time: fix optional fractional seconds range err

The optional fractional seconds overrides any range error
from the second parsing. Instead don't look for optional fractional
seconds if a range error has occured.

Change-Id: I27e0a2432740f6753668bd8833e48b9495bc4036
Reviewed-on: https://go-review.googlesource.com/27590
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/time/format.go

@@ -844,6 +844,7 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
 			sec, value, err = getnum(value, std == stdZeroSecond)
 			if sec < 0 || 60 <= sec {
 				rangeErrString = "second"
+				break
 			}
 			// Special case: do we have a fractional second but no
 			// fractional second in the format?

src/time/format_test.go

@@ -440,6 +440,8 @@ var parseErrorTests = []ParseErrorTest{
 	{RFC3339, "2006-01-02T15:04_abc", `parsing time "2006-01-02T15:04_abc" as "2006-01-02T15:04:05Z07:00": cannot parse "_abc" as ":"`},
 	{RFC3339, "2006-01-02T15:04:05_abc", `parsing time "2006-01-02T15:04:05_abc" as "2006-01-02T15:04:05Z07:00": cannot parse "_abc" as "Z07:00"`},
 	{RFC3339, "2006-01-02T15:04:05Z_abc", `parsing time "2006-01-02T15:04:05Z_abc": extra text: _abc`},
+	// invalid second followed by optional fractional seconds
+	{RFC3339, "2010-02-04T21:00:67.012345678-08:00", "second out of range"},
 }
 
 func TestParseErrors(t *testing.T) {