diff --git a/vlib/compiler/expression.v b/vlib/compiler/expression.v
index 490031b8c1..de11e6c2dc 100644
--- a/vlib/compiler/expression.v
+++ b/vlib/compiler/expression.v
@@ -4,6 +4,8 @@
 module compiler
 
 fn (p mut Parser) bool_expression() string {
+	start_ph := p.cgen.add_placeholder()
+	expected := p.expected_type
 	tok := p.tok
 	typ := p.bterm()
 	mut got_and := false // to catch `a && b || c` in one expression without ()
@@ -44,6 +46,11 @@ fn (p mut Parser) bool_expression() string {
 		println(tok.str())
 		p.error('expr() returns empty type')
 	}
+	if expected != typ && expected in p.table.sum_types { // TODO perf
+		p.cgen.set_placeholder(start_ph, '/*KUK*/($expected) { .obj = ($typ[]) { ')
+		p.gen('}, .typ = 1}')//${val}_type }')
+
+	}
 	return typ
 }
 
@@ -362,7 +369,7 @@ fn (p mut Parser) name_expr() string {
 				//println(q)
 				//println(q[idx])
 				arg_type := q[idx]
-				p.gen('($enum_type.name) { .obj = ($arg_type[]) { ')
+	p.gen('($enum_type.name) { .obj = ($arg_type[]) { ')
 				p.bool_expression()
 				p.check(.rpar)
 				p.gen('}, .typ = ${val}_type }')
diff --git a/vlib/compiler/parser.v b/vlib/compiler/parser.v
index 8c7801c9cc..6562792291 100644
--- a/vlib/compiler/parser.v
+++ b/vlib/compiler/parser.v
@@ -160,7 +160,7 @@ fn (v mut V) new_parser_from_file(path string) Parser {
 			break
 		}
 	}
-	
+
 	if v.compile_defines.len > 0 {
 		for cdefine in v.compile_defines {
 			custom_path_ending := '_d_${cdefine}.v'
@@ -171,7 +171,7 @@ fn (v mut V) new_parser_from_file(path string) Parser {
 			}
 		}
 	}
-	
+
 	mut p := v.new_parser(new_scanner_file(path))
 	p = {
 		p |
@@ -793,20 +793,79 @@ fn (p mut Parser) type_decl() {
 	if p.tok == .key_struct {
 		p.error('use `struct $name {` instead of `type $name struct {`')
 	}
+	if p.tok == .assign {
+		p.next()
+
+	}
 	parent := p.get_type2()
+	// Sum type
+	is_sum := p.tok == .pipe
+	if is_sum {
+		// Register the first child  (name we already parsed)
+		/*
+		p.table.register_type(Type{
+			parent: name
+			name: parent.name // yeah it's not a parent here
+			mod: p.mod
+			is_public: is_pub
+		})
+		*/
+		// Register the rest of them
+		for p.tok == .pipe {
+			p.next()
+			child := p.check_name()
+			if p.pass == .main {
+				// Update the type's parent
+				println('child=$child parent=$name')
+				mut t := p.table.find_type(child)
+				if t.name == '' {
+					p.error('unknown type `$child`')
+				}
+				t.parent = name
+				p.table.rewrite_type(t)
+				/*
+				p.table.register_type(Type{
+					parent: name
+					name: child
+					mod: p.mod
+					is_public: is_pub
+				})
+				*/
+			}
+		}
+		if p.pass == .decl {
+			p.table.sum_types << name
+			println(p.table.sum_types)
+		}
+		// Register the actual sum type
+		println('reging sum $name')
+		p.table.register_type(Type{
+			name: name
+			mod: p.mod
+			cat: .alias
+			is_public: is_pub
+		})
+		p.gen_typedef('typedef struct {
+void* obj;
+int typ;
+} $name;
+')
+	}
 	nt_pair := p.table.cgen_name_type_pair(name, parent.name)
 	// TODO dirty C typedef hacks for DOOM
 	// Unknown type probably means it's a struct, and it's used before the struct is defined,
 	// so specify "struct"
 	_struct := if parent.cat != .array && parent.cat != .func && !p.table.known_type(parent.name) { 'struct' } else { '' }
-	p.gen_typedef('typedef $_struct $nt_pair; //type alias name="$name" parent=`$parent.name`')
-	p.table.register_type(Type{
-		name: name
-		parent: parent.name
-		mod: p.mod
-		cat: .alias
-		is_public: is_pub
-	})
+	if !is_sum {
+		p.gen_typedef('typedef $_struct $nt_pair; //type alias name="$name" parent=`$parent.name`')
+		p.table.register_type(Type{
+			name: name
+			parent: parent.name
+			mod: p.mod
+			cat: .alias
+			is_public: is_pub
+		})
+	}
 	if p.tok != .key_type {
 		p.fspace()
 	}
diff --git a/vlib/compiler/table.v b/vlib/compiler/table.v
index f4dfed78d6..f74103cbea 100644
--- a/vlib/compiler/table.v
+++ b/vlib/compiler/table.v
@@ -21,7 +21,8 @@ pub mut:
 	// names        []Name
 	max_field_len         map[string]int // for vfmt: max_field_len['Parser'] == 12
 	generic_struct_params map[string][]string
-	tuple_variants map[string][]string
+	tuple_variants map[string][]string // enum( Bool(BoolExpr) )
+	sum_types []string
 }
 
 struct VargAccess {
@@ -593,6 +594,9 @@ fn (t &Table) find_type(name_ string) Type {
 }
 
 fn (p mut Parser) check_types2(got_, expected_ string, throw bool) bool {
+	if p.fileis('type_test') {
+		println('got=$got_ exp=$expected_')
+	}
 	mut got := got_
 	mut expected := expected_
 	// p.log('check types got="$got" exp="$expected"  ')
@@ -725,6 +729,16 @@ fn (p mut Parser) check_types2(got_, expected_ string, throw bool) bool {
 				return true
 			}
 		}
+		// Sum type
+		println(expected)
+		if expected in p.table.sum_types {
+			println('checking sum')
+			child := p.table.find_type(got)
+			if child.parent == expected {
+				println('yep $expected')
+				return true
+			}
+		}
 		if !throw {
 			return false
 		}
diff --git a/vlib/compiler/tests/type_test.v b/vlib/compiler/tests/type_test.v
index 688bd0669d..4509b11f7f 100644
--- a/vlib/compiler/tests/type_test.v
+++ b/vlib/compiler/tests/type_test.v
@@ -17,3 +17,48 @@ fn test_person_str() {
 	println(p)
 	assert p.str() == 'Person: Bilbo'
 }
+
+struct Foo {}
+
+struct WTF {
+	wtf int
+}
+
+struct BoolExpr {
+	foo int
+
+}
+
+struct BinExpr {
+
+}
+
+struct UnaryExpr {
+
+}
+
+type Expr = Foo | BoolExpr |  BinExpr | UnaryExpr
+
+fn handle_expr(e Expr) {
+
+}
+
+fn parse_bool() BoolExpr {
+	return BoolExpr{}
+}
+
+fn test_sum() {
+	b := parse_bool()
+	handle_expr(b)
+}
+
+/*
+#define ExprType_BoolExpr 0
+#define ExprType_BinExpr 1
+#define ExprType_UnaryExpr 2
+
+struct Expr {
+	int   typ;
+	void* obj;
+}
+*/