rustc_hir_typeck/op.rs
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//! Code related to processing overloaded binary and unary operators.
use rustc_data_structures::packed::Pu128;
use rustc_errors::codes::*;
use rustc_errors::{Applicability, Diag, struct_span_code_err};
use rustc_infer::traits::ObligationCauseCode;
use rustc_middle::ty::adjustment::{
Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability,
};
use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::{self, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
use rustc_middle::{bug, span_bug};
use rustc_session::errors::ExprParenthesesNeeded;
use rustc_span::source_map::Spanned;
use rustc_span::{Ident, Span, sym};
use rustc_trait_selection::infer::InferCtxtExt;
use rustc_trait_selection::traits::{FulfillmentError, Obligation, ObligationCtxt};
use rustc_type_ir::TyKind::*;
use tracing::debug;
use {rustc_ast as ast, rustc_hir as hir};
use super::FnCtxt;
use super::method::MethodCallee;
use crate::Expectation;
impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
/// Checks a `a <op>= b`
pub(crate) fn check_expr_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> {
let (lhs_ty, rhs_ty, return_ty) =
self.check_overloaded_binop(expr, lhs, rhs, op, IsAssign::Yes, expected);
let ty =
if !lhs_ty.is_ty_var() && !rhs_ty.is_ty_var() && is_builtin_binop(lhs_ty, rhs_ty, op) {
self.enforce_builtin_binop_types(lhs.span, lhs_ty, rhs.span, rhs_ty, op);
self.tcx.types.unit
} else {
return_ty
};
self.check_lhs_assignable(lhs, E0067, op.span, |err| {
if let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty) {
if self
.lookup_op_method(
(lhs, lhs_deref_ty),
Some((rhs, rhs_ty)),
Op::Binary(op, IsAssign::Yes),
expected,
)
.is_ok()
{
// If LHS += RHS is an error, but *LHS += RHS is successful, then we will have
// emitted a better suggestion during error handling in check_overloaded_binop.
if self
.lookup_op_method(
(lhs, lhs_ty),
Some((rhs, rhs_ty)),
Op::Binary(op, IsAssign::Yes),
expected,
)
.is_err()
{
err.downgrade_to_delayed_bug();
} else {
// Otherwise, it's valid to suggest dereferencing the LHS here.
err.span_suggestion_verbose(
lhs.span.shrink_to_lo(),
"consider dereferencing the left-hand side of this operation",
"*",
Applicability::MaybeIncorrect,
);
}
}
}
});
ty
}
/// Checks a potentially overloaded binary operator.
pub(crate) fn check_expr_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> {
let tcx = self.tcx;
debug!(
"check_binop(expr.hir_id={}, expr={:?}, op={:?}, lhs_expr={:?}, rhs_expr={:?})",
expr.hir_id, expr, op, lhs_expr, rhs_expr
);
match BinOpCategory::from(op) {
BinOpCategory::Shortcircuit => {
// && and || are a simple case.
self.check_expr_coercible_to_type(lhs_expr, tcx.types.bool, None);
let lhs_diverges = self.diverges.get();
self.check_expr_coercible_to_type(rhs_expr, tcx.types.bool, None);
// Depending on the LHS' value, the RHS can never execute.
self.diverges.set(lhs_diverges);
tcx.types.bool
}
_ => {
// Otherwise, we always treat operators as if they are
// overloaded. This is the way to be most flexible w/r/t
// types that get inferred.
let (lhs_ty, rhs_ty, return_ty) = self.check_overloaded_binop(
expr,
lhs_expr,
rhs_expr,
op,
IsAssign::No,
expected,
);
// Supply type inference hints if relevant. Probably these
// hints should be enforced during select as part of the
// `consider_unification_despite_ambiguity` routine, but this
// more convenient for now.
//
// The basic idea is to help type inference by taking
// advantage of things we know about how the impls for
// scalar types are arranged. This is important in a
// scenario like `1_u32 << 2`, because it lets us quickly
// deduce that the result type should be `u32`, even
// though we don't know yet what type 2 has and hence
// can't pin this down to a specific impl.
if !lhs_ty.is_ty_var()
&& !rhs_ty.is_ty_var()
&& is_builtin_binop(lhs_ty, rhs_ty, op)
{
let builtin_return_ty = self.enforce_builtin_binop_types(
lhs_expr.span,
lhs_ty,
rhs_expr.span,
rhs_ty,
op,
);
self.demand_eqtype(expr.span, builtin_return_ty, return_ty);
builtin_return_ty
} else {
return_ty
}
}
}
}
fn enforce_builtin_binop_types(
&self,
lhs_span: Span,
lhs_ty: Ty<'tcx>,
rhs_span: Span,
rhs_ty: Ty<'tcx>,
op: hir::BinOp,
) -> Ty<'tcx> {
debug_assert!(is_builtin_binop(lhs_ty, rhs_ty, op));
// Special-case a single layer of referencing, so that things like `5.0 + &6.0f32` work.
