| /*! |
| |
| # typeck: check phase |
| |
| Within the check phase of type check, we check each item one at a time |
| (bodies of function expressions are checked as part of the containing |
| function). Inference is used to supply types wherever they are unknown. |
| |
| By far the most complex case is checking the body of a function. This |
| can be broken down into several distinct phases: |
| |
| - gather: creates type variables to represent the type of each local |
| variable and pattern binding. |
| |
| - main: the main pass does the lion's share of the work: it |
| determines the types of all expressions, resolves |
| methods, checks for most invalid conditions, and so forth. In |
| some cases, where a type is unknown, it may create a type or region |
| variable and use that as the type of an expression. |
| |
| In the process of checking, various constraints will be placed on |
| these type variables through the subtyping relationships requested |
| through the `demand` module. The `infer` module is in charge |
| of resolving those constraints. |
| |
| - regionck: after main is complete, the regionck pass goes over all |
| types looking for regions and making sure that they did not escape |
| into places where they are not in scope. This may also influence the |
| final assignments of the various region variables if there is some |
| flexibility. |
| |
| - writeback: writes the final types within a function body, replacing |
| type variables with their final inferred types. These final types |
| are written into the `tcx.node_types` table, which should *never* contain |
| any reference to a type variable. |
| |
| ## Intermediate types |
| |
| While type checking a function, the intermediate types for the |
| expressions, blocks, and so forth contained within the function are |
| stored in `fcx.node_types` and `fcx.node_args`. These types |
| may contain unresolved type variables. After type checking is |
| complete, the functions in the writeback module are used to take the |
| types from this table, resolve them, and then write them into their |
| permanent home in the type context `tcx`. |
| |
| This means that during inferencing you should use `fcx.write_ty()` |
| and `fcx.expr_ty()` / `fcx.node_ty()` to write/obtain the types of |
| nodes within the function. |
| |
| The types of top-level items, which never contain unbound type |
| variables, are stored directly into the `tcx` typeck_results. |
| |
| N.B., a type variable is not the same thing as a type parameter. A |
| type variable is an instance of a type parameter. That is, |
| given a generic function `fn foo<T>(t: T)`, while checking the |
| function `foo`, the type `ty_param(0)` refers to the type `T`, which |
| is treated in abstract. However, when `foo()` is called, `T` will be |
| substituted for a fresh type variable `N`. This variable will |
| eventually be resolved to some concrete type (which might itself be |
| a type parameter). |
| |
| */ |
| |
| mod check; |
| mod compare_impl_item; |
| pub mod dropck; |
| mod entry; |
| pub mod intrinsic; |
| pub mod intrinsicck; |
| mod region; |
| pub mod wfcheck; |
| |
| pub use check::check_abi; |
| |
| use std::num::NonZeroU32; |
| |
| use check::check_mod_item_types; |
| use rustc_data_structures::fx::{FxHashMap, FxHashSet}; |
| use rustc_errors::{pluralize, struct_span_err, Diagnostic, DiagnosticBuilder}; |
| use rustc_hir::def_id::{DefId, LocalDefId}; |
| use rustc_hir::intravisit::Visitor; |
| use rustc_index::bit_set::BitSet; |
| use rustc_infer::infer::error_reporting::ObligationCauseExt as _; |
