fix: impl for type

Author: amaanq

corpus/declarations.txt

@@ -89,6 +89,8 @@ fn foo(#[attr] x: i32, #[attr] x: i64) {}
 
 fn accumulate(self) -> Machine<{State::Accumulate}> {}
 
+fn foo(bar: impl for<'a> Baz<Quux<'a>>) {}
+
 --------------------------------------------------------------------------------
 
 (source_file
@@ -200,6 +202,24 @@ fn accumulate(self) -> Machine<{State::Accumulate}> {}
           (scoped_identifier
             path: (identifier)
             name: (identifier)))))
+    body: (block))
+  (function_item
+    name: (identifier)
+    parameters: (parameters
+      (parameter
+        pattern: (identifier)
+        type: (abstract_type
+          (type_parameters
+            (lifetime
+              (identifier)))
+          trait: (generic_type
+            type: (type_identifier)
+            type_arguments: (type_arguments
+              (generic_type
+                type: (type_identifier)
+                type_arguments: (type_arguments
+                  (lifetime
+                    (identifier)))))))))
     body: (block)))
 
 ================================================================================

grammar.js

@@ -809,6 +809,7 @@ module.exports = grammar({
 
     abstract_type: $ => seq(
       'impl',
+      optional(seq('for', $.type_parameters)),
       field('trait', choice(
         $._type_identifier,
         $.scoped_type_identifier,