// (See https://github.com/rust-lang/rust/issues/57447.)
let (lhs_ty, rhs_ty) = (deref_ty_if_possible(lhs_ty), deref_ty_if_possible(rhs_ty));
let tcx = self.tcx;
match BinOpCategory::from(op) {
BinOpCategory::Shortcircuit => {
self.demand_suptype(lhs_span, tcx.types.bool, lhs_ty);
self.demand_suptype(rhs_span, tcx.types.bool, rhs_ty);
tcx.types.bool
}
BinOpCategory::Shift => {
// result type is same as LHS always
lhs_ty
}
BinOpCategory::Math | BinOpCategory::Bitwise => {
// both LHS and RHS and result will have the same type
self.demand_suptype(rhs_span, lhs_ty, rhs_ty);
lhs_ty
}
BinOpCategory::Comparison => {
// both LHS and RHS and result will have the same type
self.demand_suptype(rhs_span, lhs_ty, rhs_ty);
tcx.types.bool
}
}
}
fn 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>) {
debug!(
"check_overloaded_binop(expr.hir_id={}, op={:?}, is_assign={:?})",
expr.hir_id, op, is_assign
);
let lhs_ty = match is_assign {
IsAssign::No => {
// Find a suitable supertype of the LHS expression's type, by coercing to
// a type variable, to pass as the `Self` to the trait, avoiding invariant
// trait matching creating lifetime constraints that are too strict.
// e.g., adding `&'a T` and `&'b T`, given `&'x T: Add<&'x T>`, will result
// in `&'a T <: &'x T` and `&'b T <: &'x T`, instead of `'a = 'b = 'x`.
let lhs_ty = self.check_expr(lhs_expr);
let fresh_var = self.next_ty_var(lhs_expr.span);
self.demand_coerce(lhs_expr, lhs_ty, fresh_var, Some(rhs_expr), AllowTwoPhase::No)
}
IsAssign::Yes => {
// rust-lang/rust#52126: We have to use strict
// equivalence on the LHS of an assign-op like `+=`;
// overwritten or mutably-borrowed places cannot be
// coerced to a supertype.
self.check_expr(lhs_expr)
}
};
let lhs_ty = self.resolve_vars_with_obligations(lhs_ty);
// N.B., as we have not yet type-checked the RHS, we don't have the
// type at hand. Make a variable to represent it. The whole reason
// for this indirection is so that, below, we can check the expr
// using this variable as the expected type, which sometimes lets
// us do better coercions than we would be able to do otherwise,
// particularly for things like `String + &String`.
let rhs_ty_var = self.next_ty_var(rhs_expr.span);
let result = self.lookup_op_method(
(lhs_expr, lhs_ty),
Some((rhs_expr, rhs_ty_var)),
Op::Binary(op, is_assign),
expected,
);
// see `NB` above
let rhs_ty = self.check_expr_coercible_to_type_or_error(
rhs_expr,
rhs_ty_var,
Some(lhs_expr),
|err, ty| {
self.suggest_swapping_lhs_and_rhs(err, ty, lhs_ty, rhs_expr, lhs_expr, op);
},
);
let rhs_ty = self.resolve_vars_with_obligations(rhs_ty);
let return_ty = match result {
Ok(method) => {
let by_ref_binop = !op.node.is_by_value();
if is_assign == IsAssign::Yes || by_ref_binop {
if let ty::Ref(_, _, mutbl) = method.sig.inputs()[0].kind() {
let mutbl = AutoBorrowMutability::new(*mutbl, AllowTwoPhase::Yes);
let autoref = Adjustment {
kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
target: method.sig.inputs()[0],
};
self.apply_adjustments(lhs_expr, vec![autoref]);
}
}
if by_ref_binop {
if let ty::Ref(_, _, mutbl) = method.sig.inputs()[1].kind() {
// Allow two-phase borrows for binops in initial deployment
// since they desugar to methods
let mutbl = AutoBorrowMutability::new(*mutbl, AllowTwoPhase::Yes);
let autoref = Adjustment {
kind: Adjust::Borrow(AutoBorrow::Ref(mutbl)),
target: method.sig.inputs()[1],
};
// HACK(eddyb) Bypass checks due to reborrows being in
// some cases applied on the RHS, on top of which we need
// to autoref, which is not allowed by apply_adjustments.
