diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs | 1715 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/lib.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/hir/map/mod.rs | 6 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/generics.rs | 29 |
4 files changed, 864 insertions, 887 deletions
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs index e1a2a237c23..7b5c377f7b4 100644 --- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs +++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs @@ -1,263 +1,22 @@ use crate::infer::type_variable::TypeVariableOriginKind; -use crate::infer::{InferCtxt, Symbol}; -use rustc_errors::{ - pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, -}; +use crate::infer::InferCtxt; +use rustc_errors::{pluralize, struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed}; use rustc_hir as hir; -use rustc_hir::def::{DefKind, Namespace}; +use rustc_hir::def::{CtorOf, DefKind, Namespace}; use rustc_hir::def_id::DefId; use rustc_hir::intravisit::{self, Visitor}; -use rustc_hir::{Body, Expr, ExprKind, FnRetTy, HirId, Local, MatchSource, Pat}; +use rustc_hir::{Body, Expr, ExprKind, FnRetTy, HirId, Local, LocalSource}; use rustc_middle::hir::nested_filter; use rustc_middle::infer::unify_key::ConstVariableOriginKind; -use rustc_middle::ty::print::Print; -use rustc_middle::ty::subst::{GenericArg, GenericArgKind}; -use rustc_middle::ty::{self, Const, DefIdTree, InferConst, Ty, TyCtxt, TypeFoldable, TypeFolder}; -use rustc_span::symbol::kw; -use rustc_span::{sym, Span}; +use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability}; +use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter, Print, Printer}; +use rustc_middle::ty::subst::{GenericArg, GenericArgKind, Subst, SubstsRef}; +use rustc_middle::ty::{self, DefIdTree, GenericParamDefKind, InferConst}; +use rustc_middle::ty::{Ty, TyCtxt, TypeckResults}; +use rustc_span::symbol::{kw, Ident}; +use rustc_span::{BytePos, Span}; use std::borrow::Cow; - -struct FindHirNodeVisitor<'a, 'tcx> { - infcx: &'a InferCtxt<'a, 'tcx>, - target: GenericArg<'tcx>, - target_span: Span, - found_node_ty: Option<Ty<'tcx>>, - found_local_pattern: Option<&'tcx Pat<'tcx>>, - found_arg_pattern: Option<&'tcx Pat<'tcx>>, - found_closure: Option<&'tcx Expr<'tcx>>, - found_method_call: Option<&'tcx Expr<'tcx>>, - found_exact_method_call: Option<&'tcx Expr<'tcx>>, - found_for_loop_iter: Option<&'tcx Expr<'tcx>>, - found_use_diagnostic: Option<UseDiagnostic<'tcx>>, -} - -impl<'a, 'tcx> FindHirNodeVisitor<'a, 'tcx> { - fn new(infcx: &'a InferCtxt<'a, 'tcx>, target: GenericArg<'tcx>, target_span: Span) -> Self { - Self { - infcx, - target, - target_span, - found_node_ty: None, - found_local_pattern: None, - found_arg_pattern: None, - found_closure: None, - found_method_call: None, - found_exact_method_call: None, - found_for_loop_iter: None, - found_use_diagnostic: None, - } - } - - fn node_type_opt(&self, hir_id: HirId) -> Option<Ty<'tcx>> { - self.infcx.in_progress_typeck_results?.borrow().node_type_opt(hir_id) - } - - fn node_ty_contains_target(&self, hir_id: HirId) -> Option<Ty<'tcx>> { - self.node_type_opt(hir_id).map(|ty| self.infcx.resolve_vars_if_possible(ty)).filter(|ty| { - ty.walk().any(|inner| { - inner == self.target - || match (inner.unpack(), self.target.unpack()) { - (GenericArgKind::Type(inner_ty), GenericArgKind::Type(target_ty)) => { - use ty::{Infer, TyVar}; - match (inner_ty.kind(), target_ty.kind()) { - (&Infer(TyVar(a_vid)), &Infer(TyVar(b_vid))) => self - .infcx - .inner - .borrow_mut() - .type_variables() - .sub_unified(a_vid, b_vid), - _ => false, - } - } - _ => false, - } - }) - }) - } - - /// Determine whether the expression, assumed to be the callee within a `Call`, - /// corresponds to the `From::from` emitted in desugaring of the `?` operator. - fn is_try_conversion(&self, callee: &Expr<'tcx>) -> bool { - self.infcx - .trait_def_from_hir_fn(callee.hir_id) - .map_or(false, |def_id| self.infcx.is_try_conversion(callee.span, def_id)) - } -} - -impl<'a, 'tcx> Visitor<'tcx> for FindHirNodeVisitor<'a, 'tcx> { - type NestedFilter = nested_filter::OnlyBodies; - - fn nested_visit_map(&mut self) -> Self::Map { - self.infcx.tcx.hir() - } - - fn visit_local(&mut self, local: &'tcx Local<'tcx>) { - if let (None, Some(ty)) = - (self.found_local_pattern, self.node_ty_contains_target(local.hir_id)) - { - self.found_local_pattern = Some(&*local.pat); - self.found_node_ty = Some(ty); - } - intravisit::walk_local(self, local); - } - - fn visit_body(&mut self, body: &'tcx Body<'tcx>) { - for param in body.params { - if let (None, Some(ty)) = - (self.found_arg_pattern, self.node_ty_contains_target(param.hir_id)) - { - self.found_arg_pattern = Some(&*param.pat); - self.found_node_ty = Some(ty); - } - } - intravisit::walk_body(self, body); - } - - fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { - if let ExprKind::Match(scrutinee, [_, arm], MatchSource::ForLoopDesugar) = expr.kind - && let Some(pat) = arm.pat.for_loop_some() - && let Some(ty) = self.node_ty_contains_target(pat.hir_id) - { - self.found_for_loop_iter = Some(scrutinee); - self.found_node_ty = Some(ty); - return; - } - if let ExprKind::MethodCall(segment, exprs, _) = expr.kind - && segment.ident.span == self.target_span - && Some(self.target) == self.infcx.in_progress_typeck_results.and_then(|typeck_results| { - typeck_results - .borrow() - .node_type_opt(exprs.first().unwrap().hir_id) - .map(Into::into) - }) - { - self.found_exact_method_call = Some(&expr); - return; - } - - // FIXME(const_generics): Currently, any uninferred `const` generics arguments - // are handled specially, but instead they should be handled in `annotate_method_call`, - // which currently doesn't work because this evaluates to `false` for const arguments. - // See https://github.com/rust-lang/rust/pull/77758 for more details. - if let Some(ty) = self.node_ty_contains_target(expr.hir_id) { - match expr.kind { - ExprKind::Closure(..) => self.found_closure = Some(&expr), - ExprKind::MethodCall(..) => self.found_method_call = Some(&expr), - - // If the given expression falls within the target span and is a - // `From::from(e)` call emitted during desugaring of the `?` operator, - // extract the types inferred before and after the call - ExprKind::Call(callee, [arg]) - if self.target_span.contains(expr.span) - && self.found_use_diagnostic.is_none() - && self.is_try_conversion(callee) => - { - self.found_use_diagnostic = self.node_type_opt(arg.hir_id).map(|pre_ty| { - UseDiagnostic::TryConversion { pre_ty, post_ty: ty, span: callee.span } - }); - } - _ => {} - } - } - intravisit::walk_expr(self, expr); - } -} - -/// An observation about the use site of a type to be emitted as an additional -/// note in an inference failure error. -enum UseDiagnostic<'tcx> { - /// Records the types inferred before and after `From::from` is called on the - /// error value within the desugaring of the `?` operator. - TryConversion { pre_ty: Ty<'tcx>, post_ty: Ty<'tcx>, span: Span }, -} - -impl UseDiagnostic<'_> { - /// Return a descriptor of the value at the use site - fn descr(&self) -> &'static str { - match self { - Self::TryConversion { .. } => "error for `?` operator", - } - } - - /// Return a descriptor of the type at the use site - fn type_descr(&self) -> &'static str { - match self { - Self::TryConversion { .. } => "error type for `?` operator", - } - } - - fn applies_to(&self, span: Span) -> bool { - match *self { - // In some cases the span for an inference failure due to try - // conversion contains the antecedent expression as well as the `?` - Self::TryConversion { span: s, .. } => span.contains(s) && span.hi() == s.hi(), - } - } - - fn attach_note(&self, err: &mut Diagnostic) { - match *self { - Self::TryConversion { pre_ty, post_ty, .. } => { - let intro = "`?