builtin,math: fix math.min_i64.str() (fix #16086) (#16089)

vlib/builtin/int.v

@@ -177,6 +177,9 @@ pub fn (nn i64) str() string {
 		mut d := i64(0)
 		if n == 0 {
 			return '0'
+		} else if n == i64(-9223372036854775807 - 1) {
+			// math.min_i64
+			return '-9223372036854775808'
 		}
 		max := 20
 		mut buf := malloc_noscan(max + 1)

vlib/math/const.v

@@ -42,19 +42,23 @@ pub const (
 
 // Integer limit values
 pub const (
-	max_i8  = 127
+	min_i8  = i8(-128)
-	min_i8  = -128
+	max_i8  = i8(127)
-	max_i16 = 32767
+	min_i16 = i16(-32768)
-	min_i16 = -32768
+	max_i16 = i16(32767)
-	max_i32 = 2147483647
+	min_i32 = int(-2147483648)
-	min_i32 = -2147483648
+	max_i32 = int(2147483647)
-	// -9223372036854775808 is wrong because C compilers parse literal values
+	// -9223372036854775808 is wrong, because C compilers parse literal values
 	// without sign first, and 9223372036854775808 overflows i64, hence the
 	// consecutive subtraction by 1
 	min_i64 = i64(-9223372036854775807 - 1)
 	max_i64 = i64(9223372036854775807)
-	max_u8  = 255
+	min_u8  = u8(0)
-	max_u16 = 65535
+	max_u8  = u8(255)
+	min_u16 = u16(0)
+	max_u16 = u16(65535)
+	min_u32 = u32(0)
 	max_u32 = u32(4294967295)
+	min_u64 = u64(0)
 	max_u64 = u64(18446744073709551615)
 )

vlib/math/math_test.v

@@ -1048,3 +1048,14 @@ fn test_count_digits() {
 	assert count_digits(123456789012345) == 15
 	assert count_digits(-67345) == 5
 }
+
+fn test_min_max_int_str() {
+	assert min_i64.str() == '-9223372036854775808'
+	assert max_i64.str() == '9223372036854775807'
+	assert min_i32.str() == '-2147483648'
+	assert max_i32.str() == '2147483647'
+	assert min_i16.str() == '-32768'
+	assert max_i16.str() == '32767'
+	assert min_i8.str() == '-128'
+	assert max_i8.str() == '127'
+}