diff options
Diffstat (limited to 'compiler/rustc_hir_analysis/src/check/demand.rs')
| -rw-r--r-- | compiler/rustc_hir_analysis/src/check/demand.rs | 1425 |
1 files changed, 1425 insertions, 0 deletions
diff --git a/compiler/rustc_hir_analysis/src/check/demand.rs b/compiler/rustc_hir_analysis/src/check/demand.rs new file mode 100644 index 00000000000..264df8b914b --- /dev/null +++ b/compiler/rustc_hir_analysis/src/check/demand.rs @@ -0,0 +1,1425 @@ +use crate::check::FnCtxt; +use rustc_infer::infer::InferOk; +use rustc_middle::middle::stability::EvalResult; +use rustc_trait_selection::infer::InferCtxtExt as _; +use rustc_trait_selection::traits::ObligationCause; + +use rustc_ast::util::parser::PREC_POSTFIX; +use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed}; +use rustc_hir as hir; +use rustc_hir::lang_items::LangItem; +use rustc_hir::{is_range_literal, Node}; +use rustc_middle::lint::in_external_macro; +use rustc_middle::ty::adjustment::AllowTwoPhase; +use rustc_middle::ty::error::{ExpectedFound, TypeError}; +use rustc_middle::ty::print::with_no_trimmed_paths; +use rustc_middle::ty::{self, Article, AssocItem, Ty, TypeAndMut}; +use rustc_span::symbol::{sym, Symbol}; +use rustc_span::{BytePos, Span}; + +use super::method::probe; + +use std::iter; + +impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + pub fn emit_coerce_suggestions( + &self, + err: &mut Diagnostic, + expr: &hir::Expr<'tcx>, + expr_ty: Ty<'tcx>, + expected: Ty<'tcx>, + expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>, + error: Option<TypeError<'tcx>>, + ) { + self.annotate_expected_due_to_let_ty(err, expr, error); + self.suggest_deref_ref_or_into(err, expr, expected, expr_ty, expected_ty_expr); + self.suggest_compatible_variants(err, expr, expected, expr_ty); + self.suggest_non_zero_new_unwrap(err, expr, expected, expr_ty); + if self.suggest_calling_boxed_future_when_appropriate(err, expr, expected, expr_ty) { + return; + } + self.suggest_no_capture_closure(err, expected, expr_ty); + self.suggest_boxing_when_appropriate(err, expr, expected, expr_ty); + self.suggest_missing_parentheses(err, expr); + self.suggest_block_to_brackets_peeling_refs(err, expr, expr_ty, expected); + self.suggest_copied_or_cloned(err, expr, expr_ty, expected); + self.note_type_is_not_clone(err, expected, expr_ty, expr); + self.note_need_for_fn_pointer(err, expected, expr_ty); + self.note_internal_mutation_in_method(err, expr, expected, expr_ty); + } + + // Requires that the two types unify, and prints an error message if + // they don't. + pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) { + if let Some(mut e) = self.demand_suptype_diag(sp, expected, actual) { + e.emit(); + } + } + + pub fn demand_suptype_diag( + &self, + sp: Span, + expected: Ty<'tcx>, + actual: Ty<'tcx>, + ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> { + self.demand_suptype_with_origin(&self.misc(sp), expected, actual) + } + + #[instrument(skip(self), level = "debug")] + pub fn demand_suptype_with_origin( + &self, + cause: &ObligationCause<'tcx>, + expected: Ty<'tcx>, + actual: Ty<'tcx>, + ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> { + match self.at(cause, self.param_env).sup(expected, actual) { + Ok(InferOk { obligations, value: () }) => { + self.register_predicates(obligations); + None + } + Err(e) => Some(self.report_mismatched_types(&cause, expected, actual, e)), + } + } + + pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) { + if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) { + err.emit(); + } + } + + pub fn demand_eqtype_diag( + &self, + sp: Span, + expected: Ty<'tcx>, + actual: Ty<'tcx>, + ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> { + self.demand_eqtype_with_origin(&self.misc(sp), expected, actual) + } + + pub fn demand_eqtype_with_origin( + &self, + cause: &ObligationCause<'tcx>, + expected: Ty<'tcx>, + actual: Ty<'tcx>, + ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> { + match self.at(cause, self.param_env).eq(expected, actual) { + Ok(InferOk { obligations, value: () }) => { + self.register_predicates(obligations); + None + } + Err(e) => Some(self.report_mismatched_types(cause, expected, actual, e)), + } + } + + pub fn demand_coerce( + &self, + expr: &hir::Expr<'tcx>, + checked_ty: Ty<'tcx>, + expected: Ty<'tcx>, + expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>, + allow_two_phase: AllowTwoPhase, + ) -> Ty<'tcx> { + let (ty, err) = + self.demand_coerce_diag(expr, checked_ty, expected, expected_ty_expr, allow_two_phase); + if let Some(mut err) = err { + err.emit(); + } + ty + } + + /// Checks that the type of `expr` can be coerced to `expected`. + /// + /// N.B., this code relies on `self.diverges` to be accurate. In particular, assignments to `!` + /// will be permitted if the diverges flag is currently "always". + #[instrument(level = "debug", skip(self, expr, expected_ty_expr, allow_two_phase))] + pub fn demand_coerce_diag( + &self, + expr: &hir::Expr<'tcx>, + checked_ty: Ty<'tcx>, + expected: Ty<'tcx>, + expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>, + allow_two_phase: AllowTwoPhase, + ) -> (Ty<'tcx>, Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>>) { + let expected = self.resolve_vars_with_obligations(expected); + + let e = match self.try_coerce(expr, checked_ty, expected, allow_two_phase, None) { + Ok(ty) => return (ty, None), + Err(e) => e, + }; + + self.set_tainted_by_errors(); + let expr = expr.peel_drop_temps(); + let cause = self.misc(expr.span); + let expr_ty = self.resolve_vars_with_obligations(checked_ty); + let mut err = self.report_mismatched_types(&cause, expected, expr_ty, e.clone()); + + let is_insufficiently_polymorphic = + matches!