checker: fix match expr with auto promote number

vlib/v/checker/match.v

@@ -114,6 +114,9 @@ fn (mut c Checker) match_expr(mut node ast.MatchExpr) ast.Type {
 							stmt.typ = ast.error_type
 						} else {
 							c.check_match_branch_last_stmt(stmt, ret_type, expr_type)
+							if ret_type.is_number() && expr_type.is_number() && !c.inside_return {
+								ret_type = c.promote_num(ret_type, expr_type)
+							}
 						}
 					}
 					if stmt.typ != ast.error_type {

vlib/v/tests/match_expr_with_auto_promote_number_test.v

@@ -0,0 +1,102 @@
+// convert strings like 10K to i164
+const block = 512
+// const block = i64(512)
+
+// **1
+const kilo = i64(1024)
+const kilobyte = i64(1000)
+
+// **2
+const mega = kilo * kilo
+const megabyte = kilobyte * kilobyte
+
+// **3
+const giga = mega * kilo
+const gigabyte = megabyte * kilobyte
+
+// **4
+const terra = giga * kilo
+const terrabyte = gigabyte * kilobyte
+
+// **5
+const peta = mega * kilo
+const petabyte = megabyte * kilobyte
+
+// **6
+const exa = peta * kilo
+const exabyte = peta * kilo
+
+// **7
+const zetta = exa * kilo
+const zettabyte = exabyte * kilobyte
+
+// **8
+const yotta = zetta * kilo
+const yottabyte = zettabyte * kilobyte
+
+// **9
+const ronna = yotta * kilo
+const ronnabyte = yottabyte * kilobyte
+
+// **10
+const quetta = ronna * kilo
+const quettabyte = ronnabyte * kilobyte
+
+fn string_to_i64(s string) ?i64 {
+	if s.len == 0 {
+		return none
+	}
+
+	mut index := 0
+	for index < s.len {
+		match true {
+			s[index].is_digit() {}
+			s[index] == `+` && index == 0 {}
+			s[index] == `-` && index == 0 {}
+			else { break }
+		}
+		index += 1
+	}
+
+	number := s[0..index].i64()
+	suffix := if index < s.len { s[index..] } else { 'c' }
+
+	multiplier := match suffix.to_lower() {
+		'b' { block }
+		'k' { kilo }
+		'kb', 'kib' { kilobyte }
+		'm' { mega }
+		'mb', 'mib' { megabyte }
+		'g' { giga }
+		'gb', 'gib' { gigabyte }
+		't' { terra }
+		'tb', 'tib' { terrabyte }
+		'p' { peta }
+		'pb', 'pib' { petabyte }
+		'e' { exa }
+		'eb', 'eib' { exabyte }
+		'z' { zetta }
+		'zb', 'zib' { zettabyte }
+		'y' { yotta }
+		'yb', 'yib' { yottabyte }
+		'r' { ronna }
+		'rb', 'rib' { ronnabyte }
+		'q' { quetta }
+		'qb', 'qib' { quettabyte }
+		// oddball formats found in __xstrtol source
+		'c' { 1 }
+		'w' { 2 }
+		else { return none }
+	}
+
+	result := number * multiplier
+	if result == 0 && number != 0 {
+		return none
+	}
+	return result
+}
+
+fn test_match_expr_with_auto_promote_number() {
+	assert string_to_i64('19P')! == 19 * peta
+	assert string_to_i64('18T')! == 18 * terra
+}