| use crate::structured_errors::StructuredDiagnostic; |
| use rustc_errors::{DiagnosticBuilder, DiagnosticId}; |
| use rustc_middle::ty::{Ty, TypeFoldable}; |
| use rustc_session::Session; |
| use rustc_span::Span; |
| |
| pub struct SizedUnsizedCast<'tcx> { |
| pub sess: &'tcx Session, |
| pub span: Span, |
| pub expr_ty: Ty<'tcx>, |
| pub cast_ty: String, |
| } |
| |
| impl<'tcx> StructuredDiagnostic<'tcx> for SizedUnsizedCast<'tcx> { |
| fn session(&self) -> &Session { |
| self.sess |
| } |
| |
| fn code(&self) -> DiagnosticId { |
| rustc_errors::error_code!(E0607) |
| } |
| |
| fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx> { |
| if self.expr_ty.references_error() { |
| self.sess.diagnostic().struct_dummy() |
| } else { |
| self.sess.struct_span_fatal_with_code( |
| self.span, |
| &format!( |
| "cannot cast thin pointer `{}` to fat pointer `{}`", |
| self.expr_ty, self.cast_ty |
| ), |
| self.code(), |
| ) |
| } |
| } |
| |
| fn diagnostic_extended(&self, mut err: DiagnosticBuilder<'tcx>) -> DiagnosticBuilder<'tcx> { |
| err.help( |
| "Thin pointers are \"simple\" pointers: they are purely a reference to a |
| memory address. |
| |
| Fat pointers are pointers referencing \"Dynamically Sized Types\" (also |
| called DST). DST don't have a statically known size, therefore they can |
| only exist behind some kind of pointers that contain additional |
| information. Slices and trait objects are DSTs. In the case of slices, |
| the additional information the fat pointer holds is their size. |
| |
| To fix this error, don't try to cast directly between thin and fat |
| pointers. |
| |
| For more information about casts, take a look at The Book: |
| https://doc.rust-lang.org/reference/expressions/operator-expr.html#type-cast-expressions", |
| ); |
| err |
| } |
| } |