diff --git a/cmd/tools/vpm.v b/cmd/tools/vpm.v
index e591526e1b..4d9983a2df 100644
--- a/cmd/tools/vpm.v
+++ b/cmd/tools/vpm.v
@@ -141,7 +141,7 @@ fn vpm_install(module_names []string) {
 		if vcs == '' {
 			vcs = supported_vcs_systems[0]
 		}
-		if !vcs in supported_vcs_systems {
+		if vcs !in supported_vcs_systems {
 			errors++
 			println('Skipping module "$name", since it uses an unsupported VCS {$vcs} .')
 			continue
diff --git a/vlib/json/json_primitives.v b/vlib/json/json_primitives.v
index 5adb206b6a..ad274daa21 100644
--- a/vlib/json/json_primitives.v
+++ b/vlib/json/json_primitives.v
@@ -13,11 +13,12 @@ struct C.cJSON {
 }
 
 pub fn decode() voidptr {
-
+	return 0
 }
 
-pub fn encode() voidptr {
-
+pub fn encode(x voidptr) string {
+	// compiler implementation
+	return ''
 }
 
 fn jsdecode_int(root &C.cJSON) int {
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 2e16ac247a..7b0093dae1 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -890,6 +890,9 @@ fn (c mut Checker) stmt(node ast.Stmt) {
 			// c.warn('duplicate method `$it.name`', it.pos)
 			// }
 			// }
+			if f := c.table.find_fn(it.name) {
+				c.warn('redefinition of `$it.name`', it.pos)
+			}
 			c.expected_type = table.void_type
 			c.fn_return_type = it.return_type
 			c.stmts(it.stmts)
@@ -1551,7 +1554,7 @@ pub fn (c mut Checker) error(message string, pos token.Position) {
 fn (c mut Checker) warn_or_error(message string, pos token.Position, warn bool) {
 	// add backtrace to issue struct, how?
 	// if c.pref.is_verbose {
-	//	print_backtrace()
+	// print_backtrace()
 	// }
 	if !warn {
 		c.nr_errors++
@@ -1571,7 +1574,6 @@ fn (c mut Checker) warn_or_error(message string, pos token.Position, warn bool)
 			file_path: c.file.path
 			message: message
 		}
-
 	}
 }
 
diff --git a/vlib/v/fmt/fmt.v b/vlib/v/fmt/fmt.v
index 572a0d1bfa..b4469c5c93 100644
--- a/vlib/v/fmt/fmt.v
+++ b/vlib/v/fmt/fmt.v
@@ -111,7 +111,8 @@ fn (f mut Fmt) imports(imports []ast.Import) {
 		// f.indent++
 		for imp in imports {
 			if !(imp.mod in f.used_imports) {
-				continue
+				// TODO bring back once only unused imports are removed
+				// continue
 			}
 			f.out_imports.write('\t')
 			f.out_imports.writeln(f.imp_stmt_str(imp))
@@ -529,7 +530,7 @@ fn (f mut Fmt) expr(node ast.Expr) {
 				f.write('_')
 			} else {
 				name := short_module(it.name)
-				//f.write('<$it.name => $name>')
+				// f.write('<$it.name => $name>')
 				f.write(name)
 				if name.contains('.') {
 					f.mark_module_as_used(name)
@@ -673,7 +674,7 @@ fn (f mut Fmt) expr(node ast.Expr) {
 		}
 		ast.StructInit {
 			type_sym := f.table.get_type_symbol(it.typ)
-			//f.write('<old name: $type_sym.name>')
+			// f.write('<old name: $type_sym.name>')
 			mut name := short_module(type_sym.name).replace(f.cur_mod + '.', '')			// TODO f.type_to_str?
 			if name == 'void' {
 				name = ''
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 3c12c81abf..eba5508e4b 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -7,11 +7,11 @@ import (
 	strings
 	v.ast
 	v.table
-	v.depgraph
-	v.token
 	v.pref
-	term
+	v.token
 	v.util
+	v.depgraph
+	term
 )
 
 const (
@@ -21,6 +21,10 @@ const (
 		'void', 'volatile', 'while']
 )
 
+fn foo(t token.Token) {
+	util.full_hash()
+}
+
 struct Gen {
 	out                  strings.Builder
 	typedefs             strings.Builder
@@ -809,109 +813,6 @@ fn (g mut Gen) gen_clone_assignment(val ast.Expr, right_sym table.TypeSymbol, ad
 	return true
 }
 
