diff --git a/compiler/rustc_typeck/src/check/fn_ctxt_impl.rs b/compiler/rustc_typeck/src/check/fn_ctxt_impl.rs index 17ced624e4b7..90daed976a22 100644 --- a/compiler/rustc_typeck/src/check/fn_ctxt_impl.rs +++ b/compiler/rustc_typeck/src/check/fn_ctxt_impl.rs @@ -12,7 +12,6 @@ use crate::astconv::{ }; use rustc_ast as ast; -use rustc_ast::util::parser::ExprPrecedence; use rustc_data_structures::captures::Captures; use rustc_data_structures::fx::FxHashSet; use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticId, ErrorReported}; @@ -20,10 +19,10 @@ use rustc_hir as hir; use rustc_hir::def::{CtorOf, DefKind, Res}; use rustc_hir::def_id::DefId; use rustc_hir::lang_items::LangItem; -use rustc_hir::{ExprKind, GenericArg, ItemKind, Node, QPath}; +use rustc_hir::{ExprKind, GenericArg, Node, QPath}; use rustc_infer::infer::canonical::{Canonical, OriginalQueryValues, QueryResponse}; use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282; -use rustc_infer::infer::{self, InferOk, InferResult}; +use rustc_infer::infer::{InferOk, InferResult}; use rustc_middle::ty::adjustment::{ Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, }; @@ -43,18 +42,13 @@ use rustc_span::{self, BytePos, MultiSpan, Span}; use rustc_trait_selection::infer::InferCtxtExt as _; use rustc_trait_selection::opaque_types::InferCtxtExt as _; use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _; -use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _; -use rustc_trait_selection::traits::{ - self, ObligationCause, ObligationCauseCode, TraitEngine, TraitEngineExt, -}; +use rustc_trait_selection::traits::{self, ObligationCauseCode, TraitEngine, TraitEngineExt}; use std::collections::hash_map::Entry; -use std::iter; use std::mem::replace; use std::slice; impl<'a, 'tcx> FnCtxt<'a, 'tcx> { - /// Produces warning on the given node, if the current point in the /// function is unreachable, and there hasn't been another warning. pub(super) fn warn_if_unreachable(&self, id: hir::HirId, span: Span, kind: &str) { @@ -1606,15 +1600,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } } - pub(super) fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) { - err.span_suggestion_short( - span.shrink_to_hi(), - "consider using a semicolon here", - ";".to_string(), - Applicability::MachineApplicable, - ); - } - pub fn check_stmt(&self, stmt: &'tcx hir::Stmt<'tcx>) { // Don't do all the complex logic below for `DeclItem`. match stmt.kind { @@ -1886,264 +1871,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { }) } - /// On implicit return expressions with mismatched types, provides the following suggestions: - /// - /// - Points out the method's return type as the reason for the expected type. - /// - Possible missing semicolon. - /// - Possible missing return type if the return type is the default, and not `fn main()`. - pub fn suggest_mismatched_types_on_tail( - &self, - err: &mut DiagnosticBuilder<'_>, - expr: &'tcx hir::Expr<'tcx>, - expected: Ty<'tcx>, - found: Ty<'tcx>, - cause_span: Span, - blk_id: hir::HirId, - ) -> bool { - let expr = expr.peel_drop_temps(); - self.suggest_missing_semicolon(err, expr, expected, cause_span); - let mut pointing_at_return_type = false; - if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) { - pointing_at_return_type = - self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest); - } - 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: - /// ``` - /// fn foo(x: usize) -> usize { x } - /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)` - /// ``` - fn suggest_fn_call( - &self, - err: &mut DiagnosticBuilder<'_>, - expr: &hir::Expr<'_>, - expected: Ty<'tcx>, - found: Ty<'tcx>, - ) -> bool { - let hir = self.tcx.hir(); - let (def_id, sig) = match *found.kind() { - ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)), - ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig()), - _ => return false, - }; - - let sig = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig).0; - let sig = self.normalize_associated_types_in(expr.span, &sig); - if