// self.apply_adjustments(rhs_expr, vec![autoref]);
self.typeck_results
.borrow_mut()
.adjustments_mut()
.entry(rhs_expr.hir_id)
.or_default()
.push(autoref);
}
}
self.write_method_call_and_enforce_effects(expr.hir_id, expr.span, method);
method.sig.output()
}
// error types are considered "builtin"
Err(_) if lhs_ty.references_error() || rhs_ty.references_error() => {
Ty::new_misc_error(self.tcx)
}
Err(errors) => {
let (_, trait_def_id) =
lang_item_for_op(self.tcx, Op::Binary(op, is_assign), op.span);
let missing_trait = trait_def_id
.map(|def_id| with_no_trimmed_paths!(self.tcx.def_path_str(def_id)));
let (mut err, output_def_id) = match is_assign {
IsAssign::Yes => {
let mut err = struct_span_code_err!(
self.dcx(),
expr.span,
E0368,
"binary assignment operation `{}=` cannot be applied to type `{}`",
op.node.as_str(),
lhs_ty,
);
err.span_label(
lhs_expr.span,
format!("cannot use `{}=` on type `{}`", op.node.as_str(), lhs_ty),
);
self.note_unmet_impls_on_type(&mut err, errors, false);
(err, None)
}
IsAssign::No => {
let message = match op.node {
hir::BinOpKind::Add => {
format!("cannot add `{rhs_ty}` to `{lhs_ty}`")
}
hir::BinOpKind::Sub => {
format!("cannot subtract `{rhs_ty}` from `{lhs_ty}`")
}
hir::BinOpKind::Mul => {
format!("cannot multiply `{lhs_ty}` by `{rhs_ty}`")
}
hir::BinOpKind::Div => {
format!("cannot divide `{lhs_ty}` by `{rhs_ty}`")
}
hir::BinOpKind::Rem => {
format!(
"cannot calculate the remainder of `{lhs_ty}` divided by `{rhs_ty}`"
)
}
hir::BinOpKind::BitAnd => {
format!("no implementation for `{lhs_ty} & {rhs_ty}`")
}
hir::BinOpKind::BitXor => {
format!("no implementation for `{lhs_ty} ^ {rhs_ty}`")
}
hir::BinOpKind::BitOr => {
format!("no implementation for `{lhs_ty} | {rhs_ty}`")
}
hir::BinOpKind::Shl => {
format!("no implementation for `{lhs_ty} << {rhs_ty}`")
}
hir::BinOpKind::Shr => {
format!("no implementation for `{lhs_ty} >> {rhs_ty}`")
}
_ => format!(
"binary operation `{}` cannot be applied to type `{}`",
op.node.as_str(),
lhs_ty
),
};
let output_def_id = trait_def_id.and_then(|def_id| {
self.tcx
.associated_item_def_ids(def_id)
.iter()
.find(|item_def_id| {
self.tcx.associated_item(*item_def_id).name == sym::Output
})
.cloned()
});
let mut err =
struct_span_code_err!(self.dcx(), op.span, E0369, "{message}");
if !lhs_expr.span.eq(&rhs_expr.span) {
err.span_label(lhs_expr.span, lhs_ty.to_string());
err.span_label(rhs_expr.span, rhs_ty.to_string());
}
let suggest_derive = self.can_eq(self.param_env, lhs_ty, rhs_ty);
self.note_unmet_impls_on_type(&mut err, errors, suggest_derive);
(err, output_def_id)
}
};
// Try to suggest a semicolon if it's `A \n *B` where `B` is a place expr
let maybe_missing_semi = self.check_for_missing_semi(expr, &mut err);
// We defer to the later error produced by `check_lhs_assignable`.
// We only downgrade this if it's the LHS, though, and if this is a
// valid assignment statement.
if maybe_missing_semi
&& let hir::Node::Expr(parent) = self.tcx.parent_hir_node(expr.hir_id)
&& let hir::ExprKind::Assign(lhs, _, _) = parent.kind
&& let hir::Node::Stmt(stmt) = self.tcx.parent_hir_node(parent.hir_id)
&& let hir::StmtKind::Expr(_) | hir::StmtKind::Semi(_) = stmt.kind
&& lhs.hir_id == expr.hir_id
{
err.downgrade_to_delayed_bug();
}
let suggest_deref_binop = |err: &mut Diag<'_, _>, lhs_deref_ty: Ty<'tcx>| {
if self
.lookup_op_method(
(lhs_expr, lhs_deref_ty),
Some((rhs_expr, rhs_ty)),
Op::Binary(op, is_assign),
expected,
)
.is_ok()
{
let msg = format!(
"`{}{}` can be used on `{}` if you dereference the left-hand side",
op.node.as_str(),
match is_assign {
IsAssign::Yes => "=",
IsAssign::No => "",
},
lhs_deref_ty,
);
err.span_suggestion_verbose(
lhs_expr.span.shrink_to_lo(),
msg,
"*",
rustc_errors::Applicability::MachineApplicable,
);
}
};
let suggest_different_borrow =
