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Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_typeck/src/structured_errors/sized_unsized_cast.rs | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/compiler/rustc_typeck/src/structured_errors/sized_unsized_cast.rs b/compiler/rustc_typeck/src/structured_errors/sized_unsized_cast.rs new file mode 100644 index 000000000..bb6088054 --- /dev/null +++ b/compiler/rustc_typeck/src/structured_errors/sized_unsized_cast.rs @@ -0,0 +1,62 @@ +use crate::structured_errors::StructuredDiagnostic; +use rustc_errors::{DiagnosticBuilder, DiagnosticId, ErrorGuaranteed}; +use rustc_middle::ty::{Ty, TypeVisitable}; +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, ErrorGuaranteed> { + let mut err = self.sess.struct_span_err_with_code( + self.span, + &format!( + "cannot cast thin pointer `{}` to fat pointer `{}`", + self.expr_ty, self.cast_ty + ), + self.code(), + ); + + if self.expr_ty.references_error() { + err.downgrade_to_delayed_bug(); + } + + err + } + + fn diagnostic_extended( + &self, + mut err: DiagnosticBuilder<'tcx, ErrorGuaranteed>, + ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { + 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 + } +} |