1 //! Code related to processing overloaded binary and unary operators.
2
3 use super::method::MethodCallee;
4 use super::{has_expected_num_generic_args, FnCtxt};
5 use crate::Expectation;
6 use rustc_ast as ast;
7 use rustc_errors::{self, struct_span_err, Applicability, Diagnostic};
8 use rustc_hir as hir;
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,
13 };
14 use rustc_middle::ty::print::with_no_trimmed_paths;
15 use rustc_middle::ty::{self, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
16 use rustc_session::errors::ExprParenthesesNeeded;
17 use rustc_span::source_map::Spanned;
18 use rustc_span::symbol::{sym, Ident};
19 use rustc_span::Span;
20 use rustc_trait_selection::infer::InferCtxtExt;
21 use rustc_trait_selection::traits::error_reporting::suggestions::TypeErrCtxtExt as _;
22 use rustc_trait_selection::traits::{self, FulfillmentError, ObligationCtxt};
23 use rustc_type_ir::sty::TyKind::*;
24
25 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
26 /// Checks a `a <op>= b`
check_binop_assign( &self, expr: &'tcx hir::Expr<'tcx>, op: hir::BinOp, lhs: &'tcx hir::Expr<'tcx>, rhs: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>, ) -> Ty<'tcx>27 pub fn check_binop_assign(
28 &self,
29 expr: &'tcx hir::Expr<'tcx>,
30 op: hir::BinOp,
31 lhs: &'tcx hir::Expr<'tcx>,
32 rhs: &'tcx hir::Expr<'tcx>,
33 expected: Expectation<'tcx>,
34 ) -> Ty<'tcx> {
35 let (lhs_ty, rhs_ty, return_ty) =
36 self.check_overloaded_binop(expr, lhs, rhs, op, IsAssign::Yes, expected);
37
38 let ty =
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);
41 Ty::new_unit(self.tcx)
42 } else {
43 return_ty
44 };
45
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) {
48 if self
49 .lookup_op_method(
50 lhs_deref_ty,
51 Some((rhs, rhs_ty)),
52 Op::Binary(op, IsAssign::Yes),
53 expected,
54 )
55 .is_ok()
56 {
57 // If LHS += RHS is an error, but *LHS += RHS is successful, then we will have
58 // emitted a better suggestion during error handling in check_overloaded_binop.
59 if self
60 .lookup_op_method(
61 lhs_ty,
62 Some((rhs, rhs_ty)),
63 Op::Binary(op, IsAssign::Yes),
64 expected,
65 )
66 .is_err()
67 {
68 err.downgrade_to_delayed_bug();
69 } else {
70 // Otherwise, it's valid to suggest dereferencing the LHS here.
71 err.span_suggestion_verbose(
72 lhs.span.shrink_to_lo(),
73 "consider dereferencing the left-hand side of this operation",
74 "*",
75 Applicability::MaybeIncorrect,
76 );
77 }
78 }
79 }
80 });
81
82 ty
83 }
84
85 /// Checks a potentially overloaded binary operator.
check_binop( &self, expr: &'tcx hir::Expr<'tcx>, op: hir::BinOp, lhs_expr: &'tcx hir::Expr<'tcx>, rhs_expr: &'tcx hir::Expr<'tcx>, expected: Expectation<'tcx>, ) -> Ty<'tcx>86 pub fn check_binop(
87 &self,
88 expr: &'tcx hir::Expr<'tcx>,
89 op: hir::BinOp,
90 lhs_expr: &'tcx hir::Expr<'tcx>,
91 rhs_expr: &'tcx hir::Expr<'tcx>,
92 expected: Expectation<'tcx>,
93 ) -> Ty<'tcx> {
94 let tcx = self.tcx;
95
96 debug!(
97 "check_binop(expr.hir_id={}, expr={:?}, op={:?}, lhs_expr={:?}, rhs_expr={:?})",
98 expr.hir_id, expr, op, lhs_expr, rhs_expr
99 );
100
101 match BinOpCategory::from(op) {
102 BinOpCategory::Shortcircuit => {
103 // && and || are a simple case.
104 self.check_expr_coercible_to_type(lhs_expr, tcx.types.bool, None);
105 let lhs_diverges = self.diverges.get();
106 self.check_expr_coercible_to_type(rhs_expr, tcx.types.bool, None);
107
108 // Depending on the LHS' value, the RHS can never execute.
109 self.diverges.set(lhs_diverges);
110
111 tcx.types.bool
112 }
113 _ => {
114 // Otherwise, we always treat operators as if they are
115 // overloaded. This is the way to be most flexible w/r/t
116 // types that get inferred.
117 let (lhs_ty, rhs_ty, return_ty) = self.check_overloaded_binop(
118 expr,
119 lhs_expr,
120 rhs_expr,
121 op,
122 IsAssign::No,
123 expected,
124 );
125
126 // Supply type inference hints if relevant. Probably these
127 // hints should be enforced during select as part of the
128 // `consider_unification_despite_ambiguity` routine, but this
129 // more convenient for now.
130 //
131 // The basic idea is to help type inference by taking
132 // advantage of things we know about how the impls for
133 // scalar types are arranged. This is important in a
134 // scenario like `1_u32 << 2`, because it lets us quickly
135 // deduce that the result type should be `u32`, even
136 // though we don't know yet what type 2 has and hence
137 // can't pin this down to a specific impl.
