This is somewhat
// subtle in the event that `T` is defined in a supertrait of
// `SomeTrait`, because in that case we need to upcast.
//
// That is, consider this case:
//
// ```
// trait SubTrait : SuperTrait<int> { }
// trait SuperTrait<A> { type T; }
//
// ... B : SubTrait<T=foo> ...
// ```
//
// We want to produce `<B as SuperTrait<int>>::T == foo`.
// Find any late-bound regions declared in `ty` that are not
// declared in the trait-ref. These are not wellformed.
//
// Example:
//
// for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
// for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
let late_bound_in_ty =
tcx.collect_referenced_late_bound_regions(&ty::Binder::bind(binding.ty));
debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
let br_name = match *br {
ty::BrNamed(_, name) => name,
_ => {
span_bug!(
binding.span,
"anonymous bound region {:?} in binding but not trait ref",
br);
}
};
struct_span_err!(tcx.sess,
binding.span,
E0582,
"binding for associated type `{}` references lifetime `{}`, \
which does not appear in the trait input types",
binding.item_name, br_name)
.emit();
}
}
let candidate = if self.trait_defines_associated_type_named(trait_ref.def_id(),
binding.item_name) {
// Simple case: X is defined in the current trait.
Ok(trait_ref)
} else {
// Otherwise, we have to walk through the supertraits to find
// those that do.
let candidates = traits::supertraits(tcx, trait_ref).filter(|r| {
self.trait_defines_associated_type_named(r.def_id(), binding.item_name)
});
self.one_bound_for_assoc_type(candidates, &trait_ref.to_string(),
binding.item_name, binding.span)
}?;
let (assoc_ident, def_scope) =
tcx.adjust_ident(binding.item_name, candidate.def_id(), ref_id);
let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
i.kind == ty::AssociatedKind::Type && i.ident.modern() == assoc_ident
}).expect("missing associated type");
if !assoc_ty.vis.is_accessible_from(def_scope, tcx) {
let msg = format!("associated type `{}` is private", binding.item_name);
tcx.sess.span_err(binding.span, &msg);
}
tcx.check_stability(assoc_ty.def_id, Some(ref_id), binding.span);
if !speculative {
dup_bindings.entry(assoc_ty.def_id)
.and_modify(|prev_span| {
let mut err = self.tcx().struct_span_lint_node(
::rustc::lint::builtin::DUPLICATE_ASSOCIATED_TYPE_BINDINGS,
ref_id,
binding.span,
&format!("associated type binding `{}` specified more than once",
binding.item_name)
);
err.span_label(binding.span, "used more than once");
err.span_label(*prev_span, format!("first use of `{}`", binding.item_name));
err.emit();
})
.or_insert(binding.span);
}
Ok(candidate.map_bound(|trait_ref| {
ty::ProjectionPredicate {
projection_ty: ty::ProjectionTy::from_ref_and_name(
tcx,
trait_ref,
binding.item_name,
),
ty: binding.ty,
}
}))
}
fn ast_path_to_ty(&self,
span: Span,
did: DefId,
item_segment: &hir::PathSegment)
-> Ty<'tcx>
{
let substs = self.ast_path_substs_for_ty(span, did, item_segment);
self.normalize_ty(
span,
self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
)
}
/// Transform a PolyTraitRef into a PolyExistentialTraitRef by
/// removing the dummy Self type (TRAIT_OBJECT_DUMMY_SELF).
fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
-> ty::ExistentialTraitRef<'tcx> {
assert_eq!(trait_ref.self_ty().sty, TRAIT_OBJECT_DUMMY_SELF);
ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
}
fn conv_object_ty_poly_trait_ref(&self,
span: Span,
trait_bounds: &[hir::PolyTraitRef],
lifetime: &hir::Lifetime)
-> Ty<'tcx>
{
let tcx = self.tcx();
if trait_bounds.is_empty() {
span_err!(tcx.sess, span, E0224,
"at least one non-builtin trait is required for an object type");
return tcx.types.err;
}
let mut projection_bounds = vec![];
let dummy_self = tcx.mk_ty(TRAIT_OBJECT_DUMMY_SELF);
let principal = self.instantiate_poly_trait_ref(&trait_bounds[0],
dummy_self,
&mut projection_bounds);
for trait_bound in trait_bounds[1..].iter() {
// Sanity check for non-principal trait bounds
self.instantiate_poly_trait_ref(trait_bound,
dummy_self,
&mut vec![]);
}
let (mut auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
if !trait_bounds.is_empty() {
let b = &trait_bounds[0];
let span = b.trait_ref.path.span;
struct_span_err!(self.tcx().sess, span, E0225,
"only auto traits can be used as additional traits in a trait object")
.span_label(span, "non-auto additional trait")
.emit();
}
// Erase the dummy_self (TRAIT_OBJECT_DUMMY_SELF) used above.
let existential_principal = principal.map_bound(|trait_ref| {
self.trait_ref_to_existential(trait_ref)
});
let existential_projections = projection_bounds.iter().map(|(bound, _)| {
bound.map_bound(|b| {
let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
ty::ExistentialProjection {
ty: b.ty,
item_def_id: b.projection_ty.item_def_id,
substs: trait_ref.substs,
}
})
});
// check that there are no gross object safety violations,
// most importantly, that the supertraits don't contain Self,
// to avoid ICE-s.
let object_safety_violations =
tcx.astconv_object_safety_violations(principal.def_id());
if !object_safety_violations.is_empty() {
tcx.report_object_safety_error(
span, principal.def_id(), object_safety_violations)
.emit();
return tcx.types.err;
}
// use a btreeset to keep output in a more consistent order
let mut associated_types = BTreeSet::default();
for tr in traits::supertraits(tcx, principal) {
associated_types.extend(tcx.associated_items(tr.def_id())
.filter(|item| item.kind == ty::AssociatedKind::Type)
.map(|item| item.def_id));
}
for (projection_bound, _) in &projection_bounds {
associated_types.remove(&projection_bound.projection_def_id());
}
for item_def_id in associated_types {
let assoc_item = tcx.associated_item(item_def_id);
let trait_def_id = assoc_item.container.id();
struct_span_err!(tcx.sess, span, E0191, "the value of the associated type `{}` \
(from the trait `{}`) must be specified",
assoc_item.ident,
tcx.item_path_str(trait_def_id))
.span_label(span, format!("missing associated type `{}` value",
assoc_item.ident))
.emit();
}
// Dedup auto traits so that `dyn Trait + Send + Send` is the same as `dyn Trait + Send`.
auto_traits.sort();
auto_traits.dedup();
// skip_binder is okay, because the predicates are re-bound.
let mut v =
iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
.chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
.chain(existential_projections
.map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
.collect::<SmallVec<[_; 8]>>();
v.sort_by(|a, b| a.stable_cmp(tcx, b));
let existential_predicates = ty::Binder::bind(tcx.mk_existential_predicates(v.into_iter()));
// Explicitly specified region bound. Use that.
let region_bound = if !lifetime.is_elided() {
self.ast_region_to_region(lifetime, None)
} else {
self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
if tcx.named_region(hir_id).is_some() {
self.ast_region_to_region(lifetime, None)
} else {
self.re_infer(span, None).unwrap_or_else(|| {
span_err!(tcx.sess, span, E0228,
"the lifetime bound for this object type cannot be deduced \
from context; please supply an explicit bound");
tcx.types.re_static
})
}
})
};
debug!("region_bound: {:?}", region_bound);
let ty = tcx.mk_dynamic(existential_predicates, region_bound);
debug!("trait_object_type: {:?}", ty);
ty
}
fn report_ambiguous_associated_type(&self,
span: Span,
type_str: &str,
trait_str: &str,
name: &str) {
struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
.span_suggestion_with_applicability(
span,
"use fully-qualified syntax",
format!("<{} as {}>::{}", type_str, trait_str, name),
Applicability::HasPlaceholders
).emit();
}
// Search for a bound on a type parameter which includes the associated item
// given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
// This function will fail if there are no suitable bounds or there is
// any ambiguity.
