diff --git a/vlib/builtin/array.v b/vlib/builtin/array.v
index 740aeabd70..4bd6aa7fea 100644
--- a/vlib/builtin/array.v
+++ b/vlib/builtin/array.v
@@ -376,7 +376,7 @@ pub fn (a &array) clone_to_depth(depth int) array {
 		}
 		return arr
 	} else {
-		if a.data != 0 {
+		if !isnil(a.data) {
 			unsafe { C.memcpy(&byte(arr.data), a.data, a.cap * a.element_size) }
 		}
 		return arr
@@ -409,7 +409,7 @@ fn (mut a array) push(val voidptr) {
 // `val` is array.data and user facing usage is `a << [1,2,3]`
 [unsafe]
 pub fn (mut a3 array) push_many(val voidptr, size int) {
-	if a3.data == val && val != 0 {
+	if a3.data == val && !isnil(a3.data) {
 		// handle `arr << arr`
 		copy := a3.clone()
 		a3.ensure_cap(a3.len + size)
@@ -419,7 +419,7 @@ pub fn (mut a3 array) push_many(val voidptr, size int) {
 		}
 	} else {
 		a3.ensure_cap(a3.len + size)
-		if a3.data != 0 && val != 0 {
+		if !isnil(a3.data) && !isnil(val) {
 			unsafe { C.memcpy(a3.get_unsafe(a3.len), val, a3.element_size * size) }
 		}
 	}
diff --git a/vlib/builtin/array_d_gcboehm_opt.v b/vlib/builtin/array_d_gcboehm_opt.v
index 08feca96fe..330977da5d 100644
--- a/vlib/builtin/array_d_gcboehm_opt.v
+++ b/vlib/builtin/array_d_gcboehm_opt.v
@@ -204,7 +204,7 @@ fn (a &array) clone_to_depth_noscan(depth int) array {
 		}
 		return arr
 	} else {
-		if a.data != 0 {
+		if !isnil(a.data) {
 			unsafe { C.memcpy(&byte(arr.data), a.data, a.cap * a.element_size) }
 		}
 		return arr
@@ -221,7 +221,7 @@ fn (mut a array) push_noscan(val voidptr) {
 // `val` is array.data and user facing usage is `a << [1,2,3]`
 [unsafe]
 fn (mut a3 array) push_many_noscan(val voidptr, size int) {
-	if a3.data == val && val != 0 {
+	if a3.data == val && !isnil(a3.data) {
 		// handle `arr << arr`
 		copy := a3.clone()
 		a3.ensure_cap_noscan(a3.len + size)
@@ -231,7 +231,7 @@ fn (mut a3 array) push_many_noscan(val voidptr, size int) {
 		}
 	} else {
 		a3.ensure_cap_noscan(a3.len + size)
-		if a3.data != 0 && val != 0 {
+		if !isnil(a3.data) && !isnil(val) {
 			unsafe { C.memcpy(a3.get_unsafe(a3.len), val, a3.element_size * size) }
 		}
 	}
diff --git a/vlib/builtin/builtin_nix.c.v b/vlib/builtin/builtin_nix.c.v
index 0eba14efc4..1d1cf0d02b 100644
--- a/vlib/builtin/builtin_nix.c.v
+++ b/vlib/builtin/builtin_nix.c.v
@@ -110,7 +110,7 @@ fn print_backtrace_skipping_top_frames_linux(skipframes int) bool {
 				cmd := 'addr2line -e $executable $addr'
 				// taken from os, to avoid depending on the os module inside builtin.v
 				f := C.popen(&char(cmd.str), c'r')
-				if f == 0 {
+				if isnil(f) {
 					eprintln(sframe)
 					continue
 				}
diff --git a/vlib/builtin/sorted_map.v b/vlib/builtin/sorted_map.v
index 391d1c7c5b..2567a3cca4 100644
--- a/vlib/builtin/sorted_map.v
+++ b/vlib/builtin/sorted_map.v
@@ -73,7 +73,7 @@ fn (mut m SortedMap) set(key string, value voidptr) {
 	mut parent := &mapnode(0)
 	for {
 		if node.len == max_len {
-			if parent != 0 {
+			if isnil(parent) {
 				parent = new_node()
 				m.root = parent
 			}
@@ -100,7 +100,7 @@ fn (mut m SortedMap) set(key string, value voidptr) {
 			}
 			return
 		}
-		if node.children == 0 {
+		if isnil(node.children) {
 			mut j := node.len - 1
 			for j >= 0 && key < node.keys[j] {
 				node.keys[j + 1] = node.keys[j]
@@ -130,7 +130,7 @@ fn (mut n mapnode) split_child(child_index int, mut y mapnode) {
 		z.keys[j] = y.keys[j + degree]
 		z.values[j] = y.values[j + degree]
 	}
-	if y.children != 0 {
+	if !isnil(y.children) {
 		z.children = unsafe { &voidptr(malloc(int(children_bytes))) }
 		for jj := degree - 1; jj >= 0; jj-- {
 			unsafe {
@@ -139,7 +139,7 @@ fn (mut n mapnode) split_child(child_index int, mut y mapnode) {
 		}
 	}
 	unsafe {
-		if n.children == 0 {
+		if isnil(n.children) {
 			n.children = &voidptr(malloc(int(children_bytes)))
 		}
 		n.children[n.len + 1] = n.children[n.len]
@@ -173,7 +173,7 @@ fn (m SortedMap) get(key string, out voidptr) bool {
 			}
 			return true
 		}
-		if node.children == 0 {
+		if isnil(node.children) {
 			break
 		}
 		node = unsafe { &mapnode(node.children[i + 1]) }
@@ -182,7 +182,7 @@ fn (m SortedMap) get(key string, out voidptr) bool {
 }
 
