fixes yet another gensym regression (#12145)

tests/template/mtempl5.nim

@@ -7,4 +7,18 @@ template templ*(): int =
   bind gx, gy
   gx + gy
 
+import json
+
+const
+  codeField = "foobar"
+  messageField = "more"
+
+template trap*(path: string, body: untyped): untyped =
+  #bind codeField, messageField
+  try:
+    body
+  except:
+    let msg = getCurrentExceptionMsg()
+    #debug "Error occurred within RPC ", path = path, errorMessage = msg
+    result = %*{codeField: "SERVER_ERROR", messageField: msg}
 

tests/template/template_issues.nim

@@ -7,6 +7,7 @@ a
 hi
 Hello, World!
 (e: 42)
+hey
 '''
 """
 
@@ -235,3 +236,12 @@ var
   x = X.fails(42)
 
 echo x
+
+import mtempl5
+
+
+proc foo(): auto =
+  trap "foo":
+    echo "hey"
+
+discard foo()