diff --git a/vlib/v/ast/cflags.v b/vlib/v/ast/cflags.v
index 5f0be4cfec..559325bb26 100644
--- a/vlib/v/ast/cflags.v
+++ b/vlib/v/ast/cflags.v
@@ -17,12 +17,12 @@ fn (t &Table) has_cflag(flag cflag.CFlag) bool {
 
 // parse the flags to (ast.cflags) []CFlag
 // Note: clean up big time (joe-c)
-pub fn (mut t Table) parse_cflag(cflg string, mod string, ctimedefines []string) ?bool {
+pub fn (mut t Table) parse_cflag(cflg string, mod string, ctimedefines []string) ! {
 	allowed_flags := ['framework', 'library', 'Wa', 'Wl', 'Wp', 'I', 'l', 'L', 'D']
 	flag_orig := cflg.trim_space()
 	mut flag := flag_orig
 	if flag == '' {
-		return none
+		return error('flag is empty')
 	}
 	mut fos := ''
 	mut allowed_os_overrides := ['linux', 'darwin', 'freebsd', 'openbsd', 'windows', 'mingw',
@@ -32,7 +32,7 @@ pub fn (mut t Table) parse_cflag(cflg string, mod string, ctimedefines []string)
 		if !flag.starts_with(os_override) {
 			continue
 		}
-		pos := flag.index(' ') or { return none }
+		pos := flag.index(' ') or { return error('none') }
 		fos = flag[..pos].trim_space()
 		flag = flag[pos..].trim_space()
 	}
@@ -86,5 +86,4 @@ pub fn (mut t Table) parse_cflag(cflg string, mod string, ctimedefines []string)
 			break
 		}
 	}
-	return true
 }
diff --git a/vlib/v/ast/table.v b/vlib/v/ast/table.v
index a62e7949a9..4f7bd3d9e5 100644
--- a/vlib/v/ast/table.v
+++ b/vlib/v/ast/table.v
@@ -337,7 +337,7 @@ pub fn (mut t TypeSymbol) register_method(new_fn Fn) int {
 	return t.methods.len - 1
 }
 
-pub fn (t &Table) register_aggregate_method(mut sym TypeSymbol, name string) ?Fn {
+pub fn (t &Table) register_aggregate_method(mut sym TypeSymbol, name string) !Fn {
 	if sym.kind != .aggregate {
 		t.panic('Unexpected type symbol: $sym.kind')
 	}
@@ -369,21 +369,25 @@ pub fn (t &Table) has_method(s &TypeSymbol, name string) bool {
 }
 
 // find_method searches from current type up through each parent looking for method
-pub fn (t &Table) find_method(s &TypeSymbol, name string) ?Fn {
+pub fn (t &Table) find_method(s &TypeSymbol, name string) !Fn {
 	mut ts := unsafe { s }
 	for {
 		if method := ts.find_method(name) {
 			return method
 		}
 		if ts.kind == .aggregate {
-			return t.register_aggregate_method(mut ts, name)
+			if method := t.register_aggregate_method(mut ts, name) {
+				return method
+			} else {
+				return err
+			}
 		}
 		if ts.parent_idx == 0 {
 			break
 		}
 		ts = t.type_symbols[ts.parent_idx]
 	}
-	return none
+	return error('unknown method `$name`')
 }
 
 [params]
@@ -410,7 +414,7 @@ pub fn (t &Table) get_embeds(sym &TypeSymbol, options GetEmbedsOptions) [][]Type
 	return embeds
 }
 
-pub fn (t &Table) find_method_from_embeds(sym &TypeSymbol, method_name string) ?(Fn, []Type) {
+pub fn (t &Table) find_method_from_embeds(sym &TypeSymbol, method_name string) !(Fn, []Type) {
 	if sym.info is Struct {
 		mut found_methods := []Fn{}
 		mut embed_of_found_methods := []Type{}
@@ -460,17 +464,16 @@ pub fn (t &Table) find_method_from_embeds(sym &TypeSymbol, method_name string) ?
 			}
 		}
 	}
-	return none
+	return error('')
 }
 
