diff --git a/vlib/bitfield/bitfield.v b/vlib/bitfield/bitfield.v
index b05db4d733..e7ae271145 100644
--- a/vlib/bitfield/bitfield.v
+++ b/vlib/bitfield/bitfield.v
@@ -84,7 +84,7 @@ pub fn (instance BitField) get_bit(bitnr int) int {
 	if bitnr >= instance.size {
 		return 0
 	}
-	return (instance.field[bitslot(bitnr)] >> (bitnr % slot_size)) & u32(1)
+	return int((instance.field[bitslot(bitnr)] >> (bitnr % slot_size)) & u32(1))
 }
 
 // set_bit sets bit number 'bit_nr' to 1 (count from 0).
diff --git a/vlib/bitfield/bitfield_test.v b/vlib/bitfield/bitfield_test.v
index 71c679418a..9ded88c4e3 100644
--- a/vlib/bitfield/bitfield_test.v
+++ b/vlib/bitfield/bitfield_test.v
@@ -19,7 +19,7 @@ fn test_bf_set_clear_toggle_get() {
 }
 
 fn test_bf_and_not_or_xor() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input1 := bitfield.new(len)
 	mut input2 := bitfield.new(len)
@@ -46,7 +46,7 @@ fn test_bf_and_not_or_xor() {
 }
 
 fn test_clone_cmp() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input := bitfield.new(len)
 	for i in 0..len {
@@ -60,7 +60,7 @@ fn test_clone_cmp() {
 }
 
 fn test_slice_join() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input := bitfield.new(len)
 	for i in 0..len {
@@ -83,7 +83,7 @@ fn test_slice_join() {
 }
 
 fn test_pop_count() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut count0 := 0
 	mut input := bitfield.new(len)
@@ -98,7 +98,7 @@ fn test_pop_count() {
 }
 
 fn test_hamming() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut count := 0
 	mut input1 := bitfield.new(len)
@@ -138,7 +138,7 @@ fn test_bf_from_bytes() {
 }
 
 fn test_bf_from_str() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input := ''
 	for _ in 0..len {
@@ -160,7 +160,7 @@ fn test_bf_from_str() {
 }
 
 fn test_bf_bf2str() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input := bitfield.new(len)
 	for i in 0..len {
@@ -188,7 +188,7 @@ fn test_bf_bf2str() {
 }
 
 fn test_bf_set_all() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input := bitfield.new(len)
 	input.set_all()
@@ -202,7 +202,7 @@ fn test_bf_set_all() {
 }
 
 fn test_bf_clear_all() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input := bitfield.new(len)
 	for i in 0..len {
@@ -221,7 +221,7 @@ fn test_bf_clear_all() {
 }
 
 fn test_bf_reverse() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input := bitfield.new(len)
 	for i in 0..len {
@@ -241,7 +241,7 @@ fn test_bf_reverse() {
 }
 
 fn test_bf_resize() {
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input := bitfield.new(rand.next(len) + 1)
 	for _ in 0..100 {
@@ -259,7 +259,7 @@ fn test_bf_pos() {
 	 * all haystacks here contain exactly one instanse of needle,
 	 * so search should return non-negative-values
 	**/
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut result := 1
 	for i := 1; i < len; i++ {	// needle size
@@ -322,7 +322,7 @@ fn test_bf_rotate() {
 }
 
 fn test_bf_printing(){
-	rand.seed(time.now().unix)
+	rand.seed(int(time.now().unix))
 	len := 80
 	mut input := bitfield.new(len)
 	for i in 0..len {
diff --git a/vlib/builtin/map.v b/vlib/builtin/map.v
index 9d60e2fad3..2ca00ea647 100644
--- a/vlib/builtin/map.v
+++ b/vlib/builtin/map.v
@@ -111,7 +111,7 @@ fn new_dense_array(value_bytes int) DenseArray {
 		cap: 8
 		size: 0
 		deletes: 0
-		keys: &string(malloc(8 * sizeof(string)))
+		keys: &string(malloc(int(8 * sizeof(string))))
 		values: malloc(8 * value_bytes)
 	}
 }
@@ -198,7 +198,7 @@ fn new_map_1(value_bytes int) map {
 		cached_hashbits: max_cached_hashbits
 		shift: init_log_capicity
 		key_values: new_dense_array(value_bytes)
-		metas: &u32(vcalloc(sizeof(u32) * (init_capicity + extra_metas_inc)))
+		metas: &u32(vcalloc(int(sizeof(u32) * (init_capicity + extra_metas_inc))))
 		extra_metas: extra_metas_inc
 		size: 0
 	}
@@ -323,7 +323,7 @@ fn (mut m map) rehash() {
 