138 if !lhs_ty.is_ty_var()
139 && !rhs_ty.is_ty_var()
140 && is_builtin_binop(lhs_ty, rhs_ty, op)
141 {
142 let builtin_return_ty = self.enforce_builtin_binop_types(
143 lhs_expr.span,
144 lhs_ty,
145 rhs_expr.span,
146 rhs_ty,
147 op,
148 );
149 self.demand_eqtype(expr.span, builtin_return_ty, return_ty);
150 builtin_return_ty
151 } else {
152 return_ty
153 }
154 }
155 }
156 }
157
enforce_builtin_binop_types( &self, lhs_span: Span, lhs_ty: Ty<'tcx>, rhs_span: Span, rhs_ty: Ty<'tcx>, op: hir::BinOp, ) -> Ty<'tcx>158 fn enforce_builtin_binop_types(
159 &self,
160 lhs_span: Span,
161 lhs_ty: Ty<'tcx>,
162 rhs_span: Span,
163 rhs_ty: Ty<'tcx>,
164 op: hir::BinOp,
165 ) -> Ty<'tcx> {
166 debug_assert!(is_builtin_binop(lhs_ty, rhs_ty, op));
167
168 // Special-case a single layer of referencing, so that things like `5.0 + &6.0f32` work.
169 // (See https://github.com/rust-lang/rust/issues/57447.)
170 let (lhs_ty, rhs_ty) = (deref_ty_if_possible(lhs_ty), deref_ty_if_possible(rhs_ty));
171
172 let tcx = self.tcx;
173 match BinOpCategory::from(op) {
174 BinOpCategory::Shortcircuit => {
175 self.demand_suptype(lhs_span, tcx.types.bool, lhs_ty);
176 self.demand_suptype(rhs_span, tcx.types.bool, rhs_ty);
177 tcx.types.bool
178 }
179
180 BinOpCategory::Shift => {
181 // result type is same as LHS always
182 lhs_ty
183 }
184
185 BinOpCategory::Math | BinOpCategory::Bitwise => {
186 // both LHS and RHS and result will have the same type
187 self.demand_suptype(rhs_span, lhs_ty, rhs_ty);
188 lhs_ty
189 }
190
191 BinOpCategory::Comparison => {
192 // both LHS and RHS and result will have the same type
193 self.demand_suptype(rhs_span, lhs_ty, rhs_ty);
194 tcx.types.bool
195 }
196 }
197 }
198
check_overloaded_binop( &self, expr: &'tcx hir::Expr<'tcx>, lhs_expr: &'tcx hir::Expr<'tcx>, rhs_expr: &'tcx hir::Expr<'tcx>, op: hir::BinOp, is_assign: IsAssign, expected: Expectation<'tcx>, ) -> (Ty<'tcx>, Ty<'tcx>, Ty<'tcx>)199 fn check_overloaded_binop(
200 &self,
201 expr: &'tcx hir::Expr<'tcx>,
202 lhs_expr: &'tcx hir::Expr<'tcx>,
203 rhs_expr: &'tcx hir::Expr<'tcx>,
204 op: hir::BinOp,
205 is_assign: IsAssign,
206 expected: Expectation<'tcx>,
207 ) -> (Ty<'tcx>, Ty<'tcx>, Ty<'tcx>) {
208 debug!(
209 "check_overloaded_binop(expr.hir_id={}, op={:?}, is_assign={:?})",
210 expr.hir_id, op, is_assign
211 );
212
213 let lhs_ty = match is_assign {
214 IsAssign::No => {
215 // Find a suitable supertype of the LHS expression's type, by coercing to
216 // a type variable, to pass as the `Self` to the trait, avoiding invariant
217 // trait matching creating lifetime constraints that are too strict.
218 // e.g., adding `&'a T` and `&'b T`, given `&'x T: Add<&'x T>`, will result
219 // in `&'a T <: &'x T` and `&'b T <: &'x T`, instead of `'a = 'b = 'x`.
220 let lhs_ty = self.check_expr(lhs_expr);
221 let fresh_var = self.next_ty_var(TypeVariableOrigin {
222 kind: TypeVariableOriginKind::MiscVariable,
223 span: lhs_expr.span,
224 });
225 self.demand_coerce(lhs_expr, lhs_ty, fresh_var, Some(rhs_expr), AllowTwoPhase::No)
226 }
227 IsAssign::Yes => {
228 // rust-lang/rust#52126: We have to use strict
229 // equivalence on the LHS of an assign-op like `+=`;
230 // overwritten or mutably-borrowed places cannot be
231 // coerced to a supertype.
232 self.check_expr(lhs_expr)
233 }
234 };
235 let lhs_ty = self.resolve_vars_with_obligations(lhs_ty);
236
237 // N.B., as we have not yet type-checked the RHS, we don't have the
238 // type at hand. Make a variable to represent it. The whole reason
239 // for this indirection is so that, below, we can check the expr
240 // using this variable as the expected type, which sometimes lets
241 // us do better coercions than we would be able to do otherwise,
242 // particularly for things like `String + &String`.