self.can_coerce(sig.output(), expected) { - let (mut sugg_call, applicability) = if sig.inputs().is_empty() { - (String::new(), Applicability::MachineApplicable) - } else { - ("...".to_string(), Applicability::HasPlaceholders) - }; - let mut msg = "call this function"; - match hir.get_if_local(def_id) { - Some( - Node::Item(hir::Item { kind: ItemKind::Fn(.., body_id), .. }) - | Node::ImplItem(hir::ImplItem { - kind: hir::ImplItemKind::Fn(_, body_id), .. - }) - | Node::TraitItem(hir::TraitItem { - kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Provided(body_id)), - .. - }), - ) => { - let body = hir.body(*body_id); - sugg_call = body - .params - .iter() - .map(|param| match ¶m.pat.kind { - hir::PatKind::Binding(_, _, ident, None) - if ident.name != kw::SelfLower => - { - ident.to_string() - } - _ => "_".to_string(), - }) - .collect::>() - .join(", "); - } - Some(Node::Expr(hir::Expr { - kind: ExprKind::Closure(_, _, body_id, _, _), - span: full_closure_span, - .. - })) => { - if *full_closure_span == expr.span { - return false; - } - msg = "call this closure"; - let body = hir.body(*body_id); - sugg_call = body - .params - .iter() - .map(|param| match ¶m.pat.kind { - hir::PatKind::Binding(_, _, ident, None) - if ident.name != kw::SelfLower => - { - ident.to_string() - } - _ => "_".to_string(), - }) - .collect::>() - .join(", "); - } - Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => { - sugg_call = fields.iter().map(|_| "_").collect::>().join(", "); - match def_id.as_local().map(|def_id| hir.def_kind(def_id)) { - Some(DefKind::Ctor(hir::def::CtorOf::Variant, _)) => { - msg = "instantiate this tuple variant"; - } - Some(DefKind::Ctor(CtorOf::Struct, _)) => { - msg = "instantiate this tuple struct"; - } - _ => {} - } - } - Some(Node::ForeignItem(hir::ForeignItem { - kind: hir::ForeignItemKind::Fn(_, idents, _), - .. - })) => { - sugg_call = idents - .iter() - .map(|ident| { - if ident.name != kw::SelfLower { - ident.to_string() - } else { - "_".to_string() - } - }) - .collect::>() - .join(", ") - } - Some(Node::TraitItem(hir::TraitItem { - kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Required(idents)), - .. - })) => { - sugg_call = idents - .iter() - .map(|ident| { - if ident.name != kw::SelfLower { - ident.to_string() - } else { - "_".to_string() - } - }) - .collect::>() - .join(", ") - } - _ => {} - } - err.span_suggestion_verbose( - expr.span.shrink_to_hi(), - &format!("use parentheses to {}", msg), - format!("({})", sugg_call), - applicability, - ); - return true; - } - false - } - - pub fn suggest_deref_ref_or_into( - &self, - err: &mut DiagnosticBuilder<'_>, - expr: &hir::Expr<'_>, - expected: Ty<'tcx>, - found: Ty<'tcx>, - expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>, - ) { - if let Some((sp, msg, suggestion, applicability)) = self.check_ref(expr, found, expected) { - 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)) - { - if let Some(sp) = self.tcx.hir().span_if_local(*def_id) { - let sp = self.sess().source_map().guess_head_span(sp); - err.span_label(sp, &format!("{} defined here", found)); - } - } else if !self.check_for_cast(err, expr, found, expected, expected_ty_expr) { - let is_struct_pat_shorthand_field = - self.is_hir_id_from_struct_pattern_shorthand_field(expr.hir_id, expr.span); - let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id); - if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) { - let mut suggestions = iter::repeat(&expr_text) - .zip(methods.iter()) - .filter_map(|(receiver, method)| { - let method_call = format!(".{}()", method.ident); - if receiver.ends_with(&method_call) { - None // do not suggest code that is already there (#53348) - } else { - let method_call_list = [".to_vec()", ".to_string()"]; - let sugg = if receiver.ends_with(".clone()") - && method_call_list.contains(&method_call.as_str()) - { - let max_len = receiver.rfind('.').unwrap(); - format!("{}{}", &receiver[..max_len], method_call) - } else { - if expr.precedence().order() < ExprPrecedence::MethodCall.order() { - format!("({}){}", receiver, method_call) - } else { - format!