1 //! Code related to processing overloaded binary and unary operators.
3 use super::method::MethodCallee;
4 use super::{has_expected_num_generic_args, FnCtxt};
5 use crate::check::Expectation;
7 use rustc_errors::{self, struct_span_err, Applicability, Diagnostic};
9 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
10 use rustc_infer::traits::ObligationCauseCode;
11 use rustc_middle::ty::adjustment::{
12 Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability,
14 use rustc_middle::ty::{
15 self, Ty, TyCtxt, TypeFolder, TypeSuperFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitor,
17 use rustc_span::source_map::Spanned;
18 use rustc_span::symbol::{sym, Ident};
20 use rustc_trait_selection::infer::InferCtxtExt;
21 use rustc_trait_selection::traits::error_reporting::suggestions::InferCtxtExt as _;
22 use rustc_trait_selection::traits::{FulfillmentError, TraitEngine, TraitEngineExt};
23 use rustc_type_ir::sty::TyKind::*;
25 use std::ops::ControlFlow;
27 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
28 /// Checks a `a <op>= b`
29 pub fn check_binop_assign(
31 expr: &'tcx hir::Expr<'tcx>,
33 lhs: &'tcx hir::Expr<'tcx>,
34 rhs: &'tcx hir::Expr<'tcx>,
35 expected: Expectation<'tcx>,
37 let (lhs_ty, rhs_ty, return_ty) =
38 self.check_overloaded_binop(expr, lhs, rhs, op, IsAssign::Yes, expected);
41 if !lhs_ty.is_ty_var() && !rhs_ty.is_ty_var() && is_builtin_binop(lhs_ty, rhs_ty, op) {
42 self.enforce_builtin_binop_types(lhs.span, lhs_ty, rhs.span, rhs_ty, op);
48 self.check_lhs_assignable(lhs, "E0067", op.span, |err| {
49 if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
55 Op::Binary(op, IsAssign::Yes),
60 // Suppress this error, since we already emitted
61 // a deref suggestion in check_overloaded_binop
62 err.downgrade_to_delayed_bug();
70 /// Checks a potentially overloaded binary operator.
73 expr: &'tcx hir::Expr<'tcx>,
75 lhs_expr: &'tcx hir::Expr<'tcx>,
76 rhs_expr: &'tcx hir::Expr<'tcx>,
77 expected: Expectation<'tcx>,
82 "check_binop(expr.hir_id={}, expr={:?}, op={:?}, lhs_expr={:?}, rhs_expr={:?})",
83 expr.hir_id, expr, op, lhs_expr, rhs_expr
86 match BinOpCategory::from(op) {
87 BinOpCategory::Shortcircuit => {
88 // && and || are a simple case.
89 self.check_expr_coercable_to_type(lhs_expr, tcx.types.bool, None);
90 let lhs_diverges = self.diverges.get();
91 self.check_expr_coercable_to_type(rhs_expr, tcx.types.bool, None);
93 // Depending on the LHS' value, the RHS can never execute.
94 self.diverges.set(lhs_diverges);
99 // Otherwise, we always treat operators as if they are
100 // overloaded. This is the way to be most flexible w/r/t
101 // types that get inferred.
102 let (lhs_ty, rhs_ty, return_ty) = self.check_overloaded_binop(
111 // Supply type inference hints if relevant. Probably these
112 // hints should be enforced during select as part of the
113 // `consider_unification_despite_ambiguity` routine, but this
114 // more convenient for now.
116 // The basic idea is to help type inference by taking
117 // advantage of things we know about how the impls for
118 // scalar types are arranged. This is important in a
119 // scenario like `1_u32 << 2`, because it lets us quickly
120 // deduce that the result type should be `u32`, even
121 // though we don't know yet what type 2 has and hence
122 // can't pin this down to a specific impl.