` implicitly converts the error value"; - - let msg = match (pre_ty.is_ty_infer(), post_ty.is_ty_infer()) { - (true, true) => format!("{} using the `From` trait", intro), - (false, true) => { - format!("{} into a type implementing `From<{}>`", intro, pre_ty) - } - (true, false) => { - format!("{} into `{}` using the `From` trait", intro, post_ty) - } - (false, false) => { - format!( - "{} into `{}` using its implementation of `From<{}>`", - intro, post_ty, pre_ty - ) - } - }; - - err.note(&msg); - } - } - } -} - -/// Suggest giving an appropriate return type to a closure expression. -fn closure_return_type_suggestion( - err: &mut Diagnostic, - output: &FnRetTy<'_>, - body: &Body<'_>, - ret: &str, -) { - let (arrow, post) = match output { - FnRetTy::DefaultReturn(_) => ("-> ", " "), - _ => ("", ""), - }; - let suggestion = match body.value.kind { - ExprKind::Block(..) => vec![(output.span(), format!("{}{}{}", arrow, ret, post))], - _ => vec![ - (output.span(), format!("{}{}{}{{ ", arrow, ret, post)), - (body.value.span.shrink_to_hi(), " }".to_string()), - ], - }; - err.multipart_suggestion( - "give this closure an explicit return type without `_` placeholders", - suggestion, - Applicability::HasPlaceholders, - ); -} - -/// Given a closure signature, return a `String` containing a list of all its argument types. -fn closure_args(fn_sig: &ty::PolyFnSig<'_>) -> String { - fn_sig - .inputs() - .skip_binder() - .iter() - .next() - .map(|args| { - args.tuple_fields().iter().map(|arg| arg.to_string()).collect::<Vec<_>>().join(", ") - }) - .unwrap_or_default() -} +use std::iter; pub enum TypeAnnotationNeeded { /// ```compile_fail,E0282 @@ -296,9 +55,8 @@ pub struct InferenceDiagnosticsData { /// Data on the parent definition where a generic argument was declared. pub struct InferenceDiagnosticsParentData { - pub prefix: &'static str, - pub name: String, - pub def_id: DefId, + prefix: &'static str, + name: String, } pub enum UnderspecifiedArgKind { @@ -306,52 +64,58 @@ pub enum UnderspecifiedArgKind { Const { is_parameter: bool }, } -impl UnderspecifiedArgKind { - fn descr(&self) -> &'static str { - match self { - Self::Type { .. } => "type", - Self::Const { .. } => "const", - } - } -} - impl InferenceDiagnosticsData { /// Generate a label for a generic argument which can't be inferred. When not /// much is known about the argument, `use_diag` may be used to describe the /// labeled value. - fn cannot_infer_msg(&self, use_diag: Option<&UseDiagnostic<'_>>) -> String { + fn cannot_infer_msg(&self) -> String { if self.name == "_" && matches!(self.kind, UnderspecifiedArgKind::Type { .. }) { - if let Some(use_diag) = use_diag { - return format!("cannot infer type of {}", use_diag.descr()); - } - return "cannot infer type".to_string(); } - let suffix = match (&self.parent, use_diag) { - (Some(parent), _) => format!(" declared on the {} `{}`", parent.prefix, parent.name), - (None, Some(use_diag)) => format!(" in {}", use_diag.type_descr()), - (None, None) => String::new(), + let suffix = match &self.parent { + Some(parent) => parent.suffix_string(), + None => String::new(), }; // For example: "cannot infer type for type parameter `T`" format!("cannot infer {} `{}`{}", self.kind.prefix_string(), self.name, suffix) } + + fn where_x_is_specified(&self, in_type: Ty<'_>) -> String { + if in_type.is_ty_infer() { + String::new() + } else if self.name == "_" { + // FIXME: Consider specializing this message if there is a single `_` + // in the type. + ", where the placeholders `_` are specified".to_string() + } else { + format!(", where the {} `{}` is specified", self.kind.prefix_string(), self.name) + } + } } impl InferenceDiagnosticsParentData { - fn for_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<InferenceDiagnosticsParentData> { - let parent_def_id = tcx.parent(def_id); - + fn for_parent_def_id( + tcx: TyCtxt<'_>, + parent_def_id: DefId, + ) -> Option<InferenceDiagnosticsParentData> { let parent_name = tcx.def_key(parent_def_id).disambiguated_data.data.get_opt_name()?.to_string(); Some(InferenceDiagnosticsParentData { prefix: tcx.def_kind(parent_def_id).descr(parent_def_id), name: parent_name, - def_id: parent_def_id, }) } + + fn for_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<InferenceDiagnosticsParentData> { + Self::for_parent_def_id(tcx, tcx.parent(def_id)) + } + + fn suffix_string(&self) -> String { + format!(" declared on the {} `{}`", self.prefix, self.name) + } } impl UnderspecifiedArgKind { @@ -364,6 +128,80 @@ impl UnderspecifiedArgKind { } } +fn fmt_printer<'a, 'tcx>(infcx: &'a InferCtxt<'_, 'tcx>, ns: Namespace) -> FmtPrinter<'a, 'tcx> { + let mut printer = FmtPrinter::new(infcx.tcx, ns); + let ty_getter = move |ty_vid| { + if infcx.probe_ty_var(ty_vid).is_ok() { + warn!("resolved ty var in error message"); + } + if let TypeVariableOriginKind::TypeParameterDefinition(name, _) = + infcx.inner.borrow_mut().type_variables().var_origin(ty_vid).kind + { + Some(name.to_string()) + } else { + None + } + }; + printer.ty_infer_name_resolver = Some(Box::new(ty_getter)); + let const_getter = move |ct_vid| { + if infcx.probe_const_var(ct_vid).is_ok() { + warn!("resolved const var in error message"); + } + if let ConstVariableOriginKind::ConstParameterDefinition(name, _) = + infcx.inner.borrow_mut().const_unification_table().probe_value(ct_vid).origin.kind + { + return Some(name.to_string()); + } else { + None + } + }; + printer.const_infer_name_resolver = Some(Box::new(const_getter)); + printer +} + +fn ty_to_string<'tcx>(infcx: &InferCtxt<'_, 'tcx>, ty: Ty<'tcx>) -> String { + let printer = fmt_printer(infcx, Namespace::TypeNS); + let ty = infcx.resolve_vars_if_possible(ty); + match ty.kind() { + // We don't want the regular output for `fn`s because it includes its path in + // invalid pseudo-syntax, we want the `fn`-pointer output instead. + ty::FnDef(..) => ty.fn_sig(infcx.tcx).print(printer).unwrap().into_buffer(), + // FIXME: The same thing for closures, but this only works when the closure + // does not capture anything. + // + // We do have to hide the `extern "rust-call"` ABI in that case though, + // which is too much of a bother for now. + _ => ty.print(printer).unwrap().into_buffer(), + } +} + +/// We don't want to directly use `ty_to_string` for closures as their type isn't really +/// something users are familar with. Directly printing the `fn_sig` of closures also +/// doesn't work as they actually use the "rust-call" API. +fn closure_as_fn_str<'tcx>(infcx: &InferCtxt<'_, 'tcx>, ty: Ty<'tcx>) -> String { + let ty::Closure(_, substs) = ty.kind() else { unreachable!() }; + let fn_sig = substs.as_closure().sig(); + let args = fn_sig + .inputs() + .skip_binder() + .iter() + .next() + .map(|args| { + args.tuple_fields() + .iter() + .map(|arg| ty_to_string(infcx, arg)) + .collect::<Vec<_>>() + .join(", ") + }) + .unwrap_or_default(); + let ret = if fn_sig.output().skip_binder().is_unit() { + String::new() + } else { + format!(" -> {}", ty_to_string(infcx, fn_sig.output().skip_binder())) + }; + format!("fn({}){}", args, ret) +} + impl<'a, 'tcx> InferCtxt<'a, 'tcx> { /// Extracts data used by diagnostic for either types or constants /// which were stuck during inference. @@ -400,79 +238,55 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { if let Some(highlight) = highlight { printer.region_highlight_mode = highlight; } - let name = ty.print(printer).unwrap().into_buffer(); InferenceDiagnosticsData { - name, + name: ty.print(printer).unwrap().into_buffer(), span: None, kind: UnderspecifiedArgKind::Type { prefix: ty.prefix_string(self.tcx) }, parent: None, } } GenericArgKind::Const(ct) => { - match ct.val() { - ty::ConstKind::Infer(InferConst::Var(vid)) => { - let origin = self - .inner - .borrow_mut() - .const_unification_table() - .probe_value(vid) - .origin; - if let ConstVariableOriginKind::ConstParameterDefinition(name, def_id) = - origin.kind - { - return InferenceDiagnosticsData { - name: name.to_string(), - span: Some(origin.span), - kind: UnderspecifiedArgKind::Const { is_parameter: true }, - parent: InferenceDiagnosticsParentData::for_def_id( - self.tcx, def_id, - ), - }; - } - - debug_assert!