From 253a18f93893ffa0e2804937c913fed84df5f8d3 Mon Sep 17 00:00:00 2001
From: Dylan MacKenzie <ecstaticmorse@gmail.com>
Date: Sat, 14 Sep 2019 15:59:24 -0700
Subject: Allow an underscore as the identifier in `const` items

---
 crates/ra_parser/src/grammar/items.rs        |  2 +-
 crates/ra_parser/src/grammar/items/consts.rs | 11 ++++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

(limited to 'crates/ra_parser/src/grammar')

diff --git a/crates/ra_parser/src/grammar/items.rs b/crates/ra_parser/src/grammar/items.rs
index eff9d67e4..4dd80d443 100644
--- a/crates/ra_parser/src/grammar/items.rs
+++ b/crates/ra_parser/src/grammar/items.rs
@@ -258,7 +258,7 @@ fn items_without_modifiers(p: &mut Parser, m: Marker) -> Result<(), Marker> {
         }
         T![enum] => nominal::enum_def(p, m),
         T![use] => use_item::use_item(p, m),
-        T![const] if (la == IDENT || la == T![mut]) => consts::const_def(p, m),
+        T![const] if (la == IDENT || la == T![_] || la == T![mut]) => consts::const_def(p, m),
         T![static] => consts::static_def(p, m),
         // test extern_block
         // extern {}
diff --git a/crates/ra_parser/src/grammar/items/consts.rs b/crates/ra_parser/src/grammar/items/consts.rs
index e11546333..63e0e6e0c 100644
--- a/crates/ra_parser/src/grammar/items/consts.rs
+++ b/crates/ra_parser/src/grammar/items/consts.rs
@@ -12,7 +12,16 @@ fn const_or_static(p: &mut Parser, m: Marker, kw: SyntaxKind, def: SyntaxKind) {
     assert!(p.at(kw));
     p.bump_any();
     p.eat(T![mut]); // FIXME: validator to forbid const mut
-    name(p);
+
+    // Allow `_` in place of an identifier in a `const`.
+    let is_const_underscore = kw == T![const] && p.eat(T![_]);
+    if !is_const_underscore {
+        name(p);
+    }
+
+    // test_err static_underscore
+    // static _: i32 = 5;
+
     types::ascription(p);
     if p.eat(T![=]) {
         expressions::expr(p);
-- 
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