 fn (mut m map) cached_rehash(old_cap u32) {
 	old_metas := m.metas
-	m.metas = &u32(vcalloc(sizeof(u32) * (m.cap + 2 + m.extra_metas)))
+	m.metas = &u32(vcalloc(int(sizeof(u32) * (m.cap + 2 + m.extra_metas))))
 	old_extra_metas := m.extra_metas
 	for i := u32(0); i <= old_cap + old_extra_metas; i += 2 {
 		if old_metas[i] == 0 {
@@ -430,8 +430,8 @@ pub fn (d DenseArray) clone() DenseArray {
 		cap:         d.cap
 		size:        d.size
 		deletes:     d.deletes
-		keys:        &string(malloc(d.cap * sizeof(string)))
-		values:      byteptr(malloc(d.cap * u32(d.value_bytes)))
+		keys:        &string(malloc(int(d.cap * sizeof(string))))
+		values:      byteptr(malloc(int(d.cap * u32(d.value_bytes))))
 	}
 	C.memcpy(res.keys, d.keys, d.cap * sizeof(string))
 	C.memcpy(res.values, d.values, d.cap * u32(d.value_bytes))
@@ -447,7 +447,7 @@ pub fn (m map) clone() map {
 		cached_hashbits: m.cached_hashbits
 		shift:           m.shift
 		key_values:      m.key_values.clone()
-		metas:           &u32(malloc(metas_size))
+		metas:           &u32(malloc(int(metas_size)))
 		extra_metas:     m.extra_metas
 		size:            m.size
 	}
diff --git a/vlib/builtin/sorted_map.v b/vlib/builtin/sorted_map.v
index 93538a9af3..2e35c7ee57 100644
--- a/vlib/builtin/sorted_map.v
+++ b/vlib/builtin/sorted_map.v
@@ -121,13 +121,13 @@ fn (mut n mapnode) split_child(child_index int, y mut mapnode) {
 		z.values[j] = y.values[j + degree]
 	}
 	if !isnil(y.children) {
-		z.children = &voidptr(malloc(children_bytes))
+		z.children = &voidptr(malloc(int(children_bytes)))
 		for jj := degree - 1; jj >= 0; jj-- {
 			z.children[jj] = y.children[jj + degree]
 		}
 	}
 	if isnil(n.children) {
-		n.children = &voidptr(malloc(children_bytes))
+		n.children = &voidptr(malloc(int(children_bytes)))
 	}
 	n.children[n.size + 1] = n.children[n.size]
 	for j := n.size; j > child_index; j-- {
diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 32a8b8bff9..72f89f115d 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -982,7 +982,7 @@ pub fn (s string) ustring() ustring {
 		// runes will have at least s.len elements, save reallocations
 		// TODO use VLA for small strings?
 
-		runes: __new_array(0, s.len, sizeof(int))
+		runes: __new_array(0, s.len, int(sizeof(int)))
 	}
 	for i := 0; i < s.len; i++ {
 		char_len := utf8_char_len(s.str[i])
@@ -1000,7 +1000,7 @@ __global g_ustring_runes []int
 
