Optional patterns in fn types

3 files changed, 25 insertions, 11 deletions

diff --git a/src/grammar/params.rs b/src/grammar/params.rs
index c7f17168b..32e905cb2 100644
--- a/src/grammar/params.rs
+++ b/src/grammar/params.rs
@@ -33,12 +33,6 @@ impl Flavor {
             _ => true,
         }
     }
-    fn pattern_required(self) -> bool {
-        match self {
-            Flavor::OptionalPattern => false,
-            _ => true,
-        }
-    }
 }
 
 fn list_(p: &mut Parser, flavor: Flavor) {
@@ -65,9 +59,29 @@ fn list_(p: &mut Parser, flavor: Flavor) {
 
 fn value_parameter(p: &mut Parser, flavor: Flavor) {
     let m = p.start();
-    patterns::pattern(p);
-    if p.at(COLON) || flavor.type_required() {
-        types::ascription(p)
+    match flavor {
+        Flavor::OptionalType | Flavor::Normal => {
+            patterns::pattern(p);
+            if p.at(COLON) || flavor.type_required() {
+                types::ascription(p)
+            }
+        },
+        // test value_parameters_no_patterns
+        // type F = Box<Fn(a: i32, &b: &i32, &mut c: &i32, ())>;
+        Flavor::OptionalPattern => {
+            let la0 = p.current();
+            let la1 = p.nth(1);
+            let la2 = p.nth(2);
+            let la3 = p.nth(3);
+            if la0 == IDENT && la1 == COLON
+                || la0 == AMP && la1 == IDENT && la2 == COLON
+                || la0 == AMP && la1 == MUT_KW && la2 == IDENT && la3 == COLON {
+                patterns::pattern(p);
+                types::ascription(p);
+            } else {
+                types::type_(p);
+            }
+        },
     }
     m.complete(p, PARAM);
 }
diff --git a/src/grammar/paths.rs b/src/grammar/paths.rs
index 6d406645f..c277e2a6b 100644
--- a/src/grammar/paths.rs
+++ b/src/grammar/paths.rs
@@ -75,7 +75,7 @@ fn path_generic_args(p: &mut Parser, mode: Mode) {
             // test path_fn_trait_args
             // type F = Box<Fn(x: i32) -> ()>;
             if p.at(L_PAREN) {
-                params::param_list(p);
+                params::param_list_opt_patterns(p);
                 fn_ret_type(p);
             } else {
                 type_args::type_arg_list(p, false)
diff --git a/src/grammar/types.rs b/src/grammar/types.rs
index 03a087acd..c8ced3d28 100644
--- a/src/grammar/types.rs
+++ b/src/grammar/types.rs
@@ -166,7 +166,7 @@ fn fn_pointer_type(p: &mut Parser) {
         return;
     }
 
-    params::param_list(p);
+    params::param_list_opt_patterns(p);
     // test fn_pointer_type_with_ret
     // type F = fn() -> ();
     fn_ret_type(p);