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::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::print::with_no_trimmed_paths;
15 use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt, TypeFolder, TypeSuperFoldable, TypeVisitable};
16 use rustc_session::errors::ExprParenthesesNeeded;
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::TypeErrCtxtExt as _;
22 use rustc_trait_selection::traits::FulfillmentError;
23 use rustc_type_ir::sty::TyKind::*;
25 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
26 /// Checks a `a <op>= b`
27 pub fn check_binop_assign(
29 expr: &'tcx hir::Expr<'tcx>,
31 lhs: &'tcx hir::Expr<'tcx>,
32 rhs: &'tcx hir::Expr<'tcx>,
33 expected: Expectation<'tcx>,
35 let (lhs_ty, rhs_ty, return_ty) =
36 self.check_overloaded_binop(expr, lhs, rhs, op, IsAssign::Yes, expected);
39 if !lhs_ty.is_ty_var() && !rhs_ty.is_ty_var() && is_builtin_binop(lhs_ty, rhs_ty, op) {
40 self.enforce_builtin_binop_types(lhs.span, lhs_ty, rhs.span, rhs_ty, op);
46 self.check_lhs_assignable(lhs, "E0067", op.span, |err| {
47 if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
53 Op::Binary(op, IsAssign::Yes),
58 // If LHS += RHS is an error, but *LHS += RHS is successful, then we will have
59 // emitted a better suggestion during error handling in check_overloaded_binop.
65 Op::Binary(op, IsAssign::Yes),
70 err.downgrade_to_delayed_bug();
72 // Otherwise, it's valid to suggest dereferencing the LHS here.
73 err.span_suggestion_verbose(
74 lhs.span.shrink_to_lo(),
75 "consider dereferencing the left-hand side of this operation",
77 Applicability::MaybeIncorrect,
87 /// Checks a potentially overloaded binary operator.
90 expr: &'tcx hir::Expr<'tcx>,
92 lhs_expr: &'tcx hir::Expr<'tcx>,
93 rhs_expr: &'tcx hir::Expr<'tcx>,
94 expected: Expectation<'tcx>,
99 "check_binop(expr.hir_id={}, expr={:?}, op={:?}, lhs_expr={:?}, rhs_expr={:?})",
100 expr.hir_id, expr, op, lhs_expr, rhs_expr
103 match BinOpCategory::from(op) {
104 BinOpCategory::Shortcircuit => {
105 // && and || are a simple case.
106 self.check_expr_coercable_to_type(lhs_expr, tcx.types.bool, None);
107 let lhs_diverges = self.diverges.get();
108 self.check_expr_coercable_to_type(rhs_expr, tcx.types.bool, None);
110 // Depending on the LHS' value, the RHS can never execute.
111 self.diverges.set(lhs_diverges);
116 // Otherwise, we always treat operators as if they are
117 // overloaded. This is the way to be most flexible w/r/t
118 // types that get inferred.
119 let (lhs_ty, rhs_ty, return_ty) = self.check_overloaded_binop(
128 // Supply type inference hints if relevant. Probably these
129 // hints should be enforced during select as part of the
130 // `consider_unification_despite_ambiguity` routine, but this
131 // more convenient for now.
133 // The basic idea is to help type inference by taking
134 // advantage of things we know about how the impls for
135 // scalar types are arranged. This is important in a
136 // scenario like `1_u32 << 2`, because it lets us quickly
137 // deduce that the result type should be `u32`, even
138 // though we don't know yet what type 2 has and hence
139 // can't pin this down to a specific impl.
140 if !lhs_ty.is_ty_var()
141 && !rhs_ty.is_ty_var()
142 && is_builtin_binop(lhs_ty, rhs_ty, op)
144 let builtin_return_ty = self.enforce_builtin_binop_types(
151 self.demand_suptype(expr.span, builtin_return_ty, return_ty);
159 fn enforce_builtin_binop_types(
167 debug_assert!(is_builtin_binop(lhs_ty, rhs_ty, op));
169 // Special-case a single layer of referencing, so that things like `5.0 + &6.0f32` work.
170 // (See https://github.com/rust-lang/rust/issues/57447.)