243 let rhs_ty_var = self.next_ty_var(TypeVariableOrigin {
244 kind: TypeVariableOriginKind::MiscVariable,
245 span: rhs_expr.span,
246 });
247
248 let result = self.lookup_op_method(
249 lhs_ty,
250 Some((rhs_expr, rhs_ty_var)),
251 Op::Binary(op, is_assign),
252 expected,
253 );
254
255 // see `NB` above
256 let rhs_ty = self.check_expr_coercible_to_type(rhs_expr, rhs_ty_var, Some(lhs_expr));
257 let rhs_ty = self.resolve_vars_with_obligations(rhs_ty);
258
259 let return_ty = match result {
260 Ok(method) => {
261 let by_ref_binop = !op.node.is_by_value();
262 if is_assign == IsAssign::Yes || by_ref_binop {
263 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].kind() {
264 let mutbl = AutoBorrowMutability::new(*mutbl, AllowTwoPhase::Yes);
265 let autoref = Adjustment {
266 kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)),
267 target: method.sig.inputs()[0],
268 };
269 self.apply_adjustments(lhs_expr, vec![autoref]);
270 }
271 }
272 if by_ref_binop {
273 if let ty::Ref(region, _, mutbl) = method.sig.inputs()[1].kind() {
274 // Allow two-phase borrows for binops in initial deployment
275 // since they desugar to methods
276 let mutbl = AutoBorrowMutability::new(*mutbl, AllowTwoPhase::Yes);
277
278 let autoref = Adjustment {
279 kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)),
280 target: method.sig.inputs()[1],
281 };
282 // HACK(eddyb) Bypass checks due to reborrows being in
283 // some cases applied on the RHS, on top of which we need
284 // to autoref, which is not allowed by apply_adjustments.
285 // self.apply_adjustments(rhs_expr, vec![autoref]);
286 self.typeck_results
287 .borrow_mut()
288 .adjustments_mut()
289 .entry(rhs_expr.hir_id)
290 .or_default()
291 .push(autoref);
292 }
293 }
294 self.write_method_call(expr.hir_id, method);
295
296 method.sig.output()
297 }
298 // error types are considered "builtin"
299 Err(_) if lhs_ty.references_error() || rhs_ty.references_error() => {
300 Ty::new_misc_error(self.tcx)
301 }
302 Err(errors) => {
303 let (_, trait_def_id) =
304 lang_item_for_op(self.tcx, Op::Binary(op, is_assign), op.span);
305 let missing_trait = trait_def_id
306 .map(|def_id| with_no_trimmed_paths!(self.tcx.def_path_str(def_id)));
307 let (mut err, output_def_id) = match is_assign {
308 IsAssign::Yes => {
309 let mut err = struct_span_err!(
310 self.tcx.sess,
311 expr.span,
312 E0368,
313 "binary assignment operation `{}=` cannot be applied to type `{}`",
314 op.node.as_str(),
315 lhs_ty,
316 );
317 err.span_label(
318 lhs_expr.span,
319 format!("cannot use `{}=` on type `{}`", op.node.as_str(), lhs_ty),
320 );
321 self.note_unmet_impls_on_type(&mut err, errors);
322 (err, None)
323 }
324 IsAssign::No => {
325 let message = match op.node {
326 hir::BinOpKind::Add => {
327 format!("cannot add `{rhs_ty}` to `{lhs_ty}`")
328 }
329 hir::BinOpKind::Sub => {
330 format!("cannot subtract `{rhs_ty}` from `{lhs_ty}`")
331 }
332 hir::BinOpKind::Mul => {
333 format!("cannot multiply `{lhs_ty}` by `{rhs_ty}`")
334 }
335 hir::BinOpKind::Div => {
336 format!("cannot divide `{lhs_ty}` by `{rhs_ty}`")
337 }
338 hir::BinOpKind::Rem => {
339 format!(
340 "cannot calculate the remainder of `{lhs_ty}` divided by `{rhs_ty}`"
341 )
342 }
343 hir::BinOpKind::BitAnd => {
344 format!("no implementation for `{lhs_ty} & {rhs_ty}`")
345 }
346 hir::BinOpKind::BitXor => {
347 format!("no implementation for `{lhs_ty} ^ {rhs_ty}`")
348 }
349 hir::BinOpKind::BitOr => {
350 format!("no implementation for `{lhs_ty} | {rhs_ty}`")
351 }
352 hir::BinOpKind::Shl => {
353 format!("no implementation for `{lhs_ty} << {rhs_ty}`")
354 }
355 hir::BinOpKind::Shr => {
356 format!("no implementation for `{lhs_ty} >> {rhs_ty}`")
357 }
358 _ => format!(
359 "binary operation `{}` cannot be applied to type `{}`",
360 op.node.as_str(),
361 lhs_ty
362 ),
363 };
364 let output_def_id = trait_def_id.and_then(|def_id| {
365 self.tcx
366 .associated_item_def_ids(def_id)
367 .iter()
368 .find(|item_def_id| {
369 self.tcx.associated_item(*item_def_id).name == sym::Output
370 })
371 .cloned()
372 });
373 let mut err = struct_span_err!(self.tcx.sess, op.span, E0369, "{message}");
374 if !lhs_expr.span.eq(&rhs_expr.span) {
375 err.span_label(lhs_expr.span, lhs_ty.to_string());
376 err.span_label(rhs_expr.span, rhs_ty.to_string());
377 }
378 self.note_unmet_impls_on_type(&mut err, errors);
379 (err, output_def_id)
380 }
381 };
382
383 let mut suggest_deref_binop = |lhs_deref_ty: Ty<'tcx>| {
384 if self
385 .lookup_op_method(
386 lhs_deref_ty,
387 Some((rhs_expr, rhs_ty)),
388 Op::Binary(op, is_assign),
389 expected,
390 )
391 .is_ok()
392 {
393 let msg = format!(
394 "`{}{}` can be used on `{}` if you dereference the left-hand side",
395 op.node.as_str(),
396 match is_assign {
397 IsAssign::Yes => "=",
398 IsAssign::No => "",
399 },
400 lhs_deref_ty,
401 );
402 err.span_suggestion_verbose(
403 lhs_expr.span.shrink_to_lo(),
404 msg,
405 "*",
406 rustc_errors::Applicability::MachineApplicable,
407 );
408 }
409 };
410
411 let is_compatible_after_call = |lhs_ty, rhs_ty| {
412 self.lookup_op_method(
413 lhs_ty,
414 Some((rhs_expr, rhs_ty)),
415 Op::Binary(op, is_assign),
416 expected,
417 )
418 .is_ok()
419 // Suggest calling even if, after calling, the types don't
420 // implement the operator, since it'll lead to better
421 // diagnostics later.
