--- /dev/null
+//! Code related to processing overloaded binary and unary operators.
+
+use super::method::MethodCallee;
+use super::{has_expected_num_generic_args, FnCtxt};
+use crate::Expectation;
+use rustc_ast as ast;
+use rustc_errors::{self, struct_span_err, Applicability, Diagnostic};
+use rustc_hir as hir;
+use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+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, DefIdTree, Ty, TyCtxt, TypeFolder, TypeSuperFoldable, TypeVisitable};
+use rustc_session::errors::ExprParenthesesNeeded;
+use rustc_span::source_map::Spanned;
+use rustc_span::symbol::{sym, Ident};
+use rustc_span::Span;
+use rustc_trait_selection::infer::InferCtxtExt;
+use rustc_trait_selection::traits::error_reporting::suggestions::TypeErrCtxtExt as _;
+use rustc_trait_selection::traits::{FulfillmentError, TraitEngine, TraitEngineExt};
+use rustc_type_ir::sty::TyKind::*;
+
+impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+ /// Checks a `a <op>= b`
+ pub fn 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> {
+ 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.mk_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_deref_ty,
+ Some(rhs_ty),
+ Some(rhs),
+ 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_ty,
+ Some(rhs_ty),
+ Some(rhs),
+ 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 fn 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> {
+ 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_coercable_to_type(lhs_expr, tcx.types.bool, None);
+ let lhs_diverges = self.diverges.get();
+ self.check_expr_coercable_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_suptype(expr.span, builtin_return_ty, return_ty);
+ }
+
+ 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(TypeVariableOrigin {
+ kind: TypeVariableOriginKind::MiscVariable,
+ span: 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(TypeVariableOrigin {
+ kind: TypeVariableOriginKind::MiscVariable,
+ span: rhs_expr.span,
+ });
+
+ let result = self.lookup_op_method(
+ lhs_ty,
+ Some(rhs_ty_var),
+ Some(rhs_expr),
+ Op::Binary(op, is_assign),
+ expected,
+ );
+
+ // see `NB` above
+ let rhs_ty = self.check_expr_coercable_to_type(rhs_expr, rhs_ty_var, Some(lhs_expr));
+ 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(region, _, mutbl) = method.sig.inputs()[0].kind() {
+ let mutbl = match mutbl {
+ hir::Mutability::Not => AutoBorrowMutability::Not,
+ hir::Mutability::Mut => AutoBorrowMutability::Mut {
+ // Allow two-phase borrows for binops in initial deployment
+ // since they desugar to methods
+ allow_two_phase_borrow: AllowTwoPhase::Yes,
+ },
+ };
+ let autoref = Adjustment {
+ kind: Adjust::Borrow(AutoBorrow::Ref(*region, mutbl)),
+ target: method.sig.inputs()[0],
+ };
+ self.apply_adjustments(lhs_expr, vec![autoref]);
+ }
+ }
+ if by_ref_binop {
+ if let ty::Ref(region, _, mutbl) = method.sig.inputs()[1].kind() {
+ let mutbl = match mutbl {
+ hir::Mutability::Not => AutoBorrowMutability::Not,
+ hir::Mutability::Mut => AutoBorrowMutability::Mut {
+ // Allow two-phase borrows for binops in initial deployment
+ // since they desugar to methods
+ allow_two_phase_borrow: AllowTwoPhase::Yes,
+ },
+ };
+ let autoref = Adjustment {
+ kind: Adjust::Borrow(AutoBorrow::Ref(*region, 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(expr.hir_id, method);
+
+ method.sig.output()
+ }
+ // error types are considered "builtin"
+ Err(_) if lhs_ty.references_error() || rhs_ty.references_error() => self.tcx.ty_error(),
+ 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_err!(
+ self.tcx.sess,
+ 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);
+ (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 mod `{lhs_ty}` 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_err!(self.tcx.sess, 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());
+ }
+ self.note_unmet_impls_on_type(&mut err, errors);
+ (err, output_def_id)
+ }
+ };
+
+ let mut suggest_deref_binop = |lhs_deref_ty: Ty<'tcx>| {
+ if self
+ .lookup_op_method(
+ lhs_deref_ty,
+ Some(rhs_ty),
+ Some(rhs_expr),
+ 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 is_compatible = |lhs_ty, rhs_ty| {
+ self.lookup_op_method(
+ lhs_ty,
+ Some(rhs_ty),
+ Some(rhs_expr),
+ Op::Binary(op, is_assign),
+ expected,
+ )
+ .is_ok()
+ };
+
+ // 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(lhs_deref_ty);