("{}{}", receiver, method_call) - } - }; - Some(if is_struct_pat_shorthand_field { - format!("{}: {}", receiver, sugg) - } else { - sugg - }) - } - }) - .peekable(); - if suggestions.peek().is_some() { - err.span_suggestions( - expr.span, - "try using a conversion method", - suggestions, - Applicability::MaybeIncorrect, - ); - } - } - } - } - - /// When encountering the expected boxed value allocated in the stack, suggest allocating it - /// in the heap by calling `Box::new()`. - pub(super) fn suggest_boxing_when_appropriate( - &self, - err: &mut DiagnosticBuilder<'_>, - expr: &hir::Expr<'_>, - expected: Ty<'tcx>, - found: Ty<'tcx>, - ) { - if self.tcx.hir().is_inside_const_context(expr.hir_id) { - // Do not suggest `Box::new` in const context. - return; - } - if !expected.is_box() || found.is_box() { - return; - } - let boxed_found = self.tcx.mk_box(found); - if let (true, Ok(snippet)) = ( - self.can_coerce(boxed_found, expected), - self.sess().source_map().span_to_snippet(expr.span), - ) { - err.span_suggestion( - expr.span, - "store this in the heap by calling `Box::new`", - format!("Box::new({})", snippet), - Applicability::MachineApplicable, - ); - err.note( - "for more on the distinction between the stack and the heap, read \ - https://doc.rust-lang.org/book/ch15-01-box.html, \ - https://doc.rust-lang.org/rust-by-example/std/box.html, and \ - https://doc.rust-lang.org/std/boxed/index.html", - ); - } - } - pub(super) fn note_internal_mutation_in_method( &self, err: &mut DiagnosticBuilder<'_>, @@ -2189,243 +1916,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } } - /// When encountering an `impl Future` where `BoxFuture` is expected, suggest `Box::pin`. - pub(super) fn suggest_calling_boxed_future_when_appropriate( - &self, - err: &mut DiagnosticBuilder<'_>, - expr: &hir::Expr<'_>, - expected: Ty<'tcx>, - found: Ty<'tcx>, - ) -> bool { - // Handle #68197. - - if self.tcx.hir().is_inside_const_context(expr.hir_id) { - // Do not suggest `Box::new` in const context. - return false; - } - let pin_did = self.tcx.lang_items().pin_type(); - match expected.kind() { - ty::Adt(def, _) if Some(def.did) != pin_did => return false, - // This guards the `unwrap` and `mk_box` below. - _ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() => return false, - _ => {} - } - let boxed_found = self.tcx.mk_box(found); - let new_found = self.tcx.mk_lang_item(boxed_found, LangItem::Pin).unwrap(); - if let (true, Ok(snippet)) = ( - self.can_coerce(new_found, expected), - self.sess().source_map().span_to_snippet(expr.span), - ) { - match found.kind() { - ty::Adt(def, _) if def.is_box() => { - err.help("use `Box::pin`"); - } - _ => { - err.span_suggestion( - expr.span, - "you need to pin and box this expression", - format!("Box::pin({})", snippet), - Applicability::MachineApplicable, - ); - } - } - true - } else { - false - } - } - - /// A common error is to forget to add a semicolon at the end of a block, e.g., - /// - /// ``` - /// fn foo() { - /// bar_that_returns_u32() - /// } - /// ``` - /// - /// This routine checks if the return expression in a block would make sense on its own as a - /// statement and the return type has been left as default or has been specified as `()`. If so, - /// it suggests adding a semicolon. - fn suggest_missing_semicolon( - &self, - err: &mut DiagnosticBuilder<'_>, - expression: &'tcx hir::Expr<'tcx>, - expected: Ty<'tcx>, - cause_span: Span, - ) { - if expected.is_unit() { - // `BlockTailExpression` only relevant if the tail expr would be - // useful on its own. - match expression.kind { - ExprKind::Call(..) - | ExprKind::MethodCall(..) - | ExprKind::Loop(..) - | ExprKind::Match(..) - | ExprKind::Block(..) => { - err.span_suggestion( - cause_span.shrink_to_hi(), - "try adding a semicolon", - ";".to_string(), - Applicability::MachineApplicable, - ); - } - _ => (), - } - } - } - - /// A possible error is to forget to add a return type that is needed: - /// - /// ``` - /// fn foo() { - /// bar_that_returns_u32() - /// } - /// ``` - /// - /// This routine checks if the return type is left as default, the method is not part of an - /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return - /// type. - pub(super) fn suggest_missing_return_type( - &self, - err: &mut DiagnosticBuilder<'_>, - fn_decl: &hir::FnDecl<'_>, - expected: Ty<'tcx>, - found: Ty<'tcx>, - can_suggest: bool, - ) -> bool { - // 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(), can_suggest, expected.is_unit()) { - (&hir::FnRetTy::DefaultReturn(span), true, true, true) => { - err.span_suggestion( - span, - "try adding a return type", - format!