| use rustc_infer::infer::outlives::env::OutlivesEnvironment; |
| use rustc_infer::infer::{self, TyCtxtInferExt as _}; |
| use rustc_infer::traits::ObligationCause; |
| use rustc_middle::query::Providers; |
| use rustc_middle::ty::error::{ExpectedFound, TypeError}; |
| use rustc_middle::ty::{self, Ty, TyCtxt}; |
| use rustc_middle::ty::{GenericArgs, GenericArgsRef}; |
| use rustc_session::parse::feature_err; |
| use rustc_span::symbol::{kw, Ident}; |
| use rustc_span::{self, def_id::CRATE_DEF_ID, BytePos, Span, Symbol, DUMMY_SP}; |
| use rustc_target::abi::VariantIdx; |
| use rustc_target::spec::abi::Abi; |
| use rustc_trait_selection::traits::error_reporting::suggestions::ReturnsVisitor; |
| use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _; |
| use rustc_trait_selection::traits::ObligationCtxt; |
| |
| use crate::errors; |
| use crate::require_c_abi_if_c_variadic; |
| use crate::util::common::indenter; |
| |
| use self::compare_impl_item::collect_return_position_impl_trait_in_trait_tys; |
| use self::region::region_scope_tree; |
| |
| pub fn provide(providers: &mut Providers) { |
| wfcheck::provide(providers); |
| *providers = Providers { |
| adt_destructor, |
| check_mod_item_types, |
| region_scope_tree, |
| collect_return_position_impl_trait_in_trait_tys, |
| compare_impl_const: compare_impl_item::compare_impl_const_raw, |
| check_coroutine_obligations: check::check_coroutine_obligations, |
| ..*providers |
| }; |
| } |
| |
| fn adt_destructor(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<ty::Destructor> { |
| tcx.calculate_dtor(def_id.to_def_id(), dropck::check_drop_impl) |
| } |
| |
| /// Given a `DefId` for an opaque type in return position, find its parent item's return |
| /// expressions. |
| fn get_owner_return_paths( |
| tcx: TyCtxt<'_>, |
| def_id: LocalDefId, |
| ) -> Option<(LocalDefId, ReturnsVisitor<'_>)> { |
| let hir_id = tcx.hir().local_def_id_to_hir_id(def_id); |
| let parent_id = tcx.hir().get_parent_item(hir_id).def_id; |
| tcx.hir().find_by_def_id(parent_id).and_then(|node| node.body_id()).map(|body_id| { |
| let body = tcx.hir().body(body_id); |
| let mut visitor = ReturnsVisitor::default(); |
| visitor.visit_body(body); |
| (parent_id, visitor) |
| }) |
| } |
| |
| /// Forbid defining intrinsics in Rust code, |
| /// as they must always be defined by the compiler. |
| // FIXME: Move this to a more appropriate place. |
| pub fn fn_maybe_err(tcx: TyCtxt<'_>, sp: Span, abi: Abi) { |
| if let Abi::RustIntrinsic | Abi::PlatformIntrinsic = abi { |
| tcx.sess.span_err(sp, "intrinsic must be in `extern \"rust-intrinsic\" { ... }` block"); |
| } |
| } |
| |
| fn maybe_check_static_with_link_section(tcx: TyCtxt<'_>, id: LocalDefId) { |
| // Only restricted on wasm target for now |
| if !tcx.sess.target.is_like_wasm { |
| return; |
| } |
| |
| // If `#[link_section]` is missing, then nothing to verify |
| let attrs = tcx.codegen_fn_attrs(id); |
| if attrs.link_section.is_none() { |
| return; |
| } |
| |
| // For the wasm32 target statics with `#[link_section]` are placed into custom |
| // sections of the final output file, but this isn't link custom sections of |
| // other executable formats. Namely we can only embed a list of bytes, |
| // nothing with provenance (pointers to anything else). If any provenance |
| // show up, reject it here. |
| // `#[link_section]` may contain arbitrary, or even undefined bytes, but it is |
| // the consumer's responsibility to ensure all bytes that have been read |
| // have defined values. |
| if let Ok(alloc) = tcx.eval_static_initializer(id.to_def_id()) |
| && alloc.inner().provenance().ptrs().len() != 0 |