(e, TypeError::RegionsInsufficientlyPolymorphic(..)); + + // FIXME(#73154): For now, we do leak check when coercing function + // pointers in typeck, instead of only during borrowck. This can lead + // to these `RegionsInsufficientlyPolymorphic` errors that aren't helpful. + if !is_insufficiently_polymorphic { + self.emit_coerce_suggestions( + &mut err, + expr, + expr_ty, + expected, + expected_ty_expr, + Some(e), + ); + } + + (expected, Some(err)) + } + + fn annotate_expected_due_to_let_ty( + &self, + err: &mut Diagnostic, + expr: &hir::Expr<'_>, + error: Option<TypeError<'_>>, + ) { + let parent = self.tcx.hir().get_parent_node(expr.hir_id); + match (self.tcx.hir().find(parent), error) { + (Some(hir::Node::Local(hir::Local { ty: Some(ty), init: Some(init), .. })), _) + if init.hir_id == expr.hir_id => + { + // Point at `let` assignment type. + err.span_label(ty.span, "expected due to this"); + } + ( + Some(hir::Node::Expr(hir::Expr { + kind: hir::ExprKind::Assign(lhs, rhs, _), .. + })), + Some(TypeError::Sorts(ExpectedFound { expected, .. })), + ) if rhs.hir_id == expr.hir_id && !expected.is_closure() => { + // We ignore closures explicitly because we already point at them elsewhere. + // Point at the assigned-to binding. + let mut primary_span = lhs.span; + let mut secondary_span = lhs.span; + let mut post_message = ""; + match lhs.kind { + hir::ExprKind::Path(hir::QPath::Resolved( + None, + hir::Path { + res: + hir::def::Res::Def( + hir::def::DefKind::Static(_) | hir::def::DefKind::Const, + def_id, + ), + .. + }, + )) => { + if let Some(hir::Node::Item(hir::Item { + ident, + kind: hir::ItemKind::Static(ty, ..) | hir::ItemKind::Const(ty, ..), + .. + })) = self.tcx.hir().get_if_local(*def_id) + { + primary_span = ty.span; + secondary_span = ident.span; + post_message = " type"; + } + } + hir::ExprKind::Path(hir::QPath::Resolved( + None, + hir::Path { res: hir::def::Res::Local(hir_id), .. }, + )) => { + if let Some(hir::Node::Pat(pat)) = self.tcx.hir().find(*hir_id) { + let parent = self.tcx.hir().get_parent_node(pat.hir_id); + primary_span = pat.span; + secondary_span = pat.span; + match self.tcx.hir().find(parent) { + Some(hir::Node::Local(hir::Local { ty: Some(ty), .. })) => { + primary_span = ty.span; + post_message = " type"; + } + Some(hir::Node::Local(hir::Local { init: Some(init), .. })) => { + primary_span = init.span; + post_message = " value"; + } + Some(hir::Node::Param(hir::Param { ty_span, .. })) => { + primary_span = *ty_span; + post_message = " parameter type"; + } + _ => {} + } + } + } + _ => {} + } + + if primary_span != secondary_span + && self + .tcx + .sess + .source_map() + .is_multiline(secondary_span.shrink_to_hi().until(primary_span)) + { + // We are pointing at the binding's type or initializer value, but it's pattern + // is in a different line, so we point at both. + err.span_label(secondary_span, "expected due to the type of this binding"); + err.span_label(primary_span, &format!("expected due to this{post_message}")); + } else if post_message == "" { + // We are pointing at either the assignment lhs or the binding def pattern. + err.span_label(primary_span, "expected due to the type of this binding"); + } else { + // We are pointing at the binding's type or initializer value. + err.span_label(primary_span, &format!("expected due to this{post_message}")); + } + + if !lhs.is_syntactic_place_expr() { + // We already emitted E0070 "invalid left-hand side of assignment", so we + // silence this. + err.downgrade_to_delayed_bug(); + } + } + _ => {} + } + } + + /// If the expected type is an enum (Issue #55250) with any variants whose + /// sole field is of the found type, suggest such variants. (Issue #42764) + fn suggest_compatible_variants( + &self, + err: &mut Diagnostic, + expr: &hir::Expr<'_>, + expected: Ty<'tcx>, + expr_ty: Ty<'tcx>, + ) { + if let ty::Adt(expected_adt, substs) = expected.kind() { + if let hir::ExprKind::Field(base, ident) = expr.kind { + let base_ty = self.typeck_results.borrow().expr_ty(base); + if self.can_eq(self.param_env, base_ty, expected).is_ok() + && let Some(base_span) = base.span.find_ancestor_inside(expr.span) + { + err.span_suggestion_verbose( + expr.span.with_lo(base_span.hi()), + format!("consider removing the tuple struct field `{ident}`"), + "", + Applicability::MaybeIncorrect, + ); + return + } + } + + // If the expression is of type () and it's the return expression of a block, + // we suggest adding a separate return expression instead. + // (To avoid things like suggesting `Ok(while .. { .. })`.) + if expr_ty.is_unit() { + let mut id = expr.hir_id; + let mut parent; + + // Unroll desugaring, to make sure this works for `for` loops etc. + loop { + parent = self.tcx.hir().get_parent_node(id); + if let Some(parent_span) = self.tcx.hir().opt_span(parent) { + if parent_span.find_ancestor_inside(expr.span).is_some() { + // The parent node is part of the same span, so is the result of the + // same expansion/desugaring and not the 'real' parent node. + id = parent; + continue; + } + } + break; + } + + if let Some(hir::Node::Block(&hir::Block { + span: block_span, expr: Some(e), .. + })) = self.tcx.hir().find(parent) + { + if e.hir_id == id { + if let Some(span) = expr.span.find_ancestor_inside(block_span) { + let return_suggestions = if self + .tcx + .is_diagnostic_item(sym::Result, expected_adt.did()) + { + vec!