1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358
mod _impl;
mod adjust_fulfillment_errors;
mod arg_matrix;
mod checks;
mod suggestions;
use rustc_errors::ErrorGuaranteed;
use crate::coercion::DynamicCoerceMany;
use crate::{Diverges, EnclosingBreakables, Inherited};
use rustc_hir as hir;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_hir_analysis::astconv::AstConv;
use rustc_infer::infer;
use rustc_infer::infer::error_reporting::TypeErrCtxt;
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
use rustc_middle::ty::{self, Const, Ty, TyCtxt, TypeVisitableExt};
use rustc_session::Session;
use rustc_span::symbol::Ident;
use rustc_span::{self, Span, DUMMY_SP};
use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode, ObligationCtxt};
use std::cell::{Cell, RefCell};
use std::ops::Deref;
/// The `FnCtxt` stores type-checking context needed to type-check bodies of
/// functions, closures, and `const`s, including performing type inference
/// with [`InferCtxt`].
///
/// This is in contrast to [`ItemCtxt`], which is used to type-check item *signatures*
/// and thus does not perform type inference.
///
/// See [`ItemCtxt`]'s docs for more.
///
/// [`ItemCtxt`]: rustc_hir_analysis::collect::ItemCtxt
/// [`InferCtxt`]: infer::InferCtxt
pub struct FnCtxt<'a, 'tcx> {
pub(super) body_id: LocalDefId,
/// The parameter environment used for proving trait obligations
/// in this function. This can change when we descend into
/// closures (as they bring new things into scope), hence it is
/// not part of `Inherited` (as of the time of this writing,
/// closures do not yet change the environment, but they will
/// eventually).
pub(super) param_env: ty::ParamEnv<'tcx>,
/// Number of errors that had been reported when we started
/// checking this function. On exit, if we find that *more* errors
/// have been reported, we will skip regionck and other work that
/// expects the types within the function to be consistent.
// FIXME(matthewjasper) This should not exist, and it's not correct
// if type checking is run in parallel.
err_count_on_creation: usize,
/// If `Some`, this stores coercion information for returned
/// expressions. If `None`, this is in a context where return is
/// inappropriate, such as a const expression.
///
/// This is a `RefCell<DynamicCoerceMany>`, which means that we
/// can track all the return expressions and then use them to
/// compute a useful coercion from the set, similar to a match
/// expression or other branching context. You can use methods
/// like `expected_ty` to access the declared return type (if
/// any).
pub(super) ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
/// First span of a return site that we find. Used in error messages.
pub(super) ret_coercion_span: Cell<Option<Span>>,
pub(super) resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>,
/// Whether the last checked node generates a divergence (e.g.,
/// `return` will set this to `Always`). In general, when entering
/// an expression or other node in the tree, the initial value
/// indicates whether prior parts of the containing expression may
/// have diverged. It is then typically set to `Maybe` (and the
/// old value remembered) for processing the subparts of the
/// current expression. As each subpart is processed, they may set
/// the flag to `Always`, etc. Finally, at the end, we take the
/// result and "union" it with the original value, so that when we
/// return the flag indicates if any subpart of the parent
/// expression (up to and including this part) has diverged. So,
/// if you read it after evaluating a subexpression `X`, the value
/// you get indicates whether any subexpression that was
/// evaluating up to and including `X` diverged.
///
/// We currently use this flag only for diagnostic purposes:
///
/// - To warn about unreachable code: if, after processing a
/// sub-expression but before we have applied the effects of the
/// current node, we see that the flag is set to `Always`, we
/// can issue a warning. This corresponds to something like
/// `foo(return)`; we warn on the `foo()` expression. (We then
/// update the flag to `WarnedAlways` to suppress duplicate
/// reports.) Similarly, if we traverse to a fresh statement (or
/// tail expression) from an `Always` setting, we will issue a
/// warning. This corresponds to something like `{return;
/// foo();}` or `{return; 22}`, where we would warn on the
/// `foo()` or `22`.
///
/// An expression represents dead code if, after checking it,
/// the diverges flag is set to something other than `Maybe`.
pub(super) diverges: Cell<Diverges>,
pub(super) enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
pub(super) inh: &'a Inherited<'tcx>,
pub(super) fallback_has_occurred: Cell<bool>,
}
impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
pub fn new(
inh: &'a Inherited<'tcx>,
param_env: ty::ParamEnv<'tcx>,
body_id: LocalDefId,
) -> FnCtxt<'a, 'tcx> {
FnCtxt {
body_id,
param_env,
err_count_on_creation: inh.tcx.sess.err_count(),
ret_coercion: None,
ret_coercion_span: Cell::new(None),
resume_yield_tys: None,
diverges: Cell::new(Diverges::Maybe),
enclosing_breakables: RefCell::new(EnclosingBreakables {
stack: Vec::new(),
by_id: Default::default(),
}),
inh,
fallback_has_occurred: Cell::new(false),
}
}
pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
ObligationCause::new(span, self.body_id, code)
}
pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
self.cause(span, ObligationCauseCode::MiscObligation)
}
pub fn sess(&self) -> &Session {
self.tcx.sess
}
/// Creates an `TypeErrCtxt` with a reference to the in-progress
/// `TypeckResults` which is used for diagnostics.
/// Use [`InferCtxt::err_ctxt`] to start one without a `TypeckResults`.
