compiler: add 'use -- instead of -= 1'

vlib/compiler/aparser.v

@@ -1606,6 +1606,13 @@ fn ($v.name mut $v.typ) ${p.cur_fn.name}(...) {
 				p.gen(' += ')
 			}
 		}
+		.minus_assign {
+				next := p.peek_token()
+				if next.tok == .number && next.lit == '1' {
+					p.error('use `--` instead of `-= 1`')
+				}
+				p.gen(' -= ')
+		}
 		else {
 			p.gen(' ' + p.tok.str() + ' ')
 		}

vlib/time/time_unix.v

@@ -8,7 +8,7 @@ pub fn unix(abs int) Time {
 	mut day_offset := abs / seconds_per_day
 	if abs % seconds_per_day < 0 {
 		// Compensate for round towards zero on integers as we want floored instead
-		day_offset -= 1
+		day_offset--
 	}
 	year,month,day := calculate_date_from_offset(day_offset)
 	hr,min,sec := calculate_time_from_offset(abs % seconds_per_day)
@@ -26,63 +26,60 @@ pub fn unix(abs int) Time {
 [inline]
 fn calculate_date_from_offset(day_offset_ int) (int,int,int) {
 	mut day_offset := day_offset_
-
 	// Move offset to year 2001 as it's the start of a new 400-year cycle
 	// Code below this rely on the fact that the day_offset is lined up with the 400-year cycle
 	// 1970-2000 (inclusive) has 31 years (8 of which are leap years)
 	mut year := 2001
 	day_offset -= 31 * 365 + 8
-
 	// Account for 400 year cycle
 	year += (day_offset / days_per_400_years) * 400
 	day_offset %= days_per_400_years
-
 	// Account for 100 year cycle
 	if day_offset == days_per_100_years * 4 {
 		year += 300
 		day_offset -= days_per_100_years * 3
-	} else {
+	}
+	else {
 		year += (day_offset / days_per_100_years) * 100
 		day_offset %= days_per_100_years
 	}
-
 	// Account for 4 year cycle
 	if day_offset == days_per_4_years * 25 {
 		year += 96
 		day_offset -= days_per_4_years * 24
-	} else {
+	}
+	else {
 		year += (day_offset / days_per_4_years) * 4
 		day_offset %= days_per_4_years
 	}
-
 	// Account for every year
 	if day_offset == 365 * 4 {
 		year += 3
 		day_offset -= 365 * 3
-	} else {
+	}
+	else {
 		year += (day_offset / 365)
 		day_offset %= 365
 	}
-
 	if day_offset < 0 {
-		year -= 1
+		year--
 		if is_leap_year(year) {
 			day_offset += 366
-		} else {
+		}
+		else {
 			day_offset += 365
 		}
 	}
-
 	if is_leap_year(year) {
 		if day_offset > 31 + 29 - 1 {
 			// After leap day; pretend it wasn't there.
 			day_offset--
-		} else if day_offset == 31 + 29 - 1 {
+		}
+		else if day_offset == 31 + 29 - 1 {
 			// Leap day.
 			return year,2,29
 		}
 	}
-
 	mut estimated_month := day_offset / 31
 	for day_offset >= days_before[estimated_month + 1] {
 		estimated_month++
@@ -93,9 +90,7 @@ fn calculate_date_from_offset(day_offset_ int) (int, int, int) {
 		}
 		estimated_month--
 	}
-
 	day_offset -= days_before[estimated_month]
-
 	return year,estimated_month + 1,day_offset + 1
 }
 
@@ -105,12 +100,9 @@ fn calculate_time_from_offset(second_offset_ int) (int, int, int) {
 	if second_offset < 0 {
 		second_offset += seconds_per_day
 	}
-
 	hour := second_offset / seconds_per_hour
 	second_offset %= seconds_per_hour
-
 	min := second_offset / seconds_per_minute
 	second_offset %= seconds_per_minute
-
 	return hour,min,second_offset
 }