["Ok(())"] + } else if self.tcx.is_diagnostic_item(sym::Option, expected_adt.did()) { + vec!["None", "Some(())"] + } else { + return; + }; + if let Some(indent) = + self.tcx.sess.source_map().indentation_before(span.shrink_to_lo()) + { + // Add a semicolon, except after `}`. + let semicolon = + match self.tcx.sess.source_map().span_to_snippet(span) { + Ok(s) if s.ends_with('}') => "", + _ => ";", + }; + err.span_suggestions( + span.shrink_to_hi(), + "try adding an expression at the end of the block", + return_suggestions + .into_iter() + .map(|r| format!("{semicolon}\n{indent}{r}")), + Applicability::MaybeIncorrect, + ); + } + return; + } + } + } + } + + let compatible_variants: Vec<(String, _, _, Option<String>)> = expected_adt + .variants() + .iter() + .filter(|variant| { + variant.fields.len() == 1 + }) + .filter_map(|variant| { + let sole_field = &variant.fields[0]; + + let field_is_local = sole_field.did.is_local(); + let field_is_accessible = + sole_field.vis.is_accessible_from(expr.hir_id.owner.def_id, self.tcx) + // Skip suggestions for unstable public fields (for example `Pin::pointer`) + && matches!(self.tcx.eval_stability(sole_field.did, None, expr.span, None), EvalResult::Allow | EvalResult::Unmarked); + + if !field_is_local && !field_is_accessible { + return None; + } + + let note_about_variant_field_privacy = (field_is_local && !field_is_accessible) + .then(|| format!(" (its field is private, but it's local to this crate and its privacy can be changed)")); + + let sole_field_ty = sole_field.ty(self.tcx, substs); + if self.can_coerce(expr_ty, sole_field_ty) { + let variant_path = + with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id)); + // FIXME #56861: DRYer prelude filtering + if let Some(path) = variant_path.strip_prefix("std::prelude::") + && let Some((_, path)) = path.split_once("::") + { + return Some((path.to_string(), variant.ctor_kind, sole_field.name, note_about_variant_field_privacy)); + } + Some((variant_path, variant.ctor_kind, sole_field.name, note_about_variant_field_privacy)) + } else { + None + } + }) + .collect(); + + let suggestions_for = |variant: &_, ctor, field_name| { + let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) { + Some(ident) => format!("{ident}: "), + None => String::new(), + }; + + let (open, close) = match ctor { + hir::def::CtorKind::Fn => ("(".to_owned(), ")"), + hir::def::CtorKind::Fictive => (format!(" {{ {field_name}: "), " }"), + + // unit variants don't have fields + hir::def::CtorKind::Const => unreachable!(), + }; + + // Suggest constructor as deep into the block tree as possible. + // This fixes https://github.com/rust-lang/rust/issues/101065, + // and also just helps make the most minimal suggestions. + let mut expr = expr; + while let hir::ExprKind::Block(block, _) = &expr.kind + && let Some(expr_) = &block.expr + { + expr = expr_ + } + + vec![ + (expr.span.shrink_to_lo(), format!("{prefix}{variant}{open}")), + (expr.span.shrink_to_hi(), close.to_owned()), + ] + }; + + match &compatible_variants[..] { + [] => { /* No variants to format */ } + [(variant, ctor_kind, field_name, note)] => { + // Just a single matching variant. + err.multipart_suggestion_verbose( + &format!( + "try wrapping the expression in `{variant}`{note}", + note = note.as_deref().unwrap_or("") + ), + suggestions_for(&**variant, *ctor_kind, *field_name), + Applicability::MaybeIncorrect, + ); + } + _ => { + // More than one matching variant. + err.multipart_suggestions( + &format!( + "try wrapping the expression in a variant of `{}`", + self.tcx.def_path_str(expected_adt.did()) + ), + compatible_variants.into_iter().map( + |(variant, ctor_kind, field_name, _)| { + suggestions_for(&variant, ctor_kind, field_name) + }, + ), + Applicability::MaybeIncorrect, + ); + } + } + } + } + + fn suggest_non_zero_new_unwrap( + &self, + err: &mut Diagnostic, + expr: &hir::Expr<'_>, + expected: Ty<'tcx>, + expr_ty: Ty<'tcx>, + ) { + let tcx = self.tcx; + let (adt, unwrap) = match expected.kind() { + // In case Option<NonZero*> is wanted, but * is provided, suggest calling new + ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => { + // Unwrap option + let ty::Adt(adt, _) = substs.type_at(0).kind() else { return }; + + (adt, "") + } + // In case NonZero* is wanted, but * is provided also add `.unwrap()` to satisfy types + ty::Adt(adt, _) => (adt, ".unwrap()"), + _ => return, + }; + + let map = [ + (sym::NonZeroU8, tcx.types.u8), + (sym::NonZeroU16, tcx.types.u16), + (sym::NonZeroU32, tcx.types.u32), + (sym::NonZeroU64, tcx.types.u64), + (sym::NonZeroU128, tcx.types.u128), + (sym::NonZeroI8, tcx.types.i8), + (sym::NonZeroI16, tcx.types.i16), + (sym::NonZeroI32, tcx.types.i32), + (sym::NonZeroI64, tcx.types.i64), + (sym::NonZeroI128, tcx.types.i128), + ]; + + let Some((s, _)) = map + .iter() + .find(|&&(s, t)| self.tcx.is_diagnostic_item(s, adt.did()) && self.can_coerce(expr_ty, t)) + else { return }; + + let path = self.tcx.def_path_str(adt.non_enum_variant().def_id); + + err.multipart_suggestion( + format!