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fix: diagnostic for casting reference to slice

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fixes: #118790
This commit is contained in:
Veera 2023-12-20 20:35:53 -05:00
parent 5ac4c8a63e
commit e6e195e27e
3 changed files with 39 additions and 18 deletions
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30
compiler/rustc_hir_typeck/src/cast.rs
View File

@ -576,25 +576,19 @@ fn report_cast_to_unsized_type(&self, fcx: &FnCtxt<'a, 'tcx>) -> ErrorGuaranteed
match self.expr_ty.kind() { match self.expr_ty.kind() {
ty::Ref(_, _, mt) => { ty::Ref(_, _, mt) => {
let mtstr = mt.prefix_str(); let mtstr = mt.prefix_str();
if self.cast_ty.is_trait() { match fcx.tcx.sess.source_map().span_to_snippet(self.cast_span) {
match fcx.tcx.sess.source_map().span_to_snippet(self.cast_span) { Ok(s) => {
Ok(s) => { err.span_suggestion(
err.span_suggestion( self.cast_span,
self.cast_span, "try casting to a reference instead",
"try casting to a reference instead", format!("&{mtstr}{s}"),
format!("&{mtstr}{s}"), Applicability::MachineApplicable,
Applicability::MachineApplicable, );
); }
} Err(_) => {
Err(_) => { let msg = format!("did you mean `&{mtstr}{tstr}`?");
let msg = format!("did you mean `&{mtstr}{tstr}`?"); err.span_help(self.cast_span, msg);
err.span_help(self.cast_span, msg);
}
} }
} else {
let msg =
format!("consider using an implicit coercion to `&{mtstr}{tstr}` instead");
err.span_help(self.span, msg);
} }
} }
ty::Adt(def, ..) if def.is_box() => { ty::Adt(def, ..) if def.is_box() => {

8
tests/ui/cast/cast-to-slice.rs Normal file
View File

@ -0,0 +1,8 @@
fn main() {
"example".as_bytes() as [char];
//~^ ERROR cast to unsized type
let arr: &[u8] = &[0, 2, 3];
arr as [char];
//~^ ERROR cast to unsized type
}

19
tests/ui/cast/cast-to-slice.stderr Normal file
View File

@ -0,0 +1,19 @@
error[E0620]: cast to unsized type: `&[u8]` as `[char]`
--> $DIR/cast-to-slice.rs:2:5
|
LL | "example".as_bytes() as [char];
| ^^^^^^^^^^^^^^^^^^^^^^^^------
| |
| help: try casting to a reference instead: `&[char]`
error[E0620]: cast to unsized type: `&[u8]` as `[char]`
--> $DIR/cast-to-slice.rs:6:5
|
LL | arr as [char];
| ^^^^^^^------
| |
| help: try casting to a reference instead: `&[char]`
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0620`.