(!origin.span.is_dummy()); - let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::ValueNS); - if let Some(highlight) = highlight { - printer.region_highlight_mode = highlight; - } - let name = ct.print(printer).unwrap().into_buffer(); - InferenceDiagnosticsData { - name, + if let ty::ConstKind::Infer(InferConst::Var(vid)) = ct.val() { + let origin = + self.inner.borrow_mut().const_unification_table().probe_value(vid).origin; + if let ConstVariableOriginKind::ConstParameterDefinition(name, def_id) = + origin.kind + { + return InferenceDiagnosticsData { + name: name.to_string(), span: Some(origin.span), - kind: UnderspecifiedArgKind::Const { is_parameter: false }, - parent: None, - } + kind: UnderspecifiedArgKind::Const { is_parameter: true }, + parent: InferenceDiagnosticsParentData::for_def_id(self.tcx, def_id), + }; } - ty::ConstKind::Unevaluated(ty::Unevaluated { substs, .. }) => { - assert!(substs.has_infer_types_or_consts()); - - // FIXME: We only use the first inference variable we encounter in - // `substs` here, this gives insufficiently informative diagnostics - // in case there are multiple inference variables - for s in substs.iter() { - match s.unpack() { - GenericArgKind::Type(t) => match t.kind() { - ty::Infer(_) => { - return self.extract_inference_diagnostics_data(s, None); - } - _ => {} - }, - GenericArgKind::Const(c) => match c.val() { - ty::ConstKind::Infer(InferConst::Var(_)) => { - return self.extract_inference_diagnostics_data(s, None); - } - _ => {} - }, - _ => {} - } - } - bug!( - "expected an inference variable in substs of unevaluated const {:?}", - ct - ); + + debug_assert!(!origin.span.is_dummy()); + let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::ValueNS); + if let Some(highlight) = highlight { + printer.region_highlight_mode = highlight; + } + InferenceDiagnosticsData { + name: ct.print(printer).unwrap().into_buffer(), + span: Some(origin.span), + kind: UnderspecifiedArgKind::Const { is_parameter: false }, + parent: None, + } + } else { + // If we end up here the `FindInferSourceVisitor` + // won't work, as its expected argument isn't an inference variable. + // + // FIXME: Ideally we should look into the generic constant + // to figure out which inference var is actually unresolved so that + // this path is unreachable. + let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::ValueNS); + if let Some(highlight) = highlight { + printer.region_highlight_mode = highlight; } - _ => { - bug!("unexpect const: {:?}", ct); + InferenceDiagnosticsData { + name: ct.print(printer).unwrap().into_buffer(), + span: None, + kind: UnderspecifiedArgKind::Const { is_parameter: false }, + parent: None, } } } @@ -480,482 +294,183 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { } } + /// Used as a fallback in [InferCtxt::emit_inference_failure_err] + /// in case we weren't able to get a better error. + fn bad_inference_failure_err( + &self, + span: Span, + arg_data: InferenceDiagnosticsData, + error_code: TypeAnnotationNeeded, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + let error_code = error_code.into(); + let mut err = self.tcx.sess.struct_span_err_with_code( + span, + &format!("type annotations needed"), + error_code, + ); + err.span_label(span, arg_data.cannot_infer_msg()); + err + } + pub fn emit_inference_failure_err( &self, body_id: Option<hir::BodyId>, span: Span, arg: GenericArg<'tcx>, - impl_candidates: Vec<ty::TraitRef<'tcx>>, + // FIXME(#94483): Either use this or remove it. + _impl_candidates: Vec<ty::TraitRef<'tcx>>, error_code: TypeAnnotationNeeded, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { let arg = self.resolve_vars_if_possible(arg); let arg_data = self.extract_inference_diagnostics_data(arg, None); - let mut local_visitor = FindHirNodeVisitor::new(&self, arg, span); - let ty_to_string = |ty: Ty<'tcx>| -> String { - let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS); - let ty_getter = move |ty_vid| { - if let TypeVariableOriginKind::TypeParameterDefinition(name, _) = - self.inner.borrow_mut().type_variables().var_origin(ty_vid).kind - { - Some(name.to_string()) - } else { - None - } - }; - printer.ty_infer_name_resolver = Some(Box::new(ty_getter)); - let const_getter = move |ct_vid| { - if let ConstVariableOriginKind::ConstParameterDefinition(name, _) = self - .inner - .borrow_mut() - .const_unification_table() - .probe_value(ct_vid) - .origin - .kind - { - return Some(name.to_string()); - } else { - None - } - }; - printer.const_infer_name_resolver = Some(Box::new(const_getter)); - - if let ty::FnDef(..) = ty.kind() { - // We don't want the regular output for `fn`s because it includes its path in - // invalid pseudo-syntax, we want the `fn`-pointer output instead. - ty.fn_sig(self.tcx).print(printer).unwrap().into_buffer() - } else { - ty.print(printer).unwrap().into_buffer() - } + let Some(typeck_results) = self.in_progress_typeck_results else { + // If we don't have any typeck results we're outside + // of a body, so we won't be able to get better info + // here. + return self.bad_inference_failure_err(span, arg_data, error_code); }; + let typeck_results = typeck_results.borrow(); + let typeck_results = &typeck_results; + let mut local_visitor = FindInferSourceVisitor::new(&self, typeck_results, arg); if let Some(body_id) = body_id { let expr = self.tcx.hir().expect_expr(body_id.hir_id); + debug!(?expr); local_visitor.visit_expr(expr); } - let err_span = if let Some(pattern) = local_visitor.found_arg_pattern { - pattern.span - } else if let Some(span) = arg_data.span { - // `span` here lets us point at `sum` instead of the entire right hand side expr: - // error[E0282]: type annotations needed - // --> file2.rs:3:15 - // | - // 3 | let _ = x.sum() as f64; - // | ^^^ cannot infer type for `S` - span - } else if let Some(ExprKind::MethodCall(segment, ..)) = - local_visitor.found_method_call.map(|e| &e.kind) - { - // Point at the call instead of the whole expression: - // error[E0284]: type annotations needed - // --> file.rs:2:5 - // | - // 2 | [Ok(2)].into_iter().collect()?; - // | ^^^^^^^ cannot infer type - // | - // = note: cannot resolve `<_ as std::ops::Try>::Ok == _` - if span.contains(segment.ident.span) { segment.ident.span } else { span } - } else { - span - }; - let is_named_and_not_impl_trait = - |ty: Ty<'_>| &ty.to_string() != "_" && !ty.is_impl_trait(); - - let ty_msg = match (local_visitor.found_node_ty, local_visitor.found_exact_method_call) { - (_, Some(_)) => String::new(), - (Some(ty), _) if ty.is_closure() => { - let ty::Closure(_, substs) = *ty.kind() else { unreachable!() }; - let fn_sig = substs.as_closure().sig(); - let args = closure_args(&fn_sig); - let ret = fn_sig.output().skip_binder().to_string(); - format!(" for the closure `fn({}) -> {}`", args, ret) - } - (Some(ty), _) if is_named_and_not_impl_trait(ty) => { - let ty = ty_to_string(ty); - format!