Added error handling for using auto in a generic constraint

src/frontend/compiler.nim

@@ -1431,6 +1431,8 @@ proc unpackGenerics(self: Compiler, condition: Expression, list: var seq[tuple[m
     case condition.kind:
         of identExpr:
             list.add((accept, self.inferOrError(condition)))
+            if list[^1].kind.kind == Auto:
+                self.error("automatic types cannot be used within generics", condition)
         of binaryExpr:
             let condition = BinaryExpr(condition)
             case condition.operator.lexeme: