followup #17777: declaredloc field error msgs now work with generics (#18259)

* followup #17777: declaredloc field error msgs now work with generics

* fix tests

* cleanup

compiler/astmsgs.nim

@@ -2,6 +2,11 @@
 import std/strutils
 import options, ast, msgs
 
+proc typSym*(t: PType): PSym =
+  result = t.sym
+  if result == nil and t.kind == tyGenericInst: # this might need to be refined
+    result = t[0].sym
+
 proc addDeclaredLoc*(result: var string, conf: ConfigRef; sym: PSym) =
   result.add " [$1 declared in $2]" % [sym.kind.toHumanStr, toFileLineCol(conf, sym.info)]