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Emit more specific diagnostics when enums fail to cast with as

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This commit is contained in:
Gurinder Singh 2024-02-09 09:19:44 +05:30
parent 384b02c082
commit 6e37f955e5
5 changed files with 110 additions and 4 deletions
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26
compiler/rustc_hir_typeck/src/cast.rs
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@ -448,13 +448,35 @@ impl<'a, 'tcx> CastCheck<'tcx> {
);
}
}
let msg = "an `as` expression can only be used to convert between primitive \
types or to coerce to a specific trait object";
let (msg, note) = if let ty::Adt(adt, _) = self.expr_ty.kind()
&& adt.is_enum()
&& self.cast_ty.is_numeric()
{
(
"an `as` expression can be used to convert enum types to numeric \
types only if the enum type is unit-only or field-less",
Some(
"see https://doc.rust-lang.org/reference/items/enumerations.html#casting for more information",
),
)
} else {
(
"an `as` expression can only be used to convert between primitive \
types or to coerce to a specific trait object",
None,
)
};
if label {
err.span_label(self.span, msg);
} else {
err.note(msg);
}
if let Some(note) = note {
err.note(note);
}
} else {
err.span_label(self.span, "invalid cast");
}