checker: prompt error on implicit int overflow by literal (#6410)

vlib/builtin/int_test.v

@@ -182,10 +182,7 @@ fn test_int_decl() {
 	assert typeof(x3) == 'int'
 	assert typeof(x4) == 'int'
 	assert typeof(x5) == 'int'
-	// integers are always 'int' by default
-	x6 := 989898932113111
 	x7 := u64(-321314588900011)
-	assert typeof(x6) == 'int'
 	assert typeof(x7) == 'u64'
 }
 

vlib/rand/mt19937/mt19937_test.v

@@ -178,8 +178,8 @@ fn test_mt19937_u64_in_range() {
 }
 
 fn test_mt19937_int31() {
-	max_u31 := 0x7FFFFFFF
-	sign_mask := 0x80000000
+	max_u31 := int(0x7FFFFFFF)
+	sign_mask := int(0x80000000)
 	for seed in seeds {
 		mut rng := mt19937.MT19937RNG{}
 		rng.seed(seed)

vlib/rand/musl/musl_rng_test.v

@@ -168,8 +168,8 @@ fn test_musl_u64_in_range() {
 }
 
 fn test_musl_int31() {
-	max_u31 := 0x7FFFFFFF
-	sign_mask := 0x80000000
+	max_u31 := int(0x7FFFFFFF)
+	sign_mask := int(0x80000000)
 	for seed in seeds {
 		mut rng := musl.MuslRNG{}
 		rng.seed(seed)

vlib/rand/pcg32/pcg32_test.v

@@ -169,8 +169,8 @@ fn test_pcg32_u64_in_range() {
 }
 
 fn test_pcg32_int31() {
-	max_u31 := 0x7FFFFFFF
-	sign_mask := 0x80000000
+	max_u31 := int(0x7FFFFFFF)
+	sign_mask := int(0x80000000)
 	for seed in seeds {
 		mut rng := pcg32.PCG32RNG{}
 		rng.seed(seed)

vlib/rand/random_numbers_test.v

@@ -100,8 +100,8 @@ fn test_rand_i64_in_range() {
 }
 
 fn test_rand_int31() {
-	max_u31 := 0x7FFFFFFF
-	sign_mask := 0x80000000
+	max_u31 := int(0x7FFFFFFF)
+	sign_mask := int(0x80000000)
 	for _ in 0 .. rnd_count {
 		value := rand.int31()
 		assert value >= 0

vlib/rand/splitmix64/splitmix64_test.v

@@ -168,8 +168,8 @@ fn test_splitmix64_u64_in_range() {
 }
 
 fn test_splitmix64_int31() {
-	max_u31 := 0x7FFFFFFF
-	sign_mask := 0x80000000
+	max_u31 := int(0x7FFFFFFF)
+	sign_mask := int(0x80000000)
 	for seed in seeds {
 		mut rng := splitmix64.SplitMix64RNG{}
 		rng.seed(seed)

vlib/rand/sys/system_rng_test.v

@@ -237,8 +237,8 @@ fn test_sys_rng_i64_in_range() {
 }
 
 fn test_sys_rng_int31() {
-	max_u31 := 0x7FFFFFFF
-	sign_mask := 0x80000000
+	max_u31 := int(0x7FFFFFFF)
+	sign_mask := int(0x80000000)
 	for seed in seeds {
 		seed_data := [seed]
 		mut rng := sys.SysRNG{}

vlib/rand/wyrand/wyrand_test.v

@@ -168,8 +168,8 @@ fn test_wyrand_u64_in_range() {
 }
 
 fn test_wyrand_int31() {
-	max_u31 := 0x7FFFFFFF
-	sign_mask := 0x80000000
+	max_u31 := int(0x7FFFFFFF)
+	sign_mask := int(0x80000000)
 	for seed in seeds {
 		mut rng := wyrand.WyRandRNG{}
 		rng.seed(seed)

vlib/v/checker/checker.v

@@ -12,8 +12,8 @@ import v.errors
 const (
 	max_nr_errors                 = 300
 	match_exhaustive_cutoff_limit = 10
-	enum_min                      = int(0x80000000)
-	enum_max                      = 0x7FFFFFFF
+	int_min                       = int(0x80000000)
+	int_max                       = 0x7FFFFFFF
 )
 
 const (
@@ -1682,7 +1682,7 @@ pub fn (mut c Checker) enum_decl(decl ast.EnumDecl) {
 			match field.expr as field_expr {
 				ast.IntegerLiteral {
 					val := field_expr.val.i64()
-					if val < enum_min || val > enum_max {
+					if val < int_min || val > int_max {
 						c.error('enum value `$val` overflows int', field_expr.pos)
 					} else if !decl.is_multi_allowed && int(val) in seen {
 						c.error('enum value `$val` already exists', field_expr.pos)
@@ -1707,7 +1707,7 @@ pub fn (mut c Checker) enum_decl(decl ast.EnumDecl) {
 		} else {
 			if seen.len > 0 {
 				last := seen[seen.len - 1]
-				if last == enum_max {
+				if last == int_max {
 					c.error('enum value overflows', field.pos)
 				}
 				seen << last + 1
@@ -1805,6 +1805,29 @@ pub fn (mut c Checker) assign_stmt(mut assign_stmt ast.AssignStmt) {
 		right_type := assign_stmt.right_types[i]
 		if is_decl {
 			left_type = c.table.mktyp(right_type)
+			if left_type == table.int_type {
+				mut expr := right
+				mut negative := false
+				if right is ast.PrefixExpr {
+					expr = right.right
+					if right.op == .minus {
+						negative = true
+					}
+				}
+				if expr is ast.IntegerLiteral {
+					mut is_large := false
+					if expr.val.len > 8 {
+						val := expr.val.i64()
+						if (!negative && val > int_max) || (negative && -val < int_min) {
+							is_large = true
+						}
+					}
+					if is_large {
+						c.error('overflow in implicit type `int`, use explicit type casting instead',
+							expr.pos)
+					}
+				}
+			}
 			// we are unwrapping here instead if check_expr_opt_call currently
 			if left_type.has_flag(.optional) {
 				left_type = left_type.clear_flag(.optional)

vlib/v/checker/tests/overflow_int_err.out

@@ -0,0 +1,14 @@
+vlib/v/checker/tests/overflow_int_err.vv:4:8: error: overflow in implicit type `int`, use explicit type casting instead
+    2 |     a := -2147483648
+    3 |     b := 2147483647
+    4 |     c := -2147483649
+      |           ~~~~~~~~~~
+    5 |     d := 2147483648
+    6 |     println(a)
+vlib/v/checker/tests/overflow_int_err.vv:5:7: error: overflow in implicit type `int`, use explicit type casting instead
+    3 |     b := 2147483647
+    4 |     c := -2147483649
+    5 |     d := 2147483648
+      |          ~~~~~~~~~~
+    6 |     println(a)
+    7 |     println(b)

vlib/v/checker/tests/overflow_int_err.vv

@@ -0,0 +1,10 @@
+fn main() {
+	a := -2147483648
+	b := 2147483647
+	c := -2147483649
+	d := 2147483648
+	println(a)
+	println(b)
+	println(c)
+	println(d)
+}