-fn (g mut Gen) gen_fn_decl(it ast.FnDecl) {
-	if it.is_c {
-		// || it.no_body {
-		return
-	}
-	g.reset_tmp_count()
-	is_main := it.name == 'main'
-	if is_main {
-		if g.pref.os == .windows {
-			g.write('int wmain(int ___argc, wchar_t *___argv[], wchar_t *___envp[]')
-		} else {
-			g.write('int ${it.name}(int ___argc, char** ___argv')
-		}
-	} else {
-		mut name := it.name
-		c := name[0]
-		if c in [`+`, `-`, `*`, `/`, `%`] {
-			name = util.replace_op(name)
-		}
-		if it.is_method {
-			name = g.table.get_type_symbol(it.receiver.typ).name + '_' + name
-		}
-		if it.is_c {
-			name = name.replace('.', '__')
-		} else {
-			name = c_name(name)
-		}
-		// if g.pref.show_cc && it.is_builtin {
-		// println(name)
-		// }
-		// type_name := g.table.Type_to_str(it.return_type)
-		type_name := g.typ(it.return_type)
-		g.write('$type_name ${name}(')
-		g.definitions.write('$type_name ${name}(')
-	}
-	// Receiver is the first argument
-	/*
-	if it.is_method {
-		mut styp := g.typ(it.receiver.typ)
-		// if table.type_nr_muls(it.receiver.typ) > 0 {
-		// if it.rec_mut {
-		// styp += '*'
-		// }
-		g.write('$styp $it.receiver.name ')
-		// TODO mut
-		g.definitions.write('$styp $it.receiver.name')
-		if it.args.len > 0 {
-			g.write(', ')
-			g.definitions.write(', ')
-		}
-	}
-*/
-	//
-	g.fn_args(it.args, it.is_variadic)
-	if it.no_body || (g.pref.is_cache && it.is_builtin) {
-		// Just a function header.
-		// Builtin function bodies are defined in builtin.o
-		g.definitions.writeln(');')
-		g.writeln(');')
-		return
-	}
-	g.writeln(') {')
-	if !is_main {
-		g.definitions.writeln(');')
-	}
-	if is_main {
-		g.writeln('\t_vinit();')
-		if g.is_importing_os() {
-			if g.autofree {
-				g.writeln('free(_const_os__args.data); // empty, inited in _vinit()')
-			}
-			if g.pref.os == .windows {
-				g.writeln('\t_const_os__args = os__init_os_args_wide(___argc, ___argv);')
-			} else {
-				g.writeln('\t_const_os__args = os__init_os_args(___argc, (byteptr*)___argv);')
-			}
-		}
-	}
-	g.stmts(it.stmts)
-	// ////////////
-	if g.autofree {
-		g.free_scope_vars(it.pos.pos - 1)
-	}
-	// /////////
-	if is_main {
-		if g.autofree {
-			g.writeln('\t_vcleanup();')
-		}
-		if g.is_test {
-			verror('test files cannot have function `main`')
-		}
-	}
-	if g.defer_stmts.len > 0 {
-		g.write_defer_stmts()
-	}
-	if is_main {
-		g.writeln('\treturn 0;')
-	}
-	g.writeln('}')
-	g.defer_stmts = []
-	g.fn_decl = 0
-}
-
 fn (g mut Gen) free_scope_vars(pos int) {
 	scope := g.file.scope.innermost(pos)
 	for _, obj in scope.objects {
@@ -953,55 +854,6 @@ fn (g mut Gen) free_scope_vars(pos int) {
 	}
 }
 