171 let (lhs_ty, rhs_ty) = (deref_ty_if_possible(lhs_ty), deref_ty_if_possible(rhs_ty));
174 match BinOpCategory::from(op) {
175 BinOpCategory::Shortcircuit => {
176 self.demand_suptype(lhs_span, tcx.types.bool, lhs_ty);
177 self.demand_suptype(rhs_span, tcx.types.bool, rhs_ty);
181 BinOpCategory::Shift => {
182 // result type is same as LHS always
186 BinOpCategory::Math | BinOpCategory::Bitwise => {
187 // both LHS and RHS and result will have the same type
188 self.demand_suptype(rhs_span, lhs_ty, rhs_ty);
192 BinOpCategory::Comparison => {
193 // both LHS and RHS and result will have the same type
194 self.demand_suptype(rhs_span, lhs_ty, rhs_ty);
200 fn check_overloaded_binop(
202 expr: &'tcx hir::Expr<'tcx>,
203 lhs_expr: &'tcx hir::Expr<'tcx>,
204 rhs_expr: &'tcx hir::Expr<'tcx>,
207 expected: Expectation<'tcx>,
208 ) -> (Ty<'tcx>, Ty<'tcx>, Ty<'tcx>) {
210 "check_overloaded_binop(expr.hir_id={}, op={:?}, is_assign={:?})",
211 expr.hir_id, op, is_assign
214 let lhs_ty = match is_assign {
216 // Find a suitable supertype of the LHS expression's type, by coercing to
217 // a type variable, to pass as the `Self` to the trait, avoiding invariant
218 // trait matching creating lifetime constraints that are too strict.
219 // e.g., adding `&'a T` and `&'b T`, given `&'x T: Add<&'x T>`, will result
220 // in `&'a T <: &'x T` and `&'b T <: &'x T`, instead of `'a = 'b = 'x`.
221 let lhs_ty = self.check_expr(lhs_expr);
222 let fresh_var = self.next_ty_var(TypeVariableOrigin {
223 kind: TypeVariableOriginKind::MiscVariable,
226 self.demand_coerce(lhs_expr, lhs_ty, fresh_var, Some(rhs_expr), AllowTwoPhase::No)
229 // rust-lang/rust#52126: We have to use strict
230 // equivalence on the LHS of an assign-op like `+=`;
231 // overwritten or mutably-borrowed places cannot be
232 // coerced to a supertype.
233 self.check_expr(lhs_expr)
236 let lhs_ty = self.resolve_vars_with_obligations(lhs_ty);
238 // N.B., as we have not yet type-checked the RHS, we don't have the
239 // type at hand. Make a variable to represent it. The whole reason
240 // for this indirection is so that, below, we can check the expr
241 // using this variable as the expected type, which sometimes lets
242 // us do better coercions than we would be able to do otherwise,
243 // particularly for things like `String + &String`.
244 let rhs_ty_var = self.next_ty_var(TypeVariableOrigin {
245 kind: TypeVariableOriginKind::MiscVariable,
249 let result = self.lookup_op_method(
253 Op::Binary(op, is_assign),
258 let rhs_ty = self.check_expr_coercable_to_type(rhs_expr, rhs_ty_var, Some(lhs_expr));
259 let rhs_ty = self.resolve_vars_with_obligations(rhs_ty);
261 let return_ty = match result {
263 let by_ref_binop = !op.node.is_by_value();
264 if is_assign == IsAssign::Yes || by_ref_binop {
265 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].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()[0],
278 self.apply_adjustments(lhs_expr, vec![autoref]);
282 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[1].kind() {
283 let mutbl = match mutbl {
284 hir::Mutability::Not => AutoBorrowMutability::Not,
285 hir::Mutability::Mut => AutoBorrowMutability::Mut {
286 // Allow two-phase borrows for binops in initial deployment
287 // since they desugar to methods
288 allow_two_phase_borrow: AllowTwoPhase::Yes,
291 let autoref = Adjustment {
292 kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)),
293 target: method.sig.inputs()[1],
295 // HACK(eddyb) Bypass checks due to reborrows being in
296 // some cases applied on the RHS, on top of which we need
297 // to autoref, which is not allowed by apply_adjustments.