(" for `{}`", ty) - } - _ => String::new(), + let Some(InferSource { span, kind }) = local_visitor.infer_source else { + return self.bad_inference_failure_err(span, arg_data, error_code) }; - // When `arg_data.name` corresponds to a type argument, show the path of the full type we're - // trying to infer. In the following example, `ty_msg` contains - // " for `std::result::Result<i32, E>`": - // ``` - // error[E0282]: type annotations needed for `std::result::Result<i32, E>` - // --> file.rs:L:CC - // | - // L | let b = Ok(4); - // | - ^^ cannot infer type for `E` in `std::result::Result<i32, E>` - // | | - // | consider giving `b` the explicit type `std::result::Result<i32, E>`, where - // | the type parameter `E` is specified - // ``` let error_code = error_code.into(); let mut err = self.tcx.sess.struct_span_err_with_code( - err_span, - &format!("type annotations needed{}", ty_msg), + span, + &format!("type annotations needed{}", kind.ty_msg(self)), error_code, ); - - let use_diag = local_visitor.found_use_diagnostic.as_ref(); - if let Some(use_diag) = use_diag && use_diag.applies_to(err_span) { - use_diag.attach_note(&mut err); - } - - let param_type = arg_data.kind.descr(); - let suffix = match local_visitor.found_node_ty { - Some(ty) if ty.is_closure() => { - let ty::Closure(_, substs) = *ty.kind() else { unreachable!() }; - let fn_sig = substs.as_closure().sig(); - let ret = fn_sig.output().skip_binder().to_string(); - - let closure_decl_and_body_id = - local_visitor.found_closure.and_then(|closure| match &closure.kind { - ExprKind::Closure(_, decl, body_id, ..) => Some((decl, *body_id)), - _ => None, - }); - - if let Some((decl, body_id)) = closure_decl_and_body_id { - closure_return_type_suggestion( - &mut err, - &decl.output, - self.tcx.hir().body(body_id), - &ret, - ); - // We don't want to give the other suggestions when the problem is the - // closure return type. - err.span_label( - span, - arg_data.cannot_infer_msg(use_diag.filter(|d| d.applies_to(span))), - ); - return err; - } - - // This shouldn't be reachable, but just in case we leave a reasonable fallback. - let args = closure_args(&fn_sig); - // This suggestion is incomplete, as the user will get further type inference - // errors due to the `_` placeholders and the introduction of `Box`, but it does - // nudge them in the right direction. - format!("a boxed closure type like `Box<dyn Fn({}) -> {}>`", args, ret) + match kind { + InferSourceKind::LetBinding { insert_span, pattern_name, ty } => { + let suggestion_msg = if let Some(name) = pattern_name { + format!( + "consider giving `{}` an explicit type{}", + name, + arg_data.where_x_is_specified(ty) + ) + } else { + format!( + "consider giving this pattern a type{}", + arg_data.where_x_is_specified(ty) + ) + }; + err.span_suggestion_verbose( + insert_span, + &suggestion_msg, + format!(": {}", ty_to_string(self, ty)), + Applicability::HasPlaceholders, + ); } - Some(ty) if is_named_and_not_impl_trait(ty) && arg_data.name == "_" => { - let ty = ty_to_string(ty); - format!("the explicit type `{}`, with the {} parameters specified", ty, param_type) + InferSourceKind::ClosureArg { insert_span, ty } => { + err.span_suggestion_verbose( + insert_span, + &format!( + "consider giving this closure parameter an explicit type{}", + arg_data.where_x_is_specified(ty) + ), + format!(": {}", ty_to_string(self, ty)), + Applicability::HasPlaceholders, + ); } - Some(ty) if is_named_and_not_impl_trait(ty) && ty.to_string() != arg_data.name => { - let ty = ResolvedTypeParamEraser::new(self.tcx).fold_ty(ty); - let ty = ErrTypeParamEraser(self.tcx).fold_ty(ty); - let ty = ty_to_string(ty); - format!( - "the explicit type `{}`, where the {} parameter `{}` is specified", - ty, param_type, arg_data.name, - ) + InferSourceKind::GenericArg { + insert_span, + argument_index, + generics_def_id, + def_id: _, + generic_args, + } => { + let generics = self.tcx.generics_of(generics_def_id); + let is_type = matches!(arg.unpack(), GenericArgKind::Type(_)); + + let cannot_infer_msg = format!( + "cannot infer {} of the {} parameter `{}`{}", + if is_type { "type" } else { "the value" }, + if is_type { "type" } else { "const" }, + generics.params[argument_index].name, + // We use the `generics_def_id` here, as even when suggesting `None::<T>`, + // the type parameter `T` was still declared on the enum, not on the + // variant. + InferenceDiagnosticsParentData::for_parent_def_id(self.tcx, generics_def_id) + .map_or(String::new(), |parent| parent.suffix_string()), + ); + + err.span_label(span, cannot_infer_msg); + + let printer = fmt_printer(self, Namespace::TypeNS); + let args = printer.comma_sep(generic_args.iter().copied()).unwrap().into_buffer(); + err.span_suggestion_verbose( + insert_span, + &format!("consider specifying the generic argument{}", pluralize!(args.len()),), + format!("::<{}>", args), + Applicability::HasPlaceholders, + ); } - _ => "a type".to_string(), - }; + InferSourceKind::FullyQualifiedMethodCall { receiver, successor, substs, def_id } => { + let printer = fmt_printer(self, Namespace::ValueNS); + let def_path = printer.print_def_path(def_id, substs).unwrap().into_buffer(); + + // We only care about whether we have to add `&` or `&mut ` for now. + // This is the case if the last adjustment is a borrow and the + // first adjustment was not a builtin deref. + let adjustment = match typeck_results.expr_adjustments(receiver) { + [ + Adjustment { kind: Adjust::Deref(None), target: _ }, + .., + Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), target: _ }, + ] => "", + [ + .., + Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(_, mut_)), target: _ }, + ] => match mut_ { + AutoBorrowMutability::Mut { .. } => "&mut ", + AutoBorrowMutability::Not => "&", + }, + _ => "", + }; - if let Some(e) = local_visitor.found_exact_method_call { - if let ExprKind::MethodCall(segment, ..) = &e.kind { - // Suggest specifying type params or point out the return type of the call: - // - // error[E0282]: type annotations needed - // --> $DIR/type-annotations-needed-expr.rs:2:39 - // | - // LL | let _ = x.into_iter().sum() as f64; - // | ^^^ - // | | - // | cannot infer type for `S` - // | help: consider specifying the type argument in - // | the method call: `sum::<S>` - // | - // = note: type must be known at this point - // - // or - // - // error[E0282]: type annotations needed - // --> $DIR/issue-65611.rs:59:20 - // | - // LL | let x = buffer.last().unwrap().0.clone(); - // | -------^^^^-- - // | | | - // | | cannot infer type for `T` - // | this method call resolves to `std::option::Option<&T>` - // | - // = note: type must be known at this point - self.annotate_method_call(segment, e, &mut err); - } - } else if let Some(pattern) = local_visitor.found_arg_pattern { - // We don't want to show the default label for closures. - // - // So, before clearing, the output would look something like this: - // ``` - // let x = |_| { }; - // - ^^^^ cannot infer type for `[_; 0]` - // | - // consider giving this closure parameter a type - // ``` - // - // After clearing, it looks something like this: - // ``` - // let x = |_| { }; - // ^ consider giving this closure parameter the type `[_; 0]` - // with the type parameter `_` specified - // ``` - err.span_label( - pattern.span, - format!("consider giving this closure parameter {}", suffix), - ); - } else if let Some(pattern) = local_visitor.found_local_pattern { - let msg = if let Some(simple_ident) = pattern.simple_ident() { - match pattern.span.desugaring_kind() { - None => format!("consider giving `{}` {}", simple_ident, suffix), - Some(_) => format!("this needs {}", suffix), - } - } else { - format!("consider giving this pattern {}", suffix) - }; - err.span_label(pattern.span, msg); - } else if let Some(e) = local_visitor.found_method_call { - if let ExprKind::MethodCall(segment, exprs, _) = &e.kind { - // Suggest impl candidates: - // - // error[E0283]: type annotations needed - // --> $DIR/E0283.rs:35:24 - // | - // LL | let bar = foo_impl.into() * 1u32; - // | ---------^^^^-- - // | | | - // | | cannot infer type for type parameter `T` declared on the trait `Into` - // | this method call resolves to `T` - // | help: specify type like: `<Impl as Into<u32>>::into(foo_impl)` - // | - // = note: cannot satisfy `Impl: Into<_>` - debug!