 // find_method_with_embeds searches for a given method, also looking through embedded fields
-pub fn (t &Table) find_method_with_embeds(sym &TypeSymbol, method_name string) ?Fn {
+pub fn (t &Table) find_method_with_embeds(sym &TypeSymbol, method_name string) !Fn {
 	if func := t.find_method(sym, method_name) {
 		return func
 	} else {
 		// look for embedded field
-		first_err := err
-		func, _ := t.find_method_from_embeds(sym, method_name) or { return first_err }
+		func, _ := t.find_method_from_embeds(sym, method_name) or { return err }
 		return func
 	}
 }
@@ -487,7 +490,7 @@ pub fn (t &Table) get_embed_methods(sym &TypeSymbol) []Fn {
 	return methods
 }
 
-fn (t &Table) register_aggregate_field(mut sym TypeSymbol, name string) ?StructField {
+fn (t &Table) register_aggregate_field(mut sym TypeSymbol, name string) !StructField {
 	if sym.kind != .aggregate {
 		t.panic('Unexpected type symbol: $sym.kind')
 	}
@@ -537,7 +540,7 @@ pub fn (t &Table) struct_fields(sym &TypeSymbol) []StructField {
 }
 
 // search from current type up through each parent looking for field
-pub fn (t &Table) find_field(s &TypeSymbol, name string) ?StructField {
+pub fn (t &Table) find_field(s &TypeSymbol, name string) !StructField {
 	mut ts := unsafe { s }
 	for {
 		match mut ts.info {
@@ -574,11 +577,11 @@ pub fn (t &Table) find_field(s &TypeSymbol, name string) ?StructField {
 		}
 		ts = t.type_symbols[ts.parent_idx]
 	}
-	return none
+	return error('')
 }
 
 // find_field_from_embeds tries to find a field in the nested embeds
-pub fn (t &Table) find_field_from_embeds(sym &TypeSymbol, field_name string) ?(StructField, []Type) {
+pub fn (t &Table) find_field_from_embeds(sym &TypeSymbol, field_name string) !(StructField, []Type) {
 	if sym.info is Struct {
 		mut found_fields := []StructField{}
 		mut embeds_of_found_fields := []Type{}
@@ -611,11 +614,11 @@ pub fn (t &Table) find_field_from_embeds(sym &TypeSymbol, field_name string) ?(S
 		unalias_sym := t.sym(sym.info.parent_type)
 		return t.find_field_from_embeds(unalias_sym, field_name)
 	}
-	return none
+	return error('')
 }
 
 // find_field_with_embeds searches for a given field, also looking through embedded fields
-pub fn (t &Table) find_field_with_embeds(sym &TypeSymbol, field_name string) ?StructField {
+pub fn (t &Table) find_field_with_embeds(sym &TypeSymbol, field_name string) !StructField {
 	if field := t.find_field(sym, field_name) {
 		return field
 	} else {
diff --git a/vlib/v/ast/walker/walker.v b/vlib/v/ast/walker/walker.v
index 6cd2c103ee..92341e3218 100644
--- a/vlib/v/ast/walker/walker.v
+++ b/vlib/v/ast/walker/walker.v
@@ -5,7 +5,7 @@ import v.ast
 // Visitor defines a visit method which is invoked by the walker in each node it encounters.
 pub interface Visitor {
 mut:
-	visit(node &ast.Node) ?
+	visit(node &ast.Node) !
 }
 
 pub type InspectorFn = fn (node &ast.Node, data voidptr) bool
@@ -16,7 +16,7 @@ mut:
 	data voidptr
 }
 
-pub fn (i &Inspector) visit(node &ast.Node) ? {
+pub fn (i &Inspector) visit(node &ast.Node) ! {
 	if i.inspector_callback(node, i.data) {
 		return
 	}
diff --git a/vlib/v/ast/walker/walker_test.v b/vlib/v/ast/walker/walker_test.v
index 66eaa31f90..4a370cacc5 100644
--- a/vlib/v/ast/walker/walker_test.v
+++ b/vlib/v/ast/walker/walker_test.v
@@ -15,7 +15,7 @@ mut:
 	node ast.Node
 }
 