|err: &mut Diag<'_, _>,
lhs_adjusted_ty,
lhs_new_mutbl: Option<ast::Mutability>,
rhs_adjusted_ty,
rhs_new_mutbl: Option<ast::Mutability>| {
if self
.lookup_op_method(
(lhs_expr, lhs_adjusted_ty),
Some((rhs_expr, rhs_adjusted_ty)),
Op::Binary(op, is_assign),
expected,
)
.is_ok()
{
let op_str = op.node.as_str();
err.note(format!("an implementation for `{lhs_adjusted_ty} {op_str} {rhs_adjusted_ty}` exists"));
if let Some(lhs_new_mutbl) = lhs_new_mutbl
&& let Some(rhs_new_mutbl) = rhs_new_mutbl
&& lhs_new_mutbl.is_not()
&& rhs_new_mutbl.is_not()
{
err.multipart_suggestion_verbose(
"consider reborrowing both sides",
vec![
(lhs_expr.span.shrink_to_lo(), "&*".to_string()),
(rhs_expr.span.shrink_to_lo(), "&*".to_string()),
],
rustc_errors::Applicability::MachineApplicable,
);
} else {
let mut suggest_new_borrow =
|new_mutbl: ast::Mutability, sp: Span| {
// Can reborrow (&mut -> &)
if new_mutbl.is_not() {
err.span_suggestion_verbose(
sp.shrink_to_lo(),
"consider reborrowing this side",
"&*",
rustc_errors::Applicability::MachineApplicable,
);
// Works on &mut but have &
} else {
err.span_help(
sp,
"consider making this expression a mutable borrow",
);
}
};
if let Some(lhs_new_mutbl) = lhs_new_mutbl {
suggest_new_borrow(lhs_new_mutbl, lhs_expr.span);
}
if let Some(rhs_new_mutbl) = rhs_new_mutbl {
suggest_new_borrow(rhs_new_mutbl, rhs_expr.span);
}
}
}
};
let is_compatible_after_call = |lhs_ty, rhs_ty| {
self.lookup_op_method(
(lhs_expr, lhs_ty),
Some((rhs_expr, rhs_ty)),
Op::Binary(op, is_assign),
expected,
)
.is_ok()
// Suggest calling even if, after calling, the types don't
// implement the operator, since it'll lead to better
// diagnostics later.
|| self.can_eq(self.param_env, lhs_ty, rhs_ty)
};
// We should suggest `a + b` => `*a + b` if `a` is copy, and suggest
// `a += b` => `*a += b` if a is a mut ref.
if !op.span.can_be_used_for_suggestions() {
// Suppress suggestions when lhs and rhs are not in the same span as the error
} else if is_assign == IsAssign::Yes
&& let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty)
{
suggest_deref_binop(&mut err, lhs_deref_ty);
} else if is_assign == IsAssign::No
&& let Ref(region, lhs_deref_ty, mutbl) = lhs_ty.kind()
{
if self.type_is_copy_modulo_regions(self.param_env, *lhs_deref_ty) {
suggest_deref_binop(&mut err, *lhs_deref_ty);
} else {
let lhs_inv_mutbl = mutbl.invert();
let lhs_inv_mutbl_ty =
Ty::new_ref(self.tcx, *region, *lhs_deref_ty, lhs_inv_mutbl);
suggest_different_borrow(
&mut err,
lhs_inv_mutbl_ty,
Some(lhs_inv_mutbl),
rhs_ty,
None,
);
if let Ref(region, rhs_deref_ty, mutbl) = rhs_ty.kind() {
let rhs_inv_mutbl = mutbl.invert();
let rhs_inv_mutbl_ty =
Ty::new_ref(self.tcx, *region, *rhs_deref_ty, rhs_inv_mutbl);
suggest_different_borrow(
&mut err,
lhs_ty,
None,
rhs_inv_mutbl_ty,
Some(rhs_inv_mutbl),
);
suggest_different_borrow(
&mut err,
lhs_inv_mutbl_ty,
Some(lhs_inv_mutbl),
rhs_inv_mutbl_ty,
Some(rhs_inv_mutbl),
);
}
}
} else if self.suggest_fn_call(&mut err, lhs_expr, lhs_ty, |lhs_ty| {
is_compatible_after_call(lhs_ty, rhs_ty)
}) || self.suggest_fn_call(&mut err, rhs_expr, rhs_ty, |rhs_ty| {
is_compatible_after_call(lhs_ty, rhs_ty)
}) || self.suggest_two_fn_call(
&mut err,
rhs_expr,
rhs_ty,
lhs_expr,
lhs_ty,
|lhs_ty, rhs_ty| is_compatible_after_call(lhs_ty, rhs_ty),
) {
// Cool
}
if let Some(missing_trait) = missing_trait {
if op.node == hir::BinOpKind::Add
&& self.check_str_addition(
lhs_expr, rhs_expr, lhs_ty, rhs_ty, &mut err, is_assign, op,
)
{
// This has nothing here because it means we did string
// concatenation (e.g., "Hello " + "World!"). This means
// we don't want the note in the else clause to be emitted
} else if lhs_ty.has_non_region_param() {
// Look for a TraitPredicate in the Fulfillment errors,
// and use it to generate a suggestion.