("consider calling `{s}::new`"), + vec![ + (expr.span.shrink_to_lo(), format!("{path}::new(")), + (expr.span.shrink_to_hi(), format!("){unwrap}")), + ], + Applicability::MaybeIncorrect, + ); + } + + pub fn get_conversion_methods( + &self, + span: Span, + expected: Ty<'tcx>, + checked_ty: Ty<'tcx>, + hir_id: hir::HirId, + ) -> Vec<AssocItem> { + let mut methods = + self.probe_for_return_type(span, probe::Mode::MethodCall, expected, checked_ty, hir_id); + methods.retain(|m| { + self.has_only_self_parameter(m) + && self + .tcx + // This special internal attribute is used to permit + // "identity-like" conversion methods to be suggested here. + // + // FIXME (#46459 and #46460): ideally + // `std::convert::Into::into` and `std::borrow:ToOwned` would + // also be `#[rustc_conversion_suggestion]`, if not for + // method-probing false-positives and -negatives (respectively). + // + // FIXME? Other potential candidate methods: `as_ref` and + // `as_mut`? + .has_attr(m.def_id, sym::rustc_conversion_suggestion) + }); + + methods + } + + /// This function checks whether the method is not static and does not accept other parameters than `self`. + fn has_only_self_parameter(&self, method: &AssocItem) -> bool { + match method.kind { + ty::AssocKind::Fn => { + method.fn_has_self_parameter + && self.tcx.fn_sig(method.def_id).inputs().skip_binder().len() == 1 + } + _ => false, + } + } + + /// Identify some cases where `as_ref()` would be appropriate and suggest it. + /// + /// Given the following code: + /// ```compile_fail,E0308 + /// struct Foo; + /// fn takes_ref(_: &Foo) {} + /// let ref opt = Some(Foo); + /// + /// opt.map(|param| takes_ref(param)); + /// ``` + /// Suggest using `opt.as_ref().map(|param| takes_ref(param));` instead. + /// + /// It only checks for `Option` and `Result` and won't work with + /// ```ignore (illustrative) + /// opt.map(|param| { takes_ref(param) }); + /// ``` + fn can_use_as_ref(&self, expr: &hir::Expr<'_>) -> Option<(Span, &'static str, String)> { + let hir::ExprKind::Path(hir::QPath::Resolved(_, ref path)) = expr.kind else { + return None; + }; + + let hir::def::Res::Local(local_id) = path.res else { + return None; + }; + + let local_parent = self.tcx.hir().get_parent_node(local_id); + let Some(Node::Param(hir::Param { hir_id: param_hir_id, .. })) = self.tcx.hir().find(local_parent) else { + return None; + }; + + let param_parent = self.tcx.hir().get_parent_node(*param_hir_id); + let Some(Node::Expr(hir::Expr { + hir_id: expr_hir_id, + kind: hir::ExprKind::Closure(hir::Closure { fn_decl: closure_fn_decl, .. }), + .. + })) = self.tcx.hir().find(param_parent) else { + return None; + }; + + let expr_parent = self.tcx.hir().get_parent_node(*expr_hir_id); + let hir = self.tcx.hir().find(expr_parent); + let closure_params_len = closure_fn_decl.inputs.len(); + let ( + Some(Node::Expr(hir::Expr { + kind: hir::ExprKind::MethodCall(method_path, receiver, ..), + .. + })), + 1, + ) = (hir, closure_params_len) else { + return None; + }; + + let self_ty = self.typeck_results.borrow().expr_ty(receiver); + let name = method_path.ident.name; + let is_as_ref_able = match self_ty.peel_refs().kind() { + ty::Adt(def, _) => { + (self.tcx.is_diagnostic_item(sym::Option, def.did()) + || self.tcx.is_diagnostic_item(sym::Result, def.did())) + && (name == sym::map || name == sym::and_then) + } + _ => false, + }; + match (is_as_ref_able, self.sess().source_map().span_to_snippet(method_path.ident.span)) { + (true, Ok(src)) => { + let suggestion = format!("as_ref().{}", src); + Some((method_path.ident.span, "consider using `as_ref` instead", suggestion)) + } + _ => None, + } + } + + pub(crate) fn maybe_get_struct_pattern_shorthand_field( + &self, + expr: &hir::Expr<'_>, + ) -> Option<Symbol> { + let hir = self.tcx.hir(); + let local = match expr { + hir::Expr { + kind: + hir::ExprKind::Path(hir::QPath::Resolved( + None, + hir::Path { + res: hir::def::Res::Local(_), + segments: [hir::PathSegment { ident, .. }], + .. + }, + )), + .. + } => Some(ident), + _ => None, + }?; + + match hir.find(hir.get_parent_node(expr.hir_id))? { + Node::ExprField(field) => { + if field.ident.name == local.name && field.is_shorthand { + return Some(local.name); + } + } + _ => {} + } + + None + } + + /// If the given `HirId` corresponds to a block with a trailing expression, return that expression + pub(crate) fn maybe_get_block_expr( + &self, + expr: &hir::Expr<'tcx>, + ) -> Option<&'tcx hir::Expr<'tcx>> { + match expr { + hir::Expr { kind: hir::ExprKind::Block(block, ..), .. } => block.expr, + _ => None, + } + } + + /// Returns whether the given expression is an `else if`. + pub(crate) fn is_else_if_block(&self, expr: &hir::Expr<'_>) -> bool { + if let hir::ExprKind::If(..) = expr.kind { + let parent_id = self.tcx.hir().get_parent_node(expr.hir_id); + if let Some(Node::Expr(hir::Expr { + kind: hir::ExprKind::If(_, _, Some(else_expr)), + .. + })) = self.tcx.hir().find(parent_id) + { + return else_expr.hir_id == expr.hir_id; + } + } + false + } + + /// This function is used to determine potential "simple" improvements or users' errors and + /// provide them useful help. For example: + /// + /// ```compile_fail,E0308 + /// fn some_fn(s: &str) {} + /// + /// let x = "hey!".to_owned(); + /// some_fn(x); // error + /// ``` + /// + /// No need to find every potential function which could make a coercion to transform a + /// `String` into a `&str` since a `&` would do the trick! + /// + /// In addition of this check, it also checks between references mutability state. If the + /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with + /// `&mut`!". + pub fn check_ref( + &self, + expr: &hir::Expr<'tcx>, + checked_ty: Ty<'tcx>, + expected: Ty<'tcx>, + ) -> Option<(Span, String, String, Applicability, bool /* verbose */)> { + let sess = self.sess(); + let sp = expr.span; + + // If the span is from an external macro, there's no suggestion we can make. + if in_external_macro(sess, sp) { + return None; + } + + let sm = sess.source_map(); + + let replace_prefix = |s: &str, old: &str, new: &str| { + s.strip_prefix(old).map(|stripped| new.to_string() + stripped) + }; + + // `ExprKind::DropTemps` is semantically irrelevant for these suggestions. + let expr = expr.peel_drop_temps(); + + match (&expr.kind, expected.kind(), checked_ty.kind()) { + (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (exp.kind(), check.kind()) { + (&ty::Str, &ty::Array(arr, _) | &ty::Slice(arr)) if arr == self.tcx.types.u8 => { + if let hir::ExprKind::Lit(_) = expr.kind + && let Ok(src) = sm.span_to_snippet(sp) + && replace_prefix(&src, "b\"", "\"").is_some() + { + let pos = sp.lo() + BytePos(1); + return Some(( + sp.with_hi(pos), + "consider removing the leading `b`".to_string(), + String::new(), + Applicability::MachineApplicable, + true, + )); + } + } + (&ty::Array(arr, _) | &ty::Slice(arr), &ty::Str) if arr == self.tcx.types.u8 => { + if let hir::ExprKind::Lit(_) = expr.kind + && let Ok(src) = sm.span_to_snippet(sp) + && replace_prefix(&src, "\"", "b\"").is_some() + { + return Some(( + sp.shrink_to_lo(), + "consider adding a leading `b`".to_string(), + "b".to_string(), + Applicability::MachineApplicable, + true, + )); + } + } + _ => {} + }, + (_, &ty::Ref(_, _, mutability), _) => { + // Check if it can work when put into a ref. For example: + // + // ``` + // fn bar(x: &mut i32) {} + // + // let x = 0u32; + // bar(&x); // error, expected &mut + // ``` + let ref_ty = match mutability { + hir::Mutability::Mut => { + self.tcx.mk_mut_ref(self.tcx.mk_region(ty::ReStatic), checked_ty) + } + hir::Mutability::Not => { + self.tcx.mk_imm_ref(self.tcx.mk_region(ty::ReStatic), checked_ty) + } + }; + if self.can_coerce(ref_ty, expected) { + let mut sugg_sp = sp; + if let hir::ExprKind::MethodCall(ref segment, receiver, args, _) = expr.kind { + let clone_trait = + self.tcx.require_lang_item(LangItem::Clone, Some(segment.ident.span)); + if args.is_empty() + && self.typeck_results.borrow().type_dependent_def_id(expr.hir_id).map( + |did| { + let ai = self.tcx.associated_item(did); + ai.trait_container(self.tcx) == Some(clone_trait) + }, + ) == Some(true) + && segment.ident.name == sym::clone + { + // If this expression had a clone call when suggesting borrowing + // we want to suggest removing it because it'd now be unnecessary. + sugg_sp = receiver.span; + } + } + if let Ok(src) = sm.span_to_snippet(sugg_sp) { + let needs_parens = match expr.kind { + // parenthesize if needed (Issue #46756) + hir::ExprKind::Cast(_, _) | hir::ExprKind::Binary(_, _, _) => true, + // parenthesize borrows of range literals (Issue #54505) + _ if is_range_literal(expr) => true, + _ => false, + }; + + if let Some(sugg) = self.can_use_as_ref(expr) { + return Some(( + sugg.0, + sugg.1.to_string(), + sugg.2, + Applicability::MachineApplicable, + false, + )); + } + + let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) { + Some(ident) => format!("{ident}: "), + None => String::new(), + }; + + if let Some(hir::Node::Expr(hir::Expr { + kind: hir::ExprKind::Assign(..), + .. + })) = self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id)) + { + if mutability == hir::Mutability::Mut { + // Suppressing this diagnostic, we'll properly print it in `check_expr_assign` + return None; + } + } + + let sugg_expr = if needs_parens { format!("({src})") } else { src }; + return Some(match mutability { + hir::Mutability::Mut => ( + sp, + "consider mutably borrowing here".to_string(), + format!("{prefix}&mut {sugg_expr}"), + Applicability::MachineApplicable, + false, + ), + hir::Mutability::Not => ( + sp, + "consider borrowing here".to_string(), + format!("{prefix}&{sugg_expr}"), + Applicability::MachineApplicable, + false, + ), + }); + } + } + } + ( + hir::ExprKind::AddrOf(hir::BorrowKind::Ref, _, ref expr), + _, + &ty::Ref(_, checked, _), + ) if self.can_sub(self.param_env, checked, expected).is_ok() => { + // We have `&T`, check if what was expected was `T`. If so, + // we may want to suggest removing a `&`. + if sm.is_imported(expr.span) { + // Go through the spans from which this span was expanded, + // and find the one that's pointing inside `sp`. + // + // E.g. for `&format!("")`, where we want the span to the + // `format!