 pub fn (s string) ustring_tmp() ustring {
 	if g_ustring_runes.len == 0 {
-		g_ustring_runes = __new_array(0, 128, sizeof(int))
+		g_ustring_runes = __new_array(0, 128, int(sizeof(int)))
 	}
 	mut res := ustring{
 		s: s
@@ -1048,7 +1048,7 @@ fn (u ustring) ge(a ustring) bool {
 pub fn (u ustring) add(a ustring) ustring {
 	mut res := ustring{
 		s: u.s + a.s
-		runes: __new_array(0, u.s.len + a.s.len, sizeof(int))
+		runes: __new_array(0, u.s.len + a.s.len, int(sizeof(int)))
 	}
 	mut j := 0
 	for i := 0; i < u.s.len; i++ {
diff --git a/vlib/builtin/utf8.v b/vlib/builtin/utf8.v
index 8273620f68..e85eec4cee 100644
--- a/vlib/builtin/utf8.v
+++ b/vlib/builtin/utf8.v
@@ -227,7 +227,7 @@ fn utf8_str_visible_length(s string) int {
 // Reads an utf8 character from standard input
 pub fn utf8_getchar() int {
 	c := C.getchar()
-	len := utf8_len(~c)
+	len := utf8_len(byte(~c))
 	if c < 0 {
 		return 0
 	}
diff --git a/vlib/freetype/freetype.v b/vlib/freetype/freetype.v
index 42e53fbee2..6ce352e4ee 100644
--- a/vlib/freetype/freetype.v
+++ b/vlib/freetype/freetype.v
@@ -183,7 +183,7 @@ pub fn new_context(cfg gg.Cfg) &FreeType {
 	C.glBlendFunc(C.GL_SRC_ALPHA, C.GL_ONE_MINUS_SRC_ALPHA)
 	shader := gl.new_shader('text')
 	shader.use()
-	projection := glm.ortho(0, width, 0, height) // 0 at BOT
+	projection := glm.ortho(0, f32(width), 0, f32(height)) // 0 at BOT
 	shader.set_mat4('projection', projection)
 	// FREETYPE
 	ft := C.FT_Library{}
diff --git a/vlib/gg/gg.v b/vlib/gg/gg.v
index 7b5e9ff2e8..b741fe6e12 100644
--- a/vlib/gg/gg.v
+++ b/vlib/gg/gg.v
@@ -100,7 +100,7 @@ pub fn new_context(cfg Cfg) &GG {
 	shader := gl.new_shader('simple')
 	shader.use()
 	if cfg.use_ortho {
-		projection := glm.ortho(0, cfg.width, cfg.height, 0)
+		projection := glm.ortho(0, f32(cfg.width), f32(cfg.height), 0)
 		shader.set_mat4('projection', projection)
 	}
 	else {
@@ -304,7 +304,7 @@ fn todo_remove_me(cfg Cfg, scale int) {
 	//# glBlendFunc(C.GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 	shader := gl.new_shader('text')
 	shader.use()
-	projection := glm.ortho(0, width, 0, height)// 0 at BOT
+	projection := glm.ortho(0, f32(width), 0, f32(height))// 0 at BOT
 	// projection_new := ortho(0, width, 0, height)// 0 at BOT
 	// projection := gl.ortho(0, width,height,0)  // 0 at TOP
 	shader.set_mat4('projection', projection)
diff --git a/vlib/glm/glm.v b/vlib/glm/glm.v
index 9db44dbdf1..40b5c3878d 100644
--- a/vlib/glm/glm.v
+++ b/vlib/glm/glm.v
@@ -398,7 +398,7 @@ fn ortho_js(left, right, bottom, top f32) &f32 {
 	bt := 1.0 / (bottom - top)
 	nf := f32(1.0) / 1.0// (mynear -myfar)
 	mut out := &f32(0)
-	unsafe { out = &f32( malloc (sizeof(f32) * 16)) }
+	unsafe { out = &f32( malloc (int(sizeof(f32) * 16))) }
 	out[0] = -2.0 * lr
 	out[1] = 0
 	out[2] = 0
diff --git a/vlib/hash/crc32/crc32.v b/vlib/hash/crc32/crc32.v
index 5ab8ef2353..5babc6ef69 100644
--- a/vlib/hash/crc32/crc32.v
+++ b/vlib/hash/crc32/crc32.v
@@ -58,6 +58,6 @@ pub fn new(poly int) &Crc32 {
 
