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Rollup merge of #114288 - Urgau:fix-issue-109352, r=b-naber
Improve diagnostic for wrong borrow on binary operations This PR improves the diagnostic for wrong borrow on binary operations by suggesting to reborrow on appropriate expressions. ```diff + = note: an implementation for `&Foo * &Foo` exist + help: consider reborrowing both sides + | + LL | let _ = &*ref_mut_foo * &*ref_mut_foo; + | ++ ++ ``` Fixes https://github.com/rust-lang/rust/issues/109352
This commit is contained in:
Matthias Krüger
GitHub
commit
c726dcb962
@ -4,7 +4,7 @@ use super::method::MethodCallee;
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use super::{has_expected_num_generic_args, FnCtxt};
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use crate::Expectation;
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use rustc_ast as ast;
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use rustc_errors::{self, struct_span_err, Applicability, Diagnostic};
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use rustc_errors::{self, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder};
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use rustc_hir as hir;
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use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
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use rustc_infer::traits::ObligationCauseCode;
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@ -380,33 +380,93 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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}
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};
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let mut suggest_deref_binop = |lhs_deref_ty: Ty<'tcx>| {
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if self
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.lookup_op_method(
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lhs_deref_ty,
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Some((rhs_expr, rhs_ty)),
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Op::Binary(op, is_assign),
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expected,
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)
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.is_ok()
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{
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let msg = format!(
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"`{}{}` can be used on `{}` if you dereference the left-hand side",
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op.node.as_str(),
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match is_assign {
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IsAssign::Yes => "=",
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IsAssign::No => "",
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},
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lhs_deref_ty,
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);
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err.span_suggestion_verbose(
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lhs_expr.span.shrink_to_lo(),
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msg,
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"*",
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rustc_errors::Applicability::MachineApplicable,
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);
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}
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};
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let suggest_deref_binop =
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|err: &mut DiagnosticBuilder<'_, _>, lhs_deref_ty: Ty<'tcx>| {
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if self
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.lookup_op_method(
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lhs_deref_ty,
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Some((rhs_expr, rhs_ty)),
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Op::Binary(op, is_assign),
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expected,
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)
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.is_ok()
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{
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let msg = format!(
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"`{}{}` can be used on `{}` if you dereference the left-hand side",
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op.node.as_str(),
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match is_assign {
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IsAssign::Yes => "=",
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IsAssign::No => "",
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},
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lhs_deref_ty,
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);
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err.span_suggestion_verbose(
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lhs_expr.span.shrink_to_lo(),
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msg,
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"*",
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rustc_errors::Applicability::MachineApplicable,
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);
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}
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};
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let suggest_different_borrow =
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|err: &mut DiagnosticBuilder<'_, _>,
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lhs_adjusted_ty,
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lhs_new_mutbl: Option<ast::Mutability>,
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rhs_adjusted_ty,
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rhs_new_mutbl: Option<ast::Mutability>| {
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if self
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.lookup_op_method(
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lhs_adjusted_ty,
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Some((rhs_expr, rhs_adjusted_ty)),
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Op::Binary(op, is_assign),
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expected,
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)
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.is_ok()
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{
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let op_str = op.node.as_str();
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err.note(format!("an implementation for `{lhs_adjusted_ty} {op_str} {rhs_adjusted_ty}` exists"));
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if let Some(lhs_new_mutbl) = lhs_new_mutbl
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&& let Some(rhs_new_mutbl) = rhs_new_mutbl
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&& lhs_new_mutbl.is_not()
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&& rhs_new_mutbl.is_not() {
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err.multipart_suggestion_verbose(
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"consider reborrowing both sides",
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vec![
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(lhs_expr.span.shrink_to_lo(), "&*".to_string()),
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(rhs_expr.span.shrink_to_lo(), "&*".to_string())
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],
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rustc_errors::Applicability::MachineApplicable,
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);
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} else {
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let mut suggest_new_borrow = |new_mutbl: ast::Mutability, sp: Span| {
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// Can reborrow (&mut -> &)
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if new_mutbl.is_not() {
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err.span_suggestion_verbose(
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sp.shrink_to_lo(),
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"consider reborrowing this side",
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"&*",
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rustc_errors::Applicability::MachineApplicable,
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);
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// Works on &mut but have &
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} else {
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err.span_help(
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sp,
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"consider making this expression a mutable borrow",
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);
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}
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};
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if let Some(lhs_new_mutbl) = lhs_new_mutbl {
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suggest_new_borrow(lhs_new_mutbl, lhs_expr.span);
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}
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if let Some(rhs_new_mutbl) = rhs_new_mutbl {
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suggest_new_borrow(rhs_new_mutbl, rhs_expr.span);
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}
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}
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}
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};
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let is_compatible_after_call = |lhs_ty, rhs_ty| {
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self.lookup_op_method(
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@ -429,15 +489,60 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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} else if is_assign == IsAssign::Yes
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&& let Some(lhs_deref_ty) = self.deref_once_mutably_for_diagnostic(lhs_ty)
