diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index c0bb87c8ad..2e55e3fbc3 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -6,11 +6,11 @@ module ast
 import v.token
 import v.table
 
-pub type TypeDecl = AliasTypeDecl | SumTypeDecl | FnTypeDecl
+pub type TypeDecl = AliasTypeDecl | FnTypeDecl | SumTypeDecl
 
-pub type Expr = AnonFn | ArrayInit | AsCast | AssignExpr | Assoc | BoolLiteral | CastExpr | CallExpr | CharLiteral | ConcatExpr | EnumVal | FloatLiteral | IfExpr | Ident | IfGuardExpr | InfixExpr | IndexExpr | IntegerLiteral | MapInit | MatchExpr | None | OrExpr | ParExpr | PostfixExpr | PrefixExpr | RangeExpr | SelectorExpr | SizeOf | StringLiteral | StringInterLiteral | StructInit | Type | TypeOf
+pub type Expr = AnonFn | ArrayInit | AsCast | AssignExpr | Assoc | BoolLiteral | CallExpr | CastExpr | CharLiteral | ConcatExpr | EnumVal | FloatLiteral | Ident | IfExpr | IfGuardExpr | IndexExpr | InfixExpr | IntegerLiteral | MapInit | MatchExpr | None | OrExpr | ParExpr | PostfixExpr | PrefixExpr | RangeExpr | SelectorExpr | SizeOf | StringInterLiteral | StringLiteral | StructInit | Type | TypeOf
 
-pub type Stmt = AssignStmt | AssertStmt | Attr | Block | BranchStmt | Comment | CompIf | ConstDecl | DeferStmt | EnumDecl | ExprStmt | FnDecl | ForCStmt | ForInStmt | ForStmt | GlobalDecl | GoStmt | GotoLabel | GotoStmt | HashStmt | Import | InterfaceDecl | Module | Return | StructDecl | TypeDecl | UnsafeStmt
+pub type Stmt = AssertStmt | AssignStmt | Attr | Block | BranchStmt | Comment | CompIf | ConstDecl | DeferStmt | EnumDecl | ExprStmt | FnDecl | ForCStmt | ForInStmt | ForStmt | GlobalDecl | GoStmt | GotoLabel | GotoStmt | HashStmt | Import | InterfaceDecl | Module | Return | StructDecl | TypeDecl | UnsafeStmt
 
 pub type ScopeObject = ConstField | GlobalDecl | Var
 
@@ -428,7 +428,6 @@ pub:
 	is_else bool
 }
 
-
 /*
 CompIf.is_opt:
 `$if xyz? {}` => this compile time `if` is optional,
@@ -438,7 +437,6 @@ if `xyz` is NOT defined.
 If .is_opt is false, then when `xyz` is not defined,
 the compilation will fail.
 */
-
 pub struct CompIf {
 pub:
 	val        string
diff --git a/vlib/v/ast/str.v b/vlib/v/ast/str.v
index cd7bcb29e7..26a61c8fde 100644
--- a/vlib/v/ast/str.v
+++ b/vlib/v/ast/str.v
@@ -28,7 +28,7 @@ pub fn (node &FnDecl) str(t &table.Table) string {
 			m = '&'
 		}
 		receiver = '($node.receiver.name $m$name) '
-*/
+		*/
 	}
 	mut name := if node.is_anon { '' } else { node.name.after('.') }
 	if node.is_c {
diff --git a/vlib/v/builder/x64.v b/vlib/v/builder/x64.v
index 0435c8cd02..a49446f8e3 100644
--- a/vlib/v/builder/x64.v
+++ b/vlib/v/builder/x64.v
@@ -30,7 +30,7 @@ pub fn (mut b Builder) build_x64(v_files []string, out_file string) {
 
