Fix parsing field to sink forwarding

Author: bbannier

Cargo.lock

@@ -127,6 +127,10 @@ public type X = unit {
     sink data;
     };
 
+type HeuristicContent = unit {
+    : bytes &eod -> other.sink_;
+};
+
 # Attributes on unit switch.
 type X = unit {
     switch ( 1 ) {

corpus/unit.spicy

@@ -150,6 +150,10 @@ public type X = unit {
     sink data;
 };
 
+type HeuristicContent = unit {
+    : bytes &eod -> other.sink_;
+};
+
 # Attributes on unit switch.
 type X = unit {
     switch (1) {

corpus/unit.spicy.expected

@@ -402,7 +402,8 @@
 ; Enforce spaces around `->` in field sink syntax.
 (field_decl
   "->" @prepend_space @append_space
-  (sink)
+  .
+  (expression)
 )
 
 (field_decl