123 if !lhs_ty.is_ty_var()
124 && !rhs_ty.is_ty_var()
125 && is_builtin_binop(lhs_ty, rhs_ty, op)
127 let builtin_return_ty = self.enforce_builtin_binop_types(
134 self.demand_suptype(expr.span, builtin_return_ty, return_ty);
142 fn enforce_builtin_binop_types(
150 debug_assert!(is_builtin_binop(lhs_ty, rhs_ty, op));
152 // Special-case a single layer of referencing, so that things like `5.0 + &6.0f32` work.
153 // (See https://github.com/rust-lang/rust/issues/57447.)
154 let (lhs_ty, rhs_ty) = (deref_ty_if_possible(lhs_ty), deref_ty_if_possible(rhs_ty));
157 match BinOpCategory::from(op) {
158 BinOpCategory::Shortcircuit => {
159 self.demand_suptype(lhs_span, tcx.types.bool, lhs_ty);
160 self.demand_suptype(rhs_span, tcx.types.bool, rhs_ty);
164 BinOpCategory::Shift => {
165 // result type is same as LHS always
169 BinOpCategory::Math | BinOpCategory::Bitwise => {
170 // both LHS and RHS and result will have the same type
171 self.demand_suptype(rhs_span, lhs_ty, rhs_ty);
175 BinOpCategory::Comparison => {
176 // both LHS and RHS and result will have the same type
177 self.demand_suptype(rhs_span, lhs_ty, rhs_ty);
183 fn check_overloaded_binop(
185 expr: &'tcx hir::Expr<'tcx>,
186 lhs_expr: &'tcx hir::Expr<'tcx>,
187 rhs_expr: &'tcx hir::Expr<'tcx>,
190 expected: Expectation<'tcx>,
191 ) -> (Ty<'tcx>, Ty<'tcx>, Ty<'tcx>) {
193 "check_overloaded_binop(expr.hir_id={}, op={:?}, is_assign={:?})",
194 expr.hir_id, op, is_assign
197 let lhs_ty = match is_assign {
199 // Find a suitable supertype of the LHS expression's type, by coercing to
200 // a type variable, to pass as the `Self` to the trait, avoiding invariant
201 // trait matching creating lifetime constraints that are too strict.
202 // e.g., adding `&'a T` and `&'b T`, given `&'x T: Add<&'x T>`, will result
203 // in `&'a T <: &'x T` and `&'b T <: &'x T`, instead of `'a = 'b = 'x`.
204 let lhs_ty = self.check_expr(lhs_expr);
205 let fresh_var = self.next_ty_var(TypeVariableOrigin {
206 kind: TypeVariableOriginKind::MiscVariable,
209 self.demand_coerce(lhs_expr, lhs_ty, fresh_var, Some(rhs_expr), AllowTwoPhase::No)
212 // rust-lang/rust#52126: We have to use strict
213 // equivalence on the LHS of an assign-op like `+=`;
214 // overwritten or mutably-borrowed places cannot be
215 // coerced to a supertype.
216 self.check_expr(lhs_expr)
219 let lhs_ty = self.resolve_vars_with_obligations(lhs_ty);
221 // N.B., as we have not yet type-checked the RHS, we don't have the
222 // type at hand. Make a variable to represent it. The whole reason
223 // for this indirection is so that, below, we can check the expr
224 // using this variable as the expected type, which sometimes lets
225 // us do better coercions than we would be able to do otherwise,
226 // particularly for things like `String + &String`.