+ } else if is_assign == IsAssign::No
+ && let Ref(_, lhs_deref_ty, _) = lhs_ty.kind()
+ {
+ if self.type_is_copy_modulo_regions(
+ self.param_env,
+ *lhs_deref_ty,
+ lhs_expr.span,
+ ) {
+ suggest_deref_binop(*lhs_deref_ty);
+ }
+ } else if self.suggest_fn_call(&mut err, lhs_expr, lhs_ty, |lhs_ty| {
+ is_compatible(lhs_ty, rhs_ty)
+ }) || self.suggest_fn_call(&mut err, rhs_expr, rhs_ty, |rhs_ty| {
+ is_compatible(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(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_ty,
+ Some(rhs_ty),
+ Some(rhs_expr),
+ Op::Binary(op, is_assign),
+ expected,
+ )
+ .unwrap_err();
+ if !errors.is_empty() {
+ for error in errors {
+ if let Some(trait_pred) =
+ error.obligation.predicate.to_opt_poly_trait_pred()
+ {
+ 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
+ {
+ 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}`"
+ ));
+ }
+ }
+ }
+ err.emit();
+ self.tcx.ty_error()
+ }
+ };
+
+ (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 Diagnostic,
+ 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 is_std_string = |ty: Ty<'tcx>| {
+ ty.ty_adt_def()
+ .map_or(false, |ty_def| self.tcx.is_diagnostic_item(sym::String, ty_def.did()))
+ };
+
+ 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 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(operand_ty, None, None, Op::Unary(op, ex.span), expected) {
+ Ok(method) => {
+ self.write_method_call(ex.hir_id, method);
+ method.sig.output()
+ }
+ Err(errors) => {
+ let actual = self.resolve_vars_if_possible(operand_ty);
+ if !actual.references_error() {
+ let mut err = struct_span_err!(
+ self.tcx.sess,
+ 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.to_opt_poly_trait_pred()
+ });
+ 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);
+ if let Some(sp) =
+ self.tcx.sess.parse_sess.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(1, _),
+ ..
+ }),
+ ..
+ },
+ ) = ex.kind
+ {
+ err.span_suggestion(
+ ex.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);
+ }
+ }
+ }
+ err.emit();
+ }
+ self.tcx.ty_error()
+ }
+ }
+ }
+
+ fn lookup_op_method(
+ &self,
+ lhs_ty: Ty<'tcx>,
+ other_ty: Option<Ty<'tcx>>,
+ other_ty_expr: Option<&'tcx hir::Expr<'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, trait_did) = lang_item_for_op(self.tcx, op, span);
+
+ debug!(
+ "lookup_op_method(lhs_ty={:?}, op={:?}, opname={:?}, trait_did={:?})",
+ lhs_ty, op, opname, trait_did
+ );
+
+ // Catches cases like #83893, where a lang item is declared with the
+ // wrong number of generic arguments. Should have yielded an error
+ // elsewhere by now, but we have to catch it here so that we do not
+ // index `other_tys` out of bounds (if the lang item has too many
+ // generic arguments, `other_tys` is too short).
+ if !has_expected_num_generic_args(
+ self.tcx,
+ trait_did,
+ match op {
+ // Binary ops have a generic right-hand side, unary ops don't
+ Op::Binary(..) => 1,
+ Op::Unary(..) => 0,
+ },
+ ) {
+ return Err(vec![]);
+ }
+
+ let opname = Ident::with_dummy_span(opname);
+ let method = trait_did.and_then(|trait_did| {
+ self.lookup_op_method_in_trait(
+ span,
+ opname,
+ trait_did,
+ lhs_ty,
+ other_ty,
+ other_ty_expr,
+ expected,
+ )
+ });
+
+ match (method, trait_did) {
+ (Some(ok), _) => {
+ let method = self.register_infer_ok_obligations(ok);
+ self.select_obligations_where_possible(false, |_| {});
+ Ok(method)
+ }
+ (None, None) => Err(vec![]),
+ (None, Some(trait_did)) => {
+ let (obligation, _) = self.obligation_for_op_method(
+ span,
+ trait_did,
+ lhs_ty,
+ other_ty,
+ other_ty_expr,
+ expected,
+ );
+ let mut fulfill = <dyn TraitEngine<'_>>::new(self.tcx);
+ fulfill.register_predicate_obligation(self, obligation);
+ Err(fulfill.select_where_possible(&self.infcx))
+ }
+ }
+ }
+}
+
+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<'tcx>(ty: Ty<'tcx>) -> Ty<'tcx> {
+ 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()
+ }
+ }
+}
+
+struct TypeParamEraser<'a, 'tcx>(&'a FnCtxt<'a, 'tcx>, Span);
+
+impl<'tcx> TypeFolder<'tcx> for TypeParamEraser<'_, 'tcx> {
+ fn tcx(&self) -> TyCtxt<'tcx> {
+ self.0.tcx
+ }
+
+ fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
+ match ty.kind() {
+ ty::Param(_) => self.0.next_ty_var(TypeVariableOrigin {
+ kind: TypeVariableOriginKind::MiscVariable,
+ span: self.1,
+ }),
+ _ => ty.super_fold_with(self),
+ }
+ }
+}
projects / rustc.git / blobdiff