-fn (mut n NodeByOffset) visit(node &ast.Node) ? {
+fn (mut n NodeByOffset) visit(node &ast.Node) ! {
 	node_pos := node.pos()
 	if n.pos >= node_pos.pos && n.pos <= node_pos.pos + node_pos.len && node !is ast.File {
 		n.node = node
diff --git a/vlib/v/builder/builder.v b/vlib/v/builder/builder.v
index fa822b1f7a..7049e0b309 100644
--- a/vlib/v/builder/builder.v
+++ b/vlib/v/builder/builder.v
@@ -88,7 +88,7 @@ pub fn new_builder(pref &pref.Preferences) Builder {
 	}
 }
 
-pub fn (mut b Builder) front_stages(v_files []string) ? {
+pub fn (mut b Builder) front_stages(v_files []string) ! {
 	mut timers := util.get_timers()
 	util.timing_start('PARSE')
 
@@ -106,7 +106,7 @@ pub fn (mut b Builder) front_stages(v_files []string) ? {
 	}
 }
 
-pub fn (mut b Builder) middle_stages() ? {
+pub fn (mut b Builder) middle_stages() ! {
 	util.timing_start('CHECK')
 
 	util.timing_start('Checker.generic_insts_to_concrete')
@@ -135,9 +135,9 @@ pub fn (mut b Builder) middle_stages() ? {
 	}
 }
 
-pub fn (mut b Builder) front_and_middle_stages(v_files []string) ? {
-	b.front_stages(v_files)?
-	b.middle_stages()?
+pub fn (mut b Builder) front_and_middle_stages(v_files []string) ! {
+	b.front_stages(v_files)!
+	b.middle_stages()!
 }
 
 // parse all deps from already parsed files
diff --git a/vlib/v/builder/cc_windows.v b/vlib/v/builder/cc_windows.v
index b9b472fa04..2fe71b77e4 100644
--- a/vlib/v/builder/cc_windows.v
+++ b/vlib/v/builder/cc_windows.v
@@ -6,7 +6,7 @@ module builder
 import os
 import v.pref
 
-pub fn (mut v Builder) find_win_cc() ? {
+pub fn (mut v Builder) find_win_cc() ! {
 	$if !windows {
 		return
 	}
diff --git a/vlib/v/builder/interpreterbuilder/v_interpret_test.v b/vlib/v/builder/interpreterbuilder/v_interpret_test.v
index 1960a90b9b..ca6b8c2b31 100644
--- a/vlib/v/builder/interpreterbuilder/v_interpret_test.v
+++ b/vlib/v/builder/interpreterbuilder/v_interpret_test.v
@@ -8,7 +8,7 @@ fn interpreter_wrap(a string) string {
 	return 'fn main() {$a}'
 }
 
-fn interp_test(expression string, expected string) ? {
+fn interp_test(expression string, expected string) ! {
 	tmpdir := os.join_path(os.temp_dir(), 'v', 'interpret_test_$rand.ulid()')
 	os.mkdir_all(tmpdir) or {}
 	defer {
@@ -17,12 +17,12 @@ fn interp_test(expression string, expected string) ? {
 	//
 	tmpfile := os.join_path(tmpdir, 'input.v')
 	outfile := os.join_path(tmpdir, 'output.txt')
-	os.write_file(tmpfile, interpreter_wrap(expression))?
+	os.write_file(tmpfile, interpreter_wrap(expression))!
 	if os.system('${os.quoted_path(vexe)} interpret ${os.quoted_path(tmpfile)} > ${os.quoted_path(outfile)}') != 0 {
 		eprintln('>>> Failed to interpret V expression: |$expression|')
 		return error('v interp')
 	}
-	res := os.read_file(outfile)?
+	res := os.read_file(outfile)!
 	output := res.trim_space()
 	if output != expected {
 		eprintln('>>> The output of the V expression, is not the same as the expected one')
@@ -49,7 +49,7 @@ fn test_interpreter() {
 	tests << InterpTest{'println(3*3)', '9'}
 	tests << InterpTest{'a := 3\nprintln(a*3)', '9'}
 	for test in tests {
-		interp_test(test.input, test.output)?
+		interp_test(test.input, test.output)!
 		assert true
 	}
 }
diff --git a/vlib/v/callgraph/callgraph.v b/vlib/v/callgraph/callgraph.v
index d8c9e4d74e..48918bd121 100644
--- a/vlib/v/callgraph/callgraph.v
+++ b/vlib/v/callgraph/callgraph.v
@@ -83,7 +83,7 @@ fn (mut m Mapper) dot_fn_name(fname string, recv_type ast.Type, is_method bool)
 	return 'Node_fn_' + m.dot_normalise_node_name(fname)
 }
 