 // calculate crc32 using ieee
 pub fn sum(b []byte) u32 {
-	c := new(ieee)
+	c := new(int(ieee))
 	return c.sum32(b)
 }
diff --git a/vlib/hash/crc32/crc32_test.v b/vlib/hash/crc32/crc32_test.v
index 777dd10fb2..bea6764d0d 100644
--- a/vlib/hash/crc32/crc32_test.v
+++ b/vlib/hash/crc32/crc32_test.v
@@ -7,7 +7,7 @@ fn test_hash_crc32() {
 	assert sum1.hex() == '483f8cf0'
 
 	
-	c := crc32.new(crc32.ieee)
+	c := crc32.new(int(crc32.ieee))
 	b2 := 'testing crc32 again'.bytes()
 	sum2 := c.checksum(b2)
 	assert sum2 == u32(1420327025)
diff --git a/vlib/math/bits/bits.v b/vlib/math/bits/bits.v
index e8eaf40149..7c5c96e40f 100644
--- a/vlib/math/bits/bits.v
+++ b/vlib/math/bits/bits.v
@@ -208,7 +208,7 @@ pub fn reverse_32(x u32) u32 {
 	mut y := ((x>>u32(1) & (m0 & max_u32)) | ((x & (m0 & max_u32))<<1))
 	y = ((y>>u32(2) & (m1 & max_u32)) | ((y & (m1 & max_u32))<<u32(2)))
 	y = ((y>>u32(4) & (m2 & max_u32)) | ((y & (m2 & max_u32))<<u32(4)))
-	return reverse_bytes_32(y)
+	return reverse_bytes_32(u32(y))
 }
 
 // reverse_64 returns the value of x with its bits in reversed order.
@@ -236,7 +236,7 @@ pub fn reverse_bytes_16(x u16) u16 {
 [inline]
 pub fn reverse_bytes_32(x u32) u32 {
 	y := ((x>>u32(8) & (m3 & max_u32)) | ((x & (m3 & max_u32))<<u32(8)))
-	return (y>>16) | (y<<16)
+	return u32((y>>16) | (y<<16))
 }
 
 // reverse_bytes_64 returns the value of x with its bytes in reversed order.
diff --git a/vlib/math/fractions/fraction.v b/vlib/math/fractions/fraction.v
index e199b29147..48d6701723 100644
--- a/vlib/math/fractions/fraction.v
+++ b/vlib/math/fractions/fraction.v
@@ -240,7 +240,7 @@ fn cmp_f64s(a, b f64) int {
 // Two integers are safe to multiply when their bit lengths
 // sum up to less than 64 (conservative estimate).
 fn safe_to_multiply(a, b i64) bool {
-	return (bits.len_64(abs(a)) + bits.len_64(abs(b))) < 64
+	return (bits.len_64(u64(abs(a))) + bits.len_64(u64(abs(b)))) < 64
 }
 
 fn cmp(f1, f2 Fraction) int {
diff --git a/vlib/net/websocket/ws.v b/vlib/net/websocket/ws.v
index 3a4fd05e9d..ee81ef93ea 100644
--- a/vlib/net/websocket/ws.v
+++ b/vlib/net/websocket/ws.v
@@ -418,7 +418,7 @@ pub fn (mut ws Client) read() int {
 	} else if frame.opcode in [.text_frame, .binary_frame] {
 		data_node:
 		l.d('read: recieved text_frame or binary_frame')
-		mut payload := malloc(sizeof(byte) * u32(payload_len) + 1)
+		mut payload := malloc(int(sizeof(byte) * u32(payload_len) + 1))
 		if payload == 0 {
 			l.f('out of memory')
 		}
@@ -438,7 +438,7 @@ pub fn (mut ws Client) read() int {
 						size += f.len
 					}
 				}
-				mut pl := malloc(sizeof(byte) * u32(size))
+				mut pl := malloc(int(sizeof(byte) * u32(size)))
 				if pl == 0 {
 					l.f('out of memory')
 				}
diff --git a/vlib/readline/readline_linux.c.v b/vlib/readline/readline_linux.c.v
index a472c4a800..09b64ebc5c 100644
--- a/vlib/readline/readline_linux.c.v
+++ b/vlib/readline/readline_linux.c.v
@@ -203,8 +203,8 @@ match c {
 			`B` { return .history_next }
 			`A` { return .history_previous }
 			`1` { return r.analyse_extended_control() }
-			`2` { return r.analyse_extended_control_no_eat(sequence) }
-			`3` { return r.analyse_extended_control_no_eat(sequence) }
+			`2` { return r.analyse_extended_control_no_eat(byte(sequence)) }
+			`3` { return r.analyse_extended_control_no_eat(byte(sequence)) }
 			else {}
 		}
 	}
diff --git a/vlib/time/format_test.v b/vlib/time/format_test.v
index b3924b04e7..2978a3f4ee 100644
--- a/vlib/time/format_test.v
+++ b/vlib/time/format_test.v
@@ -15,7 +15,7 @@ const (
 fn test_now_format() {
 	t := time.now()
 	u := t.unix
-	assert t.format() == time.unix(u).format()
+	assert t.format() == time.unix(int(u)).format()
 }
 