422 || self.can_eq(self.param_env, lhs_ty, rhs_ty)
423 };
424
425 // We should suggest `a + b` => `*a + b` if `a` is copy, and suggest
426 // `a += b` => `*a += b` if a is a mut ref.
427 if !op.span.can_be_used_for_suggestions() {
428 // Suppress suggestions when lhs and rhs are not in the same span as the error
429 } else if is_assign == IsAssign::Yes
430 && let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty)
431 {
432 suggest_deref_binop(lhs_deref_ty);
433 } else if is_assign == IsAssign::No
434 && let Ref(_, lhs_deref_ty, _) = lhs_ty.kind()
435 {
436 if self.type_is_copy_modulo_regions(
437 self.param_env,
438 *lhs_deref_ty,
439 ) {
440 suggest_deref_binop(*lhs_deref_ty);
441 }
442 } else if self.suggest_fn_call(&mut err, lhs_expr, lhs_ty, |lhs_ty| {
443 is_compatible_after_call(lhs_ty, rhs_ty)
444 }) || self.suggest_fn_call(&mut err, rhs_expr, rhs_ty, |rhs_ty| {
445 is_compatible_after_call(lhs_ty, rhs_ty)
446 }) || self.suggest_two_fn_call(
447 &mut err,
448 rhs_expr,
449 rhs_ty,
450 lhs_expr,
451 lhs_ty,
452 |lhs_ty, rhs_ty| is_compatible_after_call(lhs_ty, rhs_ty),
453 ) {
454 // Cool
455 }
456
457 if let Some(missing_trait) = missing_trait {
458 if op.node == hir::BinOpKind::Add
459 && self.check_str_addition(
460 lhs_expr, rhs_expr, lhs_ty, rhs_ty, &mut err, is_assign, op,
461 )
462 {
463 // This has nothing here because it means we did string
464 // concatenation (e.g., "Hello " + "World!"). This means
465 // we don't want the note in the else clause to be emitted
466 } else if lhs_ty.has_non_region_param() {
467 // Look for a TraitPredicate in the Fulfillment errors,
468 // and use it to generate a suggestion.
469 //
470 // Note that lookup_op_method must be called again but
471 // with a specific rhs_ty instead of a placeholder so
472 // the resulting predicate generates a more specific
473 // suggestion for the user.
474 let errors = self
475 .lookup_op_method(
476 lhs_ty,
477 Some((rhs_expr, rhs_ty)),
478 Op::Binary(op, is_assign),
479 expected,
480 )
481 .unwrap_err();
482 if !errors.is_empty() {
483 for error in errors {
484 if let Some(trait_pred) =
485 error.obligation.predicate.to_opt_poly_trait_pred()
486 {
487 let output_associated_item = match error.obligation.cause.code()
488 {
489 ObligationCauseCode::BinOp {
490 output_ty: Some(output_ty),
491 ..
492 } => {
493 // Make sure that we're attaching `Output = ..` to the right trait predicate
494 if let Some(output_def_id) = output_def_id
495 && let Some(trait_def_id) = trait_def_id
496 && self.tcx.parent(output_def_id) == trait_def_id
497 && let Some(output_ty) = output_ty.make_suggestable(self.tcx, false)
498 {
499 Some(("Output", output_ty))
500 } else {
501 None
502 }
503 }
504 _ => None,
505 };
506
507 self.err_ctxt().suggest_restricting_param_bound(
508 &mut err,
509 trait_pred,
510 output_associated_item,
511 self.body_id,
512 );
513 }
514 }
515 } else {
516 // When we know that a missing bound is responsible, we don't show
517 // this note as it is redundant.
518 err.note(format!(
519 "the trait `{missing_trait}` is not implemented for `{lhs_ty}`"
520 ));
521 }
522 }
523 }
524
525 // Suggest using `add`, `offset` or `offset_from` for pointer - {integer},
526 // pointer + {integer} or pointer - pointer.