-fn (mut m Mapper) visit(node &ast.Node) ? {
+fn (mut m Mapper) visit(node &ast.Node) ! {
 	m.node = unsafe { node }
 	match node {
 		ast.File {
diff --git a/vlib/v/checker/check_types.v b/vlib/v/checker/check_types.v
index ab2aa0356b..a869fc700a 100644
--- a/vlib/v/checker/check_types.v
+++ b/vlib/v/checker/check_types.v
@@ -599,7 +599,7 @@ fn (c &Checker) promote_num(left_type ast.Type, right_type ast.Type) ast.Type {
 	}
 }
 
-pub fn (mut c Checker) check_expected(got ast.Type, expected ast.Type) ? {
+pub fn (mut c Checker) check_expected(got ast.Type, expected ast.Type) ! {
 	if !c.check_types(got, expected) {
 		return error(c.expected_msg(got, expected))
 	}
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index e1da077e08..4747a63f62 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -3199,16 +3199,16 @@ pub fn (mut c Checker) unsafe_expr(mut node ast.UnsafeExpr) ast.Type {
 	return t
 }
 
-fn (mut c Checker) find_definition(ident ast.Ident) ?ast.Expr {
+fn (mut c Checker) find_definition(ident ast.Ident) !ast.Expr {
 	match ident.kind {
-		.unresolved, .blank_ident { return none }
+		.unresolved, .blank_ident { return error('none') }
 		.variable, .constant { return c.find_obj_definition(ident.obj) }
 		.global { return error('$ident.name is a global variable') }
 		.function { return error('$ident.name is a function') }
 	}
 }
 
-fn (mut c Checker) find_obj_definition(obj ast.ScopeObject) ?ast.Expr {
+fn (mut c Checker) find_obj_definition(obj ast.ScopeObject) !ast.Expr {
 	// TODO: remove once we have better type inference
 	mut name := ''
 	match obj {
diff --git a/vlib/v/checker/fn.v b/vlib/v/checker/fn.v
index 7a1288f4dd..085840a73e 100644
--- a/vlib/v/checker/fn.v
+++ b/vlib/v/checker/fn.v
@@ -1914,7 +1914,7 @@ fn (mut c Checker) post_process_generic_fns() {
 	}
 }
 
-pub fn (mut c Checker) check_expected_arg_count(mut node ast.CallExpr, f &ast.Fn) ? {
+pub fn (mut c Checker) check_expected_arg_count(mut node ast.CallExpr, f &ast.Fn) ! {
 	nr_args := node.args.len
 	nr_params := if node.is_method && f.params.len > 0 { f.params.len - 1 } else { f.params.len }
 	mut min_required_params := f.params.len
diff --git a/vlib/v/fmt/fmt_keep_test.v b/vlib/v/fmt/fmt_keep_test.v
index 375bc90cea..56f0fd4c53 100644
--- a/vlib/v/fmt/fmt_keep_test.v
+++ b/vlib/v/fmt/fmt_keep_test.v
@@ -97,10 +97,10 @@ fn prepare_bin2v_file(mut fmt_bench benchmark.Benchmark) {
 	eprintln(fmt_bench.step_message_ok('Prepared bin2v_keep.vv'))
 }
 
-fn write_bin2v_keep_content() ? {
+fn write_bin2v_keep_content() ! {
 	img0 := os.join_path('vlib', 'v', 'embed_file', 'tests', 'v.png')
 	img1 := os.join_path('tutorials', 'building_a_simple_web_blog_with_vweb', 'img', 'time.png')
-	os.rm(b2v_keep_path)?
+	os.rm(b2v_keep_path)!
 	res := os.execute('${os.quoted_path(vexe)} bin2v -w ${os.quoted_path(b2v_keep_path)} ${os.quoted_path(img0)} ${os.quoted_path(img1)}')
 	if res.exit_code != 0 {
 		restore_bin2v_placeholder() or {}
@@ -108,8 +108,8 @@ fn write_bin2v_keep_content() ? {
 	}
 }
 