 fn test_format() {
diff --git a/vlib/time/misc/misc.v b/vlib/time/misc/misc.v
index aa4b7efb56..a004ecc8f8 100644
--- a/vlib/time/misc/misc.v
+++ b/vlib/time/misc/misc.v
@@ -8,5 +8,5 @@ const (
 )
 // random returns a random time struct in *the past*.
 pub fn random() time.Time {
-	return time.unix(rand.next(start_time_unix))
+	return time.unix(rand.next(int(start_time_unix)))
 }
diff --git a/vlib/time/time.v b/vlib/time/time.v
index 8449b230a6..7dae0906bf 100644
--- a/vlib/time/time.v
+++ b/vlib/time/time.v
@@ -118,7 +118,7 @@ pub fn new_time(t Time) Time {
 // unix_time returns Unix time.
 pub fn (t Time) unix_time() int {
 	if t.unix != 0 {
-		return t.unix
+		return int(t.unix)
 	}
 	tt := C.tm{
 		tm_sec: t.second
@@ -134,12 +134,12 @@ pub fn (t Time) unix_time() int {
 // add_seconds returns a new time struct with an added number of seconds.
 pub fn (t Time) add_seconds(seconds int) Time {
 	// TODO Add(d time.Duration)
-	return unix(t.unix + u64(seconds))
+	return unix(int(t.unix + u64(seconds)))
 }
 
 // add_days returns a new time struct with an added number of days.
 pub fn (t Time) add_days(days int) Time {
-	return unix(t.unix + u64(i64(days) * 3600 * 24))
+	return unix(int(t.unix + u64(i64(days) * 3600 * 24)))
 }
 
 // since returns a number of seconds elapsed since a given time.
diff --git a/vlib/v/checker/check_types.v b/vlib/v/checker/check_types.v
index 543702a82a..3aec2fbbe8 100644
--- a/vlib/v/checker/check_types.v
+++ b/vlib/v/checker/check_types.v
@@ -6,7 +6,7 @@ module checker
 import v.table
 import v.token
 