///
/// [`InferCtxt::err_ctxt`]: infer::InferCtxt::err_ctxt
pub fn err_ctxt(&'a self) -> TypeErrCtxt<'a, 'tcx> {
TypeErrCtxt {
infcx: &self.infcx,
typeck_results: Some(self.typeck_results.borrow()),
fallback_has_occurred: self.fallback_has_occurred.get(),
normalize_fn_sig: Box::new(|fn_sig| {
if fn_sig.has_escaping_bound_vars() {
return fn_sig;
}
self.probe(|_| {
let ocx = ObligationCtxt::new(self);
let normalized_fn_sig =
ocx.normalize(&ObligationCause::dummy(), self.param_env, fn_sig);
if ocx.select_all_or_error().is_empty() {
let normalized_fn_sig = self.resolve_vars_if_possible(normalized_fn_sig);
if !normalized_fn_sig.has_infer() {
return normalized_fn_sig;
}
}
fn_sig
})
}),
autoderef_steps: Box::new(|ty| {
let mut autoderef = self.autoderef(DUMMY_SP, ty).silence_errors();
let mut steps = vec![];
while let Some((ty, _)) = autoderef.next() {
steps.push((ty, autoderef.current_obligations()));
}
steps
}),
}
}
pub fn errors_reported_since_creation(&self) -> bool {
self.tcx.sess.err_count() > self.err_count_on_creation
}
pub fn next_root_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
Ty::new_var(self.tcx, self.next_ty_var_id_in_universe(origin, ty::UniverseIndex::ROOT))
}
}
impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
type Target = Inherited<'tcx>;
fn deref(&self) -> &Self::Target {
self.inh
}
}
impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
self.tcx
}
fn item_def_id(&self) -> DefId {
self.body_id.to_def_id()
}
fn get_type_parameter_bounds(
&self,
_: Span,
def_id: LocalDefId,
_: Ident,
) -> ty::GenericPredicates<'tcx> {
let tcx = self.tcx;
let item_def_id = tcx.hir().ty_param_owner(def_id);
let generics = tcx.generics_of(item_def_id);
let index = generics.param_def_id_to_index[&def_id.to_def_id()];
// HACK(eddyb) should get the original `Span`.
let span = tcx.def_span(def_id);
ty::GenericPredicates {
parent: None,
predicates: tcx.arena.alloc_from_iter(
self.param_env.caller_bounds().iter().filter_map(|predicate| {
match predicate.kind().skip_binder() {
ty::ClauseKind::Trait(data) if data.self_ty().is_param(index) => {
Some((predicate, span))
}
_ => None,
}
}),
),
}
}
fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
let v = match def {
Some(def) => infer::RegionParameterDefinition(span, def.name),
None => infer::MiscVariable(span),
};
Some(self.next_region_var(v))
}
fn allow_ty_infer(&self) -> bool {
true
}
fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
match param {
Some(param) => self.var_for_def(span, param).as_type().unwrap(),
None => self.next_ty_var(TypeVariableOrigin {
kind: TypeVariableOriginKind::TypeInference,
span,
}),
}
}
fn ct_infer(
&self,
ty: Ty<'tcx>,
param: Option<&ty::GenericParamDef>,
span: Span,
) -> Const<'tcx> {
// FIXME ideally this shouldn't use unwrap
match param {
Some(
param @ ty::GenericParamDef {
kind: ty::GenericParamDefKind::Const { is_host_effect: true, .. },
..
},
) => self.var_for_effect(param).as_const().unwrap(),
Some(param) => self.var_for_def(span, param).as_const().unwrap(),
None => self.next_const_var(
ty,
ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
),
}
}
fn projected_ty_from_poly_trait_ref(
&self,
span: Span,
item_def_id: DefId,
item_segment: &hir::PathSegment<'_>,
poly_trait_ref: ty::PolyTraitRef<'tcx>,
) -> Ty<'tcx> {
let trait_ref = self.instantiate_binder_with_fresh_vars(
span,
infer::BoundRegionConversionTime::AssocTypeProjection(item_def_id),
poly_trait_ref,
);
let item_args = self.astconv().create_args_for_associated_item(
span,
item_def_id,
item_segment,
trait_ref.args,
);
Ty::new_projection(self.tcx(), item_def_id, item_args)
}
fn probe_adt(&self, span: Span, ty: Ty<'tcx>) -> Option<ty::AdtDef<'tcx>> {
match ty.kind() {
ty::Adt(adt_def, _) => Some(*adt_def),
// FIXME(#104767): Should we handle bound regions here?
ty::Alias(ty::Projection | ty::Inherent | ty::Weak, _)
if !ty.has_escaping_bound_vars() =>
{
self.normalize(span, ty).ty_adt_def()
}
_ => None,
}
}
fn set_tainted_by_errors(&self, e: ErrorGuaranteed) {
self.infcx.set_tainted_by_errors(e)
}
fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span) {
// FIXME: normalization and escaping regions
let ty = if !ty.has_escaping_bound_vars() {
// NOTE: These obligations are 100% redundant and are implied by
// WF obligations that are registered elsewhere, but they have a
// better cause code assigned to them in `add_required_obligations_for_hir`.
// This means that they should shadow obligations with worse spans.
if let ty::Alias(ty::Projection | ty::Weak, ty::AliasTy { args, def_id, .. }) =
ty.kind()
{
self.add_required_obligations_for_hir(span, *def_id, args, hir_id);
}
self.normalize(span, ty)
} else {
ty
};
self.write_ty(hir_id, ty)
}
fn infcx(&self) -> Option<&infer::InferCtxt<'tcx>> {
Some(&self.infcx)
}
}
/// Represents a user-provided type in the raw form (never normalized).
///
/// This is a bridge between the interface of `AstConv`, which outputs a raw `Ty`,
/// and the API in this module, which expect `Ty` to be fully normalized.
#[derive(Clone, Copy, Debug)]
pub struct RawTy<'tcx> {
pub raw: Ty<'tcx>,
/// The normalized form of `raw`, stored here for efficiency.
pub normalized: Ty<'tcx>,
}