(?segment); - if !impl_candidates.is_empty() && e.span.contains(span) - && let Some(expr) = exprs.first() - && let ExprKind::Path(hir::QPath::Resolved(_, path)) = expr.kind - && let [_] = path.segments - { - let mut eraser = TypeParamEraser(self.tcx); - let candidate_len = impl_candidates.len(); - let mut suggestions: Vec<_> = impl_candidates.iter().filter_map(|candidate| { - let trait_item = self.tcx - .associated_items(candidate.def_id) - .find_by_name_and_kind( - self.tcx, - segment.ident, - ty::AssocKind::Fn, - candidate.def_id - ); - if trait_item.is_none() { - return None; - } - let prefix = if let Some(trait_item) = trait_item - && let Some(trait_m) = trait_item.def_id.as_local() - && let hir::TraitItemKind::Fn(fn_, _) = &self.tcx.hir().trait_item(hir::TraitItemId { def_id: trait_m }).kind - { - match fn_.decl.implicit_self { - hir::ImplicitSelfKind::ImmRef => "&", - hir::ImplicitSelfKind::MutRef => "&mut ", - _ => "", - } - } else { - "" - }; - let candidate = candidate.super_fold_with(&mut eraser); - Some(vec![ - (expr.span.shrink_to_lo(), format!("{}::{}({}", candidate, segment.ident, prefix)), - if exprs.len() == 1 { - (expr.span.shrink_to_hi().with_hi(e.span.hi()), ")".to_string()) - } else { - (expr.span.shrink_to_hi().with_hi(exprs[1].span.lo()), ", ".to_string()) - }, - ]) - }).collect(); - suggestions.sort_by(|a, b| a[0].1.cmp(&b[0].1)); - if !suggestions.is_empty() { - err.multipart_suggestions( - &format!( - "use the fully qualified path for the potential candidate{}", - pluralize!(candidate_len), - ), - suggestions.into_iter(), - Applicability::MaybeIncorrect, - ); - } - } - // Suggest specifying type params or point out the return type of the call: - // - // error[E0282]: type annotations needed - // --> $DIR/type-annotations-needed-expr.rs:2:39 - // | - // LL | let _ = x.into_iter().sum() as f64; - // | ^^^ - // | | - // | cannot infer type for `S` - // | help: consider specifying the type argument in - // | the method call: `sum::<S>` - // | - // = note: type must be known at this point - // - // or - // - // error[E0282]: type annotations needed - // --> $DIR/issue-65611.rs:59:20 - // | - // LL | let x = buffer.last().unwrap().0.clone(); - // | -------^^^^-- - // | | | - // | | cannot infer type for `T` - // | this method call resolves to `std::option::Option<&T>` - // | - // = note: type must be known at this point - self.annotate_method_call(segment, e, &mut err); + let suggestion = vec![ + (receiver.span.shrink_to_lo(), format!("{def_path}({adjustment}")), + (receiver.span.shrink_to_hi().with_hi(successor.1), successor.0.to_string()), + ]; + err.multipart_suggestion_verbose( + "try using a fully qualified path to specify the expected types", + suggestion, + Applicability::HasPlaceholders, + ); } - } else if let Some(scrutinee) = local_visitor.found_for_loop_iter { - err.span_label( - scrutinee.span, - "the element type for this iterator is not specified".to_string(), - ); - } - // Instead of the following: - // error[E0282]: type annotations needed - // --> file2.rs:3:15 - // | - // 3 | let _ = x.sum() as f64; - // | --^^^--------- cannot infer type for `S` - // | - // = note: type must be known at this point - // We want: - // error[E0282]: type annotations needed - // --> file2.rs:3:15 - // | - // 3 | let _ = x.sum() as f64; - // | ^^^ cannot infer type for `S` - // | - // = note: type must be known at this point - let span = arg_data.span.unwrap_or(err_span); - - // Avoid multiple labels pointing at `span`. - if !err - .span - .span_labels() - .iter() - .any(|span_label| span_label.label.is_some() && span_label.span == span) - && local_visitor.found_arg_pattern.is_none() - { - // FIXME(const_generics): we would like to handle const arguments - // as part of the normal diagnostics flow below, but there appear to - // be subtleties in doing so, so for now we special-case const args - // here. - if let (UnderspecifiedArgKind::Const { .. }, Some(parent_data)) = - (&arg_data.kind, &arg_data.parent) - { - // (#83606): Do not emit a suggestion if the parent has an `impl Trait` - // as an argument otherwise it will cause the E0282 error. - if !self.tcx.generics_of(parent_data.def_id).has_impl_trait() - || self.tcx.features().explicit_generic_args_with_impl_trait - { - err.span_suggestion_verbose( - span, - "consider specifying the const argument", - format!("{}::<{}>", parent_data.name, arg_data.name), - Applicability::MaybeIncorrect, - ); - } + InferSourceKind::ClosureReturn { ty, data, should_wrap_expr } => { + let ret = ty_to_string(self, ty); + let (arrow, post) = match data { + FnRetTy::DefaultReturn(_) => ("-> ", " "), + _ => ("", ""), + }; + let suggestion = match should_wrap_expr { + Some(end_span) => vec![ + (data.span(), format!("{}{}{}{{ ", arrow, ret, post)), + (end_span, " }".to_string()), + ], + None => vec![(data.span(), format!("{}{}{}", arrow, ret, post))], + }; + err.multipart_suggestion_verbose( + "try giving this closure an explicit return type", + suggestion, + Applicability::HasPlaceholders, + ); } - - self.report_ambiguous_type_parameter(&mut err, arg); - err.span_label( - span, - arg_data.cannot_infer_msg(use_diag.filter(|d| d.applies_to(span))), - ); } - err } - fn trait_def_from_hir_fn(&self, hir_id: hir::HirId) -> Option<DefId> { - // The DefId will be the method's trait item ID unless this is an inherent impl - if let Some((DefKind::AssocFn, def_id)) = - self.in_progress_typeck_results?.borrow().type_dependent_def(hir_id) - { - let parent_def_id = self.tcx.parent(def_id); - return self.tcx.is_trait(parent_def_id).then_some(parent_def_id); - } - - None - } - - /// If the `FnSig` for the method call can be found and type arguments are identified as - /// needed, suggest annotating the call, otherwise point out the resulting type of the call. - fn annotate_method_call( - &self, - segment: &hir::PathSegment<'_>, - e: &Expr<'_>, - err: &mut Diagnostic, - ) { - if let (Some(typeck_results), None) = (self.in_progress_typeck_results, &segment.args) { - let borrow = typeck_results.borrow(); - if let Some((DefKind::AssocFn, did)) = borrow.type_dependent_def(e.hir_id) { - let generics = self.tcx.generics_of(did); - if !generics.params.is_empty() && !generics.has_impl_trait() { - err.span_suggestion_verbose( - segment.ident.span.shrink_to_hi(), - &format!( - "consider specifying the type argument{} in the method call", - pluralize!(generics.params.len()), - ), - format!( - "::<{}>", - generics - .params - .iter() - .map(|p| p.name.to_string()) - .collect::<Vec<String>>() - .join(", ") - ), - Applicability::HasPlaceholders, - ); - } else { - let sig = self.tcx.fn_sig(did); - let bound_output = sig.output(); - let output = bound_output.skip_binder(); - err.span_label(e.span, &format!("this method call resolves to `{}`", output)); - let kind = output.kind(); - if let ty::Projection(proj) = kind { - if let Some(span) = self.tcx.hir().span_if_local(proj.item_def_id) { - err.span_label(span, &format!("`{}` defined here", output)); - } - } - } - } - } - } - - fn report_ambiguous_type_parameter(&self, err: &mut Diagnostic, arg: GenericArg<'tcx>) { - if let GenericArgKind::Type(ty) = arg.unpack() - && let ty::Infer(ty::TyVar(ty_vid)) = *ty.kind() - { - let mut inner = self.inner.borrow_mut(); - let ty_vars = &inner.type_variables(); - let var_origin = ty_vars.var_origin(ty_vid); - if let TypeVariableOriginKind::TypeParameterDefinition(_, Some(def_id)) = - var_origin.kind - && let Some(parent_def_id) = self.tcx.parent(def_id).as_local() - && let Some(node) = self.tcx.hir().find_by_def_id(parent_def_id) - { - match node { - hir::Node::Item(item) if matches!