| { |
| let msg = "statics with a custom `#[link_section]` must be a \ |
| simple list of bytes on the wasm target with no \ |
| extra levels of indirection such as references"; |
| tcx.sess.span_err(tcx.def_span(id), msg); |
| } |
| } |
| |
| fn report_forbidden_specialization(tcx: TyCtxt<'_>, impl_item: DefId, parent_impl: DefId) { |
| let span = tcx.def_span(impl_item); |
| let ident = tcx.item_name(impl_item); |
| |
| let err = match tcx.span_of_impl(parent_impl) { |
| Ok(sp) => errors::ImplNotMarkedDefault::Ok { span, ident, ok_label: sp }, |
| Err(cname) => errors::ImplNotMarkedDefault::Err { span, ident, cname }, |
| }; |
| |
| tcx.sess.emit_err(err); |
| } |
| |
| fn missing_items_err( |
| tcx: TyCtxt<'_>, |
| impl_def_id: LocalDefId, |
| missing_items: &[ty::AssocItem], |
| full_impl_span: Span, |
| ) { |
| let missing_items = |
| missing_items.iter().filter(|trait_item| !trait_item.is_impl_trait_in_trait()); |
| |
| let missing_items_msg = missing_items |
| .clone() |
| .map(|trait_item| trait_item.name.to_string()) |
| .collect::<Vec<_>>() |
| .join("`, `"); |
| |
| // `Span` before impl block closing brace. |
| let hi = full_impl_span.hi() - BytePos(1); |
| // Point at the place right before the closing brace of the relevant `impl` to suggest |
| // adding the associated item at the end of its body. |
| let sugg_sp = full_impl_span.with_lo(hi).with_hi(hi); |
| // Obtain the level of indentation ending in `sugg_sp`. |
| let padding = |
| tcx.sess.source_map().indentation_before(sugg_sp).unwrap_or_else(|| String::new()); |
| let (mut missing_trait_item, mut missing_trait_item_none, mut missing_trait_item_label) = |
| (Vec::new(), Vec::new(), Vec::new()); |
| |
| for &trait_item in missing_items { |
| let snippet = suggestion_signature( |
| tcx, |
| trait_item, |
| tcx.impl_trait_ref(impl_def_id).unwrap().instantiate_identity(), |
| ); |
| let code = format!("{padding}{snippet}\n{padding}"); |
| if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) { |
| missing_trait_item_label |
| .push(errors::MissingTraitItemLabel { span, item: trait_item.name }); |
| missing_trait_item.push(errors::MissingTraitItemSuggestion { |
| span: sugg_sp, |
| code, |
| snippet, |
| }); |
| } else { |
| missing_trait_item_none.push(errors::MissingTraitItemSuggestionNone { |
| span: sugg_sp, |
| code, |
| snippet, |
| }) |
| } |
| } |
| |
| tcx.sess.emit_err(errors::MissingTraitItem { |
| span: tcx.span_of_impl(impl_def_id.to_def_id()).unwrap(), |
| missing_items_msg, |
| missing_trait_item_label, |
| missing_trait_item, |
| missing_trait_item_none, |
| }); |
| } |
| |
| fn missing_items_must_implement_one_of_err( |
| tcx: TyCtxt<'_>, |
| impl_span: Span, |
| missing_items: &[Ident], |
| annotation_span: Option<Span>, |
| ) { |
| let missing_items_msg = |
| missing_items.iter().map(Ident::to_string).collect::<Vec<_>>().join("`, `"); |
| |
| tcx.sess.emit_err(errors::MissingOneOfTraitItem { |
| span: impl_span, |
| note: annotation_span, |
| missing_items_msg, |
| }); |
| } |
| |
| fn default_body_is_unstable( |
| tcx: TyCtxt<'_>, |
| impl_span: Span, |
| item_did: DefId, |
| feature: Symbol, |
| reason: Option<Symbol>, |
| issue: Option<NonZeroU32>, |
| ) { |
| let missing_item_name = tcx.associated_item(item_did).name; |
| let (mut some_note, mut none_note, mut reason_str) = (false, false, String::new()); |
| match reason { |
| Some(r) => { |
| some_note = true; |
| reason_str = r.to_string(); |
| } |
| None => none_note = true, |
| }; |
| |
| let mut err = tcx.sess.create_err(errors::MissingTraitItemUnstable { |
| span: impl_span, |
| some_note, |
| none_note, |
