bjoernager/rust
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Reduce diagram mess in 'match arms have incompatible types' error

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This commit is contained in:
David Tolnay 2020-10-22 14:20:02 -07:00
parent f82adf5bdb
commit b0059500f6
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GPG key ID: F9BA143B95FF6D82
4 changed files with 38 additions and 28 deletions
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16
compiler/rustc_infer/src/infer/error_reporting/mod.rs
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@ -619,6 +619,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
scrut_hir_id,
opt_suggest_box_span,
arm_span,
scrut_span,
..
}) => match source {
hir::MatchSource::IfLetDesugar { .. } => {
@ -664,18 +665,29 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
Some(ty::error::ExpectedFound { expected, .. }) => expected,
_ => last_ty,
});
let msg = "`match` arms have incompatible types";
err.span_label(cause.span, msg);
let source_map = self.tcx.sess.source_map();
let mut any_multiline_arm = source_map.is_multiline(arm_span);
if prior_arms.len() <= 4 {
for sp in prior_arms {
any_multiline_arm |= source_map.is_multiline(*sp);
err.span_label(*sp, format!("this is found to be of type `{}`", t));
}
} else if let Some(sp) = prior_arms.last() {
any_multiline_arm |= source_map.is_multiline(*sp);
err.span_label(
*sp,
format!("this and all prior arms are found to be of type `{}`", t),
);
}
let outer_error_span = if any_multiline_arm {
// Cover just `match` and the scrutinee expression, not
// the entire match body, to reduce diagram noise.
cause.span.shrink_to_lo().to(scrut_span)
} else {
cause.span
};
let msg = "`match` arms have incompatible types";
err.span_label(outer_error_span, msg);
if let Some(sp) = semi_span {
err.span_suggestion_short(
sp,