7 pub use suggestions::*;
9 use crate::astconv::AstConv;
10 use crate::check::coercion::DynamicCoerceMany;
11 use crate::check::{Diverges, EnclosingBreakables, Inherited, UnsafetyState};
14 use rustc_hir::def_id::DefId;
15 use rustc_infer::infer;
16 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
17 use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
18 use rustc_middle::ty::fold::TypeFoldable;
19 use rustc_middle::ty::subst::GenericArgKind;
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 pub struct FnCtxt<'a, 'tcx> {
30 pub(super) body_id: hir::HirId,
32 /// The parameter environment used for proving trait obligations
33 /// in this function. This can change when we descend into
34 /// closures (as they bring new things into scope), hence it is
35 /// not part of `Inherited` (as of the time of this writing,
36 /// closures do not yet change the environment, but they will
38 pub(super) param_env: ty::ParamEnv<'tcx>,
40 /// Number of errors that had been reported when we started
41 /// checking this function. On exit, if we find that *more* errors
42 /// have been reported, we will skip regionck and other work that
43 /// expects the types within the function to be consistent.
44 // FIXME(matthewjasper) This should not exist, and it's not correct
45 // if type checking is run in parallel.
46 err_count_on_creation: usize,
48 /// If `Some`, this stores coercion information for returned
49 /// expressions. If `None`, this is in a context where return is
50 /// inappropriate, such as a const expression.
52 /// This is a `RefCell<DynamicCoerceMany>`, which means that we
53 /// can track all the return expressions and then use them to
54 /// compute a useful coercion from the set, similar to a match
55 /// expression or other branching context. You can use methods
56 /// like `expected_ty` to access the declared return type (if
58 pub(super) ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
60 pub(super) ret_type_span: Option<Span>,
62 /// Used exclusively to reduce cost of advanced evaluation used for
63 /// more helpful diagnostics.
64 pub(super) in_tail_expr: bool,
66 /// First span of a return site that we find. Used in error messages.
67 pub(super) ret_coercion_span: Cell<Option<Span>>,
69 pub(super) resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>,
71 pub(super) ps: Cell<UnsafetyState>,
73 /// Whether the last checked node generates a divergence (e.g.,
74 /// `return` will set this to `Always`). In general, when entering
75 /// an expression or other node in the tree, the initial value
76 /// indicates whether prior parts of the containing expression may
77 /// have diverged. It is then typically set to `Maybe` (and the
78 /// old value remembered) for processing the subparts of the
79 /// current expression. As each subpart is processed, they may set
80 /// the flag to `Always`, etc. Finally, at the end, we take the
81 /// result and "union" it with the original value, so that when we
82 /// return the flag indicates if any subpart of the parent
83 /// expression (up to and including this part) has diverged. So,
84 /// if you read it after evaluating a subexpression `X`, the value
85 /// you get indicates whether any subexpression that was
86 /// evaluating up to and including `X` diverged.
88 /// We currently use this flag only for diagnostic purposes:
90 /// - To warn about unreachable code: if, after processing a
91 /// sub-expression but before we have applied the effects of the
92 /// current node, we see that the flag is set to `Always`, we
93 /// can issue a warning. This corresponds to something like
94 /// `foo(return)`; we warn on the `foo()` expression. (We then
95 /// update the flag to `WarnedAlways` to suppress duplicate
96 /// reports.) Similarly, if we traverse to a fresh statement (or
97 /// tail expression) from an `Always` setting, we will issue a
98 /// warning. This corresponds to something like `{return;
99 /// foo();}` or `{return; 22}`, where we would warn on the
102 /// An expression represents dead code if, after checking it,
103 /// the diverges flag is set to something other than `Maybe`.
104 pub(super) diverges: Cell<Diverges>,
106 /// Whether any child nodes have any type errors.
107 pub(super) has_errors: Cell<bool>,
109 pub(super) enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
111 pub(super) inh: &'a Inherited<'a, 'tcx>,
113 /// True if the function or closure's return type is known before
114 /// entering the function/closure, i.e. if the return type is
115 /// either given explicitly or inferred from, say, an `Fn*` trait
116 /// bound. Used for diagnostic purposes only.
117 pub(super) return_type_pre_known: bool,
120 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
122 inh: &'a Inherited<'a, 'tcx>,
123 param_env: ty::ParamEnv<'tcx>,
125 ) -> FnCtxt<'a, 'tcx> {
129 err_count_on_creation: inh.tcx.sess.err_count(),
133 ret_coercion_span: Cell::new(None),
134 resume_yield_tys: None,
135 ps: Cell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)),
136 diverges: Cell::new(Diverges::Maybe),
137 has_errors: Cell::new(false),
138 enclosing_breakables: RefCell::new(EnclosingBreakables {
140 by_id: Default::default(),
143 return_type_pre_known: true,
147 pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
148 ObligationCause::new(span, self.body_id, code)
151 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
152 self.cause(span, ObligationCauseCode::MiscObligation)
155 pub fn sess(&self) -> &Session {
159 pub fn errors_reported_since_creation(&self) -> bool {
160 self.tcx.sess.err_count() > self.err_count_on_creation
164 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
165 type Target = Inherited<'a, 'tcx>;
166 fn deref(&self) -> &Self::Target {
171 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
172 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
176 fn item_def_id(&self) -> Option<DefId> {
180 fn get_type_parameter_bounds(
185 ) -> ty::GenericPredicates<'tcx> {
187 let item_def_id = tcx.hir().ty_param_owner(def_id.expect_local());
188 let generics = tcx.generics_of(item_def_id);
189 let index = generics.param_def_id_to_index[&def_id];
190 ty::GenericPredicates {
192 predicates: tcx.arena.alloc_from_iter(
193 self.param_env.caller_bounds().iter().filter_map(|predicate| {
194 match predicate.kind().skip_binder() {
195 ty::PredicateKind::Trait(data) if data.self_ty().is_param(index) => {
196 // HACK(eddyb) should get the original `Span`.
197 let span = tcx.def_span(def_id);
198 Some((predicate, span))
207 fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
209 Some(def) => infer::EarlyBoundRegion(span, def.name),
210 None => infer::MiscVariable(span),
212 Some(self.next_region_var(v))
215 fn allow_ty_infer(&self) -> bool {
219 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
220 if let Some(param) = param {
221 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
226 self.next_ty_var(TypeVariableOrigin {
227 kind: TypeVariableOriginKind::TypeInference,
236 param: Option<&ty::GenericParamDef>,
239 if let Some(param) = param {
240 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
247 ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
252 fn projected_ty_from_poly_trait_ref(
256 item_segment: &hir::PathSegment<'_>,
257 poly_trait_ref: ty::PolyTraitRef<'tcx>,
259 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
261 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
265 let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
274 self.tcx().mk_projection(item_def_id, item_substs)
277 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
278 if ty.has_escaping_bound_vars() {
279 ty // FIXME: normalization and escaping regions
281 self.normalize_associated_types_in(span, ty)
285 fn set_tainted_by_errors(&self) {
286 self.infcx.set_tainted_by_errors()
289 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
290 self.write_ty(hir_id, ty)