("-> {} ", self.resolve_vars_with_obligations(found)), - Applicability::MachineApplicable, - ); - true - } - (&hir::FnRetTy::DefaultReturn(span), false, true, true) => { - err.span_label(span, "possibly return type missing here?"); - true - } - (&hir::FnRetTy::DefaultReturn(span), _, false, true) => { - // `fn main()` must return `()`, do not suggest changing return type - err.span_label(span, "expected `()` because of default return type"); - true - } - // expectation was caused by something else, not the default return - (&hir::FnRetTy::DefaultReturn(_), _, _, false) => false, - (&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); - let sp = ty.span; - let ty = AstConv::ast_ty_to_ty(self, ty); - debug!("suggest_missing_return_type: return type {:?}", ty); - debug!("suggest_missing_return_type: expected type {:?}", ty); - if ty.kind() == expected.kind() { - err.span_label(sp, format!("expected `{}` because of return type", expected)); - return true; - } - false - } - } - } - - /// A possible error is to forget to add `.await` when using futures: - /// - /// ``` - /// async fn make_u32() -> u32 { - /// 22 - /// } - /// - /// fn take_u32(x: u32) {} - /// - /// async fn foo() { - /// let x = make_u32(); - /// take_u32(x); - /// } - /// ``` - /// - /// This routine checks if the found type `T` implements `Future` where `U` is the - /// expected type. If this is the case, and we are inside of an async body, it suggests adding - /// `.await` to the tail of the expression. - pub(super) fn suggest_missing_await( - &self, - err: &mut DiagnosticBuilder<'_>, - expr: &hir::Expr<'_>, - expected: Ty<'tcx>, - found: Ty<'tcx>, - ) { - debug!("suggest_missing_await: expr={:?} expected={:?}, found={:?}", expr, expected, found); - // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the - // body isn't `async`. - let item_id = self.tcx().hir().get_parent_node(self.body_id); - if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) { - let body = self.tcx().hir().body(body_id); - if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind { - let sp = expr.span; - // Check for `Future` implementations by constructing a predicate to - // prove: `::Output == U` - let future_trait = self.tcx.require_lang_item(LangItem::Future, Some(sp)); - let item_def_id = self - .tcx - .associated_items(future_trait) - .in_definition_order() - .next() - .unwrap() - .def_id; - // `::Output` - let projection_ty = ty::ProjectionTy { - // `T` - substs: self - .tcx - .mk_substs_trait(found, self.fresh_substs_for_item(sp, item_def_id)), - // `Future::Output` - item_def_id, - }; - - let predicate = ty::PredicateAtom::Projection(ty::ProjectionPredicate { - projection_ty, - ty: expected, - }) - .potentially_quantified(self.tcx, ty::PredicateKind::ForAll); - let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate); - - debug!("suggest_missing_await: trying obligation {:?}", obligation); - - if self.infcx.predicate_may_hold(&obligation) { - debug!("suggest_missing_await: obligation held: {:?}", obligation); - if let Ok(code) = self.sess().source_map().span_to_snippet(sp) { - err.span_suggestion( - sp, - "consider using `.await` here", - format!("{}.await", code), - Applicability::MaybeIncorrect, - ); - } else { - debug!("suggest_missing_await: no snippet for {:?}", sp); - } - } else { - debug!("suggest_missing_await: obligation did not hold: {:?