527 if op.span.can_be_used_for_suggestions() {
528 match op.node {
529 hir::BinOpKind::Add if lhs_ty.is_unsafe_ptr() && rhs_ty.is_integral() => {
530 err.multipart_suggestion(
531 "consider using `wrapping_add` or `add` for pointer + {integer}",
532 vec![
533 (
534 lhs_expr.span.between(rhs_expr.span),
535 ".wrapping_add(".to_owned(),
536 ),
537 (rhs_expr.span.shrink_to_hi(), ")".to_owned()),
538 ],
539 Applicability::MaybeIncorrect,
540 );
541 }
542 hir::BinOpKind::Sub => {
543 if lhs_ty.is_unsafe_ptr() && rhs_ty.is_integral() {
544 err.multipart_suggestion(
545 "consider using `wrapping_sub` or `sub` for pointer - {integer}",
546 vec![
547 (lhs_expr.span.between(rhs_expr.span), ".wrapping_sub(".to_owned()),
548 (rhs_expr.span.shrink_to_hi(), ")".to_owned()),
549 ],
550 Applicability::MaybeIncorrect
551 );
552 }
553
554 if lhs_ty.is_unsafe_ptr() && rhs_ty.is_unsafe_ptr() {
555 err.multipart_suggestion(
556 "consider using `offset_from` for pointer - pointer if the pointers point to the same allocation",
557 vec![
558 (lhs_expr.span.shrink_to_lo(), "unsafe { ".to_owned()),
559 (lhs_expr.span.between(rhs_expr.span), ".offset_from(".to_owned()),
560 (rhs_expr.span.shrink_to_hi(), ") }".to_owned()),
561 ],
562 Applicability::MaybeIncorrect
563 );
564 }
565 }
566 _ => {}
567 }
568 }
569
570 let reported = err.emit();
571 Ty::new_error(self.tcx, reported)
572 }
573 };
574
575 (lhs_ty, rhs_ty, return_ty)
576 }
577
578 /// Provide actionable suggestions when trying to add two strings with incorrect types,
579 /// like `&str + &str`, `String + String` and `&str + &String`.
580 ///
581 /// If this function returns `true` it means a note was printed, so we don't need
582 /// to print the normal "implementation of `std::ops::Add` might be missing" note
check_str_addition( &self, lhs_expr: &'tcx hir::Expr<'tcx>, rhs_expr: &'tcx hir::Expr<'tcx>, lhs_ty: Ty<'tcx>, rhs_ty: Ty<'tcx>, err: &mut Diagnostic, is_assign: IsAssign, op: hir::BinOp, ) -> bool583 fn check_str_addition(
584 &self,
585 lhs_expr: &'tcx hir::Expr<'tcx>,
586 rhs_expr: &'tcx hir::Expr<'tcx>,
587 lhs_ty: Ty<'tcx>,
588 rhs_ty: Ty<'tcx>,
589 err: &mut Diagnostic,
590 is_assign: IsAssign,
591 op: hir::BinOp,
592 ) -> bool {
593 let str_concat_note = "string concatenation requires an owned `String` on the left";
594 let rm_borrow_msg = "remove the borrow to obtain an owned `String`";
595 let to_owned_msg = "create an owned `String` from a string reference";
596
597 let string_type = self.tcx.lang_items().string();
598 let is_std_string =
599 |ty: Ty<'tcx>| ty.ty_adt_def().is_some_and(|ty_def| Some(ty_def.did()) == string_type);
600
601 match (lhs_ty.kind(), rhs_ty.kind()) {
602 (&Ref(_, l_ty, _), &Ref(_, r_ty, _)) // &str or &String + &str, &String or &&str
603 if (*l_ty.kind() == Str || is_std_string(l_ty))
604 && (*r_ty.kind() == Str
605 || is_std_string(r_ty)
606 || matches!(
607 r_ty.kind(), Ref(_, inner_ty, _) if *inner_ty.kind() == Str
608 )) =>
609 {
610 if let IsAssign::No = is_assign { // Do not supply this message if `&str += &str`
611 err.span_label(op.span, "`+` cannot be used to concatenate two `&str` strings");
612 err.note(str_concat_note);
613 if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
614 err.span_suggestion_verbose(
615 lhs_expr.span.until(lhs_inner_expr.span),
616 rm_borrow_msg,
617 "",
618 Applicability::MachineApplicable
619 );
620 } else {
621 err.span_suggestion_verbose(
622 lhs_expr.span.shrink_to_hi(),
623 to_owned_msg,
624 ".to_owned()",
625 Applicability::MachineApplicable
626 );
627 }
628 }
629 true
630 }
631 (&Ref(_, l_ty, _), &Adt(..)) // Handle `&str` & `&String` + `String`
632 if (*l_ty.kind() == Str || is_std_string(l_ty)) && is_std_string(rhs_ty) =>
633 {
634 err.span_label(
635 op.span,
636 "`+` cannot be used to concatenate a `&str` with a `String`",
637 );
638 match is_assign {
639 IsAssign::No => {
640 let sugg_msg;
641 let lhs_sugg = if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
642 sugg_msg = "remove the borrow on the left and add one on the right";
643 (lhs_expr.span.until(lhs_inner_expr.span), "".to_owned())
644 } else {
