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Rollup merge of rust-lang#89965 - JohnTitor:fix-let-else-ice-with-ref…
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…-mut, r=petrochenkov

Fix ICE with `let...else` and `ref mut`

Fixes rust-lang#89960, opened for review.
I'm not satisfied with the current diagnostics, any ideas?
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matthiaskrgr authored Oct 17, 2021
2 parents 84be385 + bf7c32a commit ef27866
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Showing 3 changed files with 27 additions and 8 deletions.
16 changes: 8 additions & 8 deletions compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -45,12 +45,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
let item_msg;
let reason;
let mut opt_source = None;
let access_place_desc = self.describe_place(access_place.as_ref());
let access_place_desc = self.describe_any_place(access_place.as_ref());
debug!("report_mutability_error: access_place_desc={:?}", access_place_desc);

match the_place_err {
PlaceRef { local, projection: [] } => {
item_msg = format!("`{}`", access_place_desc.unwrap());
item_msg = access_place_desc;
if access_place.as_local().is_some() {
reason = ", as it is not declared as mutable".to_string();
} else {
Expand Down Expand Up @@ -83,7 +83,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
// If we deref an immutable ref then the suggestion here doesn't help.
return;
} else {
item_msg = format!("`{}`", access_place_desc.unwrap());
item_msg = access_place_desc;
if self.is_upvar_field_projection(access_place.as_ref()).is_some() {
reason = ", as it is not declared as mutable".to_string();
} else {
Expand All @@ -96,17 +96,17 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
PlaceRef { local, projection: [ProjectionElem::Deref] }
if self.body.local_decls[local].is_ref_for_guard() =>
{
item_msg = format!("`{}`", access_place_desc.unwrap());
item_msg = access_place_desc;
reason = ", as it is immutable for the pattern guard".to_string();
}
PlaceRef { local, projection: [ProjectionElem::Deref] }
if self.body.local_decls[local].is_ref_to_static() =>
{
if access_place.projection.len() == 1 {
item_msg = format!("immutable static item `{}`", access_place_desc.unwrap());
item_msg = format!("immutable static item {}", access_place_desc);
reason = String::new();
} else {
item_msg = format!("`{}`", access_place_desc.unwrap());
item_msg = access_place_desc;
let local_info = &self.body.local_decls[local].local_info;
if let Some(box LocalInfo::StaticRef { def_id, .. }) = *local_info {
let static_name = &self.infcx.tcx.item_name(def_id);
Expand All @@ -121,7 +121,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
&& proj_base.is_empty()
&& !self.upvars.is_empty()
{
item_msg = format!("`{}`", access_place_desc.unwrap());
item_msg = access_place_desc;
debug_assert!(
self.body.local_decls[ty::CAPTURE_STRUCT_LOCAL].ty.is_region_ptr()
);
Expand All @@ -147,7 +147,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
});
let pointer_type = source.describe_for_immutable_place(self.infcx.tcx);
opt_source = Some(source);
if let Some(desc) = access_place_desc {
if let Some(desc) = self.describe_place(access_place.as_ref()) {
item_msg = format!("`{}`", desc);
reason = match error_access {
AccessKind::Mutate => format!(", which is behind {}", pointer_type),
Expand Down
7 changes: 7 additions & 0 deletions src/test/ui/let-else/issue-89960.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
#![feature(let_else)]

fn main() {
// FIXME: more precise diagnostics
let Some(ref mut meow) = Some(()) else { return };
//~^ ERROR: cannot borrow value as mutable, as `val` is not declared as mutable
}
12 changes: 12 additions & 0 deletions src/test/ui/let-else/issue-89960.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
error[E0596]: cannot borrow value as mutable, as `val` is not declared as mutable
--> $DIR/issue-89960.rs:5:14
|
LL | let Some(ref mut meow) = Some(()) else { return };
| ---------^^^^^^^^^^^^-----------------------------
| | |
| | cannot borrow as mutable
| help: consider changing this to be mutable: `mut val`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0596`.

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