 fn (m SortedMap) exists(key string) bool {
-	if m.root == 0 { // TODO: find out why root can be nil
+	if isnil(m.root) { // TODO: find out why root can be nil
 		return false
 	}
 	mut node := m.root
@@ -194,7 +194,7 @@ fn (m SortedMap) exists(key string) bool {
 		if i != -1 && key == node.keys[i] {
 			return true
 		}
-		if node.children == 0 {
+		if isnil(node.children) {
 			break
 		}
 		node = unsafe { &mapnode(node.children[i + 1]) }
@@ -213,14 +213,14 @@ fn (n &mapnode) find_key(k string) int {
 fn (mut n mapnode) remove_key(k string) bool {
 	idx := n.find_key(k)
 	if idx < n.len && n.keys[idx] == k {
-		if n.children == 0 {
+		if isnil(n.children) {
 			n.remove_from_leaf(idx)
 		} else {
 			n.remove_from_non_leaf(idx)
 		}
 		return true
 	} else {
-		if n.children == 0 {
+		if isnil(n.children) {
 			return false
 		}
 		flag := if idx == n.len { true } else { false }
@@ -250,7 +250,7 @@ fn (mut n mapnode) remove_from_non_leaf(idx int) {
 	k := n.keys[idx]
 	if unsafe { &mapnode(n.children[idx]) }.len >= degree {
 		mut current := unsafe { &mapnode(n.children[idx]) }
-		for current.children != 0 {
+		for !isnil(current.children) {
 			current = unsafe { &mapnode(current.children[current.len]) }
 		}
 		predecessor := current.keys[current.len - 1]
@@ -260,7 +260,7 @@ fn (mut n mapnode) remove_from_non_leaf(idx int) {
 		node.remove_key(predecessor)
 	} else if unsafe { &mapnode(n.children[idx + 1]) }.len >= degree {
 		mut current := unsafe { &mapnode(n.children[idx + 1]) }
-		for current.children != 0 {
+		for !isnil(current.children) {
 			current = unsafe { &mapnode(current.children[0]) }
 		}
 		successor := current.keys[0]
@@ -294,7 +294,7 @@ fn (mut n mapnode) borrow_from_prev(idx int) {
 		child.keys[i + 1] = child.keys[i]
 		child.values[i + 1] = child.values[i]
 	}
-	if child.children != 0 {
+	if !isnil(child.children) {
 		for i := child.len; i >= 0; i-- {
 			unsafe {
 				child.children[i + 1] = child.children[i]
@@ -303,7 +303,7 @@ fn (mut n mapnode) borrow_from_prev(idx int) {
 	}
 	child.keys[0] = n.keys[idx - 1]
 	child.values[0] = n.values[idx - 1]
-	if child.children != 0 {
+	if !isnil(child.children) {
 		unsafe {
 			child.children[0] = sibling.children[sibling.len]
 		}
@@ -319,7 +319,7 @@ fn (mut n mapnode) borrow_from_next(idx int) {
 	mut sibling := unsafe { &mapnode(n.children[idx + 1]) }
 	child.keys[child.len] = n.keys[idx]
 	child.values[child.len] = n.values[idx]
-	if child.children != 0 {
+	if !isnil(child.children) {
 		unsafe {
 			child.children[child.len + 1] = sibling.children[0]
 		}
@@ -330,7 +330,7 @@ fn (mut n mapnode) borrow_from_next(idx int) {
 		sibling.keys[i - 1] = sibling.keys[i]
 		sibling.values[i - 1] = sibling.values[i]
 	}
-	if sibling.children != 0 {
+	if !isnil(sibling.children) {
 		for i := 1; i <= sibling.len; i++ {
 			unsafe {
 				sibling.children[i - 1] = sibling.children[i]
@@ -350,7 +350,7 @@ fn (mut n mapnode) merge(idx int) {
 		child.keys[i + degree] = sibling.keys[i]
 		child.values[i + degree] = sibling.values[i]
 	}
-	if child.children != 0 {
+	if !isnil(child.children) {
 		for i := 0; i <= sibling.len; i++ {
 			unsafe {
 				child.children[i + degree] = sibling.children[i]
@@ -383,10 +383,11 @@ pub fn (mut m SortedMap) delete(key string) {
 
