Replace Errorf with explicit construction where practical.

base.go

@@ -103,7 +103,7 @@ func (r *Request) ParamString() string { return string(r.params) }
 
 // ErrInvalidVersion is returned by ParseRequests if one or more of the
 // requests in the input has a missing or invalid version marker.
-var ErrInvalidVersion = Errorf(code.InvalidRequest, "incorrect version marker")
+var ErrInvalidVersion error = &Error{Code: code.InvalidRequest, Message: "incorrect version marker"}
 
 // ParseRequests parses a single request or a batch of requests from JSON.
 //

client.go

@@ -421,7 +421,7 @@ func (c *Client) marshalParams(ctx context.Context, method string, params interf
  if len(pbits) == 0 || (pbits[0] != '[' && pbits[0] != '{' && !isNull(pbits)) {
  // JSON-RPC requires that if parameters are provided at all, they are
  // an array or an object.
- return nil, Errorf(code.InvalidRequest, "invalid parameters: array or object required")
+ return nil, &Error{Code: code.InvalidRequest, Message: "invalid parameters: array or object required"}
  }
  bits, err := c.enctx(ctx, method, pbits)
  if err != nil {

server.go

@@ -286,7 +286,7 @@ func (s *Server) checkAndAssign(next jmessages) tasks {
  } else if !s.versionOK(req.V) {
  t.err = ErrInvalidVersion
  } else if req.M == "" {
- t.err = Errorf(code.InvalidRequest, "empty method name")
+ t.err = &Error{Code: code.InvalidRequest, Message: "empty method name"}
  } else if s.setContext(t, id) {
  t.m = s.assign(t.ctx, req.M)
  if t.m == nil {
@@ -615,7 +615,7 @@ func (s *Server) read(ch receiver) {
  } else if derr != nil { // parse failure; report and continue
  s.pushError(derr)
  } else if len(in) == 0 {
- s.pushError(Errorf(code.InvalidRequest, "empty request batch"))
+ s.pushError(&Error{Code: code.InvalidRequest, Message: "empty request batch"})
  } else {
  s.log("Received request batch of size %d (qlen=%d)", len(in), s.inq.Len())
  s.inq.PushBack(in)