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_infer::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
18 use rustc_middle::hir::map::blocks::FnLikeNode;
19 use rustc_middle::ty::fold::TypeFoldable;
20 use rustc_middle::ty::subst::GenericArgKind;
21 use rustc_middle::ty::{self, Const, Ty, TyCtxt};
22 use rustc_session::Session;
23 use rustc_span::symbol::Ident;
24 use rustc_span::{self, Span};
25 use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode};
27 use std::cell::{Cell, RefCell};
30 pub struct FnCtxt<'a, 'tcx> {
31 pub(super) body_id: hir::HirId,
33 /// The parameter environment used for proving trait obligations
34 /// in this function. This can change when we descend into
35 /// closures (as they bring new things into scope), hence it is
36 /// not part of `Inherited` (as of the time of this writing,
37 /// closures do not yet change the environment, but they will
39 pub(super) param_env: ty::ParamEnv<'tcx>,
41 /// Number of errors that had been reported when we started
42 /// checking this function. On exit, if we find that *more* errors
43 /// have been reported, we will skip regionck and other work that
44 /// expects the types within the function to be consistent.
45 // FIXME(matthewjasper) This should not exist, and it's not correct
46 // if type checking is run in parallel.
47 err_count_on_creation: usize,
49 /// If `Some`, this stores coercion information for returned
50 /// expressions. If `None`, this is in a context where return is
51 /// inappropriate, such as a const expression.
53 /// This is a `RefCell<DynamicCoerceMany>`, which means that we
54 /// can track all the return expressions and then use them to
55 /// compute a useful coercion from the set, similar to a match
56 /// expression or other branching context. You can use methods
57 /// like `expected_ty` to access the declared return type (if
59 pub(super) ret_coercion: Option<RefCell<DynamicCoerceMany<'tcx>>>,
61 pub(super) ret_coercion_impl_trait: Option<Ty<'tcx>>,
63 pub(super) ret_type_span: Option<Span>,
65 /// Used exclusively to reduce cost of advanced evaluation used for
66 /// more helpful diagnostics.
67 pub(super) in_tail_expr: bool,
69 /// First span of a return site that we find. Used in error messages.
70 pub(super) ret_coercion_span: Cell<Option<Span>>,
72 pub(super) resume_yield_tys: Option<(Ty<'tcx>, Ty<'tcx>)>,
74 pub(super) ps: Cell<UnsafetyState>,
76 /// Whether the last checked node generates a divergence (e.g.,
77 /// `return` will set this to `Always`). In general, when entering
78 /// an expression or other node in the tree, the initial value
79 /// indicates whether prior parts of the containing expression may
80 /// have diverged. It is then typically set to `Maybe` (and the
81 /// old value remembered) for processing the subparts of the
82 /// current expression. As each subpart is processed, they may set
83 /// the flag to `Always`, etc. Finally, at the end, we take the
84 /// result and "union" it with the original value, so that when we
85 /// return the flag indicates if any subpart of the parent
86 /// expression (up to and including this part) has diverged. So,
87 /// if you read it after evaluating a subexpression `X`, the value
88 /// you get indicates whether any subexpression that was
89 /// evaluating up to and including `X` diverged.
91 /// We currently use this flag only for diagnostic purposes:
93 /// - To warn about unreachable code: if, after processing a
94 /// sub-expression but before we have applied the effects of the
95 /// current node, we see that the flag is set to `Always`, we
96 /// can issue a warning. This corresponds to something like
97 /// `foo(return)`; we warn on the `foo()` expression. (We then
98 /// update the flag to `WarnedAlways` to suppress duplicate
99 /// reports.) Similarly, if we traverse to a fresh statement (or
100 /// tail expression) from a `Always` setting, we will issue a
101 /// warning. This corresponds to something like `{return;
102 /// foo();}` or `{return; 22}`, where we would warn on the
105 /// An expression represents dead code if, after checking it,
106 /// the diverges flag is set to something other than `Maybe`.
107 pub(super) diverges: Cell<Diverges>,
109 /// Whether any child nodes have any type errors.
