diff --git a/vlib/builtin/float.v b/vlib/builtin/float.v
index ecf1ecc79f..abd3438aa8 100644
--- a/vlib/builtin/float.v
+++ b/vlib/builtin/float.v
@@ -6,7 +6,7 @@ module builtin
 #include <float.h>
 pub fn (d f64) str() string {
 	buf := malloc(sizeof(double) * 5 + 1) // TODO
-	C.sprintf(buf as charptr, '%f', d)
+	C.sprintf(charptr(buf), '%f', d)
 	return tos(buf, vstrlen(buf))
 }
 
diff --git a/vlib/builtin/int.v b/vlib/builtin/int.v
index 8dbcdd642e..144823fe09 100644
--- a/vlib/builtin/int.v
+++ b/vlib/builtin/int.v
@@ -28,7 +28,7 @@ pub fn (nn int) str() string {
 	// Fill the string from the end
 	for n > 0 {
 		d := n % 10
-		buf[max - len - 1] = d + (`0` as int)
+		buf[max - len - 1] = d + int(`0`)
 		len++
 		n = n / 10
 	}
@@ -42,31 +42,31 @@ pub fn (nn int) str() string {
 }
 
 pub fn (n i8) str() string {
-	return (n as int).str()
+	return int(n).str()
 }
 
 pub fn (n i16) str() string {
-	return (n as int).str()
+	return int(n).str()
 }
 
 pub fn (n u16) str() string {
-	return (n as int).str()
+	return int(n).str()
 }
 
 pub fn (nn u32) str() string {
 	mut n := nn
-	if n == (0 as u32) {
+	if n == 0 {
 		return '0'
 	}
 	max := 16
 	mut buf := malloc(max)
 	mut len := 0
 	// Fill the string from the end
-	for n > (0 as u32) {
-		d := n % (10 as u32)
-		buf[max - len - 1] = d + (`0` as u32)
+	for n > 0 {
+		d := n % 10
+		buf[max - len - 1] = d + u32(`0`)
 		len++
-		n = n / (10 as u32)
+		n = n / 10
 	}
 	return tos(buf + max - len, len)
 }
@@ -94,14 +94,14 @@ pub fn (nn byte) str() string {
 
 pub fn (nn i64) str() string {
 	mut n := nn
-	if n == (0 as i64) {
+	if n == 0 {
 		return '0'
 	}
 	max := 32
 	mut buf := malloc(max)
 	mut len := 0
 	mut is_neg := false
-	if n < 0 { //(0 as i64) {
+	if n < 0 {
 		n = -n
 		is_neg = true
 	}
@@ -109,7 +109,7 @@ pub fn (nn i64) str() string {
 	for n > 0 {
 		//d := int(n % (10 as i64))
 		d := n % 10
-		buf[max - len - 1] = d + `0` as int
+		buf[max - len - 1] = d + int(`0`)
 		len++
 		n /= 10
 	}
@@ -132,7 +132,7 @@ pub fn (nn u64) str() string {
 	// Fill the string from the end
 	for n > 0 {
 		d := n % 10
-		buf[max - len - 1] = d + (`0` as u64)
+		buf[max - len - 1] = d + u64(`0`)
 		len++
 		n = n / (10)
 	}
@@ -180,14 +180,14 @@ pub fn (a []byte) contains(val byte) bool {
 }
 
 pub fn (c rune) str() string {
-	fst_byte := (c as int)>>8 * 3 & 0xff
+	fst_byte := int(c)>>8 * 3 & 0xff
 	len := utf8_char_len(fst_byte)
 	mut str := string{
 		len: len
 		str: malloc(len + 1)
 	}
 	for i := 0; i < len; i++ {
-		str.str[i] = (c as int)>>8 * (3 - i) & 0xff
+		str.str[i] = int(c)>>8 * (3 - i) & 0xff
 	}
 	str[len] = `\0`
 	return str
@@ -208,7 +208,7 @@ pub fn (c byte) is_capital() bool {
 }
 
