[release-18.0] evalengine: Misc bugs (#14351) (#14354)

Co-authored-by: vitess-bot[bot] <108069721+vitess-bot[bot]@users.noreply.github.com>

go/mysql/datetime/datetime.go

@@ -244,12 +244,12 @@ func (d Date) Hash(h *vthash.Hasher) {
 	h.Write8(d.day)
 }
 
-func (dt Date) Weekday() time.Weekday {
-	return dt.ToStdTime(time.Local).Weekday()
+func (d Date) Weekday() time.Weekday {
+	return d.ToStdTime(time.Local).Weekday()
 }
 
-func (dt Date) Yearday() int {
-	return dt.ToStdTime(time.Local).YearDay()
+func (d Date) Yearday() int {
+	return d.ToStdTime(time.Local).YearDay()
 }
 
 func (d Date) ISOWeek() (int, int) {
@@ -406,7 +406,19 @@ func (t Time) ToDuration() time.Duration {
 }
 
 func (t Time) toStdTime(year int, month time.Month, day int, loc *time.Location) (out time.Time) {
-	return time.Date(year, month, day, 0, 0, 0, 0, loc).Add(t.ToDuration())
+	hours := t.Hour()
+	minutes := t.Minute()
+	secs := t.Second()
+	nsecs := t.Nanosecond()
+
+	if t.Neg() {
+		hours = -hours
+		minutes = -minutes
+		secs = -secs
+		nsecs = -nsecs
+	}
+
+	return time.Date(year, month, day, hours, minutes, secs, nsecs, loc)
 }
 
 func (t Time) ToStdTime(loc *time.Location) (out time.Time) {

go/mysql/datetime/time_zone_test.go

@@ -18,10 +18,50 @@ package datetime
 
 import (
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
+func TestDST(t *testing.T) {
+	testCases := []struct {
+		time     Time
+		year     int
+		month    time.Month
+		day      int
+		tz       string
+		expected string
+	}{
+		{
+			time: Time{hour: 130, minute: 34, second: 58},
+			year: 2023, month: 10, day: 24,
+			tz:       "Europe/Madrid",
+			expected: "2023-10-29T10:34:58+01:00",
+		},
+		{
+			time: Time{hour: 130, minute: 34, second: 58},
+			year: 2023, month: 10, day: 29,
+			tz:       "Europe/Madrid",
+			expected: "2023-11-03T10:34:58+01:00",
+		},
+		{
+			time: Time{hour: 130 | negMask, minute: 34, second: 58},
+			year: 2023, month: 11, day: 03,
+			tz:       "Europe/Madrid",
+			expected: "2023-10-28T13:25:02+02:00",
+		},
+	}
+
+	for _, tc := range testCases {
+		tz, err := ParseTimeZone(tc.tz)
+		require.NoError(t, err)
+
+		got := tc.time.toStdTime(tc.year, tc.month, tc.day, tz)
+		assert.Equal(t, tc.expected, got.Format(time.RFC3339))
+	}
+}
+
 func TestParseTimeZone(t *testing.T) {
 	testCases := []struct {
 		tz   string

go/vt/vtgate/evalengine/compiler_asm.go

@@ -2042,6 +2042,7 @@ func (asm *assembler) Fn_FROM_BASE64(t sqltypes.Type) {
 		}
 		str.tt = int16(t)
 		str.bytes = decoded
+		str.col = collationBinary
 		return 1
 	}, "FN FROM_BASE64 VARCHAR(SP-1)")
 }

go/vt/vtgate/evalengine/fn_numeric.go

@@ -1549,7 +1549,7 @@ func (expr *builtinConv) compile(c *compiler) (ctype, error) {
 		c.asm.Fn_CONV_bu(3, 2)
 	}
 
-	col := defaultCoercionCollation(n.Col.Collation)
+	col := defaultCoercionCollation(expr.collate)
 	c.asm.Fn_CONV_uc(t, col)
 	c.asm.jumpDestination(skip)