diff options
Diffstat (limited to '')
| -rw-r--r-- | compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs | 383 |
1 files changed, 305 insertions, 78 deletions
diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs b/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs index 57771e096..ee0ad7b5d 100644 --- a/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs +++ b/compiler/rustc_typeck/src/check/fn_ctxt/suggestions.rs @@ -2,6 +2,7 @@ use super::FnCtxt; use crate::astconv::AstConv; use crate::errors::{AddReturnTypeSuggestion, ExpectedReturnTypeLabel}; +use hir::def_id::DefId; use rustc_ast::util::parser::ExprPrecedence; use rustc_errors::{Applicability, Diagnostic, MultiSpan}; use rustc_hir as hir; @@ -16,6 +17,7 @@ use rustc_middle::lint::in_external_macro; use rustc_middle::ty::{self, Binder, IsSuggestable, Subst, ToPredicate, Ty}; use rustc_span::symbol::sym; use rustc_span::Span; +use rustc_trait_selection::infer::InferCtxtExt; use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _; impl<'a, 'tcx> FnCtxt<'a, 'tcx> { @@ -61,70 +63,51 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { pointing_at_return_type } - /// When encountering an fn-like ctor that needs to unify with a value, check whether calling - /// the ctor would successfully solve the type mismatch and if so, suggest it: + /// When encountering an fn-like type, try accessing the output of the type + /// // and suggesting calling it if it satisfies a predicate (i.e. if the + /// output has a method or a field): /// ```compile_fail,E0308 /// fn foo(x: usize) -> usize { x } /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)` /// ``` - fn suggest_fn_call( + pub(crate) fn suggest_fn_call( &self, err: &mut Diagnostic, expr: &hir::Expr<'_>, - expected: Ty<'tcx>, found: Ty<'tcx>, + can_satisfy: impl FnOnce(Ty<'tcx>) -> bool, ) -> bool { - let (def_id, output, inputs) = match *found.kind() { - ty::FnDef(def_id, _) => { - let fn_sig = found.fn_sig(self.tcx); - (def_id, fn_sig.output(), fn_sig.inputs().skip_binder().len()) - } - ty::Closure(def_id, substs) => { - let fn_sig = substs.as_closure().sig(); - (def_id, fn_sig.output(), fn_sig.inputs().skip_binder().len() - 1) - } - ty::Opaque(def_id, substs) => { - let sig = self.tcx.bound_item_bounds(def_id).subst(self.tcx, substs).iter().find_map(|pred| { - if let ty::PredicateKind::Projection(proj) = pred.kind().skip_binder() - && Some(proj.projection_ty.item_def_id) == self.tcx.lang_items().fn_once_output() - // args tuple will always be substs[1] - && let ty::Tuple(args) = proj.projection_ty.substs.type_at(1).kind() - { - Some(( - pred.kind().rebind(proj.term.ty().unwrap()), - args.len(), - )) - } else { - None - } - }); - if let Some((output, inputs)) = sig { - (def_id, output, inputs) - } else { - return false; - } - } - _ => return false, - }; - - let output = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, output); - let output = self.normalize_associated_types_in(expr.span, output); - if !output.is_ty_var() && self.can_coerce(output, expected) { - let (sugg_call, mut applicability) = match inputs { + let Some((def_id_or_name, output, inputs)) = self.extract_callable_info(expr, found) + else { return false; }; + if can_satisfy(output) { + let (sugg_call, mut applicability) = match inputs.len() { 0 => ("".to_string(), Applicability::MachineApplicable), 1..=4 => ( - (0..inputs).map(|_| "_").collect::<Vec<_>>().join(", "), - Applicability::MachineApplicable, + inputs + .iter() + .map(|ty| { + if ty.is_suggestable(self.tcx, false) { + format!("/* {ty} */") + } else { + "".to_string() + } + }) + .collect::<Vec<_>>() + .join(", "), + Applicability::HasPlaceholders, ), - _ => ("...".to_string(), Applicability::HasPlaceholders), + _ => ("/* ... */".to_string(), Applicability::HasPlaceholders), }; - let msg = match self.tcx.def_kind(def_id) { - DefKind::Fn => "call this function", - DefKind::Closure | DefKind::OpaqueTy => "call this closure", - DefKind::Ctor(CtorOf::Struct, _) => "instantiate this tuple struct", - DefKind::Ctor(CtorOf::Variant, _) => "instantiate this tuple variant", - _ => "call this function", + let msg = match def_id_or_name { + DefIdOrName::DefId(def_id) => match self.tcx.def_kind(def_id) { + DefKind::Ctor(CtorOf::Struct, _) => "instantiate this tuple struct".to_string(), + DefKind::Ctor(CtorOf::Variant, _) => { + "instantiate this tuple variant".to_string() + } + kind => format!