}", obligation) - } - } - } - } - - pub(super) fn suggest_missing_parentheses( - &self, - err: &mut DiagnosticBuilder<'_>, - expr: &hir::Expr<'_>, - ) { - let sp = self.tcx.sess.source_map().start_point(expr.span); - if let Some(sp) = self.tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp) { - // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }` - self.tcx.sess.parse_sess.expr_parentheses_needed(err, *sp, None); - } - } - pub(super) fn note_need_for_fn_pointer( &self, err: &mut DiagnosticBuilder<'_>, diff --git a/compiler/rustc_typeck/src/check/fn_ctxt_suggestions.rs b/compiler/rustc_typeck/src/check/fn_ctxt_suggestions.rs new file mode 100644 index 000000000000..19988938a49b --- /dev/null +++ b/compiler/rustc_typeck/src/check/fn_ctxt_suggestions.rs @@ -0,0 +1,524 @@ +use super::FnCtxt; +use crate::astconv::AstConv; + +use rustc_ast::util::parser::ExprPrecedence; +use rustc_span::{self, Span}; +use rustc_trait_selection::traits; + +use rustc_errors::{Applicability, DiagnosticBuilder}; +use rustc_hir as hir; +use rustc_hir::def::{CtorOf, DefKind}; +use rustc_hir::lang_items::LangItem; +use rustc_hir::{ExprKind, ItemKind, Node}; +use rustc_infer::infer; +use rustc_middle::ty::{self, Ty}; +use rustc_span::symbol::kw; +use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _; + +use std::iter; + +impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + pub(super) fn suggest_semicolon_at_end(&self, span: Span, err: &mut DiagnosticBuilder<'_>) { + err.span_suggestion_short( + span.shrink_to_hi(), + "consider using a semicolon here", + ";".to_string(), + Applicability::MachineApplicable, + ); + } + + /// On implicit return expressions with mismatched types, provides the following suggestions: + /// + /// - Points out the method's return type as the reason for the expected type. + /// - Possible missing semicolon. + /// - Possible missing return type if the return type is the default, and not `fn main()`. + pub fn suggest_mismatched_types_on_tail( + &self, + err: &mut DiagnosticBuilder<'_>, + expr: &'tcx hir::Expr<'tcx>, + expected: Ty<'tcx>, + found: Ty<'tcx>, + cause_span: Span, + blk_id: hir::HirId, + ) -> bool { + let expr = expr.peel_drop_temps(); + self.suggest_missing_semicolon(err, expr, expected, cause_span); + let mut pointing_at_return_type = false; + if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) { + pointing_at_return_type = + self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest); + } + 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: + /// ``` + /// fn foo(x: usize) -> usize { x } + /// let x: usize = foo; // suggest calling the `foo` function: `foo(42)` + /// ``` + fn suggest_fn_call( + &self, + err: &mut DiagnosticBuilder<'_>, + expr: &hir::Expr<'_>, + expected: Ty<'tcx>, + found: Ty<'tcx>, + ) -> bool { + let hir = self.tcx.hir(); + let (def_id, sig) = match *found.kind() { + ty::FnDef(def_id, _) => (def_id, found.fn_sig(self.tcx)), + ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig()), + _ => return false, + }; + + let sig = self.replace_bound_vars_with_fresh_vars(expr.span, infer::FnCall, &sig).0; + let sig = self.normalize_associated_types_in(expr.span, &sig); + if self.can_coerce(sig.output(), expected) { + let (mut sugg_call, applicability) = if sig.inputs().is_empty() { + (String::new(), Applicability::MachineApplicable) + } else { + ("...".to_string(), Applicability::HasPlaceholders) + }; + let mut msg = "call this function"; + match hir.get_if_local(def_id) { + Some( + Node::Item(hir::Item { kind: ItemKind::Fn(.., body_id), .. }) + | Node::ImplItem(hir::ImplItem { + kind: hir::ImplItemKind::Fn(_, body_id), .. + }) + | Node::TraitItem(hir::TraitItem { + kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Provided(body_id)), + .. + }), + ) => { + let body = hir.body(*body_id); + sugg_call = body + .params + .iter() + .map(|param| match ¶m.pat.kind { + hir::PatKind::Binding(_, _, ident, None) + if ident.name != kw::SelfLower => + { + ident.to_string() + } + _ => "_".to_string(), + }) + .collect::>() + .join(", "); + } + Some(Node::Expr(hir::Expr { + kind: ExprKind::Closure(_, _, body_id, _, _), + span: