fixes #8043

compiler/semcall.nim

@@ -189,15 +189,18 @@ proc presentFailedCandidates(c: PContext, n: PNode, errors: CandidateErrors):
     if err.firstMismatch != 0 and n.len > 1:
       let cond = n.len > 2
       if cond:
-        candidates.add("  first type mismatch at position: " & $err.firstMismatch &
-          "\n  required type: ")
+        candidates.add("  first type mismatch at position: " & $abs(err.firstMismatch))
+        if err.firstMismatch >= 0: candidates.add("\n  required type: ")
+        else: candidates.add("\n  unknown named parameter: " & $n[-err.firstMismatch][0])
       var wanted, got: PType = nil
-      if err.firstMismatch < err.sym.typ.len:
+      if err.firstMismatch < 0:
+        discard
+      elif err.firstMismatch < err.sym.typ.len:
         wanted = err.sym.typ.sons[err.firstMismatch]
         if cond: candidates.add typeToString(wanted)
       else:
         if cond: candidates.add "none"
-      if err.firstMismatch < n.len:
+      if err.firstMismatch > 0 and err.firstMismatch < n.len:
         if cond:
           candidates.add "\n  but expression '"
           candidates.add renderTree(n[err.firstMismatch])

compiler/sigmatch.nim

@@ -2252,11 +2252,13 @@ proc matchesAux(c: PContext, n, nOrig: PNode,
       if n.sons[a].sons[0].kind != nkIdent:
         localError(c.config, n.sons[a].info, "named parameter has to be an identifier")
         m.state = csNoMatch
+        m.firstMismatch = -a
         return
       formal = getSymFromList(m.callee.n, n.sons[a].sons[0].ident, 1)
       if formal == nil:
         # no error message!
         m.state = csNoMatch
+        m.firstMismatch = -a
         return
       if containsOrIncl(marker, formal.position):
         # already in namedParams, so no match
@@ -2274,6 +2276,7 @@ proc matchesAux(c: PContext, n, nOrig: PNode,
                                 n.sons[a].sons[1], n.sons[a].sons[1])
       if arg == nil:
         m.state = csNoMatch
+        m.firstMismatch = a
         return
       checkConstraint(n.sons[a].sons[1])
       if m.baseTypeMatch:

tests/errmsgs/tunknown_named_parameter.nim

@@ -0,0 +1,24 @@
+discard """
+cmd: "nim check $file"
+errormsg: "type mismatch: got <string, set[char], maxsplits: int literal(1)>"
+nimout: '''
+proc rsplit(s: string; sep: string; maxsplit: int = -1): seq[string]
+  first type mismatch at position: 2
+  required type: string
+  but expression '{':'}' is of type: set[char]
+proc rsplit(s: string; sep: char; maxsplit: int = -1): seq[string]
+  first type mismatch at position: 2
+  required type: char
+  but expression '{':'}' is of type: set[char]
+proc rsplit(s: string; seps: set[char] = Whitespace; maxsplit: int = -1): seq[string]
+  first type mismatch at position: 3
+  unknown named parameter: maxsplits
+
+expression: rsplit("abc:def", {':'}, maxsplits = 1)
+'''
+"""
+
+# bug #8043
+
+import strutils
+"abc:def".rsplit({':'}, maxsplits = 1)