645 sugg_msg = "create an owned `String` on the left and add a borrow on the right";
646 (lhs_expr.span.shrink_to_hi(), ".to_owned()".to_owned())
647 };
648 let suggestions = vec![
649 lhs_sugg,
650 (rhs_expr.span.shrink_to_lo(), "&".to_owned()),
651 ];
652 err.multipart_suggestion_verbose(
653 sugg_msg,
654 suggestions,
655 Applicability::MachineApplicable,
656 );
657 }
658 IsAssign::Yes => {
659 err.note(str_concat_note);
660 }
661 }
662 true
663 }
664 _ => false,
665 }
666 }
667
check_user_unop( &self, ex: &'tcx hir::Expr<'tcx>, operand_ty: Ty<'tcx>, op: hir::UnOp, expected: Expectation<'tcx>, ) -> Ty<'tcx>668 pub fn check_user_unop(
669 &self,
670 ex: &'tcx hir::Expr<'tcx>,
671 operand_ty: Ty<'tcx>,
672 op: hir::UnOp,
673 expected: Expectation<'tcx>,
674 ) -> Ty<'tcx> {
675 assert!(op.is_by_value());
676 match self.lookup_op_method(operand_ty, None, Op::Unary(op, ex.span), expected) {
677 Ok(method) => {
678 self.write_method_call(ex.hir_id, method);
679 method.sig.output()
680 }
681 Err(errors) => {
682 let actual = self.resolve_vars_if_possible(operand_ty);
683 let guar = actual.error_reported().err().unwrap_or_else(|| {
684 let mut err = struct_span_err!(
685 self.tcx.sess,
686 ex.span,
687 E0600,
688 "cannot apply unary operator `{}` to type `{}`",
689 op.as_str(),
690 actual
691 );
692 err.span_label(
693 ex.span,
694 format!("cannot apply unary operator `{}`", op.as_str()),
695 );
696
697 if operand_ty.has_non_region_param() {
698 let predicates = errors.iter().filter_map(|error| {
699 error.obligation.predicate.to_opt_poly_trait_pred()
700 });
701 for pred in predicates {
702 self.err_ctxt().suggest_restricting_param_bound(
703 &mut err,
704 pred,
705 None,
706 self.body_id,
707 );
708 }
709 }
710
711 let sp = self.tcx.sess.source_map().start_point(ex.span).with_parent(None);
712 if let Some(sp) =
713 self.tcx.sess.parse_sess.ambiguous_block_expr_parse.borrow().get(&sp)
714 {
715 // If the previous expression was a block expression, suggest parentheses
716 // (turning this into a binary subtraction operation instead.)
717 // for example, `{2} - 2` -> `({2}) - 2` (see src\test\ui\parser\expr-as-stmt.rs)
718 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
719 } else {
720 match actual.kind() {
721 Uint(_) if op == hir::UnOp::Neg => {
722 err.note("unsigned values cannot be negated");
723
724 if let hir::ExprKind::Unary(
725 _,
726 hir::Expr {
727 kind:
728 hir::ExprKind::Lit(Spanned {
729 node: ast::LitKind::Int(1, _),
730 ..
731 }),
732 ..
733 },
734 ) = ex.kind
735 {
736 err.span_suggestion(
737 ex.span,
738 format!(
739 "you may have meant the maximum value of `{actual}`",
740 ),
741 format!("{actual}::MAX"),
742 Applicability::MaybeIncorrect,
743 );
744 }
745 }
746 Str | Never | Char | Tuple(_) | Array(_, _) => {}
747 Ref(_, lty, _) if *lty.kind() == Str => {}
748 _ => {
749 self.note_unmet_impls_on_type(&mut err, errors);
750 }
751 }
752 }
753 err.emit()
754 });
755 Ty::new_error(self.tcx, guar)
756 }
757 }
758 }
759
lookup_op_method( &self, lhs_ty: Ty<'tcx>, opt_rhs: Option<(&'tcx hir::Expr<'tcx>, Ty<'tcx>)>, op: Op, expected: Expectation<'tcx>, ) -> Result<MethodCallee<'tcx>, Vec<FulfillmentError<'tcx>>>760 fn lookup_op_method(
761 &self,
762 lhs_ty: Ty<'tcx>,
763 opt_rhs: Option<(&'tcx hir::Expr<'tcx>, Ty<'tcx>)>,
764 op: Op,
765 expected: Expectation<'tcx>,
766 ) -> Result<MethodCallee<'tcx>, Vec<FulfillmentError<'tcx>>> {
767 let span = match op {
768 Op::Binary(op, _) => op.span,
769 Op::Unary(_, span) => span,
770 };
771 let (opname, Some(trait_did)) = lang_item_for_op(self.tcx, op, span) else {
772 // Bail if the operator trait is not defined.
773 return Err(vec![]);
774 };
775
776 debug!(
777 "lookup_op_method(lhs_ty={:?}, op={:?}, opname={:?}, trait_did={:?})",
778 lhs_ty, op, opname, trait_did
779 );
780
781 // Catches cases like #83893, where a lang item is declared with the
782 // wrong number of generic arguments. Should have yielded an error
783 // elsewhere by now, but we have to catch it here so that we do not
784 // index `other_tys` out of bounds (if the lang item has too many
785 // generic arguments, `other_tys` is too short).