227 let rhs_ty_var = self.next_ty_var(TypeVariableOrigin {
228 kind: TypeVariableOriginKind::MiscVariable,
232 let result = self.lookup_op_method(
236 Op::Binary(op, is_assign),
241 let rhs_ty = self.check_expr_coercable_to_type(rhs_expr, rhs_ty_var, Some(lhs_expr));
242 let rhs_ty = self.resolve_vars_with_obligations(rhs_ty);
244 let return_ty = match result {
246 let by_ref_binop = !op.node.is_by_value();
247 if is_assign == IsAssign::Yes || by_ref_binop {
248 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].kind() {
249 let mutbl = match mutbl {
250 hir::Mutability::Not => AutoBorrowMutability::Not,
251 hir::Mutability::Mut => AutoBorrowMutability::Mut {
252 // Allow two-phase borrows for binops in initial deployment
253 // since they desugar to methods
254 allow_two_phase_borrow: AllowTwoPhase::Yes,
257 let autoref = Adjustment {
258 kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)),
259 target: method.sig.inputs()[0],
261 self.apply_adjustments(lhs_expr, vec![autoref]);
265 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[1].kind() {
266 let mutbl = match mutbl {
267 hir::Mutability::Not => AutoBorrowMutability::Not,
268 hir::Mutability::Mut => AutoBorrowMutability::Mut {
269 // Allow two-phase borrows for binops in initial deployment
270 // since they desugar to methods
271 allow_two_phase_borrow: AllowTwoPhase::Yes,
274 let autoref = Adjustment {
275 kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)),
276 target: method.sig.inputs()[1],
278 // HACK(eddyb) Bypass checks due to reborrows being in
279 // some cases applied on the RHS, on top of which we need
280 // to autoref, which is not allowed by apply_adjustments.
281 // self.apply_adjustments(rhs_expr, vec![autoref]);
285 .entry(rhs_expr.hir_id)
290 self.write_method_call(expr.hir_id, method);
294 // error types are considered "builtin"
295 Err(_) if lhs_ty.references_error() || rhs_ty.references_error() => self.tcx.ty_error(),
297 let source_map = self.tcx.sess.source_map();
298 let (mut err, missing_trait, use_output) = match is_assign {
300 let mut err = struct_span_err!(
304 "binary assignment operation `{}=` cannot be applied to type `{}`",
310 format!("cannot use `{}=` on type `{}`", op.node.as_str(), lhs_ty),
312 let missing_trait = match op.node {
313 hir::BinOpKind::Add => Some("std::ops::AddAssign"),
314 hir::BinOpKind::Sub => Some("std::ops::SubAssign"),
315 hir::BinOpKind::Mul => Some("std::ops::MulAssign"),
316 hir::BinOpKind::Div => Some("std::ops::DivAssign"),
317 hir::BinOpKind::Rem => Some("std::ops::RemAssign"),
318 hir::BinOpKind::BitAnd => Some("std::ops::BitAndAssign"),
319 hir::BinOpKind::BitXor => Some("std::ops::BitXorAssign"),
320 hir::BinOpKind::BitOr => Some("std::ops::BitOrAssign"),
321 hir::BinOpKind::Shl => Some("std::ops::ShlAssign"),
322 hir::BinOpKind::Shr => Some("std::ops::ShrAssign"),
325 self.note_unmet_impls_on_type(&mut err, errors);
326 (err, missing_trait, false)
329 let (message, missing_trait, use_output) = match op.node {
330 hir::BinOpKind::Add => (
331 format!("cannot add `{rhs_ty}` to `{lhs_ty}`"),
332 Some("std::ops::Add"),
335 hir::BinOpKind::Sub => (
336 format!("cannot subtract `{rhs_ty}` from `{lhs_ty}`"),
337 Some("std::ops::Sub"),
340 hir::BinOpKind::Mul => (
341 format!("cannot multiply `{lhs_ty}` by `{rhs_ty}`"),
342 Some("std::ops::Mul"),
345 hir::BinOpKind::Div => (
346 format!("cannot divide `{lhs_ty}` by `{rhs_ty}`"),
347 Some("std::ops::Div"),
350 hir::BinOpKind::Rem => (
351 format!("cannot mod `{lhs_ty}` by `{rhs_ty}`"),
352 Some("std::ops::Rem"),
355 hir::BinOpKind::BitAnd => (
356 format!("no implementation for `{lhs_ty} & {rhs_ty}`"),
