diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 6a30b71305e8bd..252b97ab2f30cb 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -383,7 +383,7 @@ pub fn (s string) replace(rep string, with string) string {
 	mut stack_idxs := [replace_stack_buffer_size]int{}
 	mut pidxs := unsafe { &stack_idxs[0] }
 	if pidxs_cap > replace_stack_buffer_size {
-		pidxs = unsafe { &int(malloc(sizeof(int) * pidxs_cap)) }
+		pidxs = unsafe { &int(malloc(int(sizeof(int)) * pidxs_cap)) }
 	}
 	defer {
 		if pidxs_cap > replace_stack_buffer_size {
@@ -1277,7 +1277,7 @@ fn (s string) index_kmp(p string) int {
 	mut stack_prefixes := [kmp_stack_buffer_size]int{}
 	mut p_prefixes := unsafe { &stack_prefixes[0] }
 	if p.len > kmp_stack_buffer_size {
-		p_prefixes = unsafe { &int(vcalloc(p.len * sizeof(int))) }
+		p_prefixes = unsafe { &int(vcalloc(p.len * int(sizeof(int)))) }
 	}
 	defer {
 		if p.len > kmp_stack_buffer_size {
diff --git a/vlib/compress/zstd/zstd.c.v b/vlib/compress/zstd/zstd.c.v
index 78b7eca279fac5..e623144567e18d 100644
--- a/vlib/compress/zstd/zstd.c.v
+++ b/vlib/compress/zstd/zstd.c.v
@@ -561,7 +561,7 @@ pub fn store_array[T](fname string, array []T, params CompressParams) ! {
 	fout.write(buf_out[..output.pos])!
 	// then, write the array.data to file
 	input.src = array.data
-	input.size = usize(array.len * sizeof(T))
+	input.size = usize(array.len * int(sizeof(T)))
 	input.pos = 0
 	output.dst = buf_out.data
 	output.size = buf_out_size
diff --git a/vlib/crypto/scrypt/scrypt.v b/vlib/crypto/scrypt/scrypt.v
index a843394d88b053..ad0c6e3b8d8cbf 100644
--- a/vlib/crypto/scrypt/scrypt.v
+++ b/vlib/crypto/scrypt/scrypt.v
@@ -144,7 +144,7 @@ fn smix(mut block []u8, r u32, n u64, mut v_block []u8, mut temp_block []u8) {
 	}
 
 	for _ in 0 .. n {
-		j := binary.little_endian_u64_at(temp_block, ((2 * r) - 1) * 64) & (n - 1)
+		j := binary.little_endian_u64_at(temp_block, int(((2 * r) - 1) * 64)) & (n - 1)
 
 		v_start := j * (128 * r)
 		v_stop := v_start + (128 * r)
@@ -226,7 +226,7 @@ pub fn scrypt(password []u8, salt []u8, n u64, r u32, p u32, dk_len u64) ![]u8 {
 		}
 	}
 
-	mut b := pbkdf2.key(password, salt, 1, 128 * r * p, sha256.new())!
+	mut b := pbkdf2.key(password, salt, 1, int(128 * r * p), sha256.new())!
 
 	mut xy := []u8{len: int(256 * r), cap: int(256 * r), init: 0}
 	mut v := []u8{len: int(128 * r * n), cap: int(128 * r * n), init: 0}
@@ -235,7 +235,7 @@ pub fn scrypt(password []u8, salt []u8, n u64, r u32, p u32, dk_len u64) ![]u8 {
 		smix(mut b[i * 128 * r..], r, n, mut v, mut xy)
 	}
 
-	result := pbkdf2.key(password, b, 1, 128 * r * p, sha256.new())!
+	result := pbkdf2.key(password, b, 1, int(128 * r * p), sha256.new())!
 
 	return result[..dk_len]
 }
diff --git a/vlib/rand/rand.c.v b/vlib/rand/rand.c.v
index eeab506770aa93..e6d574097f2300 100644
--- a/vlib/rand/rand.c.v
+++ b/vlib/rand/rand.c.v
@@ -103,7 +103,7 @@ fn internal_string_from_set(mut rng PRNG, charset string, len int) string {
 	mut buf := unsafe { malloc_noscan(len + 1) }
 	for i in 0 .. len {
 		unsafe {
-			buf[i] = charset[rng.u32() % charset.len]
+			buf[i] = charset[rng.u32() % u32(charset.len)]
 		}
 	}
 	unsafe {
@@ -120,7 +120,7 @@ fn internal_fill_buffer_from_set(mut rng PRNG, charset string, mut buf []u8) {
 	blen := buf.len
 	for i in 0 .. blen {
 		unsafe {
-			buf[i] = charset[rng.u32() % charset.len]
+			buf[i] = charset[rng.u32() % u32(charset.len)]
 		}
 	}
 }
diff --git a/vlib/v/ast/table.v b/vlib/v/ast/table.v
index 1ffe3a8c82bf46..b485007c59098d 100644
--- a/vlib/v/ast/table.v
+++ b/vlib/v/ast/table.v
@@ -469,7 +469,7 @@ pub fn (t &Table) find_enum_field_val(name string, field_ string) ?i64 {
 			}
 		}
 	}
-	return if enum_decl.is_flag { u64(1) << val } else { val }
+	return if enum_decl.is_flag { i64(u64(1) << u64(val)) } else { val }
 }
 