 pub fn (b []byte) clone() []byte {
-	mut res := [(0 as byte)].repeat(b.len)
+	mut res := [byte(0)].repeat(b.len)
 	for i := 0; i < b.len; i++ {
 		res[i] = b[i]
 	}
diff --git a/vlib/compiler/expression.v b/vlib/compiler/expression.v
index e3af20c76c..353a10be1e 100644
--- a/vlib/compiler/expression.v
+++ b/vlib/compiler/expression.v
@@ -83,62 +83,37 @@ fn (p mut Parser) bool_expression() string {
 }
 
 fn (p mut Parser) key_as(typ string, start_ph int) string {
-		p.fspace()
-		p.next()
-		p.fspace()
-		cast_typ := p.get_type()
-		if typ == cast_typ {
-			p.warn('casting `$typ` to `$cast_typ` is not needed')
+	p.fspace()
+	p.next()
+	p.fspace()
+	cast_typ := p.get_type()
+	if typ == cast_typ {
+		p.error('casting `$typ` to `$cast_typ` is not needed')
+	}
+	if typ in p.table.sum_types {
+		T := p.table.find_type(cast_typ)
+		if T.parent != typ {
+			p.error('cannot cast `$typ` to `$cast_typ`. `$cast_typ` is not a variant of `$typ`' +
+			'parent=$T.parent')
 		}
-		is_byteptr := typ == 'byte*' || typ == 'byteptr'
-		is_bytearr := typ == 'array_byte'
-		if typ in p.table.sum_types {
-			T := p.table.find_type(cast_typ)
-			if T.parent != typ {
-				p.error('cannot cast `$typ` to `$cast_typ`. `$cast_typ` is not a variant of `$typ`' +
-				'parent=$T.parent')
-			}
-			p.cgen.set_placeholder(start_ph, '*($cast_typ*)')
-			p.gen('.obj')
-			// Make sure the sum type can be cast, otherwise throw a runtime error
-			/*
-			sum_type:= p.cgen.cur_line.all_after('*) (').replace('.obj', '.typ')
+		p.cgen.set_placeholder(start_ph, '*($cast_typ*)')
+		p.gen('.obj')
+		// Make sure the sum type can be cast, otherwise throw a runtime error
+		/*
+		sum_type:= p.cgen.cur_line.all_after('*) (').replace('.obj', '.typ')
 
-			n := cast_typ.all_after('__')
-			p.cgen.insert_before('if (($sum_type != SumType_$n) {
+		n := cast_typ.all_after('__')
+		p.cgen.insert_before('if (($sum_type != SumType_$n) {
 puts("runtime error: $p.file_name:$p.scanner.line_nr cannot cast sum type `$typ` to `$n`");
 exit(1);
 }
 ')
 */
-
-		} else if cast_typ == 'string' {
-			if is_byteptr || is_bytearr {
-					if p.tok == .comma {
-						p.check(.comma)
-						p.cgen.set_placeholder(start_ph, 'tos((byte *)')
-						if is_bytearr {
-							p.gen('.data')
-						}
-						p.gen(', ')
-						p.check_types(p.expression(), 'int')
-					}
-					else {
-						if is_bytearr {
-							p.gen('.data')
-						}
-						p.cgen.set_placeholder(start_ph, '/*!!!*/tos2((byte *)')
-						p.gen(')')
-					}
-				}
-			}
-		else {
-
-			p.cgen.set_placeholder(start_ph, '($cast_typ)(')
-			p.gen(')')
-		}
-		return cast_typ
-		}
+	} else {
+		p.error('`as` casts have been removed, use the old syntax: `Type(val)`')
+	}
+	return cast_typ
+}
 
 fn (p mut Parser) bterm() string {
 	ph := p.cgen.add_placeholder()
diff --git a/vlib/compiler/scanner.v b/vlib/compiler/scanner.v
index 150cd7ed23..855c1c1e3c 100644
--- a/vlib/compiler/scanner.v
+++ b/vlib/compiler/scanner.v
@@ -114,6 +114,7 @@ const(
 )
 
