Extract pattern guard parsing

Author: tomgasson

src/napkin_core.ml

@@ -3095,20 +3095,22 @@ and parseWhileExpression p =
   let loc = mkLoc startPos p.prevEndPos in
   Ast_helper.Exp.while_ ~loc expr1 expr2
 
+and parsePatternGuard p =
+  match p.Parser.token with
+    | When ->
+      Parser.next p;
+      Some (parseExpr ~context:WhenExpr p)
+    | _ ->
+      None
+
 and parsePatternMatchCase p =
   Parser.beginRegion p;
   Parser.leaveBreadcrumb p Grammar.PatternMatchCase;
   match p.Parser.token with
   | Token.Bar ->
     Parser.next p;
     let lhs = parsePattern p in
-    let guard = match p.Parser.token with
-    | When ->
-      Parser.next p;
-      Some (parseExpr ~context:WhenExpr p)
-    | _ ->
-      None
-    in
+    let guard = parsePatternGuard p in
     let () = match p.token with
     | EqualGreater -> Parser.next p
     | _ -> Recover.recoverEqualGreater p