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Make diagnostics clearer for ? operators

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This commit is contained in:
Yuki Okushi 2021-06-17 06:35:42 +09:00
parent 78a46efff0
commit 378300a63d
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GPG key ID: DABA5B072961C18A
6 changed files with 53 additions and 5 deletions
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19
compiler/rustc_infer/src/infer/error_reporting/mod.rs
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@ -1971,6 +1971,8 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
trace: TypeTrace<'tcx>,
terr: &TypeError<'tcx>,
) -> DiagnosticBuilder<'tcx> {
use crate::traits::ObligationCauseCode::MatchExpressionArm;
debug!("report_and_explain_type_error(trace={:?}, terr={:?})", trace, terr);
let span = trace.cause.span(self.tcx);
@ -2013,6 +2015,19 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
_ => {}
}
}
if let MatchExpressionArm(box MatchExpressionArmCause { source, .. }) =
trace.cause.code
{
if let hir::MatchSource::TryDesugar = source {
if let Some((expected_ty, found_ty)) = self.values_str(trace.values) {
err.note(&format!(
"`?` operator cannot convert from `{}` to `{}`",
found_ty.content(),
expected_ty.content(),
));
}
}
}
err
}
FailureCode::Error0644(failure_str) => {
@ -2585,9 +2600,7 @@ impl<'tcx> ObligationCauseExt<'tcx> for ObligationCause<'tcx> {
CompareImplTypeObligation { .. } => Error0308("type not compatible with trait"),
MatchExpressionArm(box MatchExpressionArmCause { source, .. }) => {
Error0308(match source {
hir::MatchSource::TryDesugar => {
"try expression alternatives have incompatible types"
}
hir::MatchSource::TryDesugar => "`?` operator has incompatible types",
_ => "`match` arms have incompatible types",
})
}