//
// Note that lookup_op_method must be called again but
// with a specific rhs_ty instead of a placeholder so
// the resulting predicate generates a more specific
// suggestion for the user.
let errors = self
.lookup_op_method(
(lhs_expr, lhs_ty),
Some((rhs_expr, rhs_ty)),
Op::Binary(op, is_assign),
expected,
)
.unwrap_err();
if !errors.is_empty() {
for error in errors {
if let Some(trait_pred) =
error.obligation.predicate.as_trait_clause()
{
let output_associated_item = match error.obligation.cause.code()
{
ObligationCauseCode::BinOp {
output_ty: Some(output_ty),
..
} => {
// Make sure that we're attaching `Output = ..` to the right trait predicate
if let Some(output_def_id) = output_def_id
&& let Some(trait_def_id) = trait_def_id
&& self.tcx.parent(output_def_id) == trait_def_id
&& let Some(output_ty) = output_ty
.make_suggestable(self.tcx, false, None)
{
Some(("Output", output_ty))
} else {
None
}
}
_ => None,
};
self.err_ctxt().suggest_restricting_param_bound(
&mut err,
trait_pred,
output_associated_item,
self.body_id,
);
}
}
} else {
// When we know that a missing bound is responsible, we don't show
// this note as it is redundant.
err.note(format!(
"the trait `{missing_trait}` is not implemented for `{lhs_ty}`"
));
}
}
}
// Suggest using `add`, `offset` or `offset_from` for pointer - {integer},
// pointer + {integer} or pointer - pointer.
if op.span.can_be_used_for_suggestions() {
match op.node {
hir::BinOpKind::Add if lhs_ty.is_unsafe_ptr() && rhs_ty.is_integral() => {
err.multipart_suggestion(
"consider using `wrapping_add` or `add` for pointer + {integer}",
vec![
(
lhs_expr.span.between(rhs_expr.span),
".wrapping_add(".to_owned(),
),
(rhs_expr.span.shrink_to_hi(), ")".to_owned()),
],
Applicability::MaybeIncorrect,
);
}
hir::BinOpKind::Sub => {
if lhs_ty.is_unsafe_ptr() && rhs_ty.is_integral() {
err.multipart_suggestion(
"consider using `wrapping_sub` or `sub` for pointer - {integer}",
vec![
(lhs_expr.span.between(rhs_expr.span), ".wrapping_sub(".to_owned()),
(rhs_expr.span.shrink_to_hi(), ")".to_owned()),
],
Applicability::MaybeIncorrect
);
}
if lhs_ty.is_unsafe_ptr() && rhs_ty.is_unsafe_ptr() {
err.multipart_suggestion(
"consider using `offset_from` for pointer - pointer if the pointers point to the same allocation",
vec![
(lhs_expr.span.shrink_to_lo(), "unsafe { ".to_owned()),
(lhs_expr.span.between(rhs_expr.span), ".offset_from(".to_owned()),
(rhs_expr.span.shrink_to_hi(), ") }".to_owned()),
],
Applicability::MaybeIncorrect
);
}
}
_ => {}
}
}
let reported = err.emit();
Ty::new_error(self.tcx, reported)
}
};
(lhs_ty, rhs_ty, return_ty)
}
/// Provide actionable suggestions when trying to add two strings with incorrect types,
/// like `&str + &str`, `String + String` and `&str + &String`.
///
/// If this function returns `true` it means a note was printed, so we don't need
/// to print the normal "implementation of `std::ops::Add` might be missing" note
fn 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 Diag<'_>,
is_assign: IsAssign,
op: hir::BinOp,
) -> bool {
let str_concat_note = "string concatenation requires an owned `String` on the left";
let rm_borrow_msg = "remove the borrow to obtain an owned `String`";
let to_owned_msg = "create an owned `String` from a string reference";
let string_type = self.tcx.lang_items().string();
let is_std_string =
|ty: Ty<'tcx>| ty.ty_adt_def().is_some_and(|ty_def| Some(ty_def.did()) == string_type);
match (lhs_ty.kind(), rhs_ty.kind()) {
(&Ref(_, l_ty, _), &Ref(_, r_ty, _)) // &str or &String + &str, &String or &&str
if (*l_ty.kind() == Str || is_std_string(l_ty))
&& (*r_ty.kind() == Str
|| is_std_string(r_ty)
|| matches!(
r_ty.kind(), Ref(_, inner_ty, _) if *inner_ty.kind() == Str
)) =>
{
if let IsAssign::No = is_assign { // Do not supply this message if `&str += &str`
err.span_label(op.span, "`+` cannot be used to concatenate two `&str` strings");
err.note(str_concat_note);