-fn (g mut Gen) fn_args(args []table.Arg, is_variadic bool) {
-	no_names := args.len > 0 && args[0].name == 'arg_1'
-	for i, arg in args {
-		arg_type_sym := g.table.get_type_symbol(arg.typ)
-		mut arg_type_name := g.typ(arg.typ)		// arg_type_sym.name.replace('.', '__')
-		is_varg := i == args.len - 1 && is_variadic
-		if is_varg {
-			varg_type_str := int(arg.typ).str()
-			if !(varg_type_str in g.variadic_args) {
-				g.variadic_args[varg_type_str] = 0
-			}
-			arg_type_name = 'varg_' + g.typ(arg.typ).replace('*', '_ptr')
-		}
-		if arg_type_sym.kind == .function {
-			info := arg_type_sym.info as table.FnType
-			func := info.func
-			if !info.is_anon {
-				g.write(arg_type_name + ' ' + arg.name)
-				g.definitions.write(arg_type_name + ' ' + arg.name)
-			} else {
-				g.write('${g.typ(func.return_type)} (*$arg.name)(')
-				g.definitions.write('${g.typ(func.return_type)} (*$arg.name)(')
-				g.fn_args(func.args, func.is_variadic)
-				g.write(')')
-				g.definitions.write(')')
-			}
-		} else if no_names {
-			g.write(arg_type_name)
-			g.definitions.write(arg_type_name)
-		} else {
-			mut nr_muls := table.type_nr_muls(arg.typ)
-			s := arg_type_name + ' ' + arg.name
-			if arg.is_mut {
-				// mut arg needs one *
-				nr_muls = 1
-			}
-			// if nr_muls > 0 && !is_varg {
-			// s = arg_type_name + strings.repeat(`*`, nr_muls) + ' ' + arg.name
-			// }
-			g.write(s)
-			g.definitions.write(s)
-		}
-		if i < args.len - 1 {
-			g.write(', ')
-			g.definitions.write(', ')
-		}
-	}
-}
-
 fn (g mut Gen) expr(node ast.Expr) {
 	// println('cgen expr() line_nr=$node.pos.line_nr')
 	match node {
@@ -2406,7 +2258,7 @@ fn (g mut Gen) string_inter_literal(node ast.StringInterLiteral) {
 			}
 			g.write('%' + sfmt[1..])
 		} else if node.expr_types[i] in [table.string_type, table.bool_type, table.f32_type,
-				table.f64_type] || sym.kind in [.enum_, .array, .array_fixed] {
+			table.f64_type] || sym.kind in [.enum_, .array, .array_fixed] {
 			g.write('%.*s')
 		} else {
 			g.write('%d')
@@ -2421,25 +2273,21 @@ fn (g mut Gen) string_inter_literal(node ast.StringInterLiteral) {
 			if fspec == `s` && node.expr_types[i] == table.string_type {
 				g.expr(expr)
 				g.write('.str')
-			}
-			else {
+			} else {
 				g.expr(expr)
 			}
-		}
-		else if node.expr_types[i] == table.string_type {
+		} else if node.expr_types[i] == table.string_type {
 			// `name.str, name.len,`
 			g.expr(expr)
 			g.write('.len, ')
 			g.expr(expr)
 			g.write('.str')
-		}
-		else if node.expr_types[i] == table.bool_type {
+		} else if node.expr_types[i] == table.bool_type {
 			g.expr(expr)
 			g.write(' ? 4 : 5, ')
 			g.expr(expr)
 			g.write(' ? "true" : "false"')
-		}
-		else {
+		} else {
 			sym := g.table.get_type_symbol(node.expr_types[i])
 			if sym.kind == .enum_ {
 				is_var := match node.exprs[i] {
@@ -2472,9 +2320,8 @@ fn (g mut Gen) string_inter_literal(node ast.StringInterLiteral) {
 					g.enum_expr(expr)
 					g.write('"')
 				}
-			}
-			else if node.expr_types[i] in [table.f32_type, table.f64_type, table.array_type,
-						table.map_type] || sym.kind in [.array, .array_fixed] {
+			} else if node.expr_types[i] in [table.f32_type, table.f64_type, table.array_type,
+				table.map_type] || sym.kind in [.array, .array_fixed] {
 				styp := g.typ(node.expr_types[i])
 				g.write('${styp}_str(')
 				g.expr(expr)
@@ -2483,8 +2330,7 @@ fn (g mut Gen) string_inter_literal(node ast.StringInterLiteral) {
 				g.write('${styp}_str(')
 				g.expr(expr)
 				g.write(').str')
-			}
-			else {
+			} else {
 				g.expr(expr)
 			}
 		}
diff --git a/vlib/v/gen/fn.v b/vlib/v/gen/fn.v
new file mode 100644
index 0000000000..8ba6e4a830
--- /dev/null
+++ b/vlib/v/gen/fn.v
@@ -0,0 +1,162 @@
+// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module gen
+
+import (
+	v.ast
+	v.table
+	v.util
+)
+
+fn (g mut Gen) gen_fn_decl(it ast.FnDecl) {
+	if it.is_c {
+		// || it.no_body {
+		return
+	}
+	g.reset_tmp_count()
+	is_main := it.name == 'main'
+	if is_main {
+		if g.pref.os == .windows {
+			g.write('int wmain(int ___argc, wchar_t *___argv[], wchar_t *___envp[]')