786 if !has_expected_num_generic_args(
787 self.tcx,
788 trait_did,
789 match op {
790 // Binary ops have a generic right-hand side, unary ops don't
791 Op::Binary(..) => 1,
792 Op::Unary(..) => 0,
793 },
794 ) {
795 self.tcx
796 .sess
797 .delay_span_bug(span, "operator didn't have the right number of generic args");
798 return Err(vec![]);
799 }
800
801 let opname = Ident::with_dummy_span(opname);
802 let (opt_rhs_expr, opt_rhs_ty) = opt_rhs.unzip();
803 let input_types = opt_rhs_ty.as_slice();
804 let cause = self.cause(
805 span,
806 traits::BinOp {
807 rhs_span: opt_rhs_expr.map(|expr| expr.span),
808 is_lit: opt_rhs_expr.is_some_and(|expr| matches!(expr.kind, hir::ExprKind::Lit(_))),
809 output_ty: expected.only_has_type(self),
810 },
811 );
812
813 let method = self.lookup_method_in_trait(
814 cause.clone(),
815 opname,
816 trait_did,
817 lhs_ty,
818 Some(input_types),
819 );
820 match method {
821 Some(ok) => {
822 let method = self.register_infer_ok_obligations(ok);
823 self.select_obligations_where_possible(|_| {});
824 Ok(method)
825 }
826 None => {
827 // This path may do some inference, so make sure we've really
828 // doomed compilation so as to not accidentally stabilize new
829 // inference or something here...
830 self.tcx.sess.delay_span_bug(span, "this path really should be doomed...");
831 // Guide inference for the RHS expression if it's provided --
832 // this will allow us to better error reporting, at the expense
833 // of making some error messages a bit more specific.
834 if let Some((rhs_expr, rhs_ty)) = opt_rhs
835 && rhs_ty.is_ty_var()
836 {
837 self.check_expr_coercible_to_type(rhs_expr, rhs_ty, None);
838 }
839
840 let (obligation, _) =
841 self.obligation_for_method(cause, trait_did, lhs_ty, Some(input_types));
842 // FIXME: This should potentially just add the obligation to the `FnCtxt`
843 let ocx = ObligationCtxt::new(&self.infcx);
844 ocx.register_obligation(obligation);
845 Err(ocx.select_all_or_error())
846 }
847 }
848 }
849 }
850
lang_item_for_op( tcx: TyCtxt<'_>, op: Op, span: Span, ) -> (rustc_span::Symbol, Option<hir::def_id::DefId>)851 fn lang_item_for_op(
852 tcx: TyCtxt<'_>,
853 op: Op,
854 span: Span,
855 ) -> (rustc_span::Symbol, Option<hir::def_id::DefId>) {
856 let lang = tcx.lang_items();
857 if let Op::Binary(op, IsAssign::Yes) = op {
858 match op.node {
859 hir::BinOpKind::Add => (sym::add_assign, lang.add_assign_trait()),
860 hir::BinOpKind::Sub => (sym::sub_assign, lang.sub_assign_trait()),
861 hir::BinOpKind::Mul => (sym::mul_assign, lang.mul_assign_trait()),
862 hir::BinOpKind::Div => (sym::div_assign, lang.div_assign_trait()),
863 hir::BinOpKind::Rem => (sym::rem_assign, lang.rem_assign_trait()),
864 hir::BinOpKind::BitXor => (sym::bitxor_assign, lang.bitxor_assign_trait()),
865 hir::BinOpKind::BitAnd => (sym::bitand_assign, lang.bitand_assign_trait()),
866 hir::BinOpKind::BitOr => (sym::bitor_assign, lang.bitor_assign_trait()),
867 hir::BinOpKind::Shl => (sym::shl_assign, lang.shl_assign_trait()),
868 hir::BinOpKind::Shr => (sym::shr_assign, lang.shr_assign_trait()),
869 hir::BinOpKind::Lt
870 | hir::BinOpKind::Le
871 | hir::BinOpKind::Ge
872 | hir::BinOpKind::Gt
873 | hir::BinOpKind::Eq
874 | hir::BinOpKind::Ne
875 | hir::BinOpKind::And
876 | hir::BinOpKind::Or => {
877 span_bug!(span, "impossible assignment operation: {}=", op.node.as_str())
878 }
879 }
880 } else if let Op::Binary(op, IsAssign::No) = op {
881 match op.node {
882 hir::BinOpKind::Add => (sym::add, lang.add_trait()),
883 hir::BinOpKind::Sub => (sym::sub, lang.sub_trait()),
884 hir::BinOpKind::Mul => (sym::mul, lang.mul_trait()),
885 hir::BinOpKind::Div => (sym::div, lang.div_trait()),
886 hir::BinOpKind::Rem => (sym::rem, lang.rem_trait()),
887 hir::BinOpKind::BitXor => (sym::bitxor, lang.bitxor_trait()),
888 hir::BinOpKind::BitAnd => (sym::bitand, lang.bitand_trait()),
889 hir::BinOpKind::BitOr => (sym::bitor, lang.bitor_trait()),
890 hir::BinOpKind::Shl => (sym::shl, lang.shl_trait()),
891 hir::BinOpKind::Shr => (sym::shr, lang.shr_trait()),
892 hir::BinOpKind::Lt => (sym::lt, lang.partial_ord_trait()),
893 hir::BinOpKind::Le => (sym::le, lang.partial_ord_trait()),
894 hir::BinOpKind::Ge => (sym::ge, lang.partial_ord_trait()),
895 hir::BinOpKind::Gt => (sym::gt, lang.partial_ord_trait()),
896 hir::BinOpKind::Eq => (sym::eq, lang.eq_trait()),
897 hir::BinOpKind::Ne => (sym::ne, lang.eq_trait()),
898 hir::BinOpKind::And | hir::BinOpKind::Or => {
899 span_bug!(span, "&& and || are not overloadable")
900 }
901 }
902 } else if let Op::Unary(hir::UnOp::Not, _) = op {
903 (sym::not, lang.not_trait())
904 } else if let Op::Unary(hir::UnOp::Neg, _) = op {
905 (sym::neg, lang.neg_trait())
906 } else {
907 bug!("lookup_op_method: op not supported: {:?}", op)
908 }
909 }
910
911 // Binary operator categories. These categories summarize the behavior
912 // with respect to the builtin operations supported.
