*** a/src/backend/parser/parse_coerce.c
--- b/src/backend/parser/parse_coerce.c
***************
*** 1161,1167 **** select_common_type(ParseState *pstate, List *exprs, const char *context,
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  				/*------
  				  translator: first %s is name of a SQL construct, eg CASE */
! 						 errmsg("%s types %s and %s cannot be matched",
  								context,
  								format_type_be(ptype),
  								format_type_be(ntype)),
--- 1161,1167 ----
  						(errcode(ERRCODE_DATATYPE_MISMATCH),
  				/*------
  				  translator: first %s is name of a SQL construct, eg CASE */
! 						 errmsg("%s types %s and %s cannot be matched. HINT: Postgres casts unknown types to TEXT by default.",
  								context,
  								format_type_be(ptype),
  								format_type_be(ntype)),