| missing_item_name, |
| feature, |
| reason: reason_str, |
| }); |
| |
| rustc_session::parse::add_feature_diagnostics_for_issue( |
| &mut err, |
| &tcx.sess.parse_sess, |
| feature, |
| rustc_feature::GateIssue::Library(issue), |
| false, |
| ); |
| |
| err.emit(); |
| } |
| |
| /// Re-sugar `ty::GenericPredicates` in a way suitable to be used in structured suggestions. |
| fn bounds_from_generic_predicates<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| predicates: impl IntoIterator<Item = (ty::Clause<'tcx>, Span)>, |
| ) -> (String, String) { |
| let mut types: FxHashMap<Ty<'tcx>, Vec<DefId>> = FxHashMap::default(); |
| let mut projections = vec![]; |
| for (predicate, _) in predicates { |
| debug!("predicate {:?}", predicate); |
| let bound_predicate = predicate.kind(); |
| match bound_predicate.skip_binder() { |
| ty::ClauseKind::Trait(trait_predicate) => { |
| let entry = types.entry(trait_predicate.self_ty()).or_default(); |
| let def_id = trait_predicate.def_id(); |
| if Some(def_id) != tcx.lang_items().sized_trait() { |
| // Type params are `Sized` by default, do not add that restriction to the list |
| // if it is a positive requirement. |
| entry.push(trait_predicate.def_id()); |
| } |
| } |
| ty::ClauseKind::Projection(projection_pred) => { |
| projections.push(bound_predicate.rebind(projection_pred)); |
| } |
| _ => {} |
| } |
| } |
| |
| let mut where_clauses = vec![]; |
| let mut types_str = vec![]; |
| for (ty, bounds) in types { |
| if let ty::Param(_) = ty.kind() { |
| let mut bounds_str = vec![]; |
| for bound in bounds { |
| let mut projections_str = vec![]; |
| for projection in &projections { |
| let p = projection.skip_binder(); |
| let alias_ty = p.projection_ty; |
| if bound == tcx.parent(alias_ty.def_id) && alias_ty.self_ty() == ty { |
| let name = tcx.item_name(alias_ty.def_id); |
| projections_str.push(format!("{} = {}", name, p.term)); |
| } |
| } |
| let bound_def_path = tcx.def_path_str(bound); |
| if projections_str.is_empty() { |
| where_clauses.push(format!("{}: {}", ty, bound_def_path)); |
| } else { |
| bounds_str.push(format!("{}<{}>", bound_def_path, projections_str.join(", "))); |
| } |
| } |
| if bounds_str.is_empty() { |
| types_str.push(ty.to_string()); |
| } else { |
| types_str.push(format!("{}: {}", ty, bounds_str.join(" + "))); |
| } |
| } else { |
| // Avoid suggesting the following: |
| // fn foo<T, <T as Trait>::Bar>(_: T) where T: Trait, <T as Trait>::Bar: Other {} |
| where_clauses.extend( |
| bounds.into_iter().map(|bound| format!("{}: {}", ty, tcx.def_path_str(bound))), |
| ); |
| } |
| } |
| |
| let generics = |
| if types_str.is_empty() { "".to_string() } else { format!("<{}>", types_str.join(", ")) }; |
| |
| let where_clauses = if where_clauses.is_empty() { |
| "".to_string() |
| } else { |
| format!(" where {}", where_clauses.join(", ")) |
| }; |
| |
| (generics, where_clauses) |
| } |
| |
| /// Return placeholder code for the given function. |
| fn fn_sig_suggestion<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| sig: ty::FnSig<'tcx>, |
| ident: Ident, |
| predicates: impl IntoIterator<Item = (ty::Clause<'tcx>, Span)>, |
| assoc: ty::AssocItem, |
| ) -> String { |
| let args = sig |
| .inputs() |
| .iter() |
| .enumerate() |
| .map(|(i, ty)| { |
| Some(match ty.kind() { |
| ty::Param(_) if assoc.fn_has_self_parameter && i == 0 => "self".to_string(), |
| ty::Ref(reg, ref_ty, mutability) if i == 0 => { |
| let reg = format!("{reg} "); |
| let reg = match ®[..] { |
| "'_ " | " " => "", |
| reg => reg, |
| }; |
| if assoc.fn_has_self_parameter { |
| match ref_ty.kind() { |
| ty::Param(param) if param.name == kw::SelfUpper => { |
| format!("&{}{}self", reg, mutability.prefix_str()) |
| } |
| |
| _ => format!("self: {ty}"), |
| } |
| } else { |
| format!("_: {ty}") |
| } |
| } |
| _ => { |
| if assoc.fn_has_self_parameter && i == 0 { |
| format!("self: {ty}") |
| } else { |
| format!("_: {ty}") |
| } |
| } |
| }) |
| }) |
| .chain(std::iter::once(if sig.c_variadic { Some("...".to_string()) } else { None })) |
| .flatten() |
| .collect::<Vec<String>>() |
| .join(", "); |
| let mut output = sig.output(); |
| |
| let asyncness = if tcx.asyncness(assoc.def_id).is_async() { |
| output = if let ty::Alias(_, alias_ty) = *output.kind() { |
| tcx.explicit_item_bounds(alias_ty.def_id) |
| .iter_instantiated_copied(tcx, alias_ty.args) |
| .find_map(|(bound, _)| bound.as_projection_clause()?.no_bound_vars()?.term.ty()) |
| .unwrap_or_else(|| { |
| span_bug!( |
| ident.span, |
| "expected async fn to have `impl Future` output, but it returns {output}" |
| ) |
| }) |
| } else { |
| span_bug!( |
| ident.span, |
| "expected async fn to have `impl Future` output, but it returns {output}" |
| ) |
| }; |
| "async " |
| } else { |
| "" |
| }; |
| |
| let output = if !output.is_unit() { format!(" -> {output}") } else { String::new() }; |
| |
| let unsafety = sig.unsafety.prefix_str(); |
| let (generics, where_clauses) = bounds_from_generic_predicates(tcx, predicates); |
| |
| // FIXME: this is not entirely correct, as the lifetimes from borrowed params will |
| // not be present in the `fn` definition, not will we account for renamed |
| // lifetimes between the `impl` and the `trait`, but this should be good enough to |
| // fill in a significant portion of the missing code, and other subsequent |
| // suggestions can help the user fix the code. |
| format!( |
| "{unsafety}{asyncness}fn {ident}{generics}({args}){output}{where_clauses} {{ todo!() }}" |
| ) |
| } |
| |
| pub fn ty_kind_suggestion(ty: Ty<'_>) -> Option<&'static str> { |
| Some(match ty.kind() { |
| ty::Bool => "true", |
| ty::Char => "'a'", |
| ty::Int(_) | ty::Uint(_) => "42", |
| ty::Float(_) => "3.14159", |
| ty::Error(_) | ty::Never => return None, |
| _ => "value", |
| }) |
| } |
| |
| /// Return placeholder code for the given associated item. |
| /// Similar to `ty::AssocItem::suggestion`, but appropriate for use as the code snippet of a |
| /// structured suggestion. |
| fn suggestion_signature<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| assoc: ty::AssocItem, |
| impl_trait_ref: ty::TraitRef<'tcx>, |
| ) -> String { |
| let args = ty::GenericArgs::identity_for_item(tcx, assoc.def_id).rebase_onto( |
| tcx, |
| assoc.container_id(tcx), |
| impl_trait_ref.with_self_ty(tcx, tcx.types.self_param).args, |
| ); |
| |
| match assoc.kind { |
| ty::AssocKind::Fn => fn_sig_suggestion( |
| tcx, |
| tcx.liberate_late_bound_regions( |
| assoc.def_id, |
| tcx.fn_sig(assoc.def_id).instantiate(tcx, args), |
| ), |
| assoc.ident(tcx), |
| tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args), |
| assoc, |
| ), |
| ty::AssocKind::Type => { |
| let (generics, where_clauses) = bounds_from_generic_predicates( |
| tcx, |
| tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args), |
| ); |
| format!("type {}{generics} = /* Type */{where_clauses};", assoc.name) |
| } |
| ty::AssocKind::Const => { |
| let ty = tcx.type_of(assoc.def_id).instantiate_identity(); |
| let val = ty_kind_suggestion(ty).unwrap_or("todo!()"); |
| format!("const {}: {} = {};", assoc.name, ty, val) |
| } |
| } |
| } |
| |
| /// Emit an error when encountering two or more variants in a transparent enum. |