(item.kind, hir::ItemKind::Impl(_) | hir::ItemKind::Fn(..)) => (), - hir::Node::ImplItem(impl_item) if matches!(impl_item.kind, hir::ImplItemKind::Fn(..)) => (), - _ => return, - } - err.span_help(self.tcx.def_span(def_id), "type parameter declared here"); - } - } - } - pub fn need_type_info_err_in_generator( &self, kind: hir::GeneratorKind, @@ -972,136 +487,564 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { "type inside {} must be known in this context", kind, ); - err.span_label(span, data.cannot_infer_msg(None)); + err.span_label(span, data.cannot_infer_msg()); err } } -/// Turn *resolved* type params into `[type error]` to signal we don't want to display them. After -/// performing that replacement, we'll turn all remaining infer type params to use their name from -/// their definition, and replace all the `[type error]`s back to being infer so they display in -/// the output as `_`. If we didn't go through `[type error]`, we would either show all type params -/// by their name *or* `_`, neither of which is desirable: we want to show all types that we could -/// infer as `_` to reduce verbosity and avoid telling the user about unnecessary type annotations. -struct ResolvedTypeParamEraser<'tcx> { - tcx: TyCtxt<'tcx>, - level: usize, +#[derive(Debug)] +struct InferSource<'tcx> { + span: Span, + kind: InferSourceKind<'tcx>, } -impl<'tcx> ResolvedTypeParamEraser<'tcx> { - fn new(tcx: TyCtxt<'tcx>) -> Self { - ResolvedTypeParamEraser { tcx, level: 0 } - } +#[derive(Debug)] +enum InferSourceKind<'tcx> { + LetBinding { + insert_span: Span, + pattern_name: Option<Ident>, + ty: Ty<'tcx>, + }, + ClosureArg { + insert_span: Span, + ty: Ty<'tcx>, + }, + GenericArg { + insert_span: Span, + argument_index: usize, + generics_def_id: DefId, + def_id: DefId, + generic_args: &'tcx [GenericArg<'tcx>], + }, + FullyQualifiedMethodCall { + receiver: &'tcx Expr<'tcx>, + /// If the method has other arguments, this is ", " and the start of the first argument, + /// while for methods without arguments this is ")" and the end of the method call. + successor: (&'static str, BytePos), + substs: SubstsRef<'tcx>, + def_id: DefId, + }, + ClosureReturn { + ty: Ty<'tcx>, + data: &'tcx FnRetTy<'tcx>, + should_wrap_expr: Option<Span>, + }, +} - /// Replace not yet inferred const params with their def name. - fn replace_infers(&self, c: Const<'tcx>, index: u32, name: Symbol) -> Const<'tcx> { - match c.val() { - ty::ConstKind::Infer(..) => self.tcx().mk_const_param(index, name, c.ty()), - _ => c, +impl<'tcx> InferSourceKind<'tcx> { + fn ty_msg(&self, infcx: &InferCtxt<'_, 'tcx>) -> String { + match *self { + InferSourceKind::LetBinding { ty, .. } + | InferSourceKind::ClosureArg { ty, .. } + | InferSourceKind::ClosureReturn { ty, .. } => { + if ty.is_closure() { + format!(" for the closure `{}`", closure_as_fn_str(infcx, ty)) + } else if !ty.is_ty_infer() { + format!(" for `{}`", ty_to_string(infcx, ty)) + } else { + String::new() + } + } + // FIXME: We should be able to add some additional info here. + InferSourceKind::GenericArg { .. } + | InferSourceKind::FullyQualifiedMethodCall { .. } => String::new(), } } } -impl<'tcx> TypeFolder<'tcx> for ResolvedTypeParamEraser<'tcx> { - fn tcx<'a>(&'a self) -> TyCtxt<'tcx> { - self.tcx +struct InsertableGenericArgs<'tcx> { + insert_span: Span, + substs: SubstsRef<'tcx>, + generics_def_id: DefId, + def_id: DefId, +} + +/// A visitor which searches for the "best" spot to use in the inference error. +/// +/// For this it walks over the hir body and tries to check all places where +/// inference variables could be bound. +/// +/// While doing so, the currently best spot is stored in `infer_source`. +/// For details on how we rank spots, see [Self::source_cost] +struct FindInferSourceVisitor<'a, 'tcx> { + infcx: &'a InferCtxt<'a, 'tcx>, + typeck_results: &'a TypeckResults<'tcx>, + + target: GenericArg<'tcx>, + + attempt: usize, + infer_source_cost: usize, + infer_source: Option<InferSource<'tcx>>, +} + +impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> { + fn new( + infcx: &'a InferCtxt<'a, 'tcx>, + typeck_results: &'a TypeckResults<'tcx>, + target: GenericArg<'tcx>, + ) -> Self { + FindInferSourceVisitor { + infcx, + typeck_results, + + target, + + attempt: 0, + infer_source_cost: usize::MAX, + infer_source: None, + } } - fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { - self.level += 1; - let t = match t.kind() { - // We'll hide this type only if all its type params are hidden as well. - ty::Adt(def, substs) => { - let generics = self.tcx().generics_of(def.did()); - // Account for params with default values, like `Vec`, where we - // want to show `Vec<T>`, not `Vec<T, _>`. If we replaced that - // subst, then we'd get the incorrect output, so we passthrough. - let substs: Vec<_> = substs - .iter() - .zip(generics.params.iter()) - .map(|(subst, param)| match &(subst.unpack(), ¶m.kind) { - (_, ty::GenericParamDefKind::Type { has_default: true, .. }) => subst, - (crate::infer::GenericArgKind::Const(c), _) => { - self.replace_infers(*c, param.index, param.name).into() - } - _ => subst.super_fold_with(self), - }) - .collect(); - let should_keep = |subst: &GenericArg<'_>| match subst.unpack() { - ty::subst::GenericArgKind::Type(t) => match t.kind() { - ty::Error(_) => false, - _ => true, - }, - // Account for `const` params here, otherwise `doesnt_infer.rs` - // shows `_` instead of `Foo<{ _: u32 }>` - ty::subst::GenericArgKind::Const(_) => true, - _ => false, + + /// Computes cost for the given source. + /// + /// Sources with a small cost are prefer and should result + /// in a clearer and idiomatic suggestion. + fn source_cost(&self, source: &InferSource<'tcx>) -> usize { + let tcx = self.infcx.tcx; + + fn arg_cost<'tcx>(arg: GenericArg<'tcx>) -> usize { + match arg.unpack() { + GenericArgKind::Lifetime(_) => 0, // erased + GenericArgKind::Type(ty) => ty_cost(ty), + GenericArgKind::Const(_) => 3, // some non-zero value + } + } + fn ty_cost<'tcx>(ty: Ty<'tcx>) -> usize { + match ty.kind() { + ty::Closure(..) => 100, + ty::FnDef(..) => 20, + ty::FnPtr(..) => 10, + ty::Infer(..) => 0, + _ => 1, + } + } + + // The sources are listed in order of preference here. + match source.kind { + InferSourceKind::LetBinding { ty, .. } => ty_cost(ty), + InferSourceKind::ClosureArg { ty, .. } => 5 + ty_cost(ty), + InferSourceKind::GenericArg { def_id, generic_args, .. } => { + let variant_cost = match tcx.def_kind(def_id) { + DefKind::Variant | DefKind::Ctor(CtorOf::Variant, _) => 15, // `None::<u32>` and friends are ugly. + _ => 12, }; - if self.level == 1 || substs.iter().any(should_keep) { - let substs = self.tcx().intern_substs(&substs[..]); - self.tcx().mk_ty(ty::Adt(*def, substs)) - } else { - self.tcx().ty_error() + variant_cost + generic_args.iter().map(|&arg| arg_cost(arg)).sum::<usize>() + } + InferSourceKind::FullyQualifiedMethodCall { substs, .. } => { + 20 + substs.iter().map(|arg| arg_cost(arg)).sum::<usize>() + } + InferSourceKind::ClosureReturn { ty, should_wrap_expr, .. } => { + 30 + ty_cost(ty) + if should_wrap_expr.is_some() { 10 } else { 0 } + } + } + } + + /// Uses `fn source_cost` to determine whether this inference source is preferable to + /// previous sources. We generally prefer earlier sources. + #[instrument(level = "debug", skip(self))] + fn update_infer_source(&mut self, new_source: InferSource<'tcx>) { + let cost = self.source_cost(&new_source) + self.attempt; + self.attempt += 1; + if cost < self.infer_source_cost { + self.infer_source_cost = cost; + self.infer_source = Some(new_source); + } + } + + fn opt_node_type(&self, hir_id: HirId) -> Option<Ty<'tcx>> { + let ty = self.typeck_results.node_type_opt(hir_id); + self.infcx.resolve_vars_if_possible(ty) + } + + // Check whether this generic argument is the inference variable we + // are looking for. + fn generic_arg_is_target(&self, arg: GenericArg<'tcx>) -> bool { + if arg == self.target { + return true; + } + + match (arg.unpack(), self.target.unpack()) { + (GenericArgKind::Type(inner_ty), GenericArgKind::Type(target_ty)) => { + use ty::{Infer, TyVar}; + match (inner_ty.kind(), target_ty.kind()) { + (&Infer(TyVar(a_vid)), &Infer(TyVar(b_vid))) => { + self.infcx.inner.borrow_mut().type_variables().sub_unified(a_vid, b_vid) + } + _ => false, + } + } + (GenericArgKind::Const(inner_ct), GenericArgKind::Const(target_ct)) => { + use ty::InferConst::*; + match (inner_ct.val(), target_ct.val()) { + (ty::ConstKind::Infer(Var(a_vid)), ty::ConstKind::Infer(Var(b_vid))) => self + .infcx + .inner + .borrow_mut() + .const_unification_table() + .unioned(a_vid, b_vid), + _ => false, + } + } + _ => false, + } + } + + /// Does this generic argument contain our target inference variable + /// in a way which can be written by the user. + fn generic_arg_contains_target(&self, arg: GenericArg<'tcx>) -> bool { + let mut walker = arg.walk(); + while let Some(inner) = walker.next() { + if self.generic_arg_is_target(inner) { + return true; + } + match inner.unpack() { + GenericArgKind::Lifetime(_) => {} + GenericArgKind::Type(ty) => { + if matches!(ty.kind(), ty::Opaque(..) | ty::Closure(..) | ty::Generator(..)) { + // Opaque types can't be named by the user right now. + // + // Both the generic arguments of closures and generators can + // also not be named. We may want to only look into the closure + // signature in case it has no captures, as that can be represented + // using `fn(T) -> R`. + + // FIXME(type_alias_impl_trait): These opaque types + // can actually be named, so it would make sense to + // adjust this case and add a test for it. + walker.skip_current_subtree(); + } + } + GenericArgKind::Const(ct) => { + if matches!(ct.val(), ty::ConstKind::Unevaluated(..)) { + // You can't write the generic arguments for + // unevaluated constants. + walker.skip_current_subtree(); + } } } - ty::Ref(_, ty, _) => { - let ty = self.fold_ty(*ty); - match ty.kind() { - // Avoid `&_`, these can be safely presented as `_`. - ty::Error(_) => self.tcx().ty_error(), - _ => t.super_fold_with(self), + } + false + } + + fn expr_inferred_subst_iter( + &self, + expr: &'tcx hir::Expr<'tcx>, + ) -> Box<dyn Iterator<Item = InsertableGenericArgs<'tcx>> + 'a> { + let tcx = self.infcx.tcx; + match expr.kind { + hir::ExprKind::Path(ref path) => { + if let Some(substs) = self.typeck_results.node_substs_opt(expr.hir_id) { + return self.path_inferred_subst_iter(expr.hir_id, substs, path); } } - // We could account for `()` if we wanted to replace it, but it's assured to be short. - ty::Tuple(_) - | ty::Slice(_) - | ty::RawPtr(_) - | ty::FnDef(..) - | ty::FnPtr(_) - | ty::Opaque(..) - | ty::Projection(_) - | ty::Never => t.super_fold_with(self), - ty::Array(ty, c) => { - self.tcx().mk_ty(ty::Array(self.fold_ty(*ty), self.replace_infers(*c, 0, sym::N))) + hir::ExprKind::Struct(path, _, _) => { + if let Some(ty) = self.opt_node_type(expr.hir_id) { + if let ty::Adt(_, substs) = ty.kind() { + return self.path_inferred_subst_iter(expr.hir_id, substs, path); + } + } + } + hir::ExprKind::MethodCall(segment, _, _) => { + if let Some(def_id) = self.typeck_results.type_dependent_def_id(expr.hir_id) { + let generics = tcx.generics_of(def_id); + let insertable: Option<_> = try { + if generics.has_impl_trait() { + None? + } + let substs = self.typeck_results.node_substs_opt(expr.hir_id)?; + let span = tcx.hir().span(segment.hir_id?); + let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi()); + InsertableGenericArgs { + insert_span, + substs, + generics_def_id: def_id, + def_id, + } + }; + return Box::new(insertable.into_iter()); + } + } + _ => {} + } + + Box::new(iter::empty()) + } + + fn resolved_path_inferred_subst_iter( + &self, + path: &'tcx hir::Path<'tcx>, + substs: SubstsRef<'tcx>, + ) -> impl Iterator<Item = InsertableGenericArgs<'tcx>> + 'a { + let tcx = self.infcx.tcx; + // The last segment of a path often has `Res::Err` and the + // correct `Res` is the one of the whole path. + // + // FIXME: We deal with that one separately for now, + // would be good to remove this special case. + let last_segment_using_path_data: Option<_> = try { + let generics_def_id = tcx.res_generics_def_id(path.res)?; + let generics = tcx.generics_of(generics_def_id); + if generics.has_impl_trait() { + None? + } + let insert_span = + path.segments.last().unwrap().ident.span.shrink_to_hi().with_hi(path.span.hi()); + InsertableGenericArgs { + insert_span, + substs, + generics_def_id, + def_id: path.res.def_id(), } - // We don't want to hide type params that haven't been resolved yet. - // This would be the type that will be written out with the type param - // name in the output. - ty::Infer(_) => t, - // We don't want to hide the outermost type, only its type params. - _ if self.level == 1 => t.super_fold_with(self), - // Hide this type - _ => self.tcx().ty_error(), }; - self.level -= 1; - t + + path.segments + .iter() + .filter_map(move |segment| { + let res = segment.res?; + let generics_def_id = tcx.res_generics_def_id(res)?; + let generics = tcx.generics_of(generics_def_id); + if generics.has_impl_trait() { + return None; + } + let span = tcx.hir().span(segment.hir_id?); + let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi()); + Some(InsertableGenericArgs { + insert_span, + substs, + generics_def_id, + def_id: res.def_id(), + }) + }) + .chain(last_segment_using_path_data) + } + + fn path_inferred_subst_iter( + &self, + hir_id: HirId, + substs: SubstsRef<'tcx>, + qpath: &'tcx hir::QPath<'tcx>, + ) -> Box<dyn Iterator<Item = InsertableGenericArgs<'tcx>> + 'a> { + let tcx = self.infcx.tcx; + match qpath { + hir::QPath::Resolved(_self_ty, path) => { + Box::new(self.resolved_path_inferred_subst_iter(path, substs)) + } + hir::QPath::TypeRelative(ty, segment) => { + let Some(def_id) = self.typeck_results.type_dependent_def_id(hir_id) else { + return Box::new(iter::empty()); + }; + + let generics = tcx.generics_of(def_id); + let segment: Option<_> = try { + if !segment.infer_args || generics.has_impl_trait() { + None?; + } + let span = tcx.hir().span(segment.hir_id?); + let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi()); + InsertableGenericArgs { insert_span, substs, generics_def_id: def_id, def_id } + }; + + let parent_def_id = generics.parent.unwrap(); + if tcx.def_kind(parent_def_id) == DefKind::Impl { + let parent_ty = tcx.bound_type_of(parent_def_id).subst(tcx, substs); + match (parent_ty.kind(), &ty.kind) { + ( + ty::Adt(def, substs), + hir::TyKind::Path(hir::QPath::Resolved(_self_ty, path)), + ) => { + if tcx.res_generics_def_id(path.res) != Some(def.did()) { + bug!( + "unexpected path: def={:?} substs={:?} path={:?