298 // self.apply_adjustments(rhs_expr, vec![autoref]);
302 .entry(rhs_expr.hir_id)
307 self.write_method_call(expr.hir_id, method);
311 // error types are considered "builtin"
312 Err(_) if lhs_ty.references_error() || rhs_ty.references_error() => self.tcx.ty_error(),
314 let (_, trait_def_id) =
315 lang_item_for_op(self.tcx, Op::Binary(op, is_assign), op.span);
316 let missing_trait = trait_def_id
317 .map(|def_id| with_no_trimmed_paths!(self.tcx.def_path_str(def_id)));
318 let (mut err, output_def_id) = match is_assign {
320 let mut err = struct_span_err!(
324 "binary assignment operation `{}=` cannot be applied to type `{}`",
330 format!("cannot use `{}=` on type `{}`", op.node.as_str(), lhs_ty),
332 self.note_unmet_impls_on_type(&mut err, errors);
336 let message = match op.node {
337 hir::BinOpKind::Add => {
338 format!("cannot add `{rhs_ty}` to `{lhs_ty}`")
340 hir::BinOpKind::Sub => {
341 format!("cannot subtract `{rhs_ty}` from `{lhs_ty}`")
343 hir::BinOpKind::Mul => {
344 format!("cannot multiply `{lhs_ty}` by `{rhs_ty}`")
346 hir::BinOpKind::Div => {
347 format!("cannot divide `{lhs_ty}` by `{rhs_ty}`")
349 hir::BinOpKind::Rem => {
350 format!("cannot mod `{lhs_ty}` by `{rhs_ty}`")
352 hir::BinOpKind::BitAnd => {
353 format!("no implementation for `{lhs_ty} & {rhs_ty}`")
355 hir::BinOpKind::BitXor => {
356 format!("no implementation for `{lhs_ty} ^ {rhs_ty}`")
358 hir::BinOpKind::BitOr => {
359 format!("no implementation for `{lhs_ty} | {rhs_ty}`")
361 hir::BinOpKind::Shl => {
362 format!("no implementation for `{lhs_ty} << {rhs_ty}`")
364 hir::BinOpKind::Shr => {
365 format!("no implementation for `{lhs_ty} >> {rhs_ty}`")
368 "binary operation `{}` cannot be applied to type `{}`",
373 let output_def_id = trait_def_id.and_then(|def_id| {
375 .associated_item_def_ids(def_id)
377 .find(|item_def_id| {
378 self.tcx.associated_item(*item_def_id).name == sym::Output
382 let mut err = struct_span_err!(self.tcx.sess, op.span, E0369, "{message}");
383 if !lhs_expr.span.eq(&rhs_expr.span) {
384 err.span_label(lhs_expr.span, lhs_ty.to_string());
385 err.span_label(rhs_expr.span, rhs_ty.to_string());
387 self.note_unmet_impls_on_type(&mut err, errors);
392 let mut suggest_deref_binop = |lhs_deref_ty: Ty<'tcx>| {
398 Op::Binary(op, is_assign),
404 "`{}{}` can be used on `{}` if you dereference the left-hand side",
407 IsAssign::Yes => "=",
412 err.span_suggestion_verbose(
413 lhs_expr.span.shrink_to_lo(),
416 rustc_errors::Applicability::MachineApplicable,
421 let is_compatible = |lhs_ty, rhs_ty| {
422 self.lookup_op_method(
426 Op::Binary(op, is_assign),
432 // We should suggest `a + b` => `*a + b` if `a` is copy, and suggest
433 // `a += b` => `*a += b` if a is a mut ref.