("call this {}", kind.descr(def_id)), + }, + DefIdOrName::Name(name) => format!("call this {name}"), }; let sugg = match expr.kind { @@ -161,6 +144,182 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { false } + /// Extracts information about a callable type for diagnostics. This is a + /// heuristic -- it doesn't necessarily mean that a type is always callable, + /// because the callable type must also be well-formed to be called. + pub(in super::super) fn extract_callable_info( + &self, + expr: &Expr<'_>, + found: Ty<'tcx>, + ) -> Option<(DefIdOrName, Ty<'tcx>, Vec<Ty<'tcx>>)> { + // Autoderef is useful here because sometimes we box callables, etc. + let Some((def_id_or_name, output, inputs)) = self.autoderef(expr.span, found).silence_errors().find_map(|(found, _)| { + match *found.kind() { + ty::FnPtr(fn_sig) => + Some((DefIdOrName::Name("function pointer"), fn_sig.output(), fn_sig.inputs())), + ty::FnDef(def_id, _) => { + let fn_sig = found.fn_sig(self.tcx); + Some((DefIdOrName::DefId(def_id), fn_sig.output(), fn_sig.inputs())) + } + ty::Closure(def_id, substs) => { + let fn_sig = substs.as_closure().sig(); + Some((DefIdOrName::DefId(def_id), fn_sig.output(), fn_sig.inputs().map_bound(|inputs| &inputs[1..]))) + } + ty::Opaque(def_id, substs) => { + self.tcx.bound_item_bounds(def_id).subst(self.tcx, substs).iter().find_map(|pred| { + if let ty::PredicateKind::Projection(proj) = pred.kind().skip_binder() + && Some(proj.projection_ty.item_def_id) == self.tcx.lang_items().fn_once_output() + // args tuple will always be substs[1] + && let ty::Tuple(args) = proj.projection_ty.substs.type_at(1).kind() + { + Some(( + DefIdOrName::DefId(def_id), + pred.kind().rebind(proj.term.ty().unwrap()), + pred.kind().rebind(args.as_slice()), + )) + } else { + None + } + }) + } + ty::Dynamic(data, _, ty::Dyn) => { + data.iter().find_map(|pred| { + if let ty::ExistentialPredicate::Projection(proj) = pred.skip_binder() + && Some(proj.item_def_id) == self.tcx.lang_items().fn_once_output() + // for existential projection, substs are shifted over by 1 + && let ty::Tuple(args) = proj.substs.type_at(0).kind() + { + Some(( + DefIdOrName::Name("trait object"), + pred.rebind(proj.term.ty().unwrap()), + pred.rebind(args.as_slice()), + )) + } else { + None + } + }) + } + ty::Param(param) => { + let def_id = self.tcx.generics_of(self.body_id.owner).type_param(¶m, self.tcx).def_id; + self.tcx.predicates_of(self.body_id.owner).predicates.iter().find_map(|(pred, _)| { + if let ty::PredicateKind::Projection(proj) = pred.kind().skip_binder() + && Some(proj.projection_ty.item_def_id) == self.tcx.lang_items().fn_once_output() + && proj.projection_ty.self_ty() == found + // args tuple will always be substs[1] + && let ty::Tuple(args) = proj.projection_ty.substs.type_at(1).kind() + { + Some(( + DefIdOrName::DefId(def_id), + pred.kind().rebind(proj.term.ty().unwrap()), + pred.kind().rebind(args.as_slice()), + )) + } else { + None + } + }) + } + _ => None, + } + }) else { return None; }; + + let output = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, output); + let inputs = inputs + .skip_binder() + .iter() + .map(|ty| { + self.replace_bound_vars_with_fresh_vars( + expr.span, + infer::FnCall, + inputs.rebind(*ty), + ) + }) + .collect(); + + // We don't want to register any extra obligations, which should be + // implied by wf, but also because that would possibly result in + // erroneous errors later on. + let infer::InferOk { value: output, obligations: _ } = + self.normalize_associated_types_in_as_infer_ok(expr.span, output); + + if output.is_ty_var() { None } else { Some((def_id_or_name, output, inputs)) } + } + + pub fn suggest_two_fn_call( + &self, + err: &mut Diagnostic, + lhs_expr: &'tcx hir::Expr<'tcx>, + lhs_ty: Ty<'tcx>, + rhs_expr: &'tcx hir::Expr<'tcx>, + rhs_ty: Ty<'tcx>, + can_satisfy: impl FnOnce(Ty<'tcx>, Ty<'tcx>) -> bool, + ) -> bool { + let Some((_, lhs_output_ty, lhs_inputs)) = self.extract_callable_info(lhs_expr, lhs_ty) + else { return false; }; + let Some((_, rhs_output_ty, rhs_inputs)) = self.extract_callable_info(rhs_expr, rhs_ty) + else { return false; }; + + if can_satisfy(lhs_output_ty, rhs_output_ty) { + let mut sugg = vec![]; + let mut applicability = Applicability::MachineApplicable; + + for (expr, inputs) in [(lhs_expr, lhs_inputs), (rhs_expr, rhs_inputs)] { + let (sugg_call, this_applicability) = match inputs.len() { + 0 => ("".to_string(), Applicability::MachineApplicable), + 1..=4 => ( + inputs + .iter() + .map(|ty| { + if ty.is_suggestable(self.tcx, false) { + format!("/* {ty} */") + } else { + "/* value */".to_string() + } + }) + .collect::<Vec<_>>() + .join(", "), + Applicability::HasPlaceholders, + ), + _ => ("/* ... */".to_string(), Applicability::HasPlaceholders), + }; + + applicability = applicability.max(this_applicability); + + match expr.kind { + hir::ExprKind::Call(..) + | hir::ExprKind::Path(..) + | hir::ExprKind::Index(..) + | hir::ExprKind::Lit(..) => { + sugg.extend([(expr.span.shrink_to_hi(), format!("({sugg_call})"))]); + } + hir::ExprKind::Closure { .. } => { + // Might be `{ expr } || { bool }` + applicability = Applicability::MaybeIncorrect; + sugg.extend([ + (expr.span.shrink_to_lo(), "(".to_string()), + (expr.span.shrink_to_hi(), format!(")({sugg_call})")), + ]); + } + _ => { + sugg.extend([ + (expr.span.shrink_to_lo(), "(".to_string()), + (expr.span.shrink_to_hi(), format!(")({sugg_call})")), + ]); + } + } + } + + err.multipart_suggestion_verbose( + format!("use parentheses to call these"), + sugg, + applicability, + ); + + true + } else { + false + } + } + pub fn suggest_deref_ref_or_into( &self, err: &mut Diagnostic, @@ -178,12 +337,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } else { err.span_suggestion(sp, &msg, suggestion, applicability); } - } else if let (ty::FnDef(def_id, ..), true) = - (&found.kind(), self.suggest_fn_call(err, expr, expected, found)) + } else if self.suggest_fn_call(err, expr, found, |output| self.can_coerce(output, expected)) + && let ty::FnDef(def_id, ..) = &found.kind() + && let Some(sp) = self.tcx.hir().span_if_local(*def_id) { - if let Some(sp) = self.tcx.hir().span_if_local(*def_id) { - err.span_label(sp, format!("{found} defined here")); - } + err.span_label(sp, format!("{found} defined here")); } else if !self.check_for_cast(err, expr, found, expected, expected_ty_expr) { let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id); if !methods.is_empty() { @@ -506,30 +664,30 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { self.resolve_numeric_literals_with_default(self.resolve_vars_if_possible(found)); // Only suggest changing the return type for methods that // haven't set a return type at all (and aren't `fn main()` or an impl). - match ( - &fn_decl.output, - found.is_suggestable(self.tcx, false), - can_suggest, - expected.is_unit(), - ) { - (&hir::FnRetTy::DefaultReturn(span), true, true, true) => { - err.subdiagnostic(AddReturnTypeSuggestion::Add { span, found }); - true - } - (&hir::FnRetTy::DefaultReturn(span), false, true, true) => { - // FIXME: if `found` could be `impl Iterator` or `impl Fn*`, we should suggest - // that. - err.subdiagnostic(AddReturnTypeSuggestion::MissingHere { span }); - true - } - (&hir::FnRetTy::DefaultReturn(span), _, false, true) => { + match &fn_decl.output { + &hir::FnRetTy::DefaultReturn(span) if expected.is_unit() && !can_suggest => { // `fn main()` must return `()`, do not suggest changing return type err.subdiagnostic(ExpectedReturnTypeLabel::Unit { span }); - true + return true; + } + &hir::FnRetTy::DefaultReturn(span) if expected.is_unit() => { + if