fn find_bound_for_assoc_item(&self,
ty_param_def_id: DefId,
assoc_name: ast::Ident,
span: Span)
-> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
{
let tcx = self.tcx();
let bounds: Vec<_> = self.get_type_parameter_bounds(span, ty_param_def_id)
.predicates.into_iter().filter_map(|(p, _)| p.to_opt_poly_trait_ref()).collect();
// Check that there is exactly one way to find an associated type with the
// correct name.
let suitable_bounds = traits::transitive_bounds(tcx, &bounds)
.filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
let param_node_id = tcx.hir.as_local_node_id(ty_param_def_id).unwrap();
let param_name = tcx.hir.ty_param_name(param_node_id);
self.one_bound_for_assoc_type(suitable_bounds,
&param_name.as_str(),
assoc_name,
span)
}
// Checks that bounds contains exactly one element and reports appropriate
// errors otherwise.
fn one_bound_for_assoc_type<I>(&self,
mut bounds: I,
ty_param_name: &str,
assoc_name: ast::Ident,
span: Span)
-> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
{
let bound = match bounds.next() {
Some(bound) => bound,
None => {
struct_span_err!(self.tcx().sess, span, E0220,
"associated type `{}` not found for `{}`",
assoc_name,
ty_param_name)
.span_label(span, format!("associated type `{}` not found", assoc_name))
.emit();
return Err(ErrorReported);
}
};
if let Some(bound2) = bounds.next() {
let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
let mut err = struct_span_err!(
self.tcx().sess, span, E0221,
"ambiguous associated type `{}` in bounds of `{}`",
assoc_name,
ty_param_name);
err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
for bound in bounds {
let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
item.kind == ty::AssociatedKind::Type &&
self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
})
.and_then(|item| self.tcx().hir.span_if_local(item.def_id));
if let Some(span) = bound_span {
err.span_label(span, format!("ambiguous `{}` from `{}`",
assoc_name,
bound));
} else {
span_note!(&mut err, span,
"associated type `{}` could derive from `{}`",
ty_param_name,
bound);
}
}
err.emit();
}
return Ok(bound);
}
// Create a type from a path to an associated type.
// For a path A::B::C::D, ty and ty_path_def are the type and def for A::B::C
// and item_segment is the path segment for D. We return a type and a def for
// the whole path.
// Will fail except for T::A and Self::A; i.e., if ty/ty_path_def are not a type
// parameter or Self.
pub fn associated_path_def_to_ty(&self,
ref_id: ast::NodeId,
span: Span,
ty: Ty<'tcx>,
ty_path_def: Def,
item_segment: &hir::PathSegment)
-> (Ty<'tcx>, Def)
{
let tcx = self.tcx();
let assoc_name = item_segment.ident;
debug!("associated_path_def_to_ty: {:?}::{}", ty, assoc_name);
self.prohibit_generics(slice::from_ref(item_segment));
// Find the type of the associated item, and the trait where the associated
// item is declared.
let bound = match (&ty.sty, ty_path_def) {
(_, Def::SelfTy(Some(_), Some(impl_def_id))) => {
// `Self` in an impl of a trait - we have a concrete self type and a
// trait reference.
let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
Some(trait_ref) => trait_ref,
None => {
// A cycle error occurred, most likely.
return (tcx.types.err, Def::Err);
}
};
let candidates = traits::supertraits(tcx, ty::Binder::bind(trait_ref))
.filter(|r| self.trait_defines_associated_type_named(r.def_id(), assoc_name));
match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
Ok(bound) => bound,
Err(ErrorReported) => return (tcx.types.err, Def::Err),
}
}
(&ty::Param(_), Def::SelfTy(Some(param_did), None)) |
(&ty::Param(_), Def::TyParam(param_did)) => {
match self.find_bound_for_assoc_item(param_did, assoc_name, span) {
Ok(bound) => bound,
Err(ErrorReported) => return (tcx.types.err, Def::Err),
}
}
_ => {
// Don't print TyErr to the user.
