4 files changed, 37 insertions, 2 deletions

diff --git a/crates/parser/src/event.rs b/crates/parser/src/event.rs
index a7d06a815..903668892 100644
--- a/crates/parser/src/event.rs
+++ b/crates/parser/src/event.rs
@@ -38,14 +38,16 @@ pub(crate) enum Event {
     ///
     /// The events for it would look like this:
     ///
-    ///
+    /// ```text
     /// START(PATH) IDENT('foo') FINISH START(PATH) T![::] IDENT('bar') FINISH
     ///       |                          /\
     ///       |                          |
     ///       +------forward-parent------+
+    /// ```
     ///
     /// And the tree would look like this
     ///
+    /// ```text
     ///    +--PATH---------+
     ///    |   |           |
     ///    |   |           |
@@ -54,6 +56,7 @@ pub(crate) enum Event {
     ///   PATH
     ///    |
     ///   'foo'
+    /// ```
     ///
     /// See also `CompletedMarker::precede`.
     Start {
diff --git a/crates/parser/src/grammar/items.rs b/crates/parser/src/grammar/items.rs
index 1d894e907..adec74ef3 100644
--- a/crates/parser/src/grammar/items.rs
+++ b/crates/parser/src/grammar/items.rs
@@ -83,6 +83,7 @@ pub(super) fn item_or_macro(p: &mut Parser, stop_on_r_curly: bool) {
     }
 }
 
+/// Try to parse an item, completing `m` in case of success.
 pub(super) fn maybe_item(p: &mut Parser, m: Marker) -> Result<(), Marker> {
     // test_err pub_expr
     // fn foo() { pub 92; }
@@ -143,6 +144,33 @@ pub(super) fn maybe_item(p: &mut Parser, m: Marker) -> Result<(), Marker> {
                     has_mods = true;
                 }
             }
+            T![async] => {
+                // test default_async_fn
+                // impl T for Foo {
+                //     default async fn foo() {}
+                // }
+
+                // test default_async_unsafe_fn
+                // impl T for Foo {
+                //     default async unsafe fn foo() {}
+                // }
+                let mut maybe_fn = p.nth(2);
+                let is_unsafe = if matches!(maybe_fn, T![unsafe]) {
+                    maybe_fn = p.nth(3);
+                    true
+                } else {
+                    false
+                };
+
+                if matches!(maybe_fn, T![fn]) {
+                    p.bump_remap(T![default]);
+                    p.bump(T![async]);
+                    if is_unsafe {
+                        p.bump(T![unsafe])
+                    }
+                    has_mods = true;
+                }
+            }
             _ => (),
         }
     }
diff --git a/crates/parser/src/grammar/items/consts.rs b/crates/parser/src/grammar/items/consts.rs
index eb7d1f828..12130df40 100644
--- a/crates/parser/src/grammar/items/consts.rs
+++ b/crates/parser/src/grammar/items/consts.rs
@@ -13,7 +13,7 @@ pub(super) fn konst(p: &mut Parser, m: Marker) {
 fn const_or_static(p: &mut Parser, m: Marker, kw: SyntaxKind, def: SyntaxKind) {
     assert!(p.at(kw));
     p.bump(kw);
-    p.eat(T![mut]); // FIXME: validator to forbid const mut
+    p.eat(T![mut]);
 
     // Allow `_` in place of an identifier in a `const`.
     let is_const_underscore = kw == T![const] && p.eat(T![_]);
diff --git a/crates/parser/src/grammar/items/traits.rs b/crates/parser/src/grammar/items/traits.rs
index d076974ed..d3327271c 100644
--- a/crates/parser/src/grammar/items/traits.rs
+++ b/crates/parser/src/grammar/items/traits.rs
@@ -40,6 +40,10 @@ pub(super) fn impl_(p: &mut Parser) {
         type_params::opt_generic_param_list(p);
     }
 
+    // test impl_def_const
+    // impl const Send for X {}
+    p.eat(T![const]);
+
     // FIXME: never type
     // impl ! {}