 pub fn (mut b Builder) compile_x64() {
 	// v.files << v.v_files_from_dir(os.join_path(v.pref.vlib_path,'builtin','bare'))
-	files := [ b.pref.path]
+	files := [b.pref.path]
 	b.set_module_lookup_paths()
 	b.build_x64(files, b.pref.out_name)
 }
diff --git a/vlib/v/checker/tests/inout/checker_error_test.v b/vlib/v/checker/tests/inout/checker_error_test.v
index 5ac03c4750..a7c015937f 100644
--- a/vlib/v/checker/tests/inout/checker_error_test.v
+++ b/vlib/v/checker/tests/inout/checker_error_test.v
@@ -4,7 +4,7 @@ import term
 fn test_all() {
 	mut total_errors := 0
 	vexe := os.getenv('VEXE')
-	//vroot := os.dir(vexe)
+	// vroot := os.dir(vexe)
 	dir := 'vlib/v/checker/tests/inout'
 	files := os.ls(dir) or {
 		panic(err)
@@ -28,8 +28,10 @@ fn test_all() {
 		mut expected := os.read_file(program.replace('.v', '') + '.out') or {
 			panic(err)
 		}
-		expected = expected.trim_space().replace(' \n', '\n').replace(' \r\n', '\n').replace('\r\n', '\n').trim('\n')
-		found := res.output.trim_space().replace(' \n', '\n').replace(' \r\n', '\n').replace('\r\n', '\n').trim('\n')
+		expected = expected.trim_space().replace(' \n', '\n').replace(' \r\n', '\n').replace('\r\n',
+			'\n').trim('\n')
+		found := res.output.trim_space().replace(' \n', '\n').replace(' \r\n', '\n').replace('\r\n',
+			'\n').trim('\n')
 		if expected != found {
 			println(term.red('FAIL'))
 			println('============')
@@ -40,8 +42,7 @@ fn test_all() {
 			println(found)
 			println('============\n')
 			total_errors++
-		}
-		else {
+		} else {
 			println(term.green('OK'))
 		}
 	}
diff --git a/vlib/v/doc/doc.v b/vlib/v/doc/doc.v
index 986f43eb6e..2ca2b3de2a 100644
--- a/vlib/v/doc/doc.v
+++ b/vlib/v/doc/doc.v
@@ -1,14 +1,11 @@
 module doc
 
-import (
-	strings
-	// v.builder
-	v.pref
-	v.table
-	v.parser
-	v.ast
-	os
-)
+import strings
+import v.pref
+import v.table
+import v.parser
+import v.ast
+import os
 
 struct Doc {
 	out   strings.Builder
@@ -18,7 +15,7 @@ mut:
 	stmts []ast.Stmt // all module statements from all files
 }
 
-type FilterFn fn(node ast.FnDecl)bool
+type FilterFn = fn (node ast.FnDecl) bool
 
 pub fn doc(mod string, table &table.Table) string {
 	mut d := Doc{
@@ -28,7 +25,7 @@ pub fn doc(mod string, table &table.Table) string {
 	}
 	vlib_path := os.dir(pref.vexe_path()) + '/vlib'
 	mod_path := mod.replace('.', os.path_separator)
-	path := os.join_path(vlib_path,mod_path)
+	path := os.join_path(vlib_path, mod_path)
 	if !os.exists(path) {
 		println('module "$mod" not found')
 		println(path)
@@ -45,7 +42,10 @@ pub fn doc(mod string, table &table.Table) string {
 		if file.ends_with('_test.v') || file.ends_with('_windows.c.v') || file.ends_with('_macos.c.v') {
 			continue
 		}
-		file_ast := parser.parse_file(os.join_path(path,file), table, .skip_comments,	&pref.Preferences{}, &ast.Scope{parent: 0})
+		file_ast := parser.parse_file(os.join_path(path, file), table, .skip_comments, &pref.Preferences{},
+			&ast.Scope{
+			parent: 0
+		})
 		d.stmts << file_ast.stmts
 	}
 	if d.stmts.len == 0 {
@@ -58,12 +58,11 @@ pub fn doc(mod string, table &table.Table) string {
 	d.out.writeln('')
 	d.print_methods()
 	/*
-		for stmt in file_ast.stmts {
+	for stmt in file_ast.stmts {
 			d.stmt(stmt)
 		}
 	println(path)
 	*/
-
 	return d.out.str().trim_space()
 }
 