434 if !op.span.can_be_used_for_suggestions() {
435 // Suppress suggestions when lhs and rhs are not in the same span as the error
436 } else if is_assign == IsAssign::Yes
437 && let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty)
439 suggest_deref_binop(lhs_deref_ty);
440 } else if is_assign == IsAssign::No
441 && let Ref(_, lhs_deref_ty, _) = lhs_ty.kind()
443 if self.type_is_copy_modulo_regions(
448 suggest_deref_binop(*lhs_deref_ty);
450 } else if self.suggest_fn_call(&mut err, lhs_expr, lhs_ty, |lhs_ty| {
451 is_compatible(lhs_ty, rhs_ty)
452 }) || self.suggest_fn_call(&mut err, rhs_expr, rhs_ty, |rhs_ty| {
453 is_compatible(lhs_ty, rhs_ty)
454 }) || self.suggest_two_fn_call(
460 |lhs_ty, rhs_ty| is_compatible(lhs_ty, rhs_ty),
465 if let Some(missing_trait) = missing_trait {
466 if op.node == hir::BinOpKind::Add
467 && self.check_str_addition(
468 lhs_expr, rhs_expr, lhs_ty, rhs_ty, &mut err, is_assign, op,
471 // This has nothing here because it means we did string
472 // concatenation (e.g., "Hello " + "World!"). This means
473 // we don't want the note in the else clause to be emitted
474 } else if lhs_ty.has_non_region_param() {
475 // Look for a TraitPredicate in the Fulfillment errors,
476 // and use it to generate a suggestion.
478 // Note that lookup_op_method must be called again but
479 // with a specific rhs_ty instead of a placeholder so
480 // the resulting predicate generates a more specific
481 // suggestion for the user.
487 Op::Binary(op, is_assign),
491 if !errors.is_empty() {
492 for error in errors {
493 if let Some(trait_pred) =
494 error.obligation.predicate.to_opt_poly_trait_pred()
496 let output_associated_item = match error.obligation.cause.code()
498 ObligationCauseCode::BinOp {
499 output_ty: Some(output_ty),
502 // Make sure that we're attaching `Output = ..` to the right trait predicate
503 if let Some(output_def_id) = output_def_id
504 && let Some(trait_def_id) = trait_def_id
505 && self.tcx.parent(output_def_id) == trait_def_id
507 Some(("Output", *output_ty))
515 self.err_ctxt().suggest_restricting_param_bound(
518 output_associated_item,
524 // When we know that a missing bound is responsible, we don't show
525 // this note as it is redundant.
527 "the trait `{missing_trait}` is not implemented for `{lhs_ty}`"
532 let reported = err.emit();
533 self.tcx.ty_error_with_guaranteed(reported)
537 (lhs_ty, rhs_ty, return_ty)
540 /// Provide actionable suggestions when trying to add two strings with incorrect types,
541 /// like `&str + &str`, `String + String` and `&str + &String`.
543 /// If this function returns `true` it means a note was printed, so we don't need
544 /// to print the normal "implementation of `std::ops::Add` might be missing" note
545 fn check_str_addition(
547 lhs_expr: &'tcx hir::Expr<'tcx>,
548 rhs_expr: &'tcx hir::Expr<'tcx>,
551 err: &mut Diagnostic,
555 let str_concat_note = "string concatenation requires an owned `String` on the left";
556 let rm_borrow_msg = "remove the borrow to obtain an owned `String`";
557 let to_owned_msg = "create an owned `String` from a string reference";
559 let string_type = self.tcx.lang_items().string();
560 let is_std_string = |ty: Ty<'tcx>| {
561 ty.ty_adt_def().map_or(false, |ty_def| Some(ty_def.did()) == string_type)
564 match (lhs_ty.kind(), rhs_ty.kind()) {
565 (&Ref(_, l_ty, _), &Ref(_, r_ty, _)) // &str or &String + &str, &String or &&str
566 if (*l_ty.kind() == Str || is_std_string(l_ty))
567 && (*r_ty.kind() == Str
568 || is_std_string(r_ty)
570 r_ty.kind(), Ref(_, inner_ty, _) if *inner_ty.kind() == Str
573 if let IsAssign::No = is_assign { // Do not supply this message if `&str += &str`