}", + def, + substs, + path, + ); + } else { + return Box::new( + self.resolved_path_inferred_subst_iter(path, substs) + .chain(segment), + ); + } + } + _ => (), + } + } + + Box::new(segment.into_iter()) + } + hir::QPath::LangItem(_, _, _) => Box::new(iter::empty()), + } } } -/// Replace `[type error]` with `ty::Infer(ty::Var)` to display `_`. -struct ErrTypeParamEraser<'tcx>(TyCtxt<'tcx>); -impl<'tcx> TypeFolder<'tcx> for ErrTypeParamEraser<'tcx> { - fn tcx<'a>(&'a self) -> TyCtxt<'tcx> { - self.0 +impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> { + type NestedFilter = nested_filter::OnlyBodies; + + fn nested_visit_map(&mut self) -> Self::Map { + self.infcx.tcx.hir() } - fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { - match t.kind() { - ty::Error(_) => self.tcx().mk_ty_var(ty::TyVid::from_u32(0)), - _ => t.super_fold_with(self), + + fn visit_local(&mut self, local: &'tcx Local<'tcx>) { + intravisit::walk_local(self, local); + + if let Some(ty) = self.opt_node_type(local.hir_id) { + if self.generic_arg_contains_target(ty.into()) { + match local.source { + LocalSource::Normal if local.ty.is_none() => { + self.update_infer_source(InferSource { + span: local.pat.span, + kind: InferSourceKind::LetBinding { + insert_span: local.pat.span.shrink_to_hi(), + pattern_name: local.pat.simple_ident(), + ty, + }, + }) + } + _ => {} + } + } } } -} -/// Replace type parameters with `ty::Infer(ty::Var)` to display `_`. -struct TypeParamEraser<'tcx>(TyCtxt<'tcx>); + /// For closures, we first visit the parameters and then the content, + /// as we prefer those. + fn visit_body(&mut self, body: &'tcx Body<'tcx>) { + for param in body.params { + debug!( + "param: span {:?}, ty_span {:?}, pat.span {:?}", + param.span, param.ty_span, param.pat.span + ); + if param.ty_span != param.pat.span { + debug!("skipping param: has explicit type"); + continue; + } + + let Some(param_ty) = self.opt_node_type(param.hir_id) else { + continue + }; -impl<'tcx> TypeFolder<'tcx> for TypeParamEraser<'tcx> { - fn tcx<'a>(&'a self) -> TyCtxt<'tcx> { - self.0 + if self.generic_arg_contains_target(param_ty.into()) { + self.update_infer_source(InferSource { + span: param.pat.span, + kind: InferSourceKind::ClosureArg { + insert_span: param.pat.span.shrink_to_hi(), + ty: param_ty, + }, + }) + } + } + intravisit::walk_body(self, body); } - fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { - match t.kind() { - ty::Param(_) | ty::Error(_) => self.tcx().mk_ty_var(ty::TyVid::from_u32(0)), - _ => t.super_fold_with(self), + + fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { + let tcx = self.infcx.tcx; + match expr.kind { + // When encountering `func(arg)` first look into `arg` and then `func`, + // as `arg` is "more specific". + ExprKind::Call(func, args) => { + for arg in args { + self.visit_expr(arg); + } + self.visit_expr(func); + } + _ => intravisit::walk_expr(self, expr), + } + + for InsertableGenericArgs { insert_span, substs, generics_def_id, def_id } in + self.expr_inferred_subst_iter(expr) + { + let generics = tcx.generics_of(generics_def_id); + if let Some(argument_index) = + generics.own_substs(substs).iter().position(|&arg| self.generic_arg_is_target(arg)) + { + let substs = self.infcx.resolve_vars_if_possible(substs); + let num_args = generics + .params + .iter() + .rev() + .filter(|&p| !matches!(p.kind, GenericParamDefKind::Lifetime)) + .skip_while(|¶m| { + if let Some(default) = param.default_value(tcx) { + // FIXME: Using structural comparisions has a bunch of false negatives. + // + // We should instead try to replace inference variables with placeholders and + // then use `infcx.can_eq`. That probably should be a separate method + // generally used during error reporting. + default.subst(tcx, substs) == substs[param.index as usize] + } else { + false + } + }) + .count(); + let generic_args = + &generics.own_substs(substs)[generics.own_counts().lifetimes..][..num_args]; + let span = match expr.kind { + ExprKind::MethodCall(path, _, _) => path.ident.span, + _ => expr.span, + }; + + self.update_infer_source(InferSource { + span, + kind: InferSourceKind::GenericArg { + insert_span, + argument_index, + generics_def_id, + def_id, + generic_args, + }, + }); + } + } + + if let Some(node_ty) = self.opt_node_type(expr.hir_id) { + if let (&ExprKind::Closure(_, decl, body_id, span, _), ty::Closure(_, substs)) = + (&expr.kind, node_ty.kind()) + { + let output = substs.as_closure().sig().output().skip_binder(); + if self.generic_arg_contains_target(output.into()) { + let body = self.infcx.tcx.hir().body(body_id); + let should_wrap_expr = if matches!(body.value.kind, ExprKind::Block(..)) { + None + } else { + Some(body.value.span.shrink_to_hi()) + }; + self.update_infer_source(InferSource { + span, + kind: InferSourceKind::ClosureReturn { + ty: output, + data: &decl.output, + should_wrap_expr, + }, + }) + } + } + } + + let has_impl_trait = |def_id| { + iter::successors(Some(tcx.generics_of(def_id)), |generics| { + generics.parent.map(|def_id| tcx.generics_of(def_id)) + }) + .any(|generics| generics.has_impl_trait()) + }; + if let ExprKind::MethodCall(path, args, span) = expr.kind + && let Some(substs) = self.typeck_results.node_substs_opt(expr.hir_id) + && substs.iter().any(|arg| self.generic_arg_contains_target(arg)) + && let Some(def_id) = self.typeck_results.type_dependent_def_id(expr.hir_id) + && self.infcx.tcx.trait_of_item(def_id).is_some() + && !has_impl_trait(def_id) + { + let successor = + args.get(1).map_or_else(|| (")", span.hi()), |arg| (", ", arg.span.lo())); + let substs = self.infcx.resolve_vars_if_possible(substs); + self.update_infer_source(InferSource { + span: path.ident.span, + kind: InferSourceKind::FullyQualifiedMethodCall { + receiver: args.first().unwrap(), + successor, + substs, + def_id, + } + }) } } } diff --git a/compiler/rustc_infer/src/lib.rs b/compiler/rustc_infer/src/lib.rs index 0f13a9b1388..7769a68ba2a 100644 --- a/compiler/rustc_infer/src/lib.rs +++ b/compiler/rustc_infer/src/lib.rs @@ -22,6 +22,7 @@ #![feature(let_else)] #![feature(min_specialization)] #![feature(never_type)] +#![feature(try_blocks)] #![recursion_limit = "512"] // For rustdoc #[macro_use] diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs index 2c40eab8764..aab84b718d4 100644 --- a/compiler/rustc_middle/src/hir/map/mod.rs +++ b/compiler/rustc_middle/src/hir/map/mod.rs @@ -987,7 +987,11 @@ impl<'hir> Map<'hir> { Node::AnonConst(constant) => self.body(constant.body).value.span, Node::Expr(expr) => expr.span, Node::Stmt(stmt) => stmt.span, - Node::PathSegment(seg) => seg.ident.span, + Node::PathSegment(seg) => { + let ident_span = seg.ident.span; + ident_span + .with_hi(seg.args.map_or_else(|| ident_span.hi(), |args| args.span_ext.hi())) + } Node::Ty(ty) => ty.span, Node::TraitRef(tr) => tr.path.span, Node::Binding(pat) => pat.span, diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs index d9b82ee0a76..1feabb2d6b1 100644 --- a/compiler/rustc_middle/src/ty/generics.rs +++ b/compiler/rustc_middle/src/ty/generics.rs @@ -63,6 +63,29 @@ impl GenericParamDef { bug!("cannot convert a non-lifetime parameter def to an early bound region") } } + + pub fn has_default(&self) -> bool { + match self.kind { + GenericParamDefKind::Type { has_default, .. } + | GenericParamDefKind::Const { has_default } => has_default, + GenericParamDefKind::Lifetime => false, + } + } + + pub fn default_value<'tcx>( + &self, + tcx: TyCtxt<'tcx>, + ) -> Option<EarlyBinder<ty::GenericArg<'tcx>>> { + match self.kind { + GenericParamDefKind::Type { has_default, .. } if has_default => { + Some(EarlyBinder(tcx.type_of(self.def_id).into())) + } + GenericParamDefKind::Const { has_default } if has_default => { + Some(EarlyBinder(tcx.const_param_default(self.def_id).into())) + } + _ => None, + } + } } #[derive(Default)] @@ -204,6 +227,12 @@ impl<'tcx> Generics { matches!(param.kind, ty::GenericParamDefKind::Type { synthetic: true, .. }) }) } + + /// Returns the substs corresponding to the generic parameters of this item, excluding `Self`. + pub fn own_substs(&'tcx self, substs: SubstsRef<'tcx>) -> &'tcx [ty::GenericArg<'tcx>] { + let own = &substs[self.parent_count..][..self.params.len()]; + if self.has_self && self.parent.is_none() { &own[1..] } else { &own } + } } /// Bounds on generics. |