| fn bad_variant_count<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>, sp: Span, did: DefId) { |
| let variant_spans: Vec<_> = adt |
| .variants() |
| .iter() |
| .map(|variant| tcx.hir().span_if_local(variant.def_id).unwrap()) |
| .collect(); |
| let (mut spans, mut many) = (Vec::new(), None); |
| if let [start @ .., end] = &*variant_spans { |
| spans = start.to_vec(); |
| many = Some(*end); |
| } |
| tcx.sess.emit_err(errors::TransparentEnumVariant { |
| span: sp, |
| spans, |
| many, |
| number: adt.variants().len(), |
| path: tcx.def_path_str(did), |
| }); |
| } |
| |
| /// Emit an error when encountering two or more non-zero-sized fields in a transparent |
| /// enum. |
| fn bad_non_zero_sized_fields<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| adt: ty::AdtDef<'tcx>, |
| field_count: usize, |
| field_spans: impl Iterator<Item = Span>, |
| sp: Span, |
| ) { |
| if adt.is_enum() { |
| tcx.sess.emit_err(errors::TransparentNonZeroSizedEnum { |
| span: sp, |
| spans: field_spans.collect(), |
| field_count, |
| desc: adt.descr(), |
| }); |
| } else { |
| tcx.sess.emit_err(errors::TransparentNonZeroSized { |
| span: sp, |
| spans: field_spans.collect(), |
| field_count, |
| desc: adt.descr(), |
| }); |
| } |
| } |
| |
| // FIXME: Consider moving this method to a more fitting place. |
| pub fn potentially_plural_count(count: usize, word: &str) -> String { |
| format!("{} {}{}", count, word, pluralize!(count)) |
| } |
| |
| pub fn check_function_signature<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| mut cause: ObligationCause<'tcx>, |
| fn_id: DefId, |
| expected_sig: ty::PolyFnSig<'tcx>, |
| ) { |
| let local_id = fn_id.as_local().unwrap_or(CRATE_DEF_ID); |
| |
| let param_env = ty::ParamEnv::empty(); |
| |
| let infcx = &tcx.infer_ctxt().build(); |
| let ocx = ObligationCtxt::new(infcx); |
| |
| let actual_sig = tcx.fn_sig(fn_id).instantiate_identity(); |
| |
| let norm_cause = ObligationCause::misc(cause.span, local_id); |
| let actual_sig = ocx.normalize(&norm_cause, param_env, actual_sig); |
| |
| match ocx.eq(&cause, param_env, expected_sig, actual_sig) { |
| Ok(()) => { |
| let errors = ocx.select_all_or_error(); |
| if !errors.is_empty() { |
| infcx.err_ctxt().report_fulfillment_errors(errors); |
| return; |
| } |
| } |
| Err(err) => { |
| let err_ctxt = infcx.err_ctxt(); |
| if fn_id.is_local() { |
| cause.span = extract_span_for_error_reporting(tcx, err, &cause, local_id); |
| } |
| let failure_code = cause.as_failure_code_diag(err, cause.span, vec![]); |
| let mut diag = tcx.sess.create_err(failure_code); |
| err_ctxt.note_type_err( |
| &mut diag, |
| &cause, |
| None, |
| Some(infer::ValuePairs::PolySigs(ExpectedFound { |
| expected: expected_sig, |
| found: actual_sig, |
| })), |
| err, |
| false, |
| false, |
| ); |
| diag.emit(); |
| return; |
| } |
| } |
| |
| let outlives_env = OutlivesEnvironment::new(param_env); |
| let _ = ocx.resolve_regions_and_report_errors(local_id, &outlives_env); |
| |
| fn extract_span_for_error_reporting<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| err: TypeError<'_>, |
| cause: &ObligationCause<'tcx>, |
| fn_id: LocalDefId, |
| ) -> rustc_span::Span { |
| let mut args = { |
| let node = tcx.hir().expect_owner(fn_id); |
| let decl = node.fn_decl().unwrap_or_else(|| bug!("expected fn decl, found {:?}", node)); |
| decl.inputs.iter().map(|t| t.span).chain(std::iter::once(decl.output.span())) |
| }; |
| |
| match err { |
| TypeError::ArgumentMutability(i) |
| | TypeError::ArgumentSorts(ExpectedFound { .. }, i) => args.nth(i).unwrap(), |
| _ => cause.span(), |
| } |
| } |
| } |
