compiler/rustc_hir_analysis/src/structured_errors/missing_cast_for_variadic_arg.rs

   1 use crate::structured_errors::StructuredDiagnostic;
   2 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticId, ErrorGuaranteed};
   3 use rustc_middle::ty::{Ty, TypeVisitable};
   4 use rustc_session::Session;
   5 use rustc_span::Span;
   6
   7 pub struct MissingCastForVariadicArg<'tcx, 's> {
   8     pub sess: &'tcx Session,
   9     pub span: Span,
  10     pub ty: Ty<'tcx>,
  11     pub cast_ty: &'s str,
  12 }
  13
  14 impl<'tcx> StructuredDiagnostic<'tcx> for MissingCastForVariadicArg<'tcx, '_> {
  15     fn session(&self) -> &Session {
  16         self.sess
  17     }
  18
  19     fn code(&self) -> DiagnosticId {
  20         rustc_errors::error_code!(E0617)
  21     }
  22
  23     fn diagnostic_common(&self) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
  24         let mut err = self.sess.struct_span_err_with_code(
  25             self.span,
  26             &format!("can't pass `{}` to variadic function", self.ty),
  27             self.code(),
  28         );
  29
  30         if self.ty.references_error() {
  31             err.downgrade_to_delayed_bug();
  32         }
  33
  34         if let Ok(snippet) = self.sess.source_map().span_to_snippet(self.span) {
  35             err.span_suggestion(
  36                 self.span,
  37                 &format!("cast the value to `{}`", self.cast_ty),
  38                 format!("{} as {}", snippet, self.cast_ty),
  39                 Applicability::MachineApplicable,
  40             );
  41         } else {
  42             err.help(&format!("cast the value to `{}`", self.cast_ty));
  43         }
  44
  45         err
  46     }
  47
  48     fn diagnostic_extended(
  49         &self,
  50         mut err: DiagnosticBuilder<'tcx, ErrorGuaranteed>,
  51     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
  52         err.note(&format!(
  53             "certain types, like `{}`, must be casted before passing them to a \
  54                 variadic function, because of arcane ABI rules dictated by the C \
  55                 standard",
  56             self.ty
  57         ));
  58
  59         err
  60     }
  61 }