-fn restore_bin2v_placeholder() ? {
+fn restore_bin2v_placeholder() ! {
 	text := '// This is a placeholder file which will be filled with bin2v output before the test.
 // HINT: do NOT delete, move or rename this file!\n'
-	os.write_file(b2v_keep_path, text)?
+	os.write_file(b2v_keep_path, text)!
 }
diff --git a/vlib/v/gen/c/assert.v b/vlib/v/gen/c/assert.v
index 1f3ef6ffbf..3456e1c0de 100644
--- a/vlib/v/gen/c/assert.v
+++ b/vlib/v/gen/c/assert.v
@@ -52,7 +52,7 @@ struct UnsupportedAssertCtempTransform {
 
 const unsupported_ctemp_assert_transform = IError(UnsupportedAssertCtempTransform{})
 
-fn (mut g Gen) assert_subexpression_to_ctemp(expr ast.Expr, expr_type ast.Type) ?ast.Expr {
+fn (mut g Gen) assert_subexpression_to_ctemp(expr ast.Expr, expr_type ast.Type) !ast.Expr {
 	match expr {
 		ast.CallExpr {
 			return g.new_ctemp_var_then_gen(expr, expr_type)
diff --git a/vlib/v/gen/c/fn.v b/vlib/v/gen/c/fn.v
index e679e7d69b..95315f62a6 100644
--- a/vlib/v/gen/c/fn.v
+++ b/vlib/v/gen/c/fn.v
@@ -417,7 +417,7 @@ fn (mut g Gen) gen_fn_decl(node &ast.FnDecl, skip bool) {
 	}
 }
 
-fn (mut g Gen) c_fn_name(node &ast.FnDecl) ?string {
+fn (mut g Gen) c_fn_name(node &ast.FnDecl) !string {
 	mut name := node.name
 	if name in ['+', '-', '*', '/', '%', '<', '=='] {
 		name = util.replace_op(name)
@@ -425,7 +425,7 @@ fn (mut g Gen) c_fn_name(node &ast.FnDecl) ?string {
 	if node.is_method {
 		unwrapped_rec_sym := g.table.sym(g.unwrap_generic(node.receiver.typ))
 		if unwrapped_rec_sym.kind == .placeholder {
-			return none
+			return error('none')
 		}
 		name = g.cc_type(node.receiver.typ, false) + '_' + name
 	}
diff --git a/vlib/v/gen/js/comptime.v b/vlib/v/gen/js/comptime.v
index 2bbcf0a568..97ac659169 100644
--- a/vlib/v/gen/js/comptime.v
+++ b/vlib/v/gen/js/comptime.v
@@ -168,7 +168,7 @@ fn (mut g JsGen) comptime_if_cond(cond ast.Expr, pkg_exist bool) bool {
 	}
 }
 
-fn (mut g JsGen) comptime_if_to_ifdef(name string, is_comptime_optional bool) ?string {
+fn (mut g JsGen) comptime_if_to_ifdef(name string, is_comptime_optional bool) !string {
 	match name {
 		// platforms/os-es:
 		'windows' {
@@ -313,5 +313,5 @@ fn (mut g JsGen) comptime_if_to_ifdef(name string, is_comptime_optional bool) ?s
 			return error('bad os ifdef name "$name"') // should never happen, caught in the checker
 		}
 	}
-	return none
+	return error('none')
 }
diff --git a/vlib/v/gen/js/js.v b/vlib/v/gen/js/js.v
index ab0f63f590..7d9bab0464 100644
--- a/vlib/v/gen/js/js.v
+++ b/vlib/v/gen/js/js.v
@@ -1075,7 +1075,7 @@ struct UnsupportedAssertCtempTransform {
 
 const unsupported_ctemp_assert_transform = IError(UnsupportedAssertCtempTransform{})
 
-fn (mut g JsGen) assert_subexpression_to_ctemp(expr ast.Expr, expr_type ast.Type) ?ast.Expr {
+fn (mut g JsGen) assert_subexpression_to_ctemp(expr ast.Expr, expr_type ast.Type) !ast.Expr {
 	match expr {
 		ast.CallExpr {
 			return g.new_ctemp_var_then_gen(expr, expr_type)
diff --git a/vlib/v/gen/js/program_test.v b/vlib/v/gen/js/program_test.v
index 8754854359..be7bad3f90 100644
--- a/vlib/v/gen/js/program_test.v
+++ b/vlib/v/gen/js/program_test.v
@@ -35,7 +35,7 @@ fn test_node_exists() {
 	println('Using node version: $version')
 }
 