full_closure_span, + .. + })) => { + if *full_closure_span == expr.span { + return false; + } + msg = "call this closure"; + let body = hir.body(*body_id); + sugg_call = body + .params + .iter() + .map(|param| match ¶m.pat.kind { + hir::PatKind::Binding(_, _, ident, None) + if ident.name != kw::SelfLower => + { + ident.to_string() + } + _ => "_".to_string(), + }) + .collect::>() + .join(", "); + } + Some(Node::Ctor(hir::VariantData::Tuple(fields, _))) => { + sugg_call = fields.iter().map(|_| "_").collect::>().join(", "); + match def_id.as_local().map(|def_id| hir.def_kind(def_id)) { + Some(DefKind::Ctor(hir::def::CtorOf::Variant, _)) => { + msg = "instantiate this tuple variant"; + } + Some(DefKind::Ctor(CtorOf::Struct, _)) => { + msg = "instantiate this tuple struct"; + } + _ => {} + } + } + Some(Node::ForeignItem(hir::ForeignItem { + kind: hir::ForeignItemKind::Fn(_, idents, _), + .. + })) => { + sugg_call = idents + .iter() + .map(|ident| { + if ident.name != kw::SelfLower { + ident.to_string() + } else { + "_".to_string() + } + }) + .collect::>() + .join(", ") + } + Some(Node::TraitItem(hir::TraitItem { + kind: hir::TraitItemKind::Fn(.., hir::TraitFn::Required(idents)), + .. + })) => { + sugg_call = idents + .iter() + .map(|ident| { + if ident.name != kw::SelfLower { + ident.to_string() + } else { + "_".to_string() + } + }) + .collect::>() + .join(", ") + } + _ => {} + } + err.span_suggestion_verbose( + expr.span.shrink_to_hi(), + &format!("use parentheses to {}", msg), + format!("({})", sugg_call), + applicability, + ); + return true; + } + false + } + + pub fn suggest_deref_ref_or_into( + &self, + err: &mut DiagnosticBuilder<'_>, + expr: &hir::Expr<'_>, + expected: Ty<'tcx>, + found: Ty<'tcx>, + expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>, + ) { + if let Some((sp, msg, suggestion, applicability)) = self.check_ref(expr, found, expected) { + 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)) + { + if let Some(sp) = self.tcx.hir().span_if_local(*def_id) { + let sp = self.sess().source_map().guess_head_span(sp); + err.span_label(sp, &format!("{} defined here", found)); + } + } else if !self.check_for_cast(err, expr, found, expected, expected_ty_expr) { + let is_struct_pat_shorthand_field = + self.is_hir_id_from_struct_pattern_shorthand_field(expr.hir_id, expr.span); + let methods = self.get_conversion_methods(expr.span, expected, found, expr.hir_id); + if let Ok(expr_text) = self.sess().source_map().span_to_snippet(expr.span) { + let mut suggestions = iter::repeat(&expr_text) + .zip(methods.iter()) + .filter_map(|(receiver, method)| { + let method_call = format!(".{}()", method.ident); + if receiver.ends_with(&method_call) { + None // do not suggest code that is already there (#53348) + } else { + let method_call_list = [".to_vec()", ".to_string()"]; + let sugg = if receiver.ends_with(".clone()") + && method_call_list.contains(&method_call.as_str()) + { + let max_len = receiver.rfind('.').unwrap(); + format!("{}{}", &receiver[..max_len], method_call) + } else { + if expr.precedence().order() < ExprPrecedence::MethodCall.order() { + format!("({}){}", receiver, method_call) + } else { + format!("{}{}", receiver, method_call) + } + }; + Some(if is_struct_pat_shorthand_field { + format!("{}: {}", receiver, sugg) + } else { + sugg + }) + } + }) + .peekable(); + if suggestions.peek().is_some() { + err.span_suggestions( + expr.span, + "try using a conversion method", + suggestions, + Applicability::MaybeIncorrect, + ); + } + } + } + } + + /// When encountering the expected boxed value allocated in the stack, suggest allocating it + /// in the heap by calling `Box::new()`. + pub(super) fn suggest_boxing_when_appropriate( + &self, + err: &mut DiagnosticBuilder<'_>, + expr: &hir::Expr<'_>, + expected: Ty<'tcx>, + found: Ty<'tcx>, + ) { + if self.tcx.hir().is_inside_const_context(expr.hir_id) { + // Do not suggest `Box::new` in const context. + return; + } + if !expected.is_box() || found.is_box() { + return; + } + let boxed_found = self.tcx.mk_box(found); + if let (true, Ok(snippet)) = ( + self.can_coerce(boxed_found, expected), + self.sess().source_map().span_to_snippet(expr.span), + ) { + err.span_suggestion( + expr.span, + "store this in the heap by calling `Box::new`", + format!