diff --git a/src/librustc_mir/borrow_check/conflict_errors.rs b/src/librustc_mir/borrow_check/conflict_errors.rs index 5d0e490ebea5a..77e5ac2f86514 100644 --- a/src/librustc_mir/borrow_check/conflict_errors.rs +++ b/src/librustc_mir/borrow_check/conflict_errors.rs @@ -1140,19 +1140,18 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { bug!("try_report_cannot_return_reference_to_local: not a local") }; match self.body.local_kind(*local) { - LocalKind::ReturnPointer | LocalKind::Temp => { - ( - "temporary value".to_string(), - "temporary value created here".to_string(), - ) - } - LocalKind::Arg => { - ( - "function parameter".to_string(), - "function parameter borrowed here".to_string(), - ) - }, - LocalKind::Var => bug!("local variable without a name"), + LocalKind::ReturnPointer | LocalKind::Temp => ( + "temporary value".to_string(), + "temporary value created here".to_string(), + ), + LocalKind::Arg => ( + "function parameter".to_string(), + "function parameter borrowed here".to_string(), + ), + LocalKind::Var => ( + "local binding".to_string(), + "local binding introduced here".to_string(), + ), } }; diff --git a/src/test/ui/borrowck/return-local-binding-from-desugaring.rs b/src/test/ui/borrowck/return-local-binding-from-desugaring.rs new file mode 100644 index 0000000000000..b2dcd54ec2e90 --- /dev/null +++ b/src/test/ui/borrowck/return-local-binding-from-desugaring.rs @@ -0,0 +1,33 @@ +// To avoid leaking the names of local bindings from expressions like for loops, #60984 +// explicitly ignored them, but an assertion that `LocalKind::Var` *must* have a name would +// trigger an ICE. Before this change, this file's output would be: +// ``` +// error[E0515]: cannot return value referencing local variable `__next` +// --> return-local-binding-from-desugaring.rs:LL:CC +// | +// LL | for ref x in xs { +// | ----- `__next` is borrowed here +// ... +// LL | result +// | ^^^^^^ returns a value referencing data owned by the current function +// ``` +// FIXME: ideally `LocalKind` would carry more information to more accurately explain the problem. + +use std::collections::HashMap; +use std::hash::Hash; + +fn group_by(xs: &mut I, f: F) -> HashMap> +where + I: Iterator, + F: Fn(&I::Item) -> T, + T: Eq + Hash, +{ + let mut result = HashMap::new(); + for ref x in xs { + let key = f(x); + result.entry(key).or_insert(Vec::new()).push(x); + } + result //~ ERROR cannot return value referencing local binding +} + +fn main() {} diff --git a/src/test/ui/borrowck/return-local-binding-from-desugaring.stderr b/src/test/ui/borrowck/return-local-binding-from-desugaring.stderr new file mode 100644 index 0000000000000..293dbe6281313 --- /dev/null +++ b/src/test/ui/borrowck/return-local-binding-from-desugaring.stderr @@ -0,0 +1,12 @@ +error[E0515]: cannot return value referencing local binding + --> $DIR/return-local-binding-from-desugaring.rs:30:5 + | +LL | for ref x in xs { + | -- local binding introduced here +... +LL | result + | ^^^^^^ returns a value referencing data owned by the current function + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0515`.