()` invocation instead of its expansion. + if let Some(call_span) = + iter::successors(Some(expr.span), |s| s.parent_callsite()) + .find(|&s| sp.contains(s)) + && sm.is_span_accessible(call_span) + { + return Some(( + sp.with_hi(call_span.lo()), + "consider removing the borrow".to_string(), + String::new(), + Applicability::MachineApplicable, + true, + )); + } + return None; + } + if sp.contains(expr.span) + && sm.is_span_accessible(expr.span) + { + return Some(( + sp.with_hi(expr.span.lo()), + "consider removing the borrow".to_string(), + String::new(), + Applicability::MachineApplicable, + true, + )); + } + } + ( + _, + &ty::RawPtr(TypeAndMut { ty: ty_b, mutbl: mutbl_b }), + &ty::Ref(_, ty_a, mutbl_a), + ) => { + if let Some(steps) = self.deref_steps(ty_a, ty_b) + // Only suggest valid if dereferencing needed. + && steps > 0 + // The pointer type implements `Copy` trait so the suggestion is always valid. + && let Ok(src) = sm.span_to_snippet(sp) + { + let derefs = "*".repeat(steps); + if let Some((span, src, applicability)) = match mutbl_b { + hir::Mutability::Mut => { + let new_prefix = "&mut ".to_owned() + &derefs; + match mutbl_a { + hir::Mutability::Mut => { + replace_prefix(&src, "&mut ", &new_prefix).map(|_| { + let pos = sp.lo() + BytePos(5); + let sp = sp.with_lo(pos).with_hi(pos); + (sp, derefs, Applicability::MachineApplicable) + }) + } + hir::Mutability::Not => { + replace_prefix(&src, "&", &new_prefix).map(|_| { + let pos = sp.lo() + BytePos(1); + let sp = sp.with_lo(pos).with_hi(pos); + ( + sp, + format!("mut {derefs}"), + Applicability::Unspecified, + ) + }) + } + } + } + hir::Mutability::Not => { + let new_prefix = "&".to_owned() + &derefs; + match mutbl_a { + hir::Mutability::Mut => { + replace_prefix(&src, "&mut ", &new_prefix).map(|_| { + let lo = sp.lo() + BytePos(1); + let hi = sp.lo() + BytePos(5); + let sp = sp.with_lo(lo).with_hi(hi); + (sp, derefs, Applicability::MachineApplicable) + }) + } + hir::Mutability::Not => { + replace_prefix(&src, "&", &new_prefix).map(|_| { + let pos = sp.lo() + BytePos(1); + let sp = sp.with_lo(pos).with_hi(pos); + (sp, derefs, Applicability::MachineApplicable) + }) + } + } + } + } { + return Some(( + span, + "consider dereferencing".to_string(), + src, + applicability, + true, + )); + } + } + } + _ if sp == expr.span => { + if let Some(mut steps) = self.deref_steps(checked_ty, expected) { + let mut expr = expr.peel_blocks(); + let mut prefix_span = expr.span.shrink_to_lo(); + let mut remove = String::new(); + + // Try peeling off any existing `&` and `&mut` to reach our target type + while steps > 0 { + if let hir::ExprKind::AddrOf(_, mutbl, inner) = expr.kind { + // If the expression has `&`, removing it would fix the error + prefix_span = prefix_span.with_hi(inner.span.lo()); + expr = inner; + remove += match mutbl { + hir::Mutability::Not => "&", + hir::Mutability::Mut => "&mut ", + }; + steps -= 1; + } else { + break; + } + } + // If we've reached our target type with just removing `&`, then just print now. + if steps == 0 { + return Some(( + prefix_span, + format!("consider removing the `{}`", remove.trim()), + String::new(), + // Do not remove `&&` to get to bool, because it might be something like + // { a } && b, which we have a separate fixup suggestion that is more + // likely correct... + if remove.trim() == "&&" && expected == self.tcx.types.bool { + Applicability::MaybeIncorrect + } else { + Applicability::MachineApplicable + }, + true, + )); + } + + // For this suggestion to make sense, the type would need to be `Copy`, + // or we have to be moving out of a `Box<T>` + if self.type_is_copy_modulo_regions(self.param_env, expected, sp) + // FIXME(compiler-errors): We can actually do this if the checked_ty is + // `steps` layers of boxes, not just one, but this is easier and most likely. + || (checked_ty.is_box() && steps == 1) + { + let deref_kind = if checked_ty.is_box() { + "unboxing the value" + } else if checked_ty.is_region_ptr() { + "dereferencing the borrow" + } else { + "dereferencing the type" + }; + + // Suggest removing `&` if we have removed any, otherwise suggest just + // dereferencing the remaining number of steps. + let message = if remove.is_empty() { + format!("consider {deref_kind}") + } else { + format!( + "consider removing the `{}` and {} instead", + remove.trim(), + deref_kind + ) + }; + + let prefix = match self.maybe_get_struct_pattern_shorthand_field(expr) { + Some(ident) => format!("{ident}: "), + None => String::new(), + }; + + let (span, suggestion) = if self.is_else_if_block(expr) { + // Don't suggest nonsense like `else *if` + return None; + } else if let Some(expr) = self.maybe_get_block_expr(expr) { + // prefix should be empty here.. + (expr.span.shrink_to_lo(), "*".to_string()) + } else { + (prefix_span, format!("{}{}", prefix, "*".repeat(steps))) + }; + + return Some(( + span, + message, + suggestion, + Applicability::MachineApplicable, + true, + )); + } + } + } + _ => {} + } + None + } + + pub fn check_for_cast( + &self, + err: &mut Diagnostic, + expr: &hir::Expr<'_>, + checked_ty: Ty<'tcx>, + expected_ty: Ty<'tcx>, + expected_ty_expr: Option<&'tcx hir::Expr<'tcx>>, + ) -> bool { + if self.tcx.sess.source_map().is_imported(expr.span) { + // Ignore if span is from within a macro. + return false; + } + + let Ok(src) = self.tcx.sess.source_map().span_to_snippet(expr.span) else { + return false; + }; + + // If casting this expression to a given numeric type would be appropriate in case of a type + // mismatch. + // + // We want to minimize the amount of casting operations that are suggested, as it can be a + // lossy operation with potentially bad side effects, so we only suggest when encountering + // an expression that indicates that the original type couldn't be directly changed. + // + // For now, don't suggest casting with `as`. + let can_cast = false; + + let mut sugg = vec![]; + + if let Some(hir::Node::ExprField(field)) = + self.tcx.hir().find(self.tcx.hir().get_parent_node(expr.hir_id)) + { + // `expr` is a literal field for a struct, only suggest if appropriate + if field.is_shorthand { + // This is a field literal + sugg.push((field.ident.span.shrink_to_lo(), format!