("Box::new({})", snippet), + Applicability::MachineApplicable, + ); + err.note( + "for more on the distinction between the stack and the heap, read \ + https://doc.rust-lang.org/book/ch15-01-box.html, \ + https://doc.rust-lang.org/rust-by-example/std/box.html, and \ + https://doc.rust-lang.org/std/boxed/index.html", + ); + } + } + + /// When encountering an `impl Future` where `BoxFuture` is expected, suggest `Box::pin`. + pub(super) fn suggest_calling_boxed_future_when_appropriate( + &self, + err: &mut DiagnosticBuilder<'_>, + expr: &hir::Expr<'_>, + expected: Ty<'tcx>, + found: Ty<'tcx>, + ) -> bool { + // Handle #68197. + + if self.tcx.hir().is_inside_const_context(expr.hir_id) { + // Do not suggest `Box::new` in const context. + return false; + } + let pin_did = self.tcx.lang_items().pin_type(); + match expected.kind() { + ty::Adt(def, _) if Some(def.did) != pin_did => return false, + // This guards the `unwrap` and `mk_box` below. + _ if pin_did.is_none() || self.tcx.lang_items().owned_box().is_none() => return false, + _ => {} + } + let boxed_found = self.tcx.mk_box(found); + let new_found = self.tcx.mk_lang_item(boxed_found, LangItem::Pin).unwrap(); + if let (true, Ok(snippet)) = ( + self.can_coerce(new_found, expected), + self.sess().source_map().span_to_snippet(expr.span), + ) { + match found.kind() { + ty::Adt(def, _) if def.is_box() => { + err.help("use `Box::pin`"); + } + _ => { + err.span_suggestion( + expr.span, + "you need to pin and box this expression", + format!("Box::pin({})", snippet), + Applicability::MachineApplicable, + ); + } + } + true + } else { + false + } + } + + /// A common error is to forget to add a semicolon at the end of a block, e.g., + /// + /// ``` + /// fn foo() { + /// bar_that_returns_u32() + /// } + /// ``` + /// + /// This routine checks if the return expression in a block would make sense on its own as a + /// statement and the return type has been left as default or has been specified as `()`. If so, + /// it suggests adding a semicolon. + fn suggest_missing_semicolon( + &self, + err: &mut DiagnosticBuilder<'_>, + expression: &'tcx hir::Expr<'tcx>, + expected: Ty<'tcx>, + cause_span: Span, + ) { + if expected.is_unit() { + // `BlockTailExpression` only relevant if the tail expr would be + // useful on its own. + match expression.kind { + ExprKind::Call(..) + | ExprKind::MethodCall(..) + | ExprKind::Loop(..) + | ExprKind::Match(..) + | ExprKind::Block(..) => { + err.span_suggestion( + cause_span.shrink_to_hi(), + "try adding a semicolon", + ";".to_string(), + Applicability::MachineApplicable, + ); + } + _ => (), + } + } + } + + /// A possible error is to forget to add a return type that is needed: + /// + /// ``` + /// fn foo() { + /// bar_that_returns_u32() + /// } + /// ``` + /// + /// This routine checks if the return type is left as default, the method is not part of an + /// `impl` block and that it isn't the `main` method. If so, it suggests setting the return + /// type. + pub(super) fn suggest_missing_return_type( + &self, + err: &mut DiagnosticBuilder<'_>, + fn_decl: &hir::FnDecl<'_>, + expected: Ty<'tcx>, + found: Ty<'tcx>, + can_suggest: bool, + ) -> bool { + // 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(), can_suggest, expected.is_unit()) { + (&hir::FnRetTy::DefaultReturn(span), true, true, true) => { + err.span_suggestion( + span, + "try adding a return type", + format!("-> {} ", self.resolve_vars_with_obligations(found)), + Applicability::MachineApplicable, + ); + true + } + (&hir::FnRetTy::DefaultReturn(span), false, true, true) => { + err.span_label(span, "possibly return type missing here?"); + true + } + (&hir::FnRetTy::DefaultReturn(span), _, false, true) => { + // `fn main()` must return `()`, do not suggest changing return type + err.span_label(span, "expected `()` because of default return type"); + true + } + // expectation was caused by something else, not the default return + (&hir::FnRetTy::DefaultReturn(_), _, _, false) => false, + (&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); + let sp = ty.span; + let ty = AstConv::ast_ty_to_ty(self, ty); + debug!