From 8235b6f8c37ca531279c5da5663120ea4ec8e0b3 Mon Sep 17 00:00:00 2001
From: Jakub Adam Wieczorek <jakub.adam.wieczorek@gmail.com>
Date: Fri, 2 Aug 2019 20:57:29 +0000
Subject: [PATCH] dead_code: Properly inspect fields in struct patterns with
 type relative paths

---
 src/librustc/middle/dead.rs                   |  5 ++--
 ...63151-dead-code-lint-fields-in-patterns.rs | 26 +++++++++++++++++++
 2 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 src/test/ui/type-alias-enum-variants/issue-63151-dead-code-lint-fields-in-patterns.rs

diff --git a/src/librustc/middle/dead.rs b/src/librustc/middle/dead.rs
index 88de77829a6e0..b58c46a4e1354 100644
--- a/src/librustc/middle/dead.rs
+++ b/src/librustc/middle/dead.rs
@@ -269,8 +269,9 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
 
     fn visit_pat(&mut self, pat: &'tcx hir::Pat) {
         match pat.node {
-            PatKind::Struct(hir::QPath::Resolved(_, ref path), ref fields, _) => {
-                self.handle_field_pattern_match(pat, path.res, fields);
+            PatKind::Struct(ref path, ref fields, _) => {
+                let res = self.tables.qpath_res(path, pat.hir_id);
+                self.handle_field_pattern_match(pat, res, fields);
             }
             PatKind::Path(ref qpath @ hir::QPath::TypeRelative(..)) => {
                 let res = self.tables.qpath_res(qpath, pat.hir_id);
diff --git a/src/test/ui/type-alias-enum-variants/issue-63151-dead-code-lint-fields-in-patterns.rs b/src/test/ui/type-alias-enum-variants/issue-63151-dead-code-lint-fields-in-patterns.rs
new file mode 100644
index 0000000000000..66fb8dd0deaf4
--- /dev/null
+++ b/src/test/ui/type-alias-enum-variants/issue-63151-dead-code-lint-fields-in-patterns.rs
@@ -0,0 +1,26 @@
+// check-pass
+
+// Regression test for the issue #63151:
+// Spurious unused field warning when matching variants under a `Self` scope
+//
+// This test checks that the `dead_code` lint properly inspects fields
+// in struct patterns that use a type relative path.
+
+#![deny(dead_code)]
+
+enum Enum {
+    Variant { field: usize }
+}
+
+impl Enum {
+    fn read_field(self) -> usize {
+        match self {
+            Self::Variant { field } => field
+        }
+    }
+}
+
+fn main() {
+    let e = Enum::Variant { field: 42 };
+    println!("{}", e.read_field());
+}