bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

also detect DerefMut in nested union fields

Browse source
This commit is contained in:
Ralf Jung 2020-08-16 10:24:10 +02:00
parent ec0924f964
commit 44defaea3a
3 changed files with 36 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

29
compiler/rustc_typeck/src/check/place_op.rs
View file

@ -211,13 +211,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
debug!("convert_place_derefs_to_mutable: exprs={:?}", exprs);
// Fix up autoderefs and derefs.
let mut inside_union = false;
for (i, &expr) in exprs.iter().rev().enumerate() {
debug!("convert_place_derefs_to_mutable: i={} expr={:?}", i, expr);
let mut source = self.node_ty(expr.hir_id);
if matches!(expr.kind, hir::ExprKind::Unary(hir::UnOp::UnDeref, _)) {
// Clear previous flag; after a pointer indirection it does not apply any more.
inside_union = false;
}
if source.ty_adt_def().map_or(false, |adt| adt.is_union()) {
inside_union = true;
}
// Fix up the autoderefs. Autorefs can only occur immediately preceding
// overloaded place ops, and will be fixed by them in order to get
// the correct region.
let mut source = self.node_ty(expr.hir_id);
// Do not mutate adjustments in place, but rather take them,
// and replace them after mutating them, to avoid having the
// typeck results borrowed during (`deref_mut`) method resolution.
@ -238,17 +246,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
// If this is a union field, also throw an error.
// Union fields should not get mutable auto-deref'd (see RFC 2514).
if let hir::ExprKind::Field(ref outer_expr, _) = expr.kind {
let ty = self.node_ty(outer_expr.hir_id);
if ty.ty_adt_def().map_or(false, |adt| adt.is_union()) {
let mut err = self.tcx.sess.struct_span_err(
expr.span,
"not automatically applying `DerefMut` on union field",
);
err.help("writing to this field calls the destructor for the old value");
err.help("add an explicit `*` if that is desired, or call `ptr::write` to not run the destructor");
err.emit();
}
if inside_union {
let mut err = self.tcx.sess.struct_span_err(
expr.span,
"not automatically applying `DerefMut` on union field",
);
err.help("writing to this field calls the destructor for the old value");
err.help("add an explicit `*` if that is desired, or call `ptr::write` to not run the destructor");
err.emit();
}
}
}