 	if m.root.len == 0 {
 		// tmp := t.root
-		if m.root.children == 0 {
+		if isnil(m.root.children) {
 			return
+		} else {
+			m.root = unsafe { &mapnode(m.root.children[0]) }
 		}
-		m.root = unsafe { &mapnode(m.root.children[0]) }
 		// free(tmp)
 	}
 }
@@ -395,7 +396,7 @@ pub fn (mut m SortedMap) delete(key string) {
 // starting at `at`. Keys are inserted in order.
 fn (n &mapnode) subkeys(mut keys []string, at int) int {
 	mut position := at
-	if n.children != 0 {
+	if !isnil(n.children) {
 		// Traverse children and insert
 		// keys inbetween children
 		for i in 0 .. n.len {
@@ -420,7 +421,7 @@ fn (n &mapnode) subkeys(mut keys []string, at int) int {
 
 pub fn (m &SortedMap) keys() []string {
 	mut keys := []string{len: m.len}
-	if m.root == 0 || m.root.len == 0 {
+	if isnil(m.root) || m.root.len == 0 {
 		return keys
 	}
 	m.root.subkeys(mut keys, 0)
@@ -432,7 +433,7 @@ fn (mut n mapnode) free() {
 }
 
 pub fn (mut m SortedMap) free() {
-	if m.root == 0 {
+	if isnil(m.root) {
 		return
 	}
 	m.root.free()
diff --git a/vlib/v/ast/scope.v b/vlib/v/ast/scope.v
index b32b936a94..31bc3d1d72 100644
--- a/vlib/v/ast/scope.v
+++ b/vlib/v/ast/scope.v
@@ -38,7 +38,7 @@ pub fn new_scope(parent &Scope, start_pos int) &Scope {
 */
 
 fn (s &Scope) dont_lookup_parent() bool {
-	return s.parent == 0 || s.detached_from_parent
+	return isnil(s.parent) || s.detached_from_parent
 }
 
 pub fn (s &Scope) find_with_scope(name string) ?(ScopeObject, &Scope) {
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 9f4605d74a..83baf73f41 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -2842,7 +2842,7 @@ fn (mut g Gen) trace_autofree(line string) {
 
 // fn (mut g Gen) autofree_scope_vars2(scope &ast.Scope, end_pos int) {
 fn (mut g Gen) autofree_scope_vars2(scope &ast.Scope, start_pos int, end_pos int, line_nr int, free_parent_scopes bool, stop_pos int) {
-	if scope == 0 {
+	if isnil(scope) {
 		return
 	}
 	for _, obj in scope.objects {