574 err.span_label(op.span, "`+` cannot be used to concatenate two `&str` strings");
575 err.note(str_concat_note);
576 if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
577 err.span_suggestion_verbose(
578 lhs_expr.span.until(lhs_inner_expr.span),
581 Applicability::MachineApplicable
584 err.span_suggestion_verbose(
585 lhs_expr.span.shrink_to_hi(),
588 Applicability::MachineApplicable
594 (&Ref(_, l_ty, _), &Adt(..)) // Handle `&str` & `&String` + `String`
595 if (*l_ty.kind() == Str || is_std_string(l_ty)) && is_std_string(rhs_ty) =>
599 "`+` cannot be used to concatenate a `&str` with a `String`",
604 let lhs_sugg = if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
605 sugg_msg = "remove the borrow on the left and add one on the right";
606 (lhs_expr.span.until(lhs_inner_expr.span), "".to_owned())
608 sugg_msg = "create an owned `String` on the left and add a borrow on the right";
609 (lhs_expr.span.shrink_to_hi(), ".to_owned()".to_owned())
611 let suggestions = vec![
613 (rhs_expr.span.shrink_to_lo(), "&".to_owned()),
615 err.multipart_suggestion_verbose(
618 Applicability::MachineApplicable,
622 err.note(str_concat_note);
631 pub fn check_user_unop(
633 ex: &'tcx hir::Expr<'tcx>,
634 operand_ty: Ty<'tcx>,
636 expected: Expectation<'tcx>,
638 assert!(op.is_by_value());
639 match self.lookup_op_method(operand_ty, None, None, Op::Unary(op, ex.span), expected) {
641 self.write_method_call(ex.hir_id, method);
645 let actual = self.resolve_vars_if_possible(operand_ty);
646 if !actual.references_error() {
647 let mut err = struct_span_err!(
651 "cannot apply unary operator `{}` to type `{}`",
657 format!("cannot apply unary operator `{}`", op.as_str()),
660 if operand_ty.has_non_region_param() {
661 let predicates = errors.iter().filter_map(|error| {
662 error.obligation.predicate.to_opt_poly_trait_pred()
664 for pred in predicates {
665 self.err_ctxt().suggest_restricting_param_bound(
674 let sp = self.tcx.sess.source_map().start_point(ex.span);
676 self.tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
678 // If the previous expression was a block expression, suggest parentheses
679 // (turning this into a binary subtraction operation instead.)
680 // for example, `{2} - 2` -> `({2}) - 2` (see src\test\ui\parser\expr-as-stmt.rs)
681 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
683 match actual.kind() {
684 Uint(_) if op == hir::UnOp::Neg => {
685 err.note("unsigned values cannot be negated");
687 if let hir::ExprKind::Unary(
691 hir::ExprKind::Lit(Spanned {
692 node: ast::LitKind::Int(1, _),
702 "you may have meant the maximum value of `{actual}`",
704 format!("{actual}::MAX"),
705 Applicability::MaybeIncorrect,
709 Str | Never | Char | Tuple(_) | Array(_, _) => {}
710 Ref(_, lty, _) if *lty.kind() == Str => {}
712 self.note_unmet_impls_on_type(&mut err, errors);
726 other_ty: Option<Ty<'tcx>>,
727 other_ty_expr: Option<&'tcx hir::Expr<'tcx>>,
729 expected: Expectation<'tcx>,
730 ) -> Result<MethodCallee<'tcx>, Vec<FulfillmentError<'tcx>>> {
731 let span = match op {
732 Op::Binary(op, _) => op.span,
733 Op::Unary(_, span) => span,
735 let (opname, trait_did) = lang_item_for_op(self.tcx, op, span);
738 "lookup_op_method(lhs_ty={:?}, op={:?}, opname={:?}, trait_did={:?})",
739 lhs_ty, op, opname, trait_did
742 // Catches cases like #83893, where a lang item is declared with the
743 // wrong number of generic arguments. Should have yielded an error
744 // elsewhere by now, but we have to catch it here so that we do not
745 // index `other_tys` out of bounds (if the lang item has too many
746 // generic arguments, `other_tys` is too short).