357 Some("std::ops::BitAnd"),
360 hir::BinOpKind::BitXor => (
361 format!("no implementation for `{lhs_ty} ^ {rhs_ty}`"),
362 Some("std::ops::BitXor"),
365 hir::BinOpKind::BitOr => (
366 format!("no implementation for `{lhs_ty} | {rhs_ty}`"),
367 Some("std::ops::BitOr"),
370 hir::BinOpKind::Shl => (
371 format!("no implementation for `{lhs_ty} << {rhs_ty}`"),
372 Some("std::ops::Shl"),
375 hir::BinOpKind::Shr => (
376 format!("no implementation for `{lhs_ty} >> {rhs_ty}`"),
377 Some("std::ops::Shr"),
380 hir::BinOpKind::Eq | hir::BinOpKind::Ne => (
382 "binary operation `{}` cannot be applied to type `{}`",
386 Some("std::cmp::PartialEq"),
392 | hir::BinOpKind::Ge => (
394 "binary operation `{}` cannot be applied to type `{}`",
398 Some("std::cmp::PartialOrd"),
403 "binary operation `{}` cannot be applied to type `{}`",
411 let mut err = struct_span_err!(self.tcx.sess, op.span, E0369, "{message}");
412 if !lhs_expr.span.eq(&rhs_expr.span) {
413 self.add_type_neq_err_label(
423 self.add_type_neq_err_label(
434 self.note_unmet_impls_on_type(&mut err, errors);
435 (err, missing_trait, use_output)
439 let mut suggest_deref_binop = |lhs_deref_ty: Ty<'tcx>| {
445 Op::Binary(op, is_assign),
450 if let Ok(lstring) = source_map.span_to_snippet(lhs_expr.span) {
452 "`{}{}` can be used on `{}`, you can dereference `{}`",
455 IsAssign::Yes => "=",
458 lhs_deref_ty.peel_refs(),
461 err.span_suggestion_verbose(
462 lhs_expr.span.shrink_to_lo(),
465 rustc_errors::Applicability::MachineApplicable,
471 // We should suggest `a + b` => `*a + b` if `a` is copy, and suggest
472 // `a += b` => `*a += b` if a is a mut ref.
473 if is_assign == IsAssign::Yes
474 && let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
475 suggest_deref_binop(lhs_deref_ty);
476 } else if is_assign == IsAssign::No
477 && let Ref(_, lhs_deref_ty, _) = lhs_ty.kind() {
478 if self.type_is_copy_modulo_regions(self.param_env, *lhs_deref_ty, lhs_expr.span) {
479 suggest_deref_binop(*lhs_deref_ty);
482 if let Some(missing_trait) = missing_trait {
483 let mut visitor = TypeParamVisitor(vec![]);
484 visitor.visit_ty(lhs_ty);
486 if op.node == hir::BinOpKind::Add
487 && self.check_str_addition(
488 lhs_expr, rhs_expr, lhs_ty, rhs_ty, &mut err, is_assign, op,
491 // This has nothing here because it means we did string
492 // concatenation (e.g., "Hello " + "World!"). This means
493 // we don't want the note in the else clause to be emitted
494 } else if let [ty] = &visitor.0[..] {
495 // Look for a TraitPredicate in the Fulfillment errors,
496 // and use it to generate a suggestion.
498 // Note that lookup_op_method must be called again but
499 // with a specific rhs_ty instead of a placeholder so
500 // the resulting predicate generates a more specific
501 // suggestion for the user.
507 Op::Binary(op, is_assign),
511 if !errors.is_empty() {
512 for error in errors {
513 if let Some(trait_pred) =
514 error.obligation.predicate.to_opt_poly_trait_pred()
516 let proj_pred = match error.obligation.cause.code() {
517 ObligationCauseCode::BinOp {
518 output_pred: Some(output_pred),
521 output_pred.to_opt_poly_projection_pred()
526 self.suggest_restricting_param_bound(
534 } else if *ty != lhs_ty {
535 // When we know that a missing bound is responsible, we don't show
536 // this note as it is redundant.
538 "the trait `{missing_trait}` is not implemented for `{lhs_ty}`"
548 (lhs_ty, rhs_ty, return_ty)
551 /// If one of the types is an uncalled function and calling it would yield the other type,
552 /// suggest calling the function. Returns `true` if suggestion would apply (even if not given).