if !ty.references_error() {
self.report_ambiguous_associated_type(span,
&ty.to_string(),
"Trait",
&assoc_name.as_str());
}
return (tcx.types.err, Def::Err);
}
};
let trait_did = bound.def_id();
let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_name, trait_did, ref_id);
let item = tcx.associated_items(trait_did).find(|i| {
Namespace::from(i.kind) == Namespace::Type &&
i.ident.modern() == assoc_ident
})
.expect("missing associated type");
let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
let ty = self.normalize_ty(span, ty);
let def = Def::AssociatedTy(item.def_id);
if !item.vis.is_accessible_from(def_scope, tcx) {
let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
tcx.sess.span_err(span, &msg);
}
tcx.check_stability(item.def_id, Some(ref_id), span);
(ty, def)
}
fn qpath_to_ty(&self,
span: Span,
opt_self_ty: Option<Ty<'tcx>>,
item_def_id: DefId,
trait_segment: &hir::PathSegment,
item_segment: &hir::PathSegment)
-> Ty<'tcx>
{
let tcx = self.tcx();
let trait_def_id = tcx.parent_def_id(item_def_id).unwrap();
self.prohibit_generics(slice::from_ref(item_segment));
let self_ty = if let Some(ty) = opt_self_ty {
ty
} else {
let path_str = tcx.item_path_str(trait_def_id);
self.report_ambiguous_associated_type(span,
"Type",
&path_str,
&item_segment.ident.as_str());
return tcx.types.err;
};
debug!("qpath_to_ty: self_type={:?}", self_ty);
let trait_ref = self.ast_path_to_mono_trait_ref(span,
trait_def_id,
self_ty,
trait_segment);
debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
}
pub fn prohibit_generics<'a, T: IntoIterator<Item = &'a hir::PathSegment>>(&self, segments: T) {
for segment in segments {
segment.with_generic_args(|generic_args| {
let (mut err_for_lt, mut err_for_ty) = (false, false);
for arg in &generic_args.args {
let (mut span_err, span, kind) = match arg {
hir::GenericArg::Lifetime(lt) => {
if err_for_lt { continue }
err_for_lt = true;
(struct_span_err!(self.tcx().sess, lt.span, E0110,
"lifetime parameters are not allowed on this type"),
lt.span,
"lifetime")
}
hir::GenericArg::Type(ty) => {
if err_for_ty { continue }
err_for_ty = true;
(struct_span_err!(self.tcx().sess, ty.span, E0109,
"type parameters are not allowed on this type"),
ty.span,
"type")
}
};
span_err.span_label(span, format!("{} parameter not allowed", kind))
.emit();
if err_for_lt && err_for_ty {
break;
}
}
for binding in &generic_args.bindings {
Self::prohibit_assoc_ty_binding(self.tcx(), binding.span);
break;
}
})
}
}
pub fn prohibit_assoc_ty_binding(tcx: TyCtxt, span: Span) {
let mut err = struct_span_err!(tcx.sess, span, E0229,
"associated type bindings are not allowed here");
err.span_label(span, "associated type not allowed here").emit();
}
// Check a type Path and convert it to a Ty.
pub fn def_to_ty(&self,
opt_self_ty: Option<Ty<'tcx>>,
path: &hir::Path,
permit_variants: bool)
-> Ty<'tcx> {
let tcx = self.tcx();
debug!("def_to_ty(def={:?}, opt_self_ty={:?}, path_segments={:?})",
path.def, opt_self_ty, path.segments);
let span = path.span;
match path.def {
Def::Existential(did) => {
// check for desugared impl trait
assert!(ty::is_impl_trait_defn(tcx, did).is_none());
let item_segment = path.segments.split_last().unwrap();
self.prohibit_generics(item_segment.1);
let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
self.normalize_ty(
span,
tcx.mk_opaque(did, substs),
)
}
Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) |
Def::Union(did) | Def::ForeignTy(did) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.split_last().unwrap().1);
self.ast_path_to_ty(span, did, path.segments.last().unwrap())
}
Def::Variant(did) if permit_variants => {
// Convert "variant type" as if it were a real type.