747 if !has_expected_num_generic_args(
751 // Binary ops have a generic right-hand side, unary ops don't
759 let opname = Ident::with_dummy_span(opname);
760 let method = trait_did.and_then(|trait_did| {
761 self.lookup_op_method_in_trait(
772 match (method, trait_did) {
774 let method = self.register_infer_ok_obligations(ok);
775 self.select_obligations_where_possible(|_| {});
778 (None, None) => Err(vec![]),
779 (None, Some(trait_did)) => {
780 let (obligation, _) = self.obligation_for_op_method(
788 Err(rustc_trait_selection::traits::fully_solve_obligation(self, obligation))
798 ) -> (rustc_span::Symbol, Option<hir::def_id::DefId>) {
799 let lang = tcx.lang_items();
800 if let Op::Binary(op, IsAssign::Yes) = op {
802 hir::BinOpKind::Add => (sym::add_assign, lang.add_assign_trait()),
803 hir::BinOpKind::Sub => (sym::sub_assign, lang.sub_assign_trait()),
804 hir::BinOpKind::Mul => (sym::mul_assign, lang.mul_assign_trait()),
805 hir::BinOpKind::Div => (sym::div_assign, lang.div_assign_trait()),
806 hir::BinOpKind::Rem => (sym::rem_assign, lang.rem_assign_trait()),
807 hir::BinOpKind::BitXor => (sym::bitxor_assign, lang.bitxor_assign_trait()),
808 hir::BinOpKind::BitAnd => (sym::bitand_assign, lang.bitand_assign_trait()),
809 hir::BinOpKind::BitOr => (sym::bitor_assign, lang.bitor_assign_trait()),
810 hir::BinOpKind::Shl => (sym::shl_assign, lang.shl_assign_trait()),
811 hir::BinOpKind::Shr => (sym::shr_assign, lang.shr_assign_trait()),
818 | hir::BinOpKind::And
819 | hir::BinOpKind::Or => {
820 span_bug!(span, "impossible assignment operation: {}=", op.node.as_str())
823 } else if let Op::Binary(op, IsAssign::No) = op {
825 hir::BinOpKind::Add => (sym::add, lang.add_trait()),
826 hir::BinOpKind::Sub => (sym::sub, lang.sub_trait()),
827 hir::BinOpKind::Mul => (sym::mul, lang.mul_trait()),
828 hir::BinOpKind::Div => (sym::div, lang.div_trait()),
829 hir::BinOpKind::Rem => (sym::rem, lang.rem_trait()),
830 hir::BinOpKind::BitXor => (sym::bitxor, lang.bitxor_trait()),
831 hir::BinOpKind::BitAnd => (sym::bitand, lang.bitand_trait()),
832 hir::BinOpKind::BitOr => (sym::bitor, lang.bitor_trait()),
833 hir::BinOpKind::Shl => (sym::shl, lang.shl_trait()),
834 hir::BinOpKind::Shr => (sym::shr, lang.shr_trait()),
835 hir::BinOpKind::Lt => (sym::lt, lang.partial_ord_trait()),
836 hir::BinOpKind::Le => (sym::le, lang.partial_ord_trait()),
837 hir::BinOpKind::Ge => (sym::ge, lang.partial_ord_trait()),
838 hir::BinOpKind::Gt => (sym::gt, lang.partial_ord_trait()),
839 hir::BinOpKind::Eq => (sym::eq, lang.eq_trait()),
840 hir::BinOpKind::Ne => (sym::ne, lang.eq_trait()),
841 hir::BinOpKind::And | hir::BinOpKind::Or => {
842 span_bug!(span, "&& and || are not overloadable")
845 } else if let Op::Unary(hir::UnOp::Not, _) = op {
846 (sym::not, lang.not_trait())
847 } else if let Op::Unary(hir::UnOp::Neg, _) = op {
848 (sym::neg, lang.neg_trait())
850 bug!("lookup_op_method: op not supported: {:?}", op)
854 // Binary operator categories. These categories summarize the behavior
855 // with respect to the builtin operations supported.
857 /// &&, || -- cannot be overridden
860 /// <<, >> -- when shifting a single integer, rhs can be any
861 /// integer type. For simd, types must match.