@@ -71,18 +70,18 @@ fn (d &Doc) get_fn_node(f ast.FnDecl) string {
 	return f.str(d.table).replace_each([d.mod + '.', '', 'pub ', ''])
 }
 
-fn (d mut Doc) print_fns() {
+fn (mut d Doc) print_fns() {
 	fn_signatures := d.get_fn_signatures(is_pub_function)
 	d.write_fn_signatures(fn_signatures)
 }
 
-fn (d mut Doc) print_methods() {
+fn (mut d Doc) print_methods() {
 	fn_signatures := d.get_fn_signatures(is_pub_method)
 	d.write_fn_signatures(fn_signatures)
 }
 
 [inline]
-fn (d mut Doc) write_fn_signatures(fn_signatures []string) {
+fn (mut d Doc) write_fn_signatures(fn_signatures []string) {
 	for s in fn_signatures {
 		d.out.writeln(s)
 	}
@@ -98,7 +97,7 @@ fn (d Doc) get_fn_signatures(filter_fn FilterFn) []string {
 				}
 			}
 			else {}
-	}
+		}
 	}
 	fn_signatures.sort()
 	return fn_signatures
@@ -113,7 +112,7 @@ fn is_pub_function(node ast.FnDecl) bool {
 }
 
 // TODO it's probably better to keep using AST, not `table`
-fn (d mut Doc) print_enums() {
+fn (mut d Doc) print_enums() {
 	for typ in d.table.types {
 		if typ.kind != .enum_ {
 			continue
@@ -127,7 +126,7 @@ fn (d mut Doc) print_enums() {
 	}
 }
 
-fn (d mut Doc) print_structs() {
+fn (mut d Doc) print_structs() {
 	for typ in d.table.types {
 		if typ.kind != .struct_ || !typ.name.starts_with(d.mod + '.') {
 			// !typ.name[0].is_capital() || typ.name.starts_with('C.') {
diff --git a/vlib/v/fmt/fmt.v b/vlib/v/fmt/fmt.v
index bf6bf04d13..6f1a5daa8c 100644
--- a/vlib/v/fmt/fmt.v
+++ b/vlib/v/fmt/fmt.v
@@ -375,6 +375,44 @@ fn (mut f Fmt) type_decl(node ast.TypeDecl) {
 			ptype := f.type_to_str(it.parent_type)
 			f.write('type $it.name $ptype')
 		}
+		ast.FnTypeDecl {
+			if it.is_pub {
+				f.write('pub ')
+			}
+			typ_sym := f.table.get_type_symbol(it.typ)
+			fn_typ_info := typ_sym.info as table.FnType
+			fn_info := fn_typ_info.func
+			fn_name := it.name.replace(f.cur_mod + '.', '')
+			f.write('type $fn_name = fn (')
+			for i, arg in fn_info.args {
+				f.write(arg.name)
+				mut s := f.table.type_to_str(arg.typ)
+				if arg.is_mut {
+					f.write('mut ')
+					if s.starts_with('&') {
+						s = s[1..]
+					}
+				}
+				is_last_arg := i == fn_info.args.len - 1
+				should_add_type := is_last_arg || fn_info.args[i + 1].typ != arg.typ || (fn_info.is_variadic &&
+					i == fn_info.args.len - 2)
+				if should_add_type {
+					if fn_info.is_variadic && is_last_arg {
+						f.write(' ...' + s)
+					} else {
+						f.write(' ' + s)
+					}
+				}
+				if !is_last_arg {
+					f.write(', ')
+				}
+			}
+			f.write(')')
+			if fn_info.return_type.idx() != table.void_type_idx {
+				ret_str := f.table.type_to_str(fn_info.return_type)
+				f.write(' ' + ret_str)
+			}
+		}
 		ast.SumTypeDecl {
 			if it.is_pub {
 				f.write('pub ')
@@ -384,11 +422,9 @@ fn (mut f Fmt) type_decl(node ast.TypeDecl) {
 			for t in it.sub_types {
 				sum_type_names << f.type_to_str(t)
 			}
+			sum_type_names.sort()
 			f.write(sum_type_names.join(' | '))
 		}
-		else {
-			eprintln('fmt type_decl: unknown ' + typeof(node))
-		}
 	}
 	f.writeln('\n')
 }
diff --git a/vlib/v/fmt/tests/types_expected.vv b/vlib/v/fmt/tests/types_expected.vv
index a6ef5d4a2b..ef09bd4587 100644
--- a/vlib/v/fmt/tests/types_expected.vv
+++ b/vlib/v/fmt/tests/types_expected.vv
@@ -1,9 +1,26 @@
 // Sumtype
-type FooBar = Foo | Bar
+type FooBar = Bar | Foo
 
