1 use crate::structured_errors::StructuredDiagnostic;
2 use rustc_errors::{DiagnosticBuilder, DiagnosticId};
3 use rustc_middle::ty::{Ty, TypeFoldable};
4 use rustc_session::Session;
7 pub struct SizedUnsizedCast<'tcx> {
8 pub sess: &'tcx Session,
10 pub expr_ty: Ty<'tcx>,
14 impl<'tcx> StructuredDiagnostic<'tcx> for SizedUnsizedCast<'tcx> {
15 fn session(&self) -> &Session {
19 fn code(&self) -> DiagnosticId {
20 rustc_errors::error_code!(E0607)
23 fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx> {
24 if self.expr_ty.references_error() {
25 self.sess.diagnostic().struct_dummy()
27 self.sess.struct_span_fatal_with_code(
30 "cannot cast thin pointer `{}` to fat pointer `{}`",
31 self.expr_ty, self.cast_ty
38 fn diagnostic_extended(&self, mut err: DiagnosticBuilder<'tcx>) -> DiagnosticBuilder<'tcx> {
40 "Thin pointers are \"simple\" pointers: they are purely a reference to a
43 Fat pointers are pointers referencing \"Dynamically Sized Types\" (also
44 called DST). DST don't have a statically known size, therefore they can
45 only exist behind some kind of pointers that contain additional
46 information. Slices and trait objects are DSTs. In the case of slices,
47 the additional information the fat pointer holds is their size.
49 To fix this error, don't try to cast directly between thin and fat
52 For more information about casts, take a look at The Book:
53 https://doc.rust-lang.org/reference/expressions/operator-expr.html#type-cast-expressions",