 pub fn (t &Table) get_enum_field_names(name string) []string {
diff --git a/vlib/v/ast/types.v b/vlib/v/ast/types.v
index 7dde4b4de48e36..ee1e4f168e947e 100644
--- a/vlib/v/ast/types.v
+++ b/vlib/v/ast/types.v
@@ -398,7 +398,7 @@ pub fn (t Type) clear_flags(flags ...TypeFlag) Type {
 	if flags.len == 0 {
 		return t & 0xffffff
 	} else {
-		mut typ := int(t)
+		mut typ := u32(t)
 		for flag in flags {
 			typ = typ & ~(u32(flag))
 		}
diff --git a/vlib/v/checker/check_types.v b/vlib/v/checker/check_types.v
index 11b7e14c48649b..1ff7c876846679 100644
--- a/vlib/v/checker/check_types.v
+++ b/vlib/v/checker/check_types.v
@@ -735,8 +735,16 @@ fn (c &Checker) promote_num(left_type ast.Type, right_type ast.Type) ast.Type {
 	} else if idx_lo >= ast.i8_type_idx
 		&& (idx_hi <= ast.isize_type_idx || idx_hi == ast.rune_type_idx) { // both signed
 		return if idx_lo == ast.i64_type_idx { type_lo } else { type_hi }
-	} else if idx_hi - idx_lo < (ast.u8_type_idx - ast.i8_type_idx) {
-		return type_lo // conversion unsigned -> signed if signed type is larger
+	} else if idx_hi == ast.u8_type_idx && idx_lo > ast.i8_type_idx {
+		return type_lo // conversion unsigned u8 -> signed if signed type is larger
+	} else if idx_hi == ast.u16_type_idx && idx_lo > ast.i16_type_idx {
+		return type_lo // conversion unsigned u16 -> signed if signed type is larger
+	} else if idx_hi == ast.u32_type_idx && idx_lo > ast.int_type_idx {
+		return type_lo // conversion unsigned u32 -> signed if signed type is larger
+	} else if idx_hi == ast.u64_type_idx && idx_lo > ast.i64_type_idx {
+		return type_lo // conversion unsigned u64 -> signed if signed type is larger
+	} else if idx_hi == ast.usize_type_idx && idx_lo > ast.isize_type_idx {
+		return type_lo // conversion unsigned usize -> signed if signed type is larger
 	} else if c.pref.translated {
 		return type_hi
 	} else {
diff --git a/vlib/v/checker/struct.v b/vlib/v/checker/struct.v
index b61dabe4e2e2d3..b59ecdf4a93b17 100644
--- a/vlib/v/checker/struct.v
+++ b/vlib/v/checker/struct.v
@@ -945,7 +945,7 @@ fn (mut c Checker) check_uninitialized_struct_fields_and_embeds(node ast.StructI
 				if mut field.default_expr is ast.StructInit {
 					idx := c.table.find_type(field.default_expr.typ_str)
 					if idx != 0 {
-						info.fields[i].default_expr_typ = ast.new_type(idx)
+						info.fields[i].default_expr_typ = ast.new_type(int(idx))
 					}
 				} else if field.default_expr.is_nil() {
 					if field.typ.is_any_kind_of_pointer() {
diff --git a/vlib/v/checker/tests/fn_call_arg_mismatch_err_e.out b/vlib/v/checker/tests/fn_call_arg_mismatch_err_e.out
new file mode 100644
index 00000000000000..601e0c5dafa8e3
--- /dev/null
+++ b/vlib/v/checker/tests/fn_call_arg_mismatch_err_e.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/fn_call_arg_mismatch_err_d.vv:17:26: error: cannot use `fn (string) f64` as `fn (string) ?Flag` in argument 2 to `parse_option`
+   15 |
+   16 | fn main() {
+   17 |     t := parse_option('45', parse_percent)?
+      |                             ~~~~~~~~~~~~~
+   18 |     println(t)
+   19 | }
diff --git a/vlib/v/checker/tests/fn_call_arg_mismatch_err_e.vv b/vlib/v/checker/tests/fn_call_arg_mismatch_err_e.vv
new file mode 100644
index 00000000000000..5576775d43b132
--- /dev/null
+++ b/vlib/v/checker/tests/fn_call_arg_mismatch_err_e.vv
@@ -0,0 +1,9 @@
+fn f(x int) {
+	println(x)
+}
+
+fn main() {
+	x := u32(2251797157)
+	println(x)
+	f(x)
+}
diff --git a/vlib/v/checker/tests/globals/global_receiver_var_name_err.vv b/vlib/v/checker/tests/globals/global_receiver_var_name_err.vv
index b6547e51dd02ea..5ffb79ab27c988 100644
--- a/vlib/v/checker/tests/globals/global_receiver_var_name_err.vv
+++ b/vlib/v/checker/tests/globals/global_receiver_var_name_err.vv
@@ -11,7 +11,7 @@ __global (
 )
 