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{
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suggest_deref_binop(lhs_deref_ty);
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suggest_deref_binop(&mut err, lhs_deref_ty);
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} else if is_assign == IsAssign::No
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&& let Ref(_, lhs_deref_ty, _) = lhs_ty.kind()
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&& let Ref(region, lhs_deref_ty, mutbl) = lhs_ty.kind()
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{
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if self.type_is_copy_modulo_regions(
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self.param_env,
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*lhs_deref_ty,
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) {
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suggest_deref_binop(*lhs_deref_ty);
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suggest_deref_binop(&mut err, *lhs_deref_ty);
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} else {
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let lhs_inv_mutbl = mutbl.invert();
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let lhs_inv_mutbl_ty = Ty::new_ref(
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self.tcx,
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*region,
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ty::TypeAndMut {
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ty: *lhs_deref_ty,
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mutbl: lhs_inv_mutbl,
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},
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);
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suggest_different_borrow(
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&mut err,
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lhs_inv_mutbl_ty,
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Some(lhs_inv_mutbl),
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rhs_ty,
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None,
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);
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if let Ref(region, rhs_deref_ty, mutbl) = rhs_ty.kind() {
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let rhs_inv_mutbl = mutbl.invert();
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let rhs_inv_mutbl_ty = Ty::new_ref(
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self.tcx,
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*region,
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ty::TypeAndMut {
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ty: *rhs_deref_ty,
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mutbl: rhs_inv_mutbl,
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},
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);
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suggest_different_borrow(
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&mut err,
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lhs_ty,
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None,
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rhs_inv_mutbl_ty,
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Some(rhs_inv_mutbl),
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);
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suggest_different_borrow(
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&mut err,
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lhs_inv_mutbl_ty,
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Some(lhs_inv_mutbl),
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rhs_inv_mutbl_ty,
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Some(rhs_inv_mutbl),
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);
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}
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}
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} else if self.suggest_fn_call(&mut err, lhs_expr, lhs_ty, |lhs_ty| {
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is_compatible_after_call(lhs_ty, rhs_ty)
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27
tests/ui/binop/borrow-suggestion-109352-2.rs
Normal file
27
tests/ui/binop/borrow-suggestion-109352-2.rs
Normal file
@ -0,0 +1,27 @@
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struct Bar;
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impl std::ops::Mul for &mut Bar {
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type Output = Bar;
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fn mul(self, _rhs: Self) -> Self::Output {
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unimplemented!()
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}
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}
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fn main() {
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let ref_mut_bar: &mut Bar = &mut Bar;
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let ref_bar: &Bar = &Bar;
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let owned_bar: Bar = Bar;
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let _ = ref_mut_bar * ref_mut_bar;
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// FIXME: we should be able to suggest borrowing both side
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let _ = owned_bar * owned_bar;
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//~^ ERROR cannot multiply
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let _ = ref_bar * ref_bar;
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//~^ ERROR cannot multiply
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let _ = ref_bar * ref_mut_bar;
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//~^ ERROR cannot multiply
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let _ = ref_mut_bar * ref_bar;
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//~^ ERROR mismatched types
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}
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64
tests/ui/binop/borrow-suggestion-109352-2.stderr
Normal file
64
tests/ui/binop/borrow-suggestion-109352-2.stderr
Normal file
@ -0,0 +1,64 @@
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error[E0369]: cannot multiply `Bar` by `Bar`
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--> $DIR/borrow-suggestion-109352-2.rs:19:23
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LL | let _ = owned_bar * owned_bar;
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| --------- ^ --------- Bar
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| |
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| Bar
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note: an implementation of `Mul` might be missing for `Bar`
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--> $DIR/borrow-suggestion-109352-2.rs:1:1
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LL | struct Bar;
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| ^^^^^^^^^^ must implement `Mul`
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note: the trait `Mul` must be implemented
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--> $SRC_DIR/core/src/ops/arith.rs:LL:COL
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error[E0369]: cannot multiply `&Bar` by `&Bar`
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--> $DIR/borrow-suggestion-109352-2.rs:21:21
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LL | let _ = ref_bar * ref_bar;
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| ------- ^ ------- &Bar
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| |
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| &Bar
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= note: an implementation for `&mut Bar * &mut Bar` exists
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help: consider making this expression a mutable borrow
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--> $DIR/borrow-suggestion-109352-2.rs:21:13
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LL | let _ = ref_bar * ref_bar;
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| ^^^^^^^
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help: consider making this expression a mutable borrow
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--> $DIR/borrow-suggestion-109352-2.rs:21:23
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LL | let _ = ref_bar * ref_bar;
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| ^^^^^^^
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error[E0369]: cannot multiply `&Bar` by `&mut Bar`
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--> $DIR/borrow-suggestion-109352-2.rs:23:21
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LL | let _ = ref_bar * ref_mut_bar;
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| ------- ^ ----------- &mut Bar
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| |
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| &Bar
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|
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= note: an implementation for `&mut Bar * &mut Bar` exists
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help: consider making this expression a mutable borrow
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--> $DIR/borrow-suggestion-109352-2.rs:23:13
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LL | let _ = ref_bar * ref_mut_bar;
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| ^^^^^^^
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error[E0308]: mismatched types
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--> $DIR/borrow-suggestion-109352-2.rs:25:27
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LL | let _ = ref_mut_bar * ref_bar;
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| ^^^^^^^ types differ in mutability
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= note: expected mutable reference `&mut Bar`
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found reference `&Bar`
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error: aborting due to 4 previous errors
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Some errors have detailed explanations: E0308, E0369.