found.is_suggestable(self.tcx, false) { + err.subdiagnostic(AddReturnTypeSuggestion::Add { span, found: found.to_string() }); + return true; + } else if let ty::Closure(_, substs) = found.kind() + // FIXME(compiler-errors): Get better at printing binders... + && let closure = substs.as_closure() + && closure.sig().is_suggestable(self.tcx, false) + { + err.subdiagnostic(AddReturnTypeSuggestion::Add { span, found: closure.print_as_impl_trait().to_string() }); + return true; + } else { + // FIXME: if `found` could be `impl Iterator` we should suggest that. + err.subdiagnostic(AddReturnTypeSuggestion::MissingHere { span }); + return true + } } - // expectation was caused by something else, not the default return - (&hir::FnRetTy::DefaultReturn(_), _, _, false) => false, - (&hir::FnRetTy::Return(ref ty), _, _, _) => { + &hir::FnRetTy::Return(ref ty) => { // Only point to return type if the expected type is the return type, as if they // are not, the expectation must have been caused by something else. debug!("suggest_missing_return_type: return type {:?} node {:?}", ty, ty.kind); @@ -546,9 +704,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { self.try_suggest_return_impl_trait(err, expected, ty, fn_id); return true; } - false } + _ => {} } + false } /// check whether the return type is a generic type with a trait bound @@ -770,6 +929,69 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } } + pub(crate) fn suggest_copied_or_cloned( + &self, + diag: &mut Diagnostic, + expr: &hir::Expr<'_>, + expr_ty: Ty<'tcx>, + expected_ty: Ty<'tcx>, + ) { + let ty::Adt(adt_def, substs) = expr_ty.kind() else { return; }; + let ty::Adt(expected_adt_def, expected_substs) = expected_ty.kind() else { return; }; + if adt_def != expected_adt_def { + return; + } + + let mut suggest_copied_or_cloned = || { + let expr_inner_ty = substs.type_at(0); + let expected_inner_ty = expected_substs.type_at(0); + if let ty::Ref(_, ty, hir::Mutability::Not) = expr_inner_ty.kind() + && self.can_eq(self.param_env, *ty, expected_inner_ty).is_ok() + { + let def_path = self.tcx.def_path_str(adt_def.did()); + if self.type_is_copy_modulo_regions(self.param_env, *ty, expr.span) { + diag.span_suggestion_verbose( + expr.span.shrink_to_hi(), + format!( + "use `{def_path}::copied` to copy the value inside the `{def_path}`" + ), + ".copied()", + Applicability::MachineApplicable, + ); + } else if let Some(clone_did) = self.tcx.lang_items().clone_trait() + && rustc_trait_selection::traits::type_known_to_meet_bound_modulo_regions( + self, + self.param_env, + *ty, + clone_did, + expr.span + ) + { + diag.span_suggestion_verbose( + expr.span.shrink_to_hi(), + format!( + "use `{def_path}::cloned` to clone the value inside the `{def_path}`" + ), + ".cloned()", + Applicability::MachineApplicable, + ); + } + } + }; + + if let Some(result_did) = self.tcx.get_diagnostic_item(sym::Result) + && adt_def.did() == result_did + // Check that the error types are equal + && self.can_eq(self.param_env, substs.type_at(1), expected_substs.type_at(1)).is_ok() + { + suggest_copied_or_cloned(); + } else if let Some(option_did) = self.tcx.get_diagnostic_item(sym::Option) + && adt_def.did() == option_did + { + suggest_copied_or_cloned(); + } + } + /// Suggest wrapping the block in square brackets instead of curly braces /// in case the block was mistaken array syntax, e.g. `{ 1 }` -> `[ 1 ]`. pub(crate) fn suggest_block_to_brackets( @@ -830,7 +1052,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { found_ty: Ty<'tcx>, expr: &hir::Expr<'_>, ) { - let hir::ExprKind::MethodCall(segment, &[ref callee_expr], _) = expr.kind else { return; }; + let hir::ExprKind::MethodCall(segment, callee_expr, &[], _) = expr.kind else { return; }; let Some(clone_trait_did) = self.tcx.lang_items().clone_trait() else { return; }; let ty::Ref(_, pointee_ty, _) = found_ty.kind() else { return }; let results = self.typeck_results.borrow(); @@ -910,3 +1132,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } } } + +pub enum DefIdOrName { + DefId(DefId), + Name(&'static str), +} |