decode_scan, jsonparse: Rework the behavior to make a bit more sense

 - decode_scan: Don't have .Reset() re-play an erroring rune
 - decode_Scan: Have RuneTypeEOF always be zero-width
 - jsonparse: Don't replace syntax errors with RuneTypeEOF if there's no barrier

1 files changed, 8 insertions, 10 deletions

diff --git a/decode.go b/decode.go
index 8514ec4..491971a 100644
--- a/decode.go
+++ b/decode.go
@@ -207,19 +207,17 @@ func (dec *Decoder) DecodeThenEOF(ptr any) (err error) {
 	if err := dec.Decode(ptr); err != nil {
 		return err
 	}
-	c, s, t, _ := dec.io.ReadRuneType()
-	if t != jsonparse.RuneTypeEOF {
-		panic(fmt.Errorf("should not happen: .ReadRuneType returned non-EOF after decode without .Reset being called: %v", t))
-	}
-	if s > 0 {
+	_, _, t, err := dec.io.ReadRuneType()
+	switch t {
+	case jsonparse.RuneTypeError:
 		return &DecodeError{
-			Err: &DecodeSyntaxError{
-				Err:    fmt.Errorf("invalid character %q after top-level value", c),
-				Offset: dec.InputOffset(),
-			},
+			Err: err,
 		}
+	case jsonparse.RuneTypeEOF:
+		return nil
+	default:
+		panic(fmt.Errorf("should not happen: .ReadRuneType returned non-error non-EOF after decode without .Reset being called: '%v'", t))
 	}
-	return nil
 }
 
 // Decode reads the next JSON element from the Decoder's input stream