-pub fn (c &Checker) check_types(got, expected table.Type) bool {
+pub fn (c &Checker) check_basic(got, expected table.Type) bool {
 	t := c.table
 	got_idx := t.unalias_num_type(got).idx()
 	exp_idx := t.unalias_num_type(expected).idx()
@@ -114,10 +114,10 @@ pub fn (c &Checker) check_types(got, expected table.Type) bool {
 		exp_fn := exp_info.func
 		// we are using check() to compare return type & args as they might include
 		// functions themselves. TODO: optimize, only use check() when needed
-		if got_fn.args.len == exp_fn.args.len && c.check_types(got_fn.return_type, exp_fn.return_type) {
+		if got_fn.args.len == exp_fn.args.len && c.check_basic(got_fn.return_type, exp_fn.return_type) {
 			for i, got_arg in got_fn.args {
 				exp_arg := exp_fn.args[i]
-				if !c.check_types(got_arg.typ, exp_arg.typ) {
+				if !c.check_basic(got_arg.typ, exp_arg.typ) {
 					return false
 				}
 			}
@@ -157,55 +157,57 @@ pub fn (c &Checker) promote(left_type, right_type table.Type) table.Type {
 		return left_type // strings, self defined operators
 	}
 	if right_type.is_number() && left_type.is_number() {
-		// sort the operands to save time
-		mut type_hi := left_type
-		mut type_lo := right_type
-		if type_hi.idx() < type_lo.idx() {
-			tmp := type_hi
-			type_hi = type_lo
-			type_lo = tmp
-		}
-		idx_hi := type_hi.idx()
-		idx_lo := type_lo.idx()
-		// the following comparisons rely on the order of the indices in atypes.v
-		if idx_hi == table.any_int_type_idx {
-			return type_lo
-		} else if idx_hi == table.any_flt_type_idx {
-			if idx_lo in table.float_type_idxs {
-				return type_lo
-			} else {
-				return table.void_type
-			}
-		} else if type_hi.is_float() {
-			if idx_hi == table.f32_type_idx {
-				if idx_lo in [table.int_type_idx, table.i64_type_idx, table.u32_type_idx, table.u64_type_idx] {
-					return table.void_type
-				} else {
-					return type_hi
-				}
-			} else { // f64, any_flt
-				if idx_lo in [table.i64_type_idx, table.u64_type_idx] {
-					return table.void_type
-				} else {
-					return type_hi
-				}
-			}
-		} else if idx_lo >= table.byte_type_idx { // both operands are unsigned
-			return type_hi
-		} else if idx_lo >= table.i8_type_idx && idx_hi <= table.i64_type_idx { // both signed
-			return type_hi
-		} else if idx_hi - idx_lo < (table.byte_type_idx - table.i8_type_idx) {
-			return type_lo // conversion unsigned -> signed if signed type is larger
-		} else {
-			return table.void_type // conversion signed -> unsigned not allowed
-		}
+		return c.promote_num(left_type, right_type)
 	} else {
 		return left_type // default to left if not automatic promotion possible
 	}
 }
 