913 enum BinOpCategory {
914 /// &&, || -- cannot be overridden
915 Shortcircuit,
916
917 /// <<, >> -- when shifting a single integer, rhs can be any
918 /// integer type. For simd, types must match.
919 Shift,
920
921 /// +, -, etc -- takes equal types, produces same type as input,
922 /// applicable to ints/floats/simd
923 Math,
924
925 /// &, |, ^ -- takes equal types, produces same type as input,
926 /// applicable to ints/floats/simd/bool
927 Bitwise,
928
929 /// ==, !=, etc -- takes equal types, produces bools, except for simd,
930 /// which produce the input type
931 Comparison,
932 }
933
934 impl BinOpCategory {
from(op: hir::BinOp) -> BinOpCategory935 fn from(op: hir::BinOp) -> BinOpCategory {
936 match op.node {
937 hir::BinOpKind::Shl | hir::BinOpKind::Shr => BinOpCategory::Shift,
938
939 hir::BinOpKind::Add
940 | hir::BinOpKind::Sub
941 | hir::BinOpKind::Mul
942 | hir::BinOpKind::Div
943 | hir::BinOpKind::Rem => BinOpCategory::Math,
944
945 hir::BinOpKind::BitXor | hir::BinOpKind::BitAnd | hir::BinOpKind::BitOr => {
946 BinOpCategory::Bitwise
947 }
948
949 hir::BinOpKind::Eq
950 | hir::BinOpKind::Ne
951 | hir::BinOpKind::Lt
952 | hir::BinOpKind::Le
953 | hir::BinOpKind::Ge
954 | hir::BinOpKind::Gt => BinOpCategory::Comparison,
955
956 hir::BinOpKind::And | hir::BinOpKind::Or => BinOpCategory::Shortcircuit,
957 }
958 }
959 }
960
961 /// Whether the binary operation is an assignment (`a += b`), or not (`a + b`)
962 #[derive(Clone, Copy, Debug, PartialEq)]
963 enum IsAssign {
964 No,
965 Yes,
966 }
967
968 #[derive(Clone, Copy, Debug)]
969 enum Op {
970 Binary(hir::BinOp, IsAssign),
971 Unary(hir::UnOp, Span),
972 }
973
974 /// Dereferences a single level of immutable referencing.
deref_ty_if_possible(ty: Ty<'_>) -> Ty<'_>975 fn deref_ty_if_possible(ty: Ty<'_>) -> Ty<'_> {
976 match ty.kind() {
977 ty::Ref(_, ty, hir::Mutability::Not) => *ty,
978 _ => ty,
979 }
980 }
981
982 /// Returns `true` if this is a built-in arithmetic operation (e.g., u32
983 /// + u32, i16x4 == i16x4) and false if these types would have to be
984 /// overloaded to be legal. There are two reasons that we distinguish
985 /// builtin operations from overloaded ones (vs trying to drive
986 /// everything uniformly through the trait system and intrinsics or
987 /// something like that):
988 ///
989 /// 1. Builtin operations can trivially be evaluated in constants.
990 /// 2. For comparison operators applied to SIMD types the result is
991 /// not of type `bool`. For example, `i16x4 == i16x4` yields a
992 /// type like `i16x4`. This means that the overloaded trait
993 /// `PartialEq` is not applicable.
994 ///
995 /// Reason #2 is the killer. I tried for a while to always use
996 /// overloaded logic and just check the types in constants/codegen after
997 /// the fact, and it worked fine, except for SIMD types. -nmatsakis
is_builtin_binop<'tcx>(lhs: Ty<'tcx>, rhs: Ty<'tcx>, op: hir::BinOp) -> bool998 fn is_builtin_binop<'tcx>(lhs: Ty<'tcx>, rhs: Ty<'tcx>, op: hir::BinOp) -> bool {
999 // Special-case a single layer of referencing, so that things like `5.0 + &6.0f32` work.
1000 // (See https://github.com/rust-lang/rust/issues/57447.)
1001 let (lhs, rhs) = (deref_ty_if_possible(lhs), deref_ty_if_possible(rhs));
1002
1003 match BinOpCategory::from(op) {
1004 BinOpCategory::Shortcircuit => true,
1005
1006 BinOpCategory::Shift => {
1007 lhs.references_error()
1008 || rhs.references_error()
1009 || lhs.is_integral() && rhs.is_integral()
1010 }
1011
1012 BinOpCategory::Math => {
1013 lhs.references_error()
1014 || rhs.references_error()
1015 || lhs.is_integral() && rhs.is_integral()
1016 || lhs.is_floating_point() && rhs.is_floating_point()
1017 }
1018
1019 BinOpCategory::Bitwise => {
1020 lhs.references_error()
1021 || rhs.references_error()
1022 || lhs.is_integral() && rhs.is_integral()
1023 || lhs.is_floating_point() && rhs.is_floating_point()
1024 || lhs.is_bool() && rhs.is_bool()
1025 }
1026
1027 BinOpCategory::Comparison => {
1028 lhs.references_error() || rhs.references_error() || lhs.is_scalar() && rhs.is_scalar()
1029 }
1030 }
1031 }
1032