("suggest_missing_return_type: return type {:?}", ty); + debug!("suggest_missing_return_type: expected type {:?}", ty); + if ty.kind() == expected.kind() { + err.span_label(sp, format!("expected `{}` because of return type", expected)); + return true; + } + false + } + } + } + + /// A possible error is to forget to add `.await` when using futures: + /// + /// ``` + /// async fn make_u32() -> u32 { + /// 22 + /// } + /// + /// fn take_u32(x: u32) {} + /// + /// async fn foo() { + /// let x = make_u32(); + /// take_u32(x); + /// } + /// ``` + /// + /// This routine checks if the found type `T` implements `Future` where `U` is the + /// expected type. If this is the case, and we are inside of an async body, it suggests adding + /// `.await` to the tail of the expression. + pub(super) fn suggest_missing_await( + &self, + err: &mut DiagnosticBuilder<'_>, + expr: &hir::Expr<'_>, + expected: Ty<'tcx>, + found: Ty<'tcx>, + ) { + debug!("suggest_missing_await: expr={:?} expected={:?}, found={:?}", expr, expected, found); + // `.await` is not permitted outside of `async` bodies, so don't bother to suggest if the + // body isn't `async`. + let item_id = self.tcx().hir().get_parent_node(self.body_id); + if let Some(body_id) = self.tcx().hir().maybe_body_owned_by(item_id) { + let body = self.tcx().hir().body(body_id); + if let Some(hir::GeneratorKind::Async(_)) = body.generator_kind { + let sp = expr.span; + // Check for `Future` implementations by constructing a predicate to + // prove: `::Output == U` + let future_trait = self.tcx.require_lang_item(LangItem::Future, Some(sp)); + let item_def_id = self + .tcx + .associated_items(future_trait) + .in_definition_order() + .next() + .unwrap() + .def_id; + // `::Output` + let projection_ty = ty::ProjectionTy { + // `T` + substs: self + .tcx + .mk_substs_trait(found, self.fresh_substs_for_item(sp, item_def_id)), + // `Future::Output` + item_def_id, + }; + + let predicate = ty::PredicateAtom::Projection(ty::ProjectionPredicate { + projection_ty, + ty: expected, + }) + .potentially_quantified(self.tcx, ty::PredicateKind::ForAll); + let obligation = traits::Obligation::new(self.misc(sp), self.param_env, predicate); + + debug!("suggest_missing_await: trying obligation {:?}", obligation); + + if self.infcx.predicate_may_hold(&obligation) { + debug!("suggest_missing_await: obligation held: {:?}", obligation); + if let Ok(code) = self.sess().source_map().span_to_snippet(sp) { + err.span_suggestion( + sp, + "consider using `.await` here", + format!("{}.await", code), + Applicability::MaybeIncorrect, + ); + } else { + debug!("suggest_missing_await: no snippet for {:?}", sp); + } + } else { + debug!("suggest_missing_await: obligation did not hold: {:?}", obligation) + } + } + } + } + + pub(super) fn suggest_missing_parentheses( + &self, + err: &mut DiagnosticBuilder<'_>, + expr: &hir::Expr<'_>, + ) { + let sp = self.tcx.sess.source_map().start_point(expr.span); + if let Some(sp) = self.tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp) { + // `{ 42 } &&x` (#61475) or `{ 42 } && if x { 1 } else { 0 }` + self.tcx.sess.parse_sess.expr_parentheses_needed(err, *sp, None); + } + } +} diff --git a/compiler/rustc_typeck/src/check/mod.rs b/compiler/rustc_typeck/src/check/mod.rs index 4e2dc949bccb..ec6c4c89fe16 100644 --- a/compiler/rustc_typeck/src/check/mod.rs +++ b/compiler/rustc_typeck/src/check/mod.rs @@ -77,6 +77,7 @@ mod expectation; mod expr; mod fn_ctxt; mod fn_ctxt_impl; +mod fn_ctxt_suggestions; mod gather_locals; mod generator_interior; mod inherited; @@ -99,6 +100,7 @@ pub use diverges::Diverges; pub use expectation::Expectation; pub use fn_ctxt::FnCtxt; pub use fn_ctxt_impl::*; +pub use fn_ctxt_suggestions::*; pub use inherited::{Inherited, InheritedBuilder}; use crate::astconv::AstConv;