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update E0375 to new format
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mikhail-m1 committed Aug 15, 2016
1 parent e64f688 commit 349f10a
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Showing 2 changed files with 26 additions and 8 deletions.
26 changes: 19 additions & 7 deletions src/librustc_typeck/coherence/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -458,13 +458,25 @@ impl<'a, 'gcx, 'tcx> CoherenceChecker<'a, 'gcx, 'tcx> {
being coerced, none found");
return;
} else if diff_fields.len() > 1 {
span_err!(tcx.sess, span, E0375,
"the trait `CoerceUnsized` may only be implemented \
for a coercion between structures with one field \
being coerced, but {} fields need coercions: {}",
diff_fields.len(), diff_fields.iter().map(|&(i, a, b)| {
format!("{} ({} to {})", fields[i].name, a, b)
}).collect::<Vec<_>>().join(", "));
let item = tcx.map.expect_item(impl_node_id);
let span = if let ItemImpl(_, _, _, Some(ref t), _, _) = item.node {
t.path.span
} else {
tcx.map.span(impl_node_id)
};

let mut err = struct_span_err!(tcx.sess, span, E0375,
"implementing the trait `CoerceUnsized` \
requires multiple coercions");
err.note("`CoerceUnsized` may only be implemented for \
a coercion between structures with one field being coerced");
err.note(&format!("currently, {} fields need coercions: {}",
diff_fields.len(),
diff_fields.iter().map(|&(i, a, b)| {
format!("{} ({} to {})", fields[i].name, a, b)
}).collect::<Vec<_>>().join(", ") ));
err.span_label(span, &format!("requires multiple coercions"));
err.emit();
return;
}

Expand Down
8 changes: 7 additions & 1 deletion src/test/compile-fail/E0375.rs
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,8 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// ignore-tidy-linelength

#![feature(coerce_unsized)]
use std::ops::CoerceUnsized;

Expand All @@ -17,6 +19,10 @@ struct Foo<T: ?Sized, U: ?Sized> {
c: U,
}

impl<T, U> CoerceUnsized<Foo<U, T>> for Foo<T, U> {} //~ ERROR E0375
impl<T, U> CoerceUnsized<Foo<U, T>> for Foo<T, U> {}
//~^ ERROR E0375
//~| NOTE requires multiple coercions
//~| NOTE `CoerceUnsized` may only be implemented for a coercion between structures with one field being coerced
//~| NOTE currently, 2 fields need coercions: b (T to U), c (U to T)

fn main() {}

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