553 fn add_type_neq_err_label(
555 err: &mut Diagnostic,
559 other_expr: &'tcx hir::Expr<'tcx>,
562 expected: Expectation<'tcx>,
563 ) -> bool /* did we suggest to call a function because of missing parentheses? */ {
564 err.span_label(span, ty.to_string());
565 if let FnDef(def_id, _) = *ty.kind() {
566 if !self.tcx.has_typeck_results(def_id) {
569 // FIXME: Instead of exiting early when encountering bound vars in
570 // the function signature, consider keeping the binder here and
571 // propagating it downwards.
572 let Some(fn_sig) = self.tcx.fn_sig(def_id).no_bound_vars() else {
576 let other_ty = if let FnDef(def_id, _) = *other_ty.kind() {
577 if !self.tcx.has_typeck_results(def_id) {
580 // We're emitting a suggestion, so we can just ignore regions
581 self.tcx.fn_sig(def_id).skip_binder().output()
591 Op::Binary(op, is_assign),
596 let (variable_snippet, applicability) = if !fn_sig.inputs().is_empty() {
597 ("( /* arguments */ )", Applicability::HasPlaceholders)
599 ("()", Applicability::MaybeIncorrect)
602 err.span_suggestion_verbose(
604 "you might have forgotten to call this function",
614 /// Provide actionable suggestions when trying to add two strings with incorrect types,
615 /// like `&str + &str`, `String + String` and `&str + &String`.
617 /// If this function returns `true` it means a note was printed, so we don't need
618 /// to print the normal "implementation of `std::ops::Add` might be missing" note
619 fn check_str_addition(
621 lhs_expr: &'tcx hir::Expr<'tcx>,
622 rhs_expr: &'tcx hir::Expr<'tcx>,
625 err: &mut Diagnostic,
629 let str_concat_note = "string concatenation requires an owned `String` on the left";
630 let rm_borrow_msg = "remove the borrow to obtain an owned `String`";
631 let to_owned_msg = "create an owned `String` from a string reference";
633 let is_std_string = |ty: Ty<'tcx>| {
635 .map_or(false, |ty_def| self.tcx.is_diagnostic_item(sym::String, ty_def.did()))
638 match (lhs_ty.kind(), rhs_ty.kind()) {
639 (&Ref(_, l_ty, _), &Ref(_, r_ty, _)) // &str or &String + &str, &String or &&str
640 if (*l_ty.kind() == Str || is_std_string(l_ty))
641 && (*r_ty.kind() == Str
642 || is_std_string(r_ty)
644 r_ty.kind(), Ref(_, inner_ty, _) if *inner_ty.kind() == Str
647 if let IsAssign::No = is_assign { // Do not supply this message if `&str += &str`
648 err.span_label(op.span, "`+` cannot be used to concatenate two `&str` strings");
649 err.note(str_concat_note);
650 if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
651 err.span_suggestion_verbose(
652 lhs_expr.span.until(lhs_inner_expr.span),
655 Applicability::MachineApplicable
658 err.span_suggestion_verbose(
659 lhs_expr.span.shrink_to_hi(),
662 Applicability::MachineApplicable
668 (&Ref(_, l_ty, _), &Adt(..)) // Handle `&str` & `&String` + `String`
669 if (*l_ty.kind() == Str || is_std_string(l_ty)) && is_std_string(rhs_ty) =>
673 "`+` cannot be used to concatenate a `&str` with a `String`",
678 let lhs_sugg = if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
679 sugg_msg = "remove the borrow on the left and add one on the right";
680 (lhs_expr.span.until(lhs_inner_expr.span), "".to_owned())
682 sugg_msg = "create an owned `String` on the left and add a borrow on the right";
683 (lhs_expr.span.shrink_to_hi(), ".to_owned()".to_owned())
685 let suggestions = vec![
687 (rhs_expr.span.shrink_to_lo(), "&".to_owned()),
689 err.multipart_suggestion_verbose(
692 Applicability::MachineApplicable,
696 err.note(str_concat_note);