if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
err.span_suggestion_verbose(
lhs_expr.span.until(lhs_inner_expr.span),
rm_borrow_msg,
"",
Applicability::MachineApplicable
);
} else {
err.span_suggestion_verbose(
lhs_expr.span.shrink_to_hi(),
to_owned_msg,
".to_owned()",
Applicability::MachineApplicable
);
}
}
true
}
(&Ref(_, l_ty, _), &Adt(..)) // Handle `&str` & `&String` + `String`
if (*l_ty.kind() == Str || is_std_string(l_ty)) && is_std_string(rhs_ty) =>
{
err.span_label(
op.span,
"`+` cannot be used to concatenate a `&str` with a `String`",
);
match is_assign {
IsAssign::No => {
let sugg_msg;
let lhs_sugg = if let hir::ExprKind::AddrOf(_, _, lhs_inner_expr) = lhs_expr.kind {
sugg_msg = "remove the borrow on the left and add one on the right";
(lhs_expr.span.until(lhs_inner_expr.span), "".to_owned())
} else {
sugg_msg = "create an owned `String` on the left and add a borrow on the right";
(lhs_expr.span.shrink_to_hi(), ".to_owned()".to_owned())
};
let suggestions = vec![
lhs_sugg,
(rhs_expr.span.shrink_to_lo(), "&".to_owned()),
];
err.multipart_suggestion_verbose(
sugg_msg,
suggestions,
Applicability::MachineApplicable,
);
}
IsAssign::Yes => {
err.note(str_concat_note);
}
}
true
}
_ => false,
}
}
pub(crate) fn check_user_unop(
&self,
ex: &'tcx hir::Expr<'tcx>,
operand_ty: Ty<'tcx>,
op: hir::UnOp,
expected: Expectation<'tcx>,
) -> Ty<'tcx> {
assert!(op.is_by_value());
match self.lookup_op_method((ex, operand_ty), None, Op::Unary(op, ex.span), expected) {
Ok(method) => {
self.write_method_call_and_enforce_effects(ex.hir_id, ex.span, method);
method.sig.output()
}
Err(errors) => {
let actual = self.resolve_vars_if_possible(operand_ty);
let guar = actual.error_reported().err().unwrap_or_else(|| {
let mut err = struct_span_code_err!(
self.dcx(),
ex.span,
E0600,
"cannot apply unary operator `{}` to type `{}`",
op.as_str(),
actual
);
err.span_label(
ex.span,
format!("cannot apply unary operator `{}`", op.as_str()),
);
if operand_ty.has_non_region_param() {
let predicates = errors
.iter()
.filter_map(|error| error.obligation.predicate.as_trait_clause());
for pred in predicates {
self.err_ctxt().suggest_restricting_param_bound(
&mut err,
pred,
None,
self.body_id,
);
}
}
let sp = self.tcx.sess.source_map().start_point(ex.span).with_parent(None);
if let Some(sp) =
self.tcx.sess.psess.ambiguous_block_expr_parse.borrow().get(&sp)
{
// If the previous expression was a block expression, suggest parentheses
// (turning this into a binary subtraction operation instead.)
// for example, `{2} - 2` -> `({2}) - 2` (see src\test\ui\parser\expr-as-stmt.rs)
err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
} else {
match actual.kind() {
Uint(_) if op == hir::UnOp::Neg => {
err.note("unsigned values cannot be negated");
if let hir::ExprKind::Unary(
_,
hir::Expr {
kind:
hir::ExprKind::Lit(Spanned {
node: ast::LitKind::Int(Pu128(1), _),
..
}),
..
},
) = ex.kind
{
let span = if let hir::Node::Expr(parent) =
self.tcx.parent_hir_node(ex.hir_id)
&& let hir::ExprKind::Cast(..) = parent.kind
{
// `-1 as usize` -> `usize::MAX`
parent.span
} else {
ex.span
};
err.span_suggestion_verbose(
span,
format!(
"you may have meant the maximum value of `{actual}`",
),
format!("{actual}::MAX"),
Applicability::MaybeIncorrect,
);
}
}
Str | Never | Char | Tuple(_) | Array(_, _) => {}
Ref(_, lty, _) if *lty.kind() == Str => {}
_ => {
self.note_unmet_impls_on_type(&mut err, errors, true);
}
}
}
err.emit()
});
Ty::new_error(self.tcx, guar)
}
}
}
fn lookup_op_method(
&self,
(lhs_expr, lhs_ty): (&'tcx hir::Expr<'tcx>, Ty<'tcx>),
opt_rhs: Option<(&'tcx hir::Expr<'tcx>, Ty<'tcx>)>,
op: Op,
expected: Expectation<'tcx>,
) -> Result<MethodCallee<'tcx>, Vec<FulfillmentError<'tcx>>> {
let span = match op {
Op::Binary(op, _) => op.span,
Op::Unary(_, span) => span,
};
let (opname, Some(trait_did)) = lang_item_for_op(self.tcx, op, span) else {
// Bail if the operator trait is not defined.