("{}: ", field.ident))); + } else { + // Likely a field was meant, but this field wasn't found. Do not suggest anything. + return false; + } + }; + + if let hir::ExprKind::Call(path, args) = &expr.kind + && let (hir::ExprKind::Path(hir::QPath::TypeRelative(base_ty, path_segment)), 1) = + (&path.kind, args.len()) + // `expr` is a conversion like `u32::from(val)`, do not suggest anything (#63697). + && let (hir::TyKind::Path(hir::QPath::Resolved(None, base_ty_path)), sym::from) = + (&base_ty.kind, path_segment.ident.name) + { + if let Some(ident) = &base_ty_path.segments.iter().map(|s| s.ident).next() { + match ident.name { + sym::i128 + | sym::i64 + | sym::i32 + | sym::i16 + | sym::i8 + | sym::u128 + | sym::u64 + | sym::u32 + | sym::u16 + | sym::u8 + | sym::isize + | sym::usize + if base_ty_path.segments.len() == 1 => + { + return false; + } + _ => {} + } + } + } + + let msg = format!( + "you can convert {} `{}` to {} `{}`", + checked_ty.kind().article(), + checked_ty, + expected_ty.kind().article(), + expected_ty, + ); + let cast_msg = format!( + "you can cast {} `{}` to {} `{}`", + checked_ty.kind().article(), + checked_ty, + expected_ty.kind().article(), + expected_ty, + ); + let lit_msg = format!( + "change the type of the numeric literal from `{checked_ty}` to `{expected_ty}`", + ); + + let close_paren = if expr.precedence().order() < PREC_POSTFIX { + sugg.push((expr.span.shrink_to_lo(), "(".to_string())); + ")" + } else { + "" + }; + + let mut cast_suggestion = sugg.clone(); + cast_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren} as {expected_ty}"))); + let mut into_suggestion = sugg.clone(); + into_suggestion.push((expr.span.shrink_to_hi(), format!("{close_paren}.into()"))); + let mut suffix_suggestion = sugg.clone(); + suffix_suggestion.push(( + if matches!( + (&expected_ty.kind(), &checked_ty.kind()), + (ty::Int(_) | ty::Uint(_), ty::Float(_)) + ) { + // Remove fractional part from literal, for example `42.0f32` into `42` + let src = src.trim_end_matches(&checked_ty.to_string()); + let len = src.split('.').next().unwrap().len(); + expr.span.with_lo(expr.span.lo() + BytePos(len as u32)) + } else { + let len = src.trim_end_matches(&checked_ty.to_string()).len(); + expr.span.with_lo(expr.span.lo() + BytePos(len as u32)) + }, + if expr.precedence().order() < PREC_POSTFIX { + // Readd `)` + format!("{expected_ty})") + } else { + expected_ty.to_string() + }, + )); + let literal_is_ty_suffixed = |expr: &hir::Expr<'_>| { + if let hir::ExprKind::Lit(lit) = &expr.kind { lit.node.is_suffixed() } else { false } + }; + let is_negative_int = + |expr: &hir::Expr<'_>| matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::Neg, ..)); + let is_uint = |ty: Ty<'_>| matches!(ty.kind(), ty::Uint(..)); + + let in_const_context = self.tcx.hir().is_inside_const_context(expr.hir_id); + + let suggest_fallible_into_or_lhs_from = + |err: &mut Diagnostic, exp_to_found_is_fallible: bool| { + // If we know the expression the expected type is derived from, we might be able + // to suggest a widening conversion rather than a narrowing one (which may + // panic). For example, given x: u8 and y: u32, if we know the span of "x", + // x > y + // can be given the suggestion "u32::from(x) > y" rather than + // "x > y.try_into().unwrap()". + let lhs_expr_and_src = expected_ty_expr.and_then(|expr| { + self.tcx + .sess + .source_map() + .span_to_snippet(expr.span) + .ok() + .map(|src| (expr, src)) + }); + let (msg, suggestion) = if let (Some((lhs_expr, lhs_src)), false) = + (lhs_expr_and_src, exp_to_found_is_fallible) + { + let msg = format!( + "you can convert `{lhs_src}` from `{expected_ty}` to `{checked_ty}`, matching the type of `{src}`", + ); + let suggestion = vec![ + (lhs_expr.span.shrink_to_lo(), format!("{checked_ty}::from(")), + (lhs_expr.span.shrink_to_hi(), ")".to_string()), + ]; + (msg, suggestion) + } else { + let msg = format!("{msg} and panic if the converted value doesn't fit"); + let mut suggestion = sugg.clone(); + suggestion.push(( + expr.span.shrink_to_hi(), + format!("{close_paren}.try_into().unwrap()"), + )); + (msg, suggestion) + }; + err.multipart_suggestion_verbose( + &msg, + suggestion, + Applicability::MachineApplicable, + ); + }; + + let suggest_to_change_suffix_or_into = + |err: &mut Diagnostic, + found_to_exp_is_fallible: bool, + exp_to_found_is_fallible: bool| { + let exp_is_lhs = + expected_ty_expr.map(|e| self.tcx.hir().is_lhs(e.hir_id)).unwrap_or(false); + + if exp_is_lhs { + return; + } + + let always_fallible = found_to_exp_is_fallible + && (exp_to_found_is_fallible || expected_ty_expr.is_none()); + let msg = if literal_is_ty_suffixed(expr) { + &lit_msg + } else if always_fallible && (is_negative_int(expr) && is_uint(expected_ty)) { + // We now know that converting either the lhs or rhs is fallible. Before we + // suggest a fallible conversion, check if the value can never fit in the + // expected type. + let msg = format!