-pub type PublicBar = Foo | Bar | FooBar
+pub type PublicBar = Bar | Foo | FooBar
+
+type Uint = byte | u16 | u32 | u64
+
+type Float = f32 | f64
 
 // Alias type
 type MyInt int
 
 pub type Abc f32
+
+// Fn type decl
+type EmptyFn = fn ()
+
+type OneArgFn = fn (i int)
+
+type TwoDiffArgs = fn (i int, s string) bool
+
+type TwoSameArgs = fn (i, j int) string
+
+type VarArgs = fn (s ...string) int
+
+type NOVarArgs = fn (i int, s ...string) f64
diff --git a/vlib/v/fmt/tests/types_input.vv b/vlib/v/fmt/tests/types_input.vv
index 3293566bd7..4feee90157 100644
--- a/vlib/v/fmt/tests/types_input.vv
+++ b/vlib/v/fmt/tests/types_input.vv
@@ -4,7 +4,32 @@
    type    FooBar=   Foo |     Bar
    pub type   PublicBar = Foo | Bar | FooBar
 
+type   Uint =   u16 | u64
+	| u32
+	    | byte
+type
+Float =
+	f32 |
+	f64
+
  // Alias type
      type  MyInt    int
-	 
+
  pub type Abc f32
+
+
+// Fn type decl
+
+ type EmptyFn	= fn()
+type OneArgFn =
+	fn (i    int)
+type TwoDiffArgs
+= fn (i    int, s string) bool
+
+
+	type TwoSameArgs = fn(i int, j int) string
+
+type VarArgs = fn
+(s ...string) int
+
+type NOVarArgs = fn(i int, s ...string) f64
diff --git a/vlib/v/gen/json.v b/vlib/v/gen/json.v
index 296a173a8e..eab7ccdbfb 100644
--- a/vlib/v/gen/json.v
+++ b/vlib/v/gen/json.v
@@ -3,10 +3,8 @@
 // that can be found in the LICENSE file.
 module gen
 
-import (
-	v.table
-	strings
-)
+import v.table
+import strings
 
 // TODO replace with comptime code generation.
 // TODO remove cJSON dependency.
@@ -19,7 +17,7 @@ import (
 // return res;
 // }
 // Codegen json_decode/encode funcs
-fn (g mut Gen) gen_json_for_type(typ table.Type) {
+fn (mut g Gen) gen_json_for_type(typ table.Type) {
 	mut dec := strings.new_builder(100)
 	mut enc := strings.new_builder(100)
 	sym := g.table.get_type_symbol(typ)
@@ -73,7 +71,7 @@ Option ${dec_fn.name}(cJSON* root, $t* res) {
     }
   }
 '
-*/
+	*/
 	// Code gen encoder
 	enc_fn_name := js_enc_name(sym.name)
 	enc.writeln('
diff --git a/vlib/v/table/atypes.v b/vlib/v/table/atypes.v
index 7d5f8b9ee6..d571760c47 100644
--- a/vlib/v/table/atypes.v
+++ b/vlib/v/table/atypes.v
@@ -16,7 +16,7 @@ import v.ast
 
 pub type Type int
 
-pub type TypeInfo = Array | ArrayFixed | Map | Struct | Interface | MultiReturn | Alias | Enum | SumType | FnType
+pub type TypeInfo = Alias | Array | ArrayFixed | Enum | FnType | Interface | Map | MultiReturn | Struct | SumType
 
 pub struct TypeSymbol {
 pub: