From a398994cb214c9ba022cb8e6cd97c3fee4bca6ac Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Esteban=20K=C3=BCber?= Date: Tue, 26 Jan 2021 16:53:56 -0800 Subject: [PATCH] Account for existing `_` field pattern when suggesting `..` Follow up to #80017. --- compiler/rustc_typeck/src/check/pat.rs | 22 +++++++++++++------ .../ui/pattern/pat-tuple-underfield.stderr | 4 ++-- 2 files changed, 17 insertions(+), 9 deletions(-) diff --git a/compiler/rustc_typeck/src/check/pat.rs b/compiler/rustc_typeck/src/check/pat.rs index 79234f076acd1..12256058b8715 100644 --- a/compiler/rustc_typeck/src/check/pat.rs +++ b/compiler/rustc_typeck/src/check/pat.rs @@ -1041,12 +1041,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { vec![(left, "(".to_string()), (right.shrink_to_hi(), ")".to_string())], Applicability::MachineApplicable, ); - } else if fields.len() > subpats.len() { - let after_fields_span = if pat_span == DUMMY_SP { - pat_span - } else { - pat_span.with_hi(pat_span.hi() - BytePos(1)).shrink_to_hi() - }; + } else if fields.len() > subpats.len() && pat_span != DUMMY_SP { + let after_fields_span = pat_span.with_hi(pat_span.hi() - BytePos(1)).shrink_to_hi(); let all_fields_span = match subpats { [] => after_fields_span, [field] => field.span, @@ -1055,7 +1051,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { // Check if all the fields in the pattern are wildcards. let all_wildcards = subpats.iter().all(|pat| matches!(pat.kind, PatKind::Wild)); + let first_tail_wildcard = + subpats.iter().enumerate().fold(None, |acc, (pos, pat)| match (acc, &pat.kind) { + (None, PatKind::Wild) => Some(pos), + (Some(_), PatKind::Wild) => acc, + _ => None, + }); + let tail_span = match first_tail_wildcard { + None => after_fields_span, + Some(0) => subpats[0].span.to(after_fields_span), + Some(pos) => subpats[pos - 1].span.shrink_to_hi().to(after_fields_span), + }; + // FIXME: heuristic-based suggestion to check current types for where to add `_`. let mut wildcard_sugg = vec!["_"; fields.len() - subpats.len()].join(", "); if !subpats.is_empty() { wildcard_sugg = String::from(", ") + &wildcard_sugg; @@ -1080,7 +1088,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { ); } else { err.span_suggestion_verbose( - after_fields_span, + tail_span, "use `..` to ignore the rest of the fields", String::from(", .."), Applicability::MaybeIncorrect, diff --git a/src/test/ui/pattern/pat-tuple-underfield.stderr b/src/test/ui/pattern/pat-tuple-underfield.stderr index 76323d9a7bf56..70c21dbafe9fc 100644 --- a/src/test/ui/pattern/pat-tuple-underfield.stderr +++ b/src/test/ui/pattern/pat-tuple-underfield.stderr @@ -122,8 +122,8 @@ LL | Point4( a , _ , _, _) => {} | ^^^^^^ help: use `..` to ignore the rest of the fields | -LL | Point4( a , _ , ..) => {} - | ^^^^ +LL | Point4( a, ..) => {} + | ^^^^ error: aborting due to 8 previous errors