return Err(vec![]);
};
debug!(
"lookup_op_method(lhs_ty={:?}, op={:?}, opname={:?}, trait_did={:?})",
lhs_ty, op, opname, trait_did
);
let opname = Ident::with_dummy_span(opname);
let (opt_rhs_expr, opt_rhs_ty) = opt_rhs.unzip();
let cause = self.cause(span, ObligationCauseCode::BinOp {
lhs_hir_id: lhs_expr.hir_id,
rhs_hir_id: opt_rhs_expr.map(|expr| expr.hir_id),
rhs_span: opt_rhs_expr.map(|expr| expr.span),
rhs_is_lit: opt_rhs_expr.is_some_and(|expr| matches!(expr.kind, hir::ExprKind::Lit(_))),
output_ty: expected.only_has_type(self),
});
let method =
self.lookup_method_in_trait(cause.clone(), opname, trait_did, lhs_ty, opt_rhs_ty);
match method {
Some(ok) => {
let method = self.register_infer_ok_obligations(ok);
self.select_obligations_where_possible(|_| {});
Ok(method)
}
None => {
// This path may do some inference, so make sure we've really
// doomed compilation so as to not accidentally stabilize new
// inference or something here...
self.dcx().span_delayed_bug(span, "this path really should be doomed...");
// Guide inference for the RHS expression if it's provided --
// this will allow us to better error reporting, at the expense
// of making some error messages a bit more specific.
if let Some((rhs_expr, rhs_ty)) = opt_rhs
&& rhs_ty.is_ty_var()
{
self.check_expr_coercible_to_type(rhs_expr, rhs_ty, None);
}
// Construct an obligation `self_ty : Trait<input_tys>`
let args =
ty::GenericArgs::for_item(self.tcx, trait_did, |param, _| match param.kind {
ty::GenericParamDefKind::Lifetime
| ty::GenericParamDefKind::Const { .. } => {
unreachable!("did not expect operand trait to have lifetime/const args")
}
ty::GenericParamDefKind::Type { .. } => {
if param.index == 0 {
lhs_ty.into()
} else {
opt_rhs_ty.expect("expected RHS for binop").into()
}
}
});
let obligation = Obligation::new(
self.tcx,
cause,
self.param_env,
ty::TraitRef::new_from_args(self.tcx, trait_did, args),
);
let ocx = ObligationCtxt::new_with_diagnostics(&self.infcx);
ocx.register_obligation(obligation);
Err(ocx.select_all_or_error())
}
}
}
}
fn lang_item_for_op(
tcx: TyCtxt<'_>,
op: Op,
span: Span,
) -> (rustc_span::Symbol, Option<hir::def_id::DefId>) {
let lang = tcx.lang_items();
if let Op::Binary(op, IsAssign::Yes) = op {
match op.node {
hir::BinOpKind::Add => (sym::add_assign, lang.add_assign_trait()),
hir::BinOpKind::Sub => (sym::sub_assign, lang.sub_assign_trait()),
hir::BinOpKind::Mul => (sym::mul_assign, lang.mul_assign_trait()),
hir::BinOpKind::Div => (sym::div_assign, lang.div_assign_trait()),
hir::BinOpKind::Rem => (sym::rem_assign, lang.rem_assign_trait()),
hir::BinOpKind::BitXor => (sym::bitxor_assign, lang.bitxor_assign_trait()),
hir::BinOpKind::BitAnd => (sym::bitand_assign, lang.bitand_assign_trait()),
hir::BinOpKind::BitOr => (sym::bitor_assign, lang.bitor_assign_trait()),
hir::BinOpKind::Shl => (sym::shl_assign, lang.shl_assign_trait()),
hir::BinOpKind::Shr => (sym::shr_assign, lang.shr_assign_trait()),
hir::BinOpKind::Lt
| hir::BinOpKind::Le
| hir::BinOpKind::Ge
| hir::BinOpKind::Gt
| hir::BinOpKind::Eq
| hir::BinOpKind::Ne
| hir::BinOpKind::And
| hir::BinOpKind::Or => {
span_bug!(span, "impossible assignment operation: {}=", op.node.as_str())
}
}
} else if let Op::Binary(op, IsAssign::No) = op {
match op.node {
hir::BinOpKind::Add => (sym::add, lang.add_trait()),
hir::BinOpKind::Sub => (sym::sub, lang.sub_trait()),
hir::BinOpKind::Mul => (sym::mul, lang.mul_trait()),
hir::BinOpKind::Div => (sym::div, lang.div_trait()),
hir::BinOpKind::Rem => (sym::rem, lang.rem_trait()),
hir::BinOpKind::BitXor => (sym::bitxor, lang.bitxor_trait()),
hir::BinOpKind::BitAnd => (sym::bitand, lang.bitand_trait()),
hir::BinOpKind::BitOr => (sym::bitor, lang.bitor_trait()),
hir::BinOpKind::Shl => (sym::shl, lang.shl_trait()),
hir::BinOpKind::Shr => (sym::shr, lang.shr_trait()),
hir::BinOpKind::Lt => (sym::lt, lang.partial_ord_trait()),
hir::BinOpKind::Le => (sym::le, lang.partial_ord_trait()),
hir::BinOpKind::Ge => (sym::ge, lang.partial_ord_trait()),
hir::BinOpKind::Gt => (sym::gt, lang.partial_ord_trait()),
hir::BinOpKind::Eq => (sym::eq, lang.eq_trait()),
hir::BinOpKind::Ne => (sym::ne, lang.eq_trait()),
hir::BinOpKind::And | hir::BinOpKind::Or => {
span_bug!(span, "&& and || are not overloadable")
}
}
} else if let Op::Unary(hir::UnOp::Not, _) = op {
(sym::not, lang.not_trait())
} else if let Op::Unary(hir::UnOp::Neg, _) = op {
(sym::neg, lang.neg_trait())
} else {
bug!("lookup_op_method: op not supported: {:?}", op)
}
}
// Binary operator categories. These categories summarize the behavior
// with respect to the builtin operations supported.
