4 files changed, 67 insertions, 15 deletions

diff --git a/crates/ra_parser/src/grammar/expressions/atom.rs b/crates/ra_parser/src/grammar/expressions/atom.rs
index f154077a8..b72d2e9e6 100644
--- a/crates/ra_parser/src/grammar/expressions/atom.rs
+++ b/crates/ra_parser/src/grammar/expressions/atom.rs
@@ -336,7 +336,7 @@ fn for_expr(p: &mut Parser, m: Option<Marker>) -> CompletedMarker {
 fn cond(p: &mut Parser) {
     let m = p.start();
     if p.eat(T![let]) {
-        patterns::pattern_list(p);
+        patterns::pattern_top(p);
         p.expect(T![=]);
     }
     expr_no_struct(p);
@@ -430,7 +430,7 @@ fn match_arm(p: &mut Parser) -> BlockLike {
     // }
     attributes::outer_attributes(p);
 
-    patterns::pattern_list_r(p, TokenSet::EMPTY);
+    patterns::pattern_top_r(p, TokenSet::EMPTY);
     if p.at(T![if]) {
         match_guard(p);
     }
diff --git a/crates/ra_parser/src/grammar/params.rs b/crates/ra_parser/src/grammar/params.rs
index 94edc7f35..272661b1d 100644
--- a/crates/ra_parser/src/grammar/params.rs
+++ b/crates/ra_parser/src/grammar/params.rs
@@ -114,9 +114,12 @@ fn value_parameter(p: &mut Parser, flavor: Flavor) {
         // test fn_pointer_param_ident_path
         // type Foo = fn(Bar::Baz);
         // type Qux = fn(baz: Bar::Baz);
+
+        // test fn_pointer_unnamed_arg
+        // type Foo = fn(_: bar);
         Flavor::FnPointer => {
-            if p.at(IDENT) && p.nth(1) == T![:] && !p.nth_at(1, T![::]) {
-                patterns::pattern(p);
+            if (p.at(IDENT) || p.at(UNDERSCORE)) && p.nth(1) == T![:] && !p.nth_at(1, T![::]) {
+                patterns::pattern_single(p);
                 types::ascription(p);
             } else {
                 types::type_(p);
@@ -127,7 +130,7 @@ fn value_parameter(p: &mut Parser, flavor: Flavor) {
         //    let foo = |bar, baz: Baz, qux: Qux::Quux| ();
         // }
         Flavor::Closure => {
-            patterns::pattern(p);
+            patterns::pattern_single(p);
             if p.at(T![:]) && !p.at(T![::]) {
                 types::ascription(p);
             }
diff --git a/crates/ra_parser/src/grammar/patterns.rs b/crates/ra_parser/src/grammar/patterns.rs
index 422a4e3dc..3afbaa82b 100644
--- a/crates/ra_parser/src/grammar/patterns.rs
+++ b/crates/ra_parser/src/grammar/patterns.rs
@@ -11,22 +11,47 @@ pub(crate) fn pattern(p: &mut Parser) {
 }
 
 /// Parses a pattern list separated by pipes `|`
-pub(super) fn pattern_list(p: &mut Parser) {
-    pattern_list_r(p, PAT_RECOVERY_SET)
+pub(super) fn pattern_top(p: &mut Parser) {
+    pattern_top_r(p, PAT_RECOVERY_SET)
+}
+
+pub(crate) fn pattern_single(p: &mut Parser) {
+    pattern_single_r(p, PAT_RECOVERY_SET);
 }
 
 /// Parses a pattern list separated by pipes `|`
 /// using the given `recovery_set`
-pub(super) fn pattern_list_r(p: &mut Parser, recovery_set: TokenSet) {
+pub(super) fn pattern_top_r(p: &mut Parser, recovery_set: TokenSet) {
     p.eat(T![|]);
     pattern_r(p, recovery_set);
+}
 
+/// Parses a pattern list separated by pipes `|`, with no leading `|`,using the
+/// given `recovery_set`
+// test or_pattern
+// fn main() {
+//     match () {
+//         (_ | _) => (),
+//         &(_ | _) => (),
+//         (_ | _,) => (),
+//         [_ | _,] => (),
+//     }
+// }
+fn pattern_r(p: &mut Parser, recovery_set: TokenSet) {
+    let m = p.start();
+    pattern_single_r(p, recovery_set);
+
+    if !p.at(T![|]) {
+        m.abandon(p);
+        return;
+    }
     while p.eat(T![|]) {
-        pattern_r(p, recovery_set);
+        pattern_single_r(p, recovery_set);
     }
+    m.complete(p, OR_PAT);
 }
 
-pub(super) fn pattern_r(p: &mut Parser, recovery_set: TokenSet) {
+fn pattern_single_r(p: &mut Parser, recovery_set: TokenSet) {
     if let Some(lhs) = atom_pat(p, recovery_set) {
         // test range_pat
         // fn main() {
@@ -258,19 +283,41 @@ fn ref_pat(p: &mut Parser) -> CompletedMarker {
     let m = p.start();
     p.bump(T![&]);
     p.eat(T![mut]);
-    pattern(p);
+    pattern_single(p);
     m.complete(p, REF_PAT)
 }
 
 // test tuple_pat
 // fn main() {
 //     let (a, b, ..) = ();
+//     let (a,) = ();
+//     let (..) = ();
+//     let () = ();
 // }
 fn tuple_pat(p: &mut Parser) -> CompletedMarker {
     assert!(p.at(T!['(']));
     let m = p.start();
-    tuple_pat_fields(p);
-    m.complete(p, TUPLE_PAT)
+    p.bump(T!['(']);
+    let mut has_comma = false;
+    let mut has_pat = false;
+    let mut has_rest = false;
+    while !p.at(EOF) && !p.at(T![')']) {
+        has_pat = true;
+        if !p.at_ts(PATTERN_FIRST) {
+            p.error("expected a pattern");
+            break;
+        }
+        has_rest |= p.at(T![..]);
+
+        pattern(p);
+        if !p.at(T![')']) {
+            has_comma = true;
+            p.expect(T![,]);
+        }
+    }
+    p.expect(T![')']);
+
+    m.complete(p, if !has_comma && !has_rest && has_pat { PAREN_PAT } else { TUPLE_PAT })
 }
 
 // test slice_pat
@@ -315,7 +362,7 @@ fn bind_pat(p: &mut Parser, with_at: bool) -> CompletedMarker {
     p.eat(T![mut]);
     name(p);
     if with_at && p.eat(T![@]) {
-        pattern(p);
+        pattern_single(p);
     }
     m.complete(p, BIND_PAT)
 }
@@ -330,6 +377,6 @@ fn box_pat(p: &mut Parser) -> CompletedMarker {
     assert!(p.at(T![box]));
     let m = p.start();
     p.bump(T![box]);
-    pattern(p);
+    pattern_single(p);
     m.complete(p, BOX_PAT)
 }
diff --git a/crates/ra_parser/src/syntax_kind/generated.rs b/crates/ra_parser/src/syntax_kind/generated.rs
index e27b27ffa..1068da0a0 100644
--- a/crates/ra_parser/src/syntax_kind/generated.rs
+++ b/crates/ra_parser/src/syntax_kind/generated.rs
@@ -151,6 +151,8 @@ pub enum SyntaxKind {
     FOR_TYPE,
     IMPL_TRAIT_TYPE,
     DYN_TRAIT_TYPE,
+    OR_PAT,
+    PAREN_PAT,
     REF_PAT,
     BOX_PAT,
     BIND_PAT,