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Add note clarifying why a closure no longer implements a trait

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This commit is contained in:
Roxane 2021-07-07 11:04:28 -04:00
parent 2900c1a5e8
commit 36eb5442bd
7 changed files with 46 additions and 10 deletions
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16
compiler/rustc_typeck/src/check/upvar.rs
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@ -535,6 +535,22 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
captured_names,
));
}
if reasons.contains("closure trait implementation") {
let closure_body_span = self.tcx.hir().span(body_id.hir_id);
let closure_ending_span = self.tcx.sess.source_map().guess_head_span(closure_body_span).shrink_to_lo();
let missing_trait = &reasons[..reasons.find("closure trait implementation").unwrap() - 1];
diagnostics_builder.span_label(closure_ending_span, format!("in Rust 2018, this closure would implement {} as `{}` implements {}, but in Rust 2021, this closure will no longer implement {} as {} does not implement {}",
missing_trait,
self.tcx.hir().name(*var_hir_id),
missing_trait,
missing_trait,
captured_names,
missing_trait,
));
}
}
diagnostics_builder.note("for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/disjoint-capture-in-closures.html>");
let closure_body_span = self.tcx.hir().span(body_id.hir_id);