705 pub fn check_user_unop(
707 ex: &'tcx hir::Expr<'tcx>,
708 operand_ty: Ty<'tcx>,
710 expected: Expectation<'tcx>,
712 assert!(op.is_by_value());
713 match self.lookup_op_method(operand_ty, None, None, Op::Unary(op, ex.span), expected) {
715 self.write_method_call(ex.hir_id, method);
719 let actual = self.resolve_vars_if_possible(operand_ty);
720 if !actual.references_error() {
721 let mut err = struct_span_err!(
725 "cannot apply unary operator `{}` to type `{}`",
731 format!("cannot apply unary operator `{}`", op.as_str()),
734 let mut visitor = TypeParamVisitor(vec![]);
735 visitor.visit_ty(operand_ty);
736 if let [_] = &visitor.0[..] && let ty::Param(_) = *operand_ty.kind() {
737 let predicates = errors
739 .filter_map(|error| {
740 error.obligation.predicate.to_opt_poly_trait_pred()
742 for pred in predicates {
743 self.suggest_restricting_param_bound(
752 let sp = self.tcx.sess.source_map().start_point(ex.span);
754 self.tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
756 // If the previous expression was a block expression, suggest parentheses
757 // (turning this into a binary subtraction operation instead.)
758 // for example, `{2} - 2` -> `({2}) - 2` (see src\test\ui\parser\expr-as-stmt.rs)
759 self.tcx.sess.parse_sess.expr_parentheses_needed(&mut err, *sp);
761 match actual.kind() {
762 Uint(_) if op == hir::UnOp::Neg => {
763 err.note("unsigned values cannot be negated");
765 if let hir::ExprKind::Unary(
769 hir::ExprKind::Lit(Spanned {
770 node: ast::LitKind::Int(1, _),
780 "you may have meant the maximum value of `{actual}`",
782 format!("{actual}::MAX"),
783 Applicability::MaybeIncorrect,
787 Str | Never | Char | Tuple(_) | Array(_, _) => {}
788 Ref(_, lty, _) if *lty.kind() == Str => {}
790 self.note_unmet_impls_on_type(&mut err, errors);
804 other_ty: Option<Ty<'tcx>>,
805 other_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
807 expected: Expectation<'tcx>,
808 ) -> Result<MethodCallee<'tcx>, Vec<FulfillmentError<'tcx>>> {
809 let lang = self.tcx.lang_items();
811 let span = match op {
812 Op::Binary(op, _) => op.span,
813 Op::Unary(_, span) => span,
815 let (opname, trait_did) = if let Op::Binary(op, IsAssign::Yes) = op {
817 hir::BinOpKind::Add => (sym::add_assign, lang.add_assign_trait()),
818 hir::BinOpKind::Sub => (sym::sub_assign, lang.sub_assign_trait()),
819 hir::BinOpKind::Mul => (sym::mul_assign, lang.mul_assign_trait()),
820 hir::BinOpKind::Div => (sym::div_assign, lang.div_assign_trait()),
821 hir::BinOpKind::Rem => (sym::rem_assign, lang.rem_assign_trait()),
822 hir::BinOpKind::BitXor => (sym::bitxor_assign, lang.bitxor_assign_trait()),
823 hir::BinOpKind::BitAnd => (sym::bitand_assign, lang.bitand_assign_trait()),
824 hir::BinOpKind::BitOr => (sym::bitor_assign, lang.bitor_assign_trait()),
825 hir::BinOpKind::Shl => (sym::shl_assign, lang.shl_assign_trait()),
826 hir::BinOpKind::Shr => (sym::shr_assign, lang.shr_assign_trait()),
833 | hir::BinOpKind::And
834 | hir::BinOpKind::Or => {
835 span_bug!(span, "impossible assignment operation: {}=", op.node.as_str())
838 } else if let Op::Binary(op, IsAssign::No) = op {
840 hir::BinOpKind::Add => (sym::add, lang.add_trait()),
841 hir::BinOpKind::Sub => (sym::sub, lang.sub_trait()),
842 hir::BinOpKind::Mul => (sym::mul, lang.mul_trait()),
843 hir::BinOpKind::Div => (sym::div, lang.div_trait()),
844 hir::BinOpKind::Rem => (sym::rem, lang.rem_trait()),
845 hir::BinOpKind::BitXor => (sym::bitxor, lang.bitxor_trait()),