 fn filter_num_sep(txt byteptr, start int, end int) string {
+	unsafe {
 	mut b := malloc(end-start + 1) // add a byte for the endstring 0
 	mut i := start
 	mut i1 := 0
@@ -126,6 +127,7 @@ fn filter_num_sep(txt byteptr, start int, end int) string {
 	}
 	b[i1]=0 // C string compatibility
 	return string{b,i1}
+	}
 }
 
 fn (s mut Scanner) ident_bin_number() string {
diff --git a/vlib/strconv/atof.v b/vlib/strconv/atof.v
index 9058aa75c4..e681741a51 100644
--- a/vlib/strconv/atof.v
+++ b/vlib/strconv/atof.v
@@ -94,7 +94,7 @@ const (
 // f64 constants
 //
 	DIGITS = 18
-	DOUBLE_PLUS_ZERO = u64(0x0000000000000000)// as u64
+	DOUBLE_PLUS_ZERO = u64(0x0000000000000000)
 	DOUBLE_MINUS_ZERO = 0x8000000000000000
 	DOUBLE_PLUS_INFINITY = 0x7FF0000000000000
 	DOUBLE_MINUS_INFINITY = 0xFFF0000000000000
@@ -128,7 +128,7 @@ const (
 	MINUS = `-`
 	ZERO = `0`
 	NINE = `9`
-	TEN = 10// as u32
+	TEN = u32(10)
 )
 /**********************************************************************
 *
@@ -179,7 +179,7 @@ pub struct PrepNumber {
 pub mut:
 	negative bool=false // 0 if positive number, 1 if negative
 	exponent int=0 // power of 10 exponent
-	mantissa u64=0 as u64 // integer mantissa
+	mantissa u64=u64(0) // integer mantissa
 }
 /**********************************************************************
 *
diff --git a/vlib/time/time_nix.v b/vlib/time/time_nix.v
index 9a4fdbd085..9779a61055 100644
--- a/vlib/time/time_nix.v
+++ b/vlib/time/time_nix.v
@@ -16,5 +16,5 @@ struct C.tm {
 fn C.timegm(&tm) time_t
 
 fn make_unix_time(t tm) int {
-	return C.timegm(&t) as int
+	return int(C.timegm(&t))
 }
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 33d6e30051..409b2eb08e 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -53,6 +53,7 @@ pub fn parse_stmt(text string, table &table.Table) ast.Stmt {
 	mut p := Parser{
 		scanner: s
 		table: table
+		pref: &pref.Preferences{}
 	}
 	p.init_parse_fns()
 	p.read_first_token()
diff --git a/vlib/v/scanner/scanner.v b/vlib/v/scanner/scanner.v
index 0642d94d9a..f81f72dcbd 100644
--- a/vlib/v/scanner/scanner.v
+++ b/vlib/v/scanner/scanner.v
@@ -97,23 +97,26 @@ fn (s mut Scanner) ident_name() string {
 	return name
 }
 
-const(
-	num_sep = `_`	// char used as number separator
+const (
+	num_sep = `_` // char used as number separator
 )
 
 fn filter_num_sep(txt byteptr, start int, end int) string {
-	mut b := malloc(end-start + 1) // add a byte for the endstring 0
-	mut i := start
-	mut i1 := 0
-	for i < end {
-		if txt[i] != num_sep {
-			b[i1]=txt[i]
-			i1++
+	unsafe{
+		mut b := malloc(end - start + 1) // add a byte for the endstring 0
+		mut i := start
+		mut i1 := 0
+		for i < end {
+			if txt[i] != num_sep {
+				b[i1] = txt[i]
+				i1++
+			}
+			i++
 		}
-		i++
+		b[i1] = 0 // C string compatibility
+		return string{
+			b,i1}
 	}
-	b[i1]=0 // C string compatibility
-	return string{b,i1}
 }
 
 fn (s mut Scanner) ident_bin_number() string {