 struct GameObject {
-	id int = game.object_id++
+	id u32 = game.object_id++
 }
 
 fn (mut game Game) init() {
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index b9e54cd18a5293..69f5e1a0a15a4f 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -2451,7 +2451,7 @@ struct SumtypeCastingFn {
 
 fn (mut g Gen) get_sumtype_casting_fn(got_ ast.Type, exp_ ast.Type) string {
 	mut got, exp := got_.idx_type(), exp_.idx_type()
-	i := got | int(u32(exp) << 17) | int(u32(exp_.has_flag(.option)) << 16)
+	i := int(got) | int(u32(exp) << 17) | int(u32(exp_.has_flag(.option)) << 16)
 	exp_sym := g.table.sym(exp)
 	mut got_sym := g.table.sym(got)
 	cname := if exp == ast.int_type_idx {
diff --git a/vlib/v/tests/if_guard_elseif_test.v b/vlib/v/tests/if_guard_elseif_test.v
index 975818f1d0db22..304cc661402c9a 100644
--- a/vlib/v/tests/if_guard_elseif_test.v
+++ b/vlib/v/tests/if_guard_elseif_test.v
@@ -11,7 +11,7 @@ fn test_main() {
 	mut str := ''
 	if bs := byte_str(num) {
 		str = 'byte: ${bs}'
-	} else if ss := short_str(num) {
+	} else if ss := short_str(int(num)) {
 		str = 'short: ${ss}'
 	} else {
 		str = 'err: ${err}'
diff --git a/vlib/v/tests/reflection_sym_test.v b/vlib/v/tests/reflection_sym_test.v
index 0ccec0f36ec5c2..d517fb22adba4c 100644
--- a/vlib/v/tests/reflection_sym_test.v
+++ b/vlib/v/tests/reflection_sym_test.v
@@ -77,7 +77,7 @@ fn test_multi_return_sym() {
 	assert func.receiver_typ == 0
 	assert func.is_pub == false
 
-	typ := reflection.get_type(func.return_typ)?
+	typ := reflection.get_type(int(func.return_typ))?
 	assert typ.name == '(int, f64, string)'
 	assert typ.sym.mod == ''
 	assert typ.sym.language == .v
diff --git a/vlib/v/tests/reflection_test.v b/vlib/v/tests/reflection_test.v
index fb4c63a858d5ea..5ce9be46168bb7 100644
--- a/vlib/v/tests/reflection_test.v
+++ b/vlib/v/tests/reflection_test.v
@@ -38,22 +38,22 @@ fn test_func_name() {
 
 fn test_type_name() {
 	ret_typ := reflection.get_funcs().filter(it.name == 'test3')[0].return_typ
-	assert reflection.type_name(ret_typ) == 'void'
-	assert reflection.get_type(ret_typ)?.name == 'void'
-	assert reflection.get_type_symbol(ret_typ)?.name == 'void'
-	assert reflection.type_name(reflection.get_funcs().filter(it.name == 'test3')[0].args[0].typ) == 'Function'
+	assert reflection.type_name(int(ret_typ)) == 'void'
+	assert reflection.get_type(int(ret_typ))?.name == 'void'
+	assert reflection.get_type_symbol(int(ret_typ))?.name == 'void'
+	assert reflection.type_name(int(reflection.get_funcs().filter(it.name == 'test3')[0].args[0].typ)) == 'Function'
 }
 
 fn test_type_symbol() {
 	ret_typ := reflection.get_funcs().filter(it.name == 'test3')[0].return_typ
-	assert reflection.get_type_symbol(ret_typ)?.language == .v
+	assert reflection.get_type_symbol(int(ret_typ))?.language == .v
 }
 
 fn test_method() {
 	method := reflection.get_funcs().filter(it.name == 'get_name')[0]
-	assert reflection.type_name(method.return_typ) == 'string'
-	println(reflection.get_type(method.receiver_typ)?.name)
-	assert reflection.get_type(method.receiver_typ)?.name == 'User'
+	assert reflection.type_name(int(method.return_typ)) == 'string'
+	println(reflection.get_type(int(method.receiver_typ))?.name)
+	assert reflection.get_type(int(method.receiver_typ))?.name == 'User'
 }
 
 fn test_enum() {
diff --git a/vlib/x/json2/encoder.v b/vlib/x/json2/encoder.v
index a8e9f6a15b6d3e..9795b3c636f536 100644
--- a/vlib/x/json2/encoder.v
+++ b/vlib/x/json2/encoder.v
@@ -586,7 +586,7 @@ fn (e &Encoder) encode_string(s string, mut buf []u8) ! {
 	buf << quote_rune
 }
 
-fn hex_digit(n int) u8 {
+fn hex_digit(n u32) u8 {
 	if n < 10 {
 		return `0` + n
 	}