846 hir::BinOpKind::BitAnd => (sym::bitand, lang.bitand_trait()),
847 hir::BinOpKind::BitOr => (sym::bitor, lang.bitor_trait()),
848 hir::BinOpKind::Shl => (sym::shl, lang.shl_trait()),
849 hir::BinOpKind::Shr => (sym::shr, lang.shr_trait()),
850 hir::BinOpKind::Lt => (sym::lt, lang.partial_ord_trait()),
851 hir::BinOpKind::Le => (sym::le, lang.partial_ord_trait()),
852 hir::BinOpKind::Ge => (sym::ge, lang.partial_ord_trait()),
853 hir::BinOpKind::Gt => (sym::gt, lang.partial_ord_trait()),
854 hir::BinOpKind::Eq => (sym::eq, lang.eq_trait()),
855 hir::BinOpKind::Ne => (sym::ne, lang.eq_trait()),
856 hir::BinOpKind::And | hir::BinOpKind::Or => {
857 span_bug!(span, "&& and || are not overloadable")
860 } else if let Op::Unary(hir::UnOp::Not, _) = op {
861 (sym::not, lang.not_trait())
862 } else if let Op::Unary(hir::UnOp::Neg, _) = op {
863 (sym::neg, lang.neg_trait())
865 bug!("lookup_op_method: op not supported: {:?}", op)
869 "lookup_op_method(lhs_ty={:?}, op={:?}, opname={:?}, trait_did={:?})",
870 lhs_ty, op, opname, trait_did
873 // Catches cases like #83893, where a lang item is declared with the
874 // wrong number of generic arguments. Should have yielded an error
875 // elsewhere by now, but we have to catch it here so that we do not
876 // index `other_tys` out of bounds (if the lang item has too many
877 // generic arguments, `other_tys` is too short).
878 if !has_expected_num_generic_args(
882 // Binary ops have a generic right-hand side, unary ops don't
890 let opname = Ident::with_dummy_span(opname);
891 let method = trait_did.and_then(|trait_did| {
892 self.lookup_op_method_in_trait(
903 match (method, trait_did) {
905 let method = self.register_infer_ok_obligations(ok);
906 self.select_obligations_where_possible(false, |_| {});
909 (None, None) => Err(vec![]),
910 (None, Some(trait_did)) => {
911 let (obligation, _) = self.obligation_for_op_method(
919 let mut fulfill = <dyn TraitEngine<'_>>::new(self.tcx);
920 fulfill.register_predicate_obligation(self, obligation);
921 Err(fulfill.select_where_possible(&self.infcx))
927 // Binary operator categories. These categories summarize the behavior
928 // with respect to the builtin operations supported.
930 /// &&, || -- cannot be overridden
933 /// <<, >> -- when shifting a single integer, rhs can be any
934 /// integer type. For simd, types must match.
937 /// +, -, etc -- takes equal types, produces same type as input,
938 /// applicable to ints/floats/simd
941 /// &, |, ^ -- takes equal types, produces same type as input,
942 /// applicable to ints/floats/simd/bool
945 /// ==, !=, etc -- takes equal types, produces bools, except for simd,
946 /// which produce the input type
951 fn from(op: hir::BinOp) -> BinOpCategory {
953 hir::BinOpKind::Shl | hir::BinOpKind::Shr => BinOpCategory::Shift,
956 | hir::BinOpKind::Sub
957 | hir::BinOpKind::Mul
958 | hir::BinOpKind::Div
959 | hir::BinOpKind::Rem => BinOpCategory::Math,
961 hir::BinOpKind::BitXor | hir::BinOpKind::BitAnd | hir::BinOpKind::BitOr => {
962 BinOpCategory::Bitwise
970 | hir::BinOpKind::Gt => BinOpCategory::Comparison,
972 hir::BinOpKind::And | hir::BinOpKind::Or => BinOpCategory::Shortcircuit,
977 /// Whether the binary operation is an assignment (`a += b`), or not (`a + b`)
978 #[derive(Clone, Copy, Debug, PartialEq)]
984 #[derive(Clone, Copy, Debug)]
986 Binary(hir::BinOp, IsAssign),
987 Unary(hir::UnOp, Span),
990 /// Dereferences a single level of immutable referencing.