// The resulting `Ty` is type of the variant's enum for now.
assert_eq!(opt_self_ty, None);
self.prohibit_generics(path.segments.split_last().unwrap().1);
self.ast_path_to_ty(span,
tcx.parent_def_id(did).unwrap(),
path.segments.last().unwrap())
}
Def::TyParam(did) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(&path.segments);
let node_id = tcx.hir.as_local_node_id(did).unwrap();
let item_id = tcx.hir.get_parent_node(node_id);
let item_def_id = tcx.hir.local_def_id(item_id);
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&tcx.hir.local_def_id(node_id)];
tcx.mk_ty_param(index, tcx.hir.name(node_id).as_interned_str())
}
Def::SelfTy(_, Some(def_id)) => {
// Self in impl (we know the concrete type).
assert_eq!(opt_self_ty, None);
self.prohibit_generics(&path.segments);
tcx.at(span).type_of(def_id)
}
Def::SelfTy(Some(_), None) => {
// Self in trait.
assert_eq!(opt_self_ty, None);
self.prohibit_generics(&path.segments);
tcx.mk_self_type()
}
Def::AssociatedTy(def_id) => {
self.prohibit_generics(&path.segments[..path.segments.len()-2]);
self.qpath_to_ty(span,
opt_self_ty,
def_id,
&path.segments[path.segments.len()-2],
path.segments.last().unwrap())
}
Def::PrimTy(prim_ty) => {
assert_eq!(opt_self_ty, None);
self.prohibit_generics(&path.segments);
match prim_ty {
hir::Bool => tcx.types.bool,
hir::Char => tcx.types.char,
hir::Int(it) => tcx.mk_mach_int(it),
hir::Uint(uit) => tcx.mk_mach_uint(uit),
hir::Float(ft) => tcx.mk_mach_float(ft),
hir::Str => tcx.mk_str()
}
}
Def::Err => {
self.set_tainted_by_errors();
return self.tcx().types.err;
}
_ => span_bug!(span, "unexpected definition: {:?}", path.def)
}
}
/// Parses the programmer's textual representation of a type into our
/// internal notion of a type.
pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
debug!("ast_ty_to_ty(id={:?}, ast_ty={:?})",
ast_ty.id, ast_ty);
let tcx = self.tcx();
let result_ty = match ast_ty.node {
hir::TyKind::Slice(ref ty) => {
tcx.mk_slice(self.ast_ty_to_ty(&ty))
}
hir::TyKind::Ptr(ref mt) => {
tcx.mk_ptr(ty::TypeAndMut {
ty: self.ast_ty_to_ty(&mt.ty),
mutbl: mt.mutbl
})
}
hir::TyKind::Rptr(ref region, ref mt) => {
let r = self.ast_region_to_region(region, None);
debug!("Ref r={:?}", r);
let t = self.ast_ty_to_ty(&mt.ty);
tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
}
hir::TyKind::Never => {
tcx.types.never
},
hir::TyKind::Tup(ref fields) => {
tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)))
}
hir::TyKind::BareFn(ref bf) => {
require_c_abi_if_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
}
hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
}
hir::TyKind::Path(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
let opt_self_ty = maybe_qself.as_ref().map(|qself| {
self.ast_ty_to_ty(qself)
});
self.def_to_ty(opt_self_ty, path, false)
}
hir::TyKind::Def(item_id, ref lifetimes) => {
let did = tcx.hir.local_def_id(item_id.id);
self.impl_trait_ty_to_ty(did, lifetimes)
},
hir::TyKind::Path(hir::QPath::TypeRelative(ref qself, ref segment)) => {
debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
let ty = self.ast_ty_to_ty(qself);
let def = if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = qself.node {
path.def
} else {
Def::Err
};
self.associated_path_def_to_ty(ast_ty.id, ast_ty.span, ty, def, segment).0
}
hir::TyKind::Array(ref ty, ref length) => {
let length_def_id = tcx.hir.local_def_id(length.id);
let substs = Substs::identity_for_item(tcx, length_def_id);
let length = ty::Const::unevaluated(tcx, length_def_id, substs, tcx.types.usize);
let array_ty = tcx.mk_ty(ty::Array(self.ast_ty_to_ty(&ty), length));
self.normalize_ty(ast_ty.span, array_ty)
}
hir::TyKind::Typeof(ref _e) => {
struct_span_err!(tcx.sess, ast_ty.span, E0516,
"`typeof` is a reserved keyword but unimplemented")
.span_label(ast_ty.span, "reserved keyword")
.emit();
tcx.types.err
}
hir::TyKind::Infer => {
// Infer also appears as the type of arguments or return
// values in a ExprKind::Closure, or as
// the type of local variables. Both of these cases are
// handled specially and will not descend into this routine.