-// TODO: promote(), assign_check(), symmetric_check() and check() overlap - should be rearranged
-pub fn (c &Checker) assign_check(got, expected table.Type) bool {
+fn (c &Checker) promote_num(left_type, right_type table.Type) table.Type {
+	// sort the operands to save time
+	mut type_hi := left_type
+	mut type_lo := right_type
+	if type_hi.idx() < type_lo.idx() {
+		type_hi, type_lo = type_lo, type_hi
+	}
+	idx_hi := type_hi.idx()
+	idx_lo := type_lo.idx()
+	// the following comparisons rely on the order of the indices in atypes.v
+	if idx_hi == table.any_int_type_idx {
+		return type_lo
+	} else if idx_hi == table.any_flt_type_idx {
+		if idx_lo in table.float_type_idxs {
+			return type_lo
+		} else {
+			return table.void_type
+		}
+	} else if type_hi.is_float() {
+		if idx_hi == table.f32_type_idx {
+			if idx_lo in [table.int_type_idx, table.i64_type_idx, table.u32_type_idx, table.u64_type_idx] {
+				return table.void_type
+			} else {
+				return type_hi
+			}
+		} else { // f64, any_flt
+			if idx_lo in [table.i64_type_idx, table.u64_type_idx] {
+				return table.void_type
+			} else {
+				return type_hi
+			}
+		}
+	} else if idx_lo >= table.byte_type_idx { // both operands are unsigned
+		return type_hi
+	} else if idx_lo >= table.i8_type_idx && idx_hi <= table.i64_type_idx { // both signed
+		return type_hi
+	} else if idx_hi - idx_lo < (table.byte_type_idx - table.i8_type_idx) {
+		return type_lo // conversion unsigned -> signed if signed type is larger
+	} else {
+		return table.void_type // conversion signed -> unsigned not allowed
+	}
+}
+
+// TODO: promote(), check_types(), symmetric_check() and check() overlap - should be rearranged
+pub fn (c &Checker) check_types(got, expected table.Type) bool {
 	exp_idx := expected.idx()
 	got_idx := got.idx()
 	if exp_idx == got_idx {
@@ -228,12 +230,14 @@ pub fn (c &Checker) assign_check(got, expected table.Type) bool {
 			return true
 		}
 	}
-	if !c.check_types(got, expected) { // TODO: this should go away...
+	if !c.check_basic(got, expected) { // TODO: this should go away...
 		return false
 	}
-	if c.promote(expected, got) != expected {
-		println('could not promote ${c.table.get_type_symbol(got).name} to ${c.table.get_type_symbol(expected).name}')
-		return false
+	if got.is_number() && expected.is_number() {
+		if c.promote_num(expected, got) != expected {
+			// println('could not promote ${c.table.get_type_symbol(got).name} to ${c.table.get_type_symbol(expected).name}')
+			return false
+		}
 	}
 	return true
 }
@@ -252,5 +256,5 @@ pub fn (c &Checker) symmetric_check(left, right table.Type) bool {
 			return true
 		}
 	}
-	return c.check_types(left, right)
+	return c.check_basic(left, right)
 }
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 5c964a3e28..4a9cf8e48f 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -369,7 +369,7 @@ pub fn (mut c Checker) struct_init(mut struct_init ast.StructInit) table.Type {
 				expr_type := c.expr(field.expr)
 				expr_type_sym := c.table.get_type_symbol(expr_type)
 				field_type_sym := c.table.get_type_symbol(info_field.typ)
-				if !c.assign_check(expr_type, info_field.typ) {
+				if !c.check_types(expr_type, info_field.typ) {
 					c.error('cannot assign `$expr_type_sym.name` as `$field_type_sym.name` for field `$info_field.name`',
 						field.pos)
 				}
@@ -698,7 +698,7 @@ fn (mut c Checker) assign_expr(mut assign_expr ast.AssignExpr) {
 		else {}
 	}
 	// Dual sides check (compatibility check)
-	if !c.assign_check(right_type, left_type) {
+	if !c.check_types(right_type, left_type) {
 		left_type_sym := c.table.get_type_symbol(left_type)
 		right_type_sym := c.table.get_type_symbol(right_type)
 		c.error('cannot assign `$right_type_sym.name` to variable `${assign_expr.left.str()}` of type `$left_type_sym.name`',
@@ -1434,7 +1434,7 @@ pub fn (mut c Checker) array_init(mut array_init ast.ArrayInit) table.Type {
 				c.expected_type = elem_type
 				continue
 			}
-			if !c.check_types(elem_type, typ) {
+			if !c.check_types(typ, elem_type) {
 				elem_type_sym := c.table.get_type_symbol(elem_type)
 				c.error('expected array element with type `$elem_type_sym.name`', array_init.pos)
 			}
diff --git a/vlib/v/checker/tests/function_wrong_arg_type.out b/vlib/v/checker/tests/function_wrong_arg_type.out
new file mode 100644
index 0000000000..b2efcac8b8
--- /dev/null
+++ b/vlib/v/checker/tests/function_wrong_arg_type.out
@@ -0,0 +1,7 @@
+vlib/v/checker/tests/function_wrong_arg_type.v:7:7: error: cannot use type `f64` as type `int` in argument 1 to `f`
+    5 | fn main() {
+    6 |     a := 12.3
+    7 |     q := f(a)
+      |          ~~~~
+    8 |     println('$q')
+    9 | }
diff --git a/vlib/v/checker/tests/function_wrong_arg_type.vv b/vlib/v/checker/tests/function_wrong_arg_type.vv
new file mode 100644
index 0000000000..6cd3fbb454
--- /dev/null
+++ b/vlib/v/checker/tests/function_wrong_arg_type.vv
@@ -0,0 +1,9 @@
+fn f(x int) int {
+	return x+x
+}
+
+fn main() {
+	a := 12.3
+	q := f(a)
+	println('$q')
+}
diff --git a/vlib/v/checker/tests/function_wrong_return_type.out b/vlib/v/checker/tests/function_wrong_return_type.out
new file mode 100644
index 0000000000..25f13687d7
--- /dev/null
+++ b/vlib/v/checker/tests/function_wrong_return_type.out
@@ -0,0 +1,6 @@
+vlib/v/checker/tests/function_wrong_return_type.v:2:9: error: cannot use `any_float` as type `int` in return argument
+    1 | fn h() int {
+    2 |     return 3.14
+      |            ~~~~
+    3 | }
+    4 |
diff --git a/vlib/v/checker/tests/function_wrong_return_type.vv b/vlib/v/checker/tests/function_wrong_return_type.vv
new file mode 100644
index 0000000000..0c47628e7e
--- /dev/null
+++ b/vlib/v/checker/tests/function_wrong_return_type.vv
@@ -0,0 +1,8 @@
+fn h() int {
+	return 3.14
+}
+
+fn main() {
+	d := h()
+	println('$d')
+}
diff --git a/vlib/v/gen/x64/gen.v b/vlib/v/gen/x64/gen.v
index a73a0745e5..4232000cf8 100644
--- a/vlib/v/gen/x64/gen.v
+++ b/vlib/v/gen/x64/gen.v
@@ -225,7 +225,7 @@ fn (mut g Gen) jne() int {
 	pos := g.pos()
 	g.write32(placeholder)
 	g.println('jne')
-	return pos
+	return int(pos)
 }
 