("`{src}` cannot fit into type `{expected_ty}`"); + err.note(&msg); + return; + } else if in_const_context { + // Do not recommend `into` or `try_into` in const contexts. + return; + } else if found_to_exp_is_fallible { + return suggest_fallible_into_or_lhs_from(err, exp_to_found_is_fallible); + } else { + &msg + }; + let suggestion = if literal_is_ty_suffixed(expr) { + suffix_suggestion.clone() + } else { + into_suggestion.clone() + }; + err.multipart_suggestion_verbose(msg, suggestion, Applicability::MachineApplicable); + }; + + match (&expected_ty.kind(), &checked_ty.kind()) { + (&ty::Int(ref exp), &ty::Int(ref found)) => { + let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width()) + { + (Some(exp), Some(found)) if exp < found => (true, false), + (Some(exp), Some(found)) if exp > found => (false, true), + (None, Some(8 | 16)) => (false, true), + (Some(8 | 16), None) => (true, false), + (None, _) | (_, None) => (true, true), + _ => (false, false), + }; + suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible); + true + } + (&ty::Uint(ref exp), &ty::Uint(ref found)) => { + let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width()) + { + (Some(exp), Some(found)) if exp < found => (true, false), + (Some(exp), Some(found)) if exp > found => (false, true), + (None, Some(8 | 16)) => (false, true), + (Some(8 | 16), None) => (true, false), + (None, _) | (_, None) => (true, true), + _ => (false, false), + }; + suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible); + true + } + (&ty::Int(exp), &ty::Uint(found)) => { + let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width()) + { + (Some(exp), Some(found)) if found < exp => (false, true), + (None, Some(8)) => (false, true), + _ => (true, true), + }; + suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible); + true + } + (&ty::Uint(exp), &ty::Int(found)) => { + let (f2e_is_fallible, e2f_is_fallible) = match (exp.bit_width(), found.bit_width()) + { + (Some(exp), Some(found)) if found > exp => (true, false), + (Some(8), None) => (true, false), + _ => (true, true), + }; + suggest_to_change_suffix_or_into(err, f2e_is_fallible, e2f_is_fallible); + true + } + (&ty::Float(ref exp), &ty::Float(ref found)) => { + if found.bit_width() < exp.bit_width() { + suggest_to_change_suffix_or_into(err, false, true); + } else if literal_is_ty_suffixed(expr) { + err.multipart_suggestion_verbose( + &lit_msg, + suffix_suggestion, + Applicability::MachineApplicable, + ); + } else if can_cast { + // Missing try_into implementation for `f64` to `f32` + err.multipart_suggestion_verbose( + &format!("{cast_msg}, producing the closest possible value"), + cast_suggestion, + Applicability::MaybeIncorrect, // lossy conversion + ); + } + true + } + (&ty::Uint(_) | &ty::Int(_), &ty::Float(_)) => { + if literal_is_ty_suffixed(expr) { + err.multipart_suggestion_verbose( + &lit_msg, + suffix_suggestion, + Applicability::MachineApplicable, + ); + } else if can_cast { + // Missing try_into implementation for `{float}` to `{integer}` + err.multipart_suggestion_verbose( + &format!("{msg}, rounding the float towards zero"), + cast_suggestion, + Applicability::MaybeIncorrect, // lossy conversion + ); + } + true + } + (&ty::Float(ref exp), &ty::Uint(ref found)) => { + // if `found` is `None` (meaning found is `usize`), don't suggest `.into()` + if exp.bit_width() > found.bit_width().unwrap_or(256) { + err.multipart_suggestion_verbose( + &format!( + "{msg}, producing the floating point representation of the integer", + ), + into_suggestion, + Applicability::MachineApplicable, + ); + } else if literal_is_ty_suffixed(expr) { + err.multipart_suggestion_verbose( + &lit_msg, + suffix_suggestion, + Applicability::MachineApplicable, + ); + } else { + // Missing try_into implementation for `{integer}` to `{float}` + err.multipart_suggestion_verbose( + &format!( + "{cast_msg}, producing the floating point representation of the integer, \ + rounded if necessary", + ), + cast_suggestion, + Applicability::MaybeIncorrect, // lossy conversion + ); + } + true + } + (&ty::Float(ref exp), &ty::Int(ref found)) => { + // if `found` is `None` (meaning found is `isize`), don't suggest `.into()` + if exp.bit_width() > found.bit_width().unwrap_or(256) { + err.multipart_suggestion_verbose( + &format!( + "{}, producing the floating point representation of the integer", + &msg, + ), + into_suggestion, + Applicability::MachineApplicable, + ); + } else if literal_is_ty_suffixed(expr) { + err.multipart_suggestion_verbose( + &lit_msg, + suffix_suggestion, + Applicability::MachineApplicable, + ); + } else { + // Missing try_into implementation for `{integer}` to `{float}` + err.multipart_suggestion_verbose( + &format!( + "{}, producing the floating point representation of the integer, \ + rounded if necessary", + &msg, + ), + cast_suggestion, + Applicability::MaybeIncorrect, // lossy conversion + ); + } + true + } + ( + &ty::Uint(ty::UintTy::U32 | ty::UintTy::U64 | ty::UintTy::U128) + | &ty::Int(ty::IntTy::I32 | ty::IntTy::I64 | ty::IntTy::I128), + &ty::Char, + ) => { + err.multipart_suggestion_verbose( + &format!("{cast_msg}, since a `char` always occupies 4 bytes"), + cast_suggestion, + Applicability::MachineApplicable, + ); + true + } + _ => false, + } + } +} |