test: simple termParser attribute test

tests/playground/termParserAttr.lean

@@ -0,0 +1,26 @@
+import Init.Lean
+open Lean
+open Lean.Elab
+
+def run (input : String) (failIff : Bool := true) : MetaIO Unit :=
+do env  ← MetaIO.getEnv;
+   opts ← MetaIO.getOptions;
+   let (env, messages) := process input env opts;
+   messages.toList.forM $ fun msg => IO.println msg;
+   when (failIff && messages.hasErrors) $ throw (IO.userError "errors have been found");
+   when (!failIff && !messages.hasErrors) $ throw (IO.userError "there are no errors");
+   pure ()
+
+open Lean.Parser
+@[termParser] def tst := parser! "(|" >> termParser >> "|)"
+
+@[termParser] def boo : ParserDescr :=
+ParserDescr.node `boo
+  (ParserDescr.andthen
+    (ParserDescr.symbol "[|" 0)
+    (ParserDescr.andthen
+      (ParserDescr.parser `term 0)
+      (ParserDescr.symbol "|]" 0)))
+
+#eval run "#check [| @id.{1} Nat |]"
+#eval run "#check (| id 1 |)"