7 pub use suggestions::*;
9 use crate::coercion::DynamicCoerceMany;
10 use crate::{Diverges, EnclosingBreakables, Inherited, UnsafetyState};
12 use rustc_hir::def_id::DefId;
13 use rustc_hir_analysis::astconv::AstConv;
14 use rustc_infer::infer;
15 use rustc_infer::infer::error_reporting::TypeErrCtxt;
16 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
17 use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
18 use rustc_middle::ty::subst::GenericArgKind;
19 use rustc_middle::ty::visit::TypeVisitable;
20 use rustc_middle::ty::{self, Const, Ty, TyCtxt};
21 use rustc_session::Session;
22 use rustc_span::symbol::Ident;
23 use rustc_span::{self, Span};
24 use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode};
26 use std::cell::{Cell, RefCell};
29 /// The `FnCtxt` stores type-checking context needed to type-check bodies of
30 /// functions, closures, and `const`s, including performing type inference
31 /// with [`InferCtxt`].
33 /// This is in contrast to [`ItemCtxt`], which is used to type-check item *signatures*
34 /// and thus does not perform type inference.
36 /// See [`ItemCtxt`]'s docs for more.
38 /// [`ItemCtxt`]: rustc_hir_analysis::collect::ItemCtxt
39 /// [`InferCtxt`]: infer::InferCtxt
40 pub struct FnCtxt<'a, 'tcx> {
41 pub(super) body_id: hir::HirId,
43 /// The parameter environment used for proving trait obligations
44 /// in this function. This can change when we descend into
45 /// closures (as they bring new things into scope), hence it is
46 /// not part of `Inherited` (as of the time of this writing,
47 /// closures do not yet change the environment, but they will
49 pub(super) param_env: ty::ParamEnv<'tcx>,
51 /// Number of errors that had been reported when we started
52 /// checking this function. On exit, if we find that *more* errors
53 /// have been reported, we will skip regionck and other work that
54 /// expects the types within the function to be consistent.
55 // FIXME(matthewjasper) This should not exist, and it's not correct
56 // if type checking is run in parallel.
57 err_count_on_creation: usize,
59 /// If `Some`, this stores coercion information for returned
60 /// expressions. If `None`, this is in a context where return is
61 /// inappropriate, such as a const expression.
63 /// This is a `RefCell<DynamicCoerceMany>`, which means that we
64 /// can track all the return expressions and then use them to
65 /// compute a useful coercion from the set, similar to a match
66 /// expression or other branching context. You can use methods
67 /// like `expected_ty` to access the declared return type (if
69 pub(super) ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
71 /// First span of a return site that we find. Used in error messages.
72 pub(super) ret_coercion_span: Cell<Option<Span>>,
74 pub(super) resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>,
76 pub(super) ps: Cell<UnsafetyState>,
78 /// Whether the last checked node generates a divergence (e.g.,
79 /// `return` will set this to `Always`). In general, when entering
80 /// an expression or other node in the tree, the initial value
81 /// indicates whether prior parts of the containing expression may
82 /// have diverged. It is then typically set to `Maybe` (and the
83 /// old value remembered) for processing the subparts of the
84 /// current expression. As each subpart is processed, they may set
85 /// the flag to `Always`, etc. Finally, at the end, we take the
86 /// result and "union" it with the original value, so that when we
87 /// return the flag indicates if any subpart of the parent
88 /// expression (up to and including this part) has diverged. So,
89 /// if you read it after evaluating a subexpression `X`, the value
90 /// you get indicates whether any subexpression that was
91 /// evaluating up to and including `X` diverged.
93 /// We currently use this flag only for diagnostic purposes:
95 /// - To warn about unreachable code: if, after processing a
96 /// sub-expression but before we have applied the effects of the
97 /// current node, we see that the flag is set to `Always`, we
98 /// can issue a warning. This corresponds to something like
99 /// `foo(return)`; we warn on the `foo()` expression. (We then
100 /// update the flag to `WarnedAlways` to suppress duplicate
101 /// reports.) Similarly, if we traverse to a fresh statement (or
102 /// tail expression) from an `Always` setting, we will issue a
103 /// warning. This corresponds to something like `{return;
104 /// foo();}` or `{return; 22}`, where we would warn on the
107 /// An expression represents dead code if, after checking it,
108 /// the diverges flag is set to something other than `Maybe`.