self.ty_infer(ast_ty.span)
}
hir::TyKind::Err => {
tcx.types.err
}
};
self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
result_ty
}
pub fn impl_trait_ty_to_ty(
&self,
def_id: DefId,
lifetimes: &[hir::GenericArg],
) -> Ty<'tcx> {
debug!("impl_trait_ty_to_ty(def_id={:?}, lifetimes={:?})", def_id, lifetimes);
let tcx = self.tcx();
let generics = tcx.generics_of(def_id);
debug!("impl_trait_ty_to_ty: generics={:?}", generics);
let substs = Substs::for_item(tcx, def_id, |param, _| {
if let Some(i) = (param.index as usize).checked_sub(generics.parent_count) {
// Our own parameters are the resolved lifetimes.
match param.kind {
GenericParamDefKind::Lifetime => {
if let hir::GenericArg::Lifetime(lifetime) = &lifetimes[i] {
self.ast_region_to_region(lifetime, None).into()
} else {
bug!()
}
}
_ => bug!()
}
} else {
// Replace all parent lifetimes with 'static.
match param.kind {
GenericParamDefKind::Lifetime => {
tcx.types.re_static.into()
}
_ => tcx.mk_param_from_def(param)
}
}
});
debug!("impl_trait_ty_to_ty: final substs = {:?}", substs);
let ty = tcx.mk_opaque(def_id, substs);
debug!("impl_trait_ty_to_ty: {}", ty);
ty
}
pub fn ty_of_arg(&self,
ty: &hir::Ty,
expected_ty: Option<Ty<'tcx>>)
-> Ty<'tcx>
{
match ty.node {
hir::TyKind::Infer if expected_ty.is_some() => {
self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
expected_ty.unwrap()
}
_ => self.ast_ty_to_ty(ty),
}
}
pub fn ty_of_fn(&self,
unsafety: hir::Unsafety,
abi: abi::Abi,
decl: &hir::FnDecl)
-> ty::PolyFnSig<'tcx> {
debug!("ty_of_fn");
let tcx = self.tcx();
let input_tys =
decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
let output_ty = match decl.output {
hir::Return(ref output) => self.ast_ty_to_ty(output),
hir::DefaultReturn(..) => tcx.mk_unit(),
};
debug!("ty_of_fn: output_ty={:?}", output_ty);
let bare_fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
input_tys,
output_ty,
decl.variadic,
unsafety,
abi
));
// Find any late-bound regions declared in return type that do
// not appear in the arguments. These are not well-formed.
//
// Example:
// for<'a> fn() -> &'a str <-- 'a is bad
// for<'a> fn(&'a String) -> &'a str <-- 'a is ok
let inputs = bare_fn_ty.inputs();
let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
&inputs.map_bound(|i| i.to_owned()));
let output = bare_fn_ty.output();
let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
for br in late_bound_in_ret.difference(&late_bound_in_args) {
let lifetime_name = match *br {
ty::BrNamed(_, name) => format!("lifetime `{}`,", name),
ty::BrAnon(_) | ty::BrFresh(_) | ty::BrEnv => "an anonymous lifetime".to_string(),
};
let mut err = struct_span_err!(tcx.sess,
decl.output.span(),
E0581,
"return type references {} \
which is not constrained by the fn input types",
lifetime_name);
if let ty::BrAnon(_) = *br {
// The only way for an anonymous lifetime to wind up
// in the return type but **also** be unconstrained is
// if it only appears in "associated types" in the
// input. See #47511 for an example. In this case,
// though we can easily give a hint that ought to be
// relevant.