-fn test_running_programs_compiled_with_the_js_backend() ? {
+fn test_running_programs_compiled_with_the_js_backend() {
 	os.setenv('VCOLORS', 'never', true)
 	os.chdir(vroot) or {}
 	test_dir := 'vlib/v/gen/js/tests/testdata'
@@ -50,21 +50,21 @@ fn get_main_files_in_dir(dir string) []string {
 	return mfiles
 }
 
-fn check_path(dir string, tests []string) ?int {
+fn check_path(dir string, tests []string) !int {
 	mut nb_fail := 0
 	paths := vtest.filter_vtest_only(tests, basepath: vroot)
 	for path in paths {
 		program := path.replace(vroot + os.path_separator, '')
 		program_out := program.replace('.v', '.out')
 		if !os.exists(program_out) {
-			os.write_file(program_out, '')?
+			os.write_file(program_out, '')!
 		}
 		print(program + ' ')
 		res := os.execute('${os.quoted_path(vexe)} -b js_node run ${os.quoted_path(program)}')
 		if res.exit_code < 0 {
 			panic(res.output)
 		}
-		mut expected := os.read_file(program_out)?
+		mut expected := os.read_file(program_out)!
 		expected = clean_line_endings(expected)
 		found := clean_line_endings(res.output)
 		if expected != found {
diff --git a/vlib/v/gen/native/gen.v b/vlib/v/gen/native/gen.v
index bf8221bedf..4924ffdcc4 100644
--- a/vlib/v/gen/native/gen.v
+++ b/vlib/v/gen/native/gen.v
@@ -184,7 +184,7 @@ fn (mut g Gen) get_type_from_var(var Var) ast.Type {
 	}
 }
 
-fn get_backend(arch pref.Arch) ?CodeGen {
+fn get_backend(arch pref.Arch) !CodeGen {
 	match arch {
 		.arm64 {
 			return Arm64{
diff --git a/vlib/v/live/executable/reloader.v b/vlib/v/live/executable/reloader.v
index f8643693a4..3051ddd8ef 100644
--- a/vlib/v/live/executable/reloader.v
+++ b/vlib/v/live/executable/reloader.v
@@ -54,7 +54,7 @@ fn elog(r &live.LiveReloadInfo, s string) {
 	}
 }
 
-fn compile_and_reload_shared_lib(mut r live.LiveReloadInfo) ?bool {
+fn compile_and_reload_shared_lib(mut r live.LiveReloadInfo) !bool {
 	sw := time.new_stopwatch()
 	new_lib_path := compile_lib(mut r) or { return error('errors while compiling $r.original') }
 	elog(r, '> compile_and_reload_shared_lib compiled: $new_lib_path')
diff --git a/vlib/v/parser/expr.v b/vlib/v/parser/expr.v
index eeeb387f67..44fd06d225 100644
--- a/vlib/v/parser/expr.v
+++ b/vlib/v/parser/expr.v
@@ -16,7 +16,7 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 	}
 }
 
-pub fn (mut p Parser) check_expr(precedence int) ?ast.Expr {
+pub fn (mut p Parser) check_expr(precedence int) !ast.Expr {
 	p.trace_parser('expr($precedence)')
 	mut node := ast.empty_expr
 	is_stmt_ident := p.is_stmt_ident
@@ -363,7 +363,7 @@ pub fn (mut p Parser) check_expr(precedence int) ?ast.Expr {
 			}
 			if p.tok.kind != .eof && !(p.tok.kind == .rsbr && p.inside_asm) {
 				// eof should be handled where it happens
-				return none
+				return error('none')
 				// return p.unexpected(prepend_msg: 'invalid expression: ')
 			}
 		}
diff --git a/vlib/v/parser/fn.v b/vlib/v/parser/fn.v
index 739a1d43be..1302977232 100644
--- a/vlib/v/parser/fn.v
+++ b/vlib/v/parser/fn.v
@@ -584,7 +584,7 @@ run them via `v file.v` instead',
 	return fn_decl
 }
 