+		} else {
+			g.write('int ${it.name}(int ___argc, char** ___argv')
+		}
+	} else {
+		mut name := it.name
+		c := name[0]
+		if c in [`+`, `-`, `*`, `/`, `%`] {
+			name = util.replace_op(name)
+		}
+		if it.is_method {
+			name = g.table.get_type_symbol(it.receiver.typ).name + '_' + name
+		}
+		if it.is_c {
+			name = name.replace('.', '__')
+		} else {
+			name = c_name(name)
+		}
+		// if g.pref.show_cc && it.is_builtin {
+		// println(name)
+		// }
+		// type_name := g.table.Type_to_str(it.return_type)
+		type_name := g.typ(it.return_type)
+		g.write('$type_name ${name}(')
+		g.definitions.write('$type_name ${name}(')
+	}
+	// Receiver is the first argument
+	/*
+	if it.is_method {
+		mut styp := g.typ(it.receiver.typ)
+		// if table.type_nr_muls(it.receiver.typ) > 0 {
+		// if it.rec_mut {
+		// styp += '*'
+		// }
+		g.write('$styp $it.receiver.name ')
+		// TODO mut
+		g.definitions.write('$styp $it.receiver.name')
+		if it.args.len > 0 {
+			g.write(', ')
+			g.definitions.write(', ')
+		}
+	}
+*/
+	//
+	g.fn_args(it.args, it.is_variadic)
+	if it.no_body || (g.pref.is_cache && it.is_builtin) {
+		// Just a function header.
+		// Builtin function bodies are defined in builtin.o
+		g.definitions.writeln(');')
+		g.writeln(');')
+		return
+	}
+	g.writeln(') {')
+	if !is_main {
+		g.definitions.writeln(');')
+	}
+	if is_main {
+		g.writeln('\t_vinit();')
+		if g.is_importing_os() {
+			if g.autofree {
+				g.writeln('free(_const_os__args.data); // empty, inited in _vinit()')
+			}
+			if g.pref.os == .windows {
+				g.writeln('\t_const_os__args = os__init_os_args_wide(___argc, ___argv);')
+			} else {
+				g.writeln('\t_const_os__args = os__init_os_args(___argc, (byteptr*)___argv);')
+			}
+		}
+	}
+	g.stmts(it.stmts)
+	// ////////////
+	if g.autofree {
+		g.free_scope_vars(it.pos.pos - 1)
+	}
+	// /////////
+	if is_main {
+		if g.autofree {
+			g.writeln('\t_vcleanup();')
+		}
+		if g.is_test {
+			verror('test files cannot have function `main`')
+		}
+	}
+	if g.defer_stmts.len > 0 {
+		g.write_defer_stmts()
+	}
+	if is_main {
+		g.writeln('\treturn 0;')
+	}
+	g.writeln('}')
+	g.defer_stmts = []
+	g.fn_decl = 0
+}
+
+fn (g mut Gen) fn_args(args []table.Arg, is_variadic bool) {
+	no_names := args.len > 0 && args[0].name == 'arg_1'
+	for i, arg in args {
+		arg_type_sym := g.table.get_type_symbol(arg.typ)
+		mut arg_type_name := g.typ(arg.typ)		// arg_type_sym.name.replace('.', '__')
+		is_varg := i == args.len - 1 && is_variadic
+		if is_varg {
+			varg_type_str := int(arg.typ).str()
+			if !(varg_type_str in g.variadic_args) {
+				g.variadic_args[varg_type_str] = 0
+			}
+			arg_type_name = 'varg_' + g.typ(arg.typ).replace('*', '_ptr')
+		}
+		if arg_type_sym.kind == .function {
+			info := arg_type_sym.info as table.FnType
+			func := info.func
+			if !info.is_anon {
+				g.write(arg_type_name + ' ' + arg.name)
+				g.definitions.write(arg_type_name + ' ' + arg.name)
+			} else {
+				g.write('${g.typ(func.return_type)} (*$arg.name)(')
+				g.definitions.write('${g.typ(func.return_type)} (*$arg.name)(')
+				g.fn_args(func.args, func.is_variadic)
+				g.write(')')
+				g.definitions.write(')')
+			}
+		} else if no_names {
+			g.write(arg_type_name)
+			g.definitions.write(arg_type_name)
+		} else {
+			mut nr_muls := table.type_nr_muls(arg.typ)
+			s := arg_type_name + ' ' + arg.name
+			if arg.is_mut {
+				// mut arg needs one *
+				nr_muls = 1
+			}
+			// if nr_muls > 0 && !is_varg {
+			// s = arg_type_name + strings.repeat(`*`, nr_muls) + ' ' + arg.name
+			// }
+			g.write(s)
+			g.definitions.write(s)
+		}
+		if i < args.len - 1 {
+			g.write(', ')
+			g.definitions.write(', ')
+		}
+	}
+}
diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index e9bb340d3c..d6a1b7ae2c 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -176,6 +176,9 @@ fn (p mut Parser) fn_decl() ast.FnDecl {
 		} else {
 			name = p.prepend_mod(name)
 		}
+		if _ := p.table.find_fn(name) {
+			p.error('redefinition of `$name`')
+		}
 		p.table.register_fn(table.Fn{
 			name: name
 			args: args