err.note("lifetimes appearing in an associated type \
are not considered constrained");
}
err.emit();
}
bare_fn_ty
}
/// Given the bounds on an object, determines what single region bound (if any) we can
/// use to summarize this type. The basic idea is that we will use the bound the user
/// provided, if they provided one, and otherwise search the supertypes of trait bounds
/// for region bounds. It may be that we can derive no bound at all, in which case
/// we return `None`.
fn compute_object_lifetime_bound(&self,
span: Span,
existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>)
-> Option<ty::Region<'tcx>> // if None, use the default
{
let tcx = self.tcx();
debug!("compute_opt_region_bound(existential_predicates={:?})",
existential_predicates);
// No explicit region bound specified. Therefore, examine trait
// bounds and see if we can derive region bounds from those.
let derived_region_bounds =
object_region_bounds(tcx, existential_predicates);
// If there are no derived region bounds, then report back that we
// can find no region bound. The caller will use the default.
if derived_region_bounds.is_empty() {
return None;
}
// If any of the derived region bounds are 'static, that is always
// the best choice.
if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
return Some(tcx.types.re_static);
}
// Determine whether there is exactly one unique region in the set
// of derived region bounds. If so, use that. Otherwise, report an
// error.
let r = derived_region_bounds[0];
if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
span_err!(tcx.sess, span, E0227,
"ambiguous lifetime bound, explicit lifetime bound required");
}
return Some(r);
}
}
/// Divides a list of general trait bounds into two groups: auto traits (e.g. Sync and Send) and the
/// remaining general trait bounds.
fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
trait_bounds: &'b [hir::PolyTraitRef])
-> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
{
let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
// Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
match bound.trait_ref.path.def {
Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
true
}
_ => false
}
});
let auto_traits = auto_traits.into_iter().map(|tr| {
if let Def::Trait(trait_did) = tr.trait_ref.path.def {
trait_did
} else {
unreachable!()
}
}).collect::<Vec<_>>();
(auto_traits, trait_bounds)
}
// A helper struct for conveniently grouping a set of bounds which we pass to
// and return from functions in multiple places.
#[derive(PartialEq, Eq, Clone, Debug)]
pub struct Bounds<'tcx> {
pub region_bounds: Vec<(ty::Region<'tcx>, Span)>,
pub implicitly_sized: Option<Span>,
pub trait_bounds: Vec<(ty::PolyTraitRef<'tcx>, Span)>,
pub projection_bounds: Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>,
}
impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
-> Vec<(ty::Predicate<'tcx>, Span)>
{
// If it could be sized, and is, add the sized predicate
let sized_predicate = self.implicitly_sized.and_then(|span| {
tcx.lang_items().sized_trait().map(|sized| {
let trait_ref = ty::TraitRef {
def_id: sized,
substs: tcx.mk_substs_trait(param_ty, &[])
};
(trait_ref.to_predicate(), span)
})
});
sized_predicate.into_iter().chain(
self.region_bounds.iter().map(|&(region_bound, span)| {
// account for the binder being introduced below; no need to shift `param_ty`
// because, at present at least, it can only refer to early-bound regions
let region_bound = tcx.mk_region(ty::fold::shift_region(*region_bound, 1));
let outlives = ty::OutlivesPredicate(param_ty, region_bound);
(ty::Binder::dummy(outlives).to_predicate(), span)
}).chain(
self.trait_bounds.iter().map(|&(bound_trait_ref, span)| {
(bound_trait_ref.to_predicate(), span)
})
).chain(
self.projection_bounds.iter().map(|&(projection, span)| {
(projection.to_predicate(), span)
})
)
).collect()
}
}