109 pub(super) diverges: Cell<Diverges>,
111 pub(super) enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
113 pub(super) inh: &'a Inherited<'tcx>,
115 pub(super) fallback_has_occurred: Cell<bool>,
118 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
120 inh: &'a Inherited<'tcx>,
121 param_env: ty::ParamEnv<'tcx>,
123 ) -> FnCtxt<'a, 'tcx> {
127 err_count_on_creation: inh.tcx.sess.err_count(),
129 ret_coercion_span: Cell::new(None),
130 resume_yield_tys: None,
131 ps: Cell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)),
132 diverges: Cell::new(Diverges::Maybe),
133 enclosing_breakables: RefCell::new(EnclosingBreakables {
135 by_id: Default::default(),
138 fallback_has_occurred: Cell::new(false),
142 pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
143 ObligationCause::new(span, self.body_id, code)
146 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
147 self.cause(span, ObligationCauseCode::MiscObligation)
150 pub fn sess(&self) -> &Session {
154 /// Creates an `TypeErrCtxt` with a reference to the in-progress
155 /// `TypeckResults` which is used for diagnostics.
156 /// Use [`InferCtxt::err_ctxt`] to start one without a `TypeckResults`.
158 /// [`InferCtxt::err_ctxt`]: infer::InferCtxt::err_ctxt
159 pub fn err_ctxt(&'a self) -> TypeErrCtxt<'a, 'tcx> {
162 typeck_results: Some(self.typeck_results.borrow()),
163 fallback_has_occurred: self.fallback_has_occurred.get(),
167 pub fn errors_reported_since_creation(&self) -> bool {
168 self.tcx.sess.err_count() > self.err_count_on_creation
172 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
173 type Target = Inherited<'tcx>;
174 fn deref(&self) -> &Self::Target {
179 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
180 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
184 fn item_def_id(&self) -> DefId {
185 self.body_id.owner.to_def_id()
188 fn get_type_parameter_bounds(
193 ) -> ty::GenericPredicates<'tcx> {
195 let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
196 let generics = tcx.generics_of(item_def_id);
197 let index = generics.param_def_id_to_index[&def_id];
198 ty::GenericPredicates {
200 predicates: tcx.arena.alloc_from_iter(
201 self.param_env.caller_bounds().iter().filter_map(|predicate| {
202 match predicate.kind().skip_binder() {
203 ty::PredicateKind::Trait(data) if data.self_ty().is_param(index) => {
204 // HACK(eddyb) should get the original `Span`.
205 let span = tcx.def_span(def_id);
206 Some((predicate, span))
215 fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
217 Some(def) => infer::EarlyBoundRegion(span, def.name),
218 None => infer::MiscVariable(span),
220 Some(self.next_region_var(v))
223 fn allow_ty_infer(&self) -> bool {
227 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
228 if let Some(param) = param {
229 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
234 self.next_ty_var(TypeVariableOrigin {
235 kind: TypeVariableOriginKind::TypeInference,
244 param: Option<&ty::GenericParamDef>,
247 if let Some(param) = param {
248 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
255 ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
260 fn projected_ty_from_poly_trait_ref(
264 item_segment: &hir::PathSegment<'_>,
265 poly_trait_ref: ty::PolyTraitRef<'tcx>,
267 let trait_ref = self.replace_bound_vars_with_fresh_vars(
269 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
273 let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
281 self.tcx().mk_projection(item_def_id, item_substs)
284 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
285 if ty.has_escaping_bound_vars() {
286 ty // FIXME: normalization and escaping regions
288 self.normalize_associated_types_in(span, ty)
292 fn set_tainted_by_errors(&self) {
293 self.infcx.set_tainted_by_errors()
296 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
297 self.write_ty(hir_id, ty)