991 fn deref_ty_if_possible<'tcx>(ty: Ty<'tcx>) -> Ty<'tcx> {
993 ty::Ref(_, ty, hir::Mutability::Not) => *ty,
998 /// Returns `true` if this is a built-in arithmetic operation (e.g., u32
999 /// + u32, i16x4 == i16x4) and false if these types would have to be
1000 /// overloaded to be legal. There are two reasons that we distinguish
1001 /// builtin operations from overloaded ones (vs trying to drive
1002 /// everything uniformly through the trait system and intrinsics or
1003 /// something like that):
1005 /// 1. Builtin operations can trivially be evaluated in constants.
1006 /// 2. For comparison operators applied to SIMD types the result is
1007 /// not of type `bool`. For example, `i16x4 == i16x4` yields a
1008 /// type like `i16x4`. This means that the overloaded trait
1009 /// `PartialEq` is not applicable.
1011 /// Reason #2 is the killer. I tried for a while to always use
1012 /// overloaded logic and just check the types in constants/codegen after
1013 /// the fact, and it worked fine, except for SIMD types. -nmatsakis
1014 fn is_builtin_binop<'tcx>(lhs: Ty<'tcx>, rhs: Ty<'tcx>, op: hir::BinOp) -> bool {
1015 // Special-case a single layer of referencing, so that things like `5.0 + &6.0f32` work.
1016 // (See https://github.com/rust-lang/rust/issues/57447.)
1017 let (lhs, rhs) = (deref_ty_if_possible(lhs), deref_ty_if_possible(rhs));
1019 match BinOpCategory::from(op) {
1020 BinOpCategory::Shortcircuit => true,
1022 BinOpCategory::Shift => {
1023 lhs.references_error()
1024 || rhs.references_error()
1025 || lhs.is_integral() && rhs.is_integral()
1028 BinOpCategory::Math => {
1029 lhs.references_error()
1030 || rhs.references_error()
1031 || lhs.is_integral() && rhs.is_integral()
1032 || lhs.is_floating_point() && rhs.is_floating_point()
1035 BinOpCategory::Bitwise => {
1036 lhs.references_error()
1037 || rhs.references_error()
1038 || lhs.is_integral() && rhs.is_integral()
1039 || lhs.is_floating_point() && rhs.is_floating_point()
1040 || lhs.is_bool() && rhs.is_bool()
1043 BinOpCategory::Comparison => {
1044 lhs.references_error() || rhs.references_error() || lhs.is_scalar() && rhs.is_scalar()
1049 struct TypeParamVisitor<'tcx>(Vec<Ty<'tcx>>);
1051 impl<'tcx> TypeVisitor<'tcx> for TypeParamVisitor<'tcx> {
1052 fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
1053 if let ty::Param(_) = ty.kind() {
1056 ty.super_visit_with(self)
1060 struct TypeParamEraser<'a, 'tcx>(&'a FnCtxt<'a, 'tcx>, Span);
1062 impl<'tcx> TypeFolder<'tcx> for TypeParamEraser<'_, 'tcx> {
1063 fn tcx(&self) -> TyCtxt<'tcx> {
1067 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1069 ty::Param(_) => self.0.next_ty_var(TypeVariableOrigin {
1070 kind: TypeVariableOriginKind::MiscVariable,
1073 _ => ty.super_fold_with(self),