enum BinOpCategory {
/// &&, || -- cannot be overridden
Shortcircuit,
/// <<, >> -- when shifting a single integer, rhs can be any
/// integer type. For simd, types must match.
Shift,
/// +, -, etc -- takes equal types, produces same type as input,
/// applicable to ints/floats/simd
Math,
/// &, |, ^ -- takes equal types, produces same type as input,
/// applicable to ints/floats/simd/bool
Bitwise,
/// ==, !=, etc -- takes equal types, produces bools, except for simd,
/// which produce the input type
Comparison,
}
impl BinOpCategory {
fn from(op: hir::BinOp) -> BinOpCategory {
match op.node {
hir::BinOpKind::Shl | hir::BinOpKind::Shr => BinOpCategory::Shift,
hir::BinOpKind::Add
| hir::BinOpKind::Sub
| hir::BinOpKind::Mul
| hir::BinOpKind::Div
| hir::BinOpKind::Rem => BinOpCategory::Math,
hir::BinOpKind::BitXor | hir::BinOpKind::BitAnd | hir::BinOpKind::BitOr => {
BinOpCategory::Bitwise
}
hir::BinOpKind::Eq
| hir::BinOpKind::Ne
| hir::BinOpKind::Lt
| hir::BinOpKind::Le
| hir::BinOpKind::Ge
| hir::BinOpKind::Gt => BinOpCategory::Comparison,
hir::BinOpKind::And | hir::BinOpKind::Or => BinOpCategory::Shortcircuit,
}
}
}
/// Whether the binary operation is an assignment (`a += b`), or not (`a + b`)
#[derive(Clone, Copy, Debug, PartialEq)]
enum IsAssign {
No,
Yes,
}
#[derive(Clone, Copy, Debug)]
enum Op {
Binary(hir::BinOp, IsAssign),
Unary(hir::UnOp, Span),
}
/// Dereferences a single level of immutable referencing.
fn deref_ty_if_possible(ty: Ty<'_>) -> Ty<'_> {
match ty.kind() {
ty::Ref(_, ty, hir::Mutability::Not) => *ty,
_ => ty,
}
}
/// Returns `true` if this is a built-in arithmetic operation (e.g., u32
/// + u32, i16x4 == i16x4) and false if these types would have to be
/// overloaded to be legal. There are two reasons that we distinguish
/// builtin operations from overloaded ones (vs trying to drive
/// everything uniformly through the trait system and intrinsics or
/// something like that):
///
/// 1. Builtin operations can trivially be evaluated in constants.
/// 2. For comparison operators applied to SIMD types the result is
/// not of type `bool`. For example, `i16x4 == i16x4` yields a
/// type like `i16x4`. This means that the overloaded trait
/// `PartialEq` is not applicable.
///
/// Reason #2 is the killer. I tried for a while to always use
/// overloaded logic and just check the types in constants/codegen after
/// the fact, and it worked fine, except for SIMD types. -nmatsakis
fn is_builtin_binop<'tcx>(lhs: Ty<'tcx>, rhs: Ty<'tcx>, op: hir::BinOp) -> bool {
// Special-case a single layer of referencing, so that things like `5.0 + &6.0f32` work.
// (See https://github.com/rust-lang/rust/issues/57447.)
let (lhs, rhs) = (deref_ty_if_possible(lhs), deref_ty_if_possible(rhs));
match BinOpCategory::from(op) {
BinOpCategory::Shortcircuit => true,
BinOpCategory::Shift => {
lhs.references_error()
|| rhs.references_error()
|| lhs.is_integral() && rhs.is_integral()
}
BinOpCategory::Math => {
lhs.references_error()
|| rhs.references_error()
|| lhs.is_integral() && rhs.is_integral()
|| lhs.is_floating_point() && rhs.is_floating_point()
}
BinOpCategory::Bitwise => {
lhs.references_error()
|| rhs.references_error()
|| lhs.is_integral() && rhs.is_integral()
|| lhs.is_floating_point() && rhs.is_floating_point()
|| lhs.is_bool() && rhs.is_bool()
}
BinOpCategory::Comparison => {
lhs.references_error() || rhs.references_error() || lhs.is_scalar() && rhs.is_scalar()
}
}
}