864 /// +, -, etc -- takes equal types, produces same type as input,
865 /// applicable to ints/floats/simd
868 /// &, |, ^ -- takes equal types, produces same type as input,
869 /// applicable to ints/floats/simd/bool
872 /// ==, !=, etc -- takes equal types, produces bools, except for simd,
873 /// which produce the input type
878 fn from(op: hir::BinOp) -> BinOpCategory {
880 hir::BinOpKind::Shl | hir::BinOpKind::Shr => BinOpCategory::Shift,
883 | hir::BinOpKind::Sub
884 | hir::BinOpKind::Mul
885 | hir::BinOpKind::Div
886 | hir::BinOpKind::Rem => BinOpCategory::Math,
888 hir::BinOpKind::BitXor | hir::BinOpKind::BitAnd | hir::BinOpKind::BitOr => {
889 BinOpCategory::Bitwise
897 | hir::BinOpKind::Gt => BinOpCategory::Comparison,
899 hir::BinOpKind::And | hir::BinOpKind::Or => BinOpCategory::Shortcircuit,
904 /// Whether the binary operation is an assignment (`a += b`), or not (`a + b`)
905 #[derive(Clone, Copy, Debug, PartialEq)]
911 #[derive(Clone, Copy, Debug)]
913 Binary(hir::BinOp, IsAssign),
914 Unary(hir::UnOp, Span),
917 /// Dereferences a single level of immutable referencing.
918 fn deref_ty_if_possible<'tcx>(ty: Ty<'tcx>) -> Ty<'tcx> {
920 ty::Ref(_, ty, hir::Mutability::Not) => *ty,
925 /// Returns `true` if this is a built-in arithmetic operation (e.g., u32
926 /// + u32, i16x4 == i16x4) and false if these types would have to be
927 /// overloaded to be legal. There are two reasons that we distinguish
928 /// builtin operations from overloaded ones (vs trying to drive
929 /// everything uniformly through the trait system and intrinsics or
930 /// something like that):
932 /// 1. Builtin operations can trivially be evaluated in constants.
933 /// 2. For comparison operators applied to SIMD types the result is
934 /// not of type `bool`. For example, `i16x4 == i16x4` yields a
935 /// type like `i16x4`. This means that the overloaded trait
936 /// `PartialEq` is not applicable.
938 /// Reason #2 is the killer. I tried for a while to always use
939 /// overloaded logic and just check the types in constants/codegen after
940 /// the fact, and it worked fine, except for SIMD types. -nmatsakis
941 fn is_builtin_binop<'tcx>(lhs: Ty<'tcx>, rhs: Ty<'tcx>, op: hir::BinOp) -> bool {
942 // Special-case a single layer of referencing, so that things like `5.0 + &6.0f32` work.
943 // (See https://github.com/rust-lang/rust/issues/57447.)
944 let (lhs, rhs) = (deref_ty_if_possible(lhs), deref_ty_if_possible(rhs));
946 match BinOpCategory::from(op) {
947 BinOpCategory::Shortcircuit => true,
949 BinOpCategory::Shift => {
950 lhs.references_error()
951 || rhs.references_error()
952 || lhs.is_integral() && rhs.is_integral()
955 BinOpCategory::Math => {
956 lhs.references_error()
957 || rhs.references_error()
958 || lhs.is_integral() && rhs.is_integral()
959 || lhs.is_floating_point() && rhs.is_floating_point()
962 BinOpCategory::Bitwise => {
963 lhs.references_error()
964 || rhs.references_error()
965 || lhs.is_integral() && rhs.is_integral()
966 || lhs.is_floating_point() && rhs.is_floating_point()
967 || lhs.is_bool() && rhs.is_bool()
970 BinOpCategory::Comparison => {
971 lhs.references_error() || rhs.references_error() || lhs.is_scalar() && rhs.is_scalar()
976 struct TypeParamEraser<'a, 'tcx>(&'a FnCtxt<'a, 'tcx>, Span);
978 impl<'tcx> TypeFolder<'tcx> for TypeParamEraser<'_, 'tcx> {
979 fn tcx(&self) -> TyCtxt<'tcx> {
983 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
985 ty::Param(_) => self.0.next_ty_var(TypeVariableOrigin {
986 kind: TypeVariableOriginKind::MiscVariable,
989 _ => ty.super_fold_with(self),