 fn (mut g Gen) jge() int {
@@ -233,7 +233,7 @@ fn (mut g Gen) jge() int {
 	pos := g.pos()
 	g.write32(placeholder)
 	g.println('jne')
-	return pos
+	return int(pos)
 }
 
 fn (mut g Gen) jmp(addr int) {
@@ -669,7 +669,7 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 	// The value is the relative address, difference between current position and the location
 	// after `jne 00 00 00 00`
 	// println('after if g.pos=$g.pos() jneaddr=$jne_addr')
-	g.write32_at(jne_addr, g.pos() - jne_addr - 4) // 4 is for "00 00 00 00"
+	g.write32_at(jne_addr, int(g.pos() - jne_addr - 4)) // 4 is for "00 00 00 00"
 }
 
 fn (mut g Gen) for_stmt(node ast.ForStmt) {
@@ -690,9 +690,9 @@ fn (mut g Gen) for_stmt(node ast.ForStmt) {
 	g.stmts(node.stmts)
 	// Go back to `cmp ...`
 	// Diff between `jmp 00 00 00 00 X` and `cmp`
-	g.jmp(0xffffffff - (g.pos() + 5 - start) + 1)
+	g.jmp(int(0xffffffff - (g.pos() + 5 - start) + 1))
 	// Update the jump addr to current pos
-	g.write32_at(jump_addr, g.pos() - jump_addr - 4) // 4 is for "00 00 00 00"
+	g.write32_at(jump_addr, int(g.pos() - jump_addr - 4)) // 4 is for "00 00 00 00"
 	g.println('jpm after for')
 }
 
diff --git a/vlib/v/tests/fn_high_test.v b/vlib/v/tests/fn_high_test.v
index 7ce8802866..8f70aa4982 100644
--- a/vlib/v/tests/fn_high_test.v
+++ b/vlib/v/tests/fn_high_test.v
@@ -23,7 +23,7 @@ fn high_fn_multi_return(a int, b fn (c []int, d []string) ([]int, []string)) {
 fn high_fn_return_single_anon() (fn(int)f32) {
 	_ := 1
 	correct := fn(n int)f32 {
-		return n * n
+		return f32(n * n)
 	}
 	return correct
 }
@@ -36,7 +36,7 @@ fn high_fn_return_multi_anons() (fn(int)f32, fn(int)string) {
 		return '$n'
 	}
 	correct_first := fn(n int)f32 {
-		return n * n
+		return f32(n * n)
 	}
 	// parsing trap
 	_ := fn(n int)[]int {
@@ -110,7 +110,7 @@ fn simple_fn1() int {
 }
 
 fn simple_fn2(n f32) (int, string) {
-	return 1 + n, "fish"
+	return int(1 + n), "fish"
 }
 
 fn test_assigning_fns() {