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For more information about an error, try `rustc --explain E0308`.
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27
tests/ui/binop/borrow-suggestion-109352.fixed
Normal file
27
tests/ui/binop/borrow-suggestion-109352.fixed
Normal file
@ -0,0 +1,27 @@
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// run-rustfix
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struct Foo;
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impl std::ops::Mul for &Foo {
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type Output = Foo;
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fn mul(self, _rhs: Self) -> Self::Output {
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unimplemented!()
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}
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}
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fn main() {
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let ref_mut_foo: &mut Foo = &mut Foo;
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let ref_foo: &Foo = &Foo;
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let owned_foo: Foo = Foo;
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let _ = ref_foo * ref_foo;
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let _ = ref_foo * ref_mut_foo;
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let _ = &*ref_mut_foo * ref_foo;
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//~^ ERROR cannot multiply
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let _ = &*ref_mut_foo * &*ref_mut_foo;
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//~^ ERROR cannot multiply
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let _ = &*ref_mut_foo * &owned_foo;
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//~^ ERROR cannot multiply
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}
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27
tests/ui/binop/borrow-suggestion-109352.rs
Normal file
27
tests/ui/binop/borrow-suggestion-109352.rs
Normal file
@ -0,0 +1,27 @@
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// run-rustfix
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struct Foo;
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impl std::ops::Mul for &Foo {
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type Output = Foo;
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fn mul(self, _rhs: Self) -> Self::Output {
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unimplemented!()
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}
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}
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fn main() {
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let ref_mut_foo: &mut Foo = &mut Foo;
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let ref_foo: &Foo = &Foo;
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let owned_foo: Foo = Foo;
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let _ = ref_foo * ref_foo;
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let _ = ref_foo * ref_mut_foo;
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let _ = ref_mut_foo * ref_foo;
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//~^ ERROR cannot multiply
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let _ = ref_mut_foo * ref_mut_foo;
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//~^ ERROR cannot multiply
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let _ = ref_mut_foo * &owned_foo;
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//~^ ERROR cannot multiply
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}
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45
tests/ui/binop/borrow-suggestion-109352.stderr
Normal file
45
tests/ui/binop/borrow-suggestion-109352.stderr
Normal file
@ -0,0 +1,45 @@
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error[E0369]: cannot multiply `&mut Foo` by `&Foo`
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--> $DIR/borrow-suggestion-109352.rs:21:25
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|
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LL | let _ = ref_mut_foo * ref_foo;
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| ----------- ^ ------- &Foo
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| |
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| &mut Foo
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|
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= note: an implementation for `&Foo * &Foo` exists
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help: consider reborrowing this side
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|
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LL | let _ = &*ref_mut_foo * ref_foo;
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| ++
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error[E0369]: cannot multiply `&mut Foo` by `&mut Foo`
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--> $DIR/borrow-suggestion-109352.rs:23:25
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|
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LL | let _ = ref_mut_foo * ref_mut_foo;
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| ----------- ^ ----------- &mut Foo
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| |
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| &mut Foo
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|
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= note: an implementation for `&Foo * &Foo` exists
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help: consider reborrowing both sides
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|
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LL | let _ = &*ref_mut_foo * &*ref_mut_foo;
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| ++ ++
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error[E0369]: cannot multiply `&mut Foo` by `&Foo`
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--> $DIR/borrow-suggestion-109352.rs:25:25
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|
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LL | let _ = ref_mut_foo * &owned_foo;
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| ----------- ^ ---------- &Foo
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| |
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| &mut Foo
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|
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= note: an implementation for `&Foo * &Foo` exists
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help: consider reborrowing this side
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|
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LL | let _ = &*ref_mut_foo * &owned_foo;
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| ++
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error: aborting due to 3 previous errors
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For more information about this error, try `rustc --explain E0369`.
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