110 pub(super) has_errors: Cell<bool>,
112 pub(super) enclosing_breakables: RefCell<EnclosingBreakables<'tcx>>,
114 pub(super) inh: &'a Inherited<'a, 'tcx>,
117 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
119 inh: &'a Inherited<'a, 'tcx>,
120 param_env: ty::ParamEnv<'tcx>,
122 ) -> FnCtxt<'a, 'tcx> {
126 err_count_on_creation: inh.tcx.sess.err_count(),
128 ret_coercion_impl_trait: None,
131 ret_coercion_span: Cell::new(None),
132 resume_yield_tys: None,
133 ps: Cell::new(UnsafetyState::function(hir::Unsafety::Normal, hir::CRATE_HIR_ID)),
134 diverges: Cell::new(Diverges::Maybe),
135 has_errors: Cell::new(false),
136 enclosing_breakables: RefCell::new(EnclosingBreakables {
138 by_id: Default::default(),
144 pub fn cause(&self, span: Span, code: ObligationCauseCode<'tcx>) -> ObligationCause<'tcx> {
145 ObligationCause::new(span, self.body_id, code)
148 pub fn misc(&self, span: Span) -> ObligationCause<'tcx> {
149 self.cause(span, ObligationCauseCode::MiscObligation)
152 pub fn sess(&self) -> &Session {
156 pub fn errors_reported_since_creation(&self) -> bool {
157 self.tcx.sess.err_count() > self.err_count_on_creation
161 impl<'a, 'tcx> Deref for FnCtxt<'a, 'tcx> {
162 type Target = Inherited<'a, 'tcx>;
163 fn deref(&self) -> &Self::Target {
168 impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
169 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
173 fn item_def_id(&self) -> Option<DefId> {
177 fn default_constness_for_trait_bounds(&self) -> hir::Constness {
178 // FIXME: refactor this into a method
179 let node = self.tcx.hir().get(self.body_id);
180 if let Some(fn_like) = FnLikeNode::from_node(node) {
183 hir::Constness::NotConst
187 fn get_type_parameter_bounds(
192 ) -> ty::GenericPredicates<'tcx> {
194 let hir_id = tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
195 let item_id = tcx.hir().ty_param_owner(hir_id);
196 let item_def_id = tcx.hir().local_def_id(item_id);
197 let generics = tcx.generics_of(item_def_id);
198 let index = generics.param_def_id_to_index[&def_id];
199 ty::GenericPredicates {
201 predicates: tcx.arena.alloc_from_iter(
202 self.param_env.caller_bounds().iter().filter_map(|predicate| {
203 match predicate.kind().skip_binder() {
204 ty::PredicateKind::Trait(data, _) if data.self_ty().is_param(index) => {
205 // HACK(eddyb) should get the original `Span`.
206 let span = tcx.def_span(def_id);
207 Some((predicate, span))
216 fn re_infer(&self, def: Option<&ty::GenericParamDef>, span: Span) -> Option<ty::Region<'tcx>> {
218 Some(def) => infer::EarlyBoundRegion(span, def.name),
219 None => infer::MiscVariable(span),
221 Some(self.next_region_var(v))
224 fn allow_ty_infer(&self) -> bool {
228 fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
229 if let Some(param) = param {
230 if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {
235 self.next_ty_var(TypeVariableOrigin {
236 kind: TypeVariableOriginKind::TypeInference,
245 param: Option<&ty::GenericParamDef>,
247 ) -> &'tcx Const<'tcx> {
248 if let Some(param) = param {
249 if let GenericArgKind::Const(ct) = self.var_for_def(span, param).unpack() {
256 ConstVariableOrigin { kind: ConstVariableOriginKind::ConstInference, span },
261 fn projected_ty_from_poly_trait_ref(
265 item_segment: &hir::PathSegment<'_>,
266 poly_trait_ref: ty::PolyTraitRef<'tcx>,
268 let (trait_ref, _) = self.replace_bound_vars_with_fresh_vars(
270 infer::LateBoundRegionConversionTime::AssocTypeProjection(item_def_id),
274 let item_substs = <dyn AstConv<'tcx>>::create_substs_for_associated_item(
283 self.tcx().mk_projection(item_def_id, item_substs)
286 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
287 if ty.has_escaping_bound_vars() {
288 ty // FIXME: normalization and escaping regions
290 self.normalize_associated_types_in(span, &ty)
294 fn set_tainted_by_errors(&self) {
295 self.infcx.set_tainted_by_errors()
298 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, _span: Span) {
299 self.write_ty(hir_id, ty)