fixes #13715 (#13716)

* fixes #13715

* fix test

compiler/types.nim

@@ -593,7 +593,10 @@ proc typeToString(typ: PType, prefer: TPreferedDesc = preferName): string =
     of tyUncheckedArray:
       result = "UncheckedArray[" & typeToString(t[0]) & ']'
     of tySequence:
-      result = "seq[" & typeToString(t[0]) & ']'
+      if t.sym != nil and prefer != preferResolved:
+        result = t.sym.name.s
+      else:
+        result = "seq[" & typeToString(t[0]) & ']'
     of tyOpt:
       result = "opt[" & typeToString(t[0]) & ']'
     of tyOrdinal:

tests/errmsgs/t8434.nim

@@ -3,7 +3,7 @@ discard """
   nimout: '''but expected one of:
 proc fun0[T1: int | float | object | array | seq](a1: T1; a2: int)
   first type mismatch at position: 1
-  required type for a1: T1: int or float or object or array or seq[T]
+  required type for a1: T1: int or float or object or array or seq
   but expression 'byte(1)' is of type: byte
 
 expression: fun0(byte(1), 0)

tests/types/tillegalseqrecursion.nim

@@ -0,0 +1,6 @@
+discard """
+  errormsg: "illegal recursion in type 'CyclicSeq'"
+"""
+# issue #13715
+type
+  CyclicSeq = seq[ref CyclicSeq]