compiler/rustc_typeck/src/structured_errors/missing_cast_for_variadic_arg.rs

   1 use crate::structured_errors::StructuredDiagnostic;
   2 use rustc_errors::{Applicability, DiagnosticBuilder, DiagnosticId};
   3 use rustc_middle::ty::{Ty, TypeFoldable};
   4 use rustc_session::Session;
   5 use rustc_span::Span;
   6
   7 pub struct MissingCastForVariadicArg<'tcx> {
   8     pub sess: &'tcx Session,
   9     pub span: Span,
  10     pub ty: Ty<'tcx>,
  11     pub cast_ty: &'tcx 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> {
  24         let mut err = if self.ty.references_error() {
  25             self.sess.diagnostic().struct_dummy()
  26         } else {
  27             self.sess.struct_span_fatal_with_code(
  28                 self.span,
  29                 &format!("can't pass `{}` to variadic function", self.ty),
  30                 self.code(),
  31             )
  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(&self, mut err: DiagnosticBuilder<'tcx>) -> DiagnosticBuilder<'tcx> {
  49         err.note(&format!(
  50             "certain types, like `{}`, must be casted before passing them to a \
  51                 variadic function, because of arcane ABI rules dictated by the C \
  52                 standard",
  53             self.ty
  54         ));
  55
  56         err
  57     }
  58 }