-fn (mut p Parser) fn_receiver(mut params []ast.Param, mut rec ReceiverParsingInfo) ? {
+fn (mut p Parser) fn_receiver(mut params []ast.Param, mut rec ReceiverParsingInfo) ! {
 	p.inside_receiver_param = true
 	defer {
 		p.inside_receiver_param = false
diff --git a/vlib/v/pref/options_test.v b/vlib/v/pref/options_test.v
index d709d8aab8..04ecc3d03e 100644
--- a/vlib/v/pref/options_test.v
+++ b/vlib/v/pref/options_test.v
@@ -15,7 +15,7 @@ fn testsuite_end() {
 	os.rmdir_all(tfolder) or {}
 }
 
-fn test_cflags() ? {
+fn test_cflags() {
 	os.chdir(os.real_path(@VMODROOT)) or {}
 	mut debug_arg := '-g3 -O0'
 	mut optimised_arg := '-O1'
diff --git a/vlib/v/pref/os.v b/vlib/v/pref/os.v
index 410de3205c..6779463749 100644
--- a/vlib/v/pref/os.v
+++ b/vlib/v/pref/os.v
@@ -32,7 +32,7 @@ pub enum OS {
 }
 
 // Helper function to convert string names to OS enum
-pub fn os_from_string(os_str string) ?OS {
+pub fn os_from_string(os_str string) !OS {
 	match os_str {
 		'' {
 			return ._auto
diff --git a/vlib/v/pref/pref.v b/vlib/v/pref/pref.v
index 93886e28f4..fb4ca7c796 100644
--- a/vlib/v/pref/pref.v
+++ b/vlib/v/pref/pref.v
@@ -888,7 +888,7 @@ pub fn (pref &Preferences) should_output_to_stdout() bool {
 	return pref.out_name.ends_with('/-') || pref.out_name.ends_with(r'\-')
 }
 
-pub fn arch_from_string(arch_str string) ?Arch {
+pub fn arch_from_string(arch_str string) !Arch {
 	match arch_str {
 		'amd64', 'x86_64', 'x64', 'x86' { // amd64 recommended
 
@@ -947,7 +947,7 @@ fn is_source_file(path string) bool {
 	return path.ends_with('.v') || os.exists(path)
 }
 
-pub fn backend_from_string(s string) ?Backend {
+pub fn backend_from_string(s string) !Backend {
 	match s {
 		'c' { return .c }
 		'js' { return .js_node }
diff --git a/vlib/v/preludes/test_runner.v b/vlib/v/preludes/test_runner.v
index 4c77717761..18ac7c2728 100644
--- a/vlib/v/preludes/test_runner.v
+++ b/vlib/v/preludes/test_runner.v
@@ -121,5 +121,5 @@ pub fn change_test_runner(x &TestRunner) {
 // `vlib/sync/channel_close_test.v` compiles with simpler runners,
 // that do not `import os` (which has other `fn()?`). Without it,
 // the C `Option_void` type is undefined -> C compilation error.
-fn vtest_option_cludge() ? {
+fn vtest_option_cludge() ! {
 }
diff --git a/vlib/v/token/token.v b/vlib/v/token/token.v
index e82eca74ca..8f0a221b11 100644
--- a/vlib/v/token/token.v
+++ b/vlib/v/token/token.v
@@ -628,7 +628,7 @@ pub fn kind_to_string(k Kind) string {
 	}
 }
 
-pub fn kind_from_string(s string) ?Kind {
+pub fn kind_from_string(s string) !Kind {
 	return match s {
 		'unknown' { .unknown }
 		'eof' { .eof }
diff --git a/vlib/v/util/diff.v b/vlib/v/util/diff.v
index 3e1814e9f0..ceba7073b5 100644
--- a/vlib/v/util/diff.v
+++ b/vlib/v/util/diff.v
@@ -4,7 +4,7 @@ import v.util.diff
 
 // iterates through a list of known diff cli commands
 // and returns it with basic options
-pub fn find_working_diff_command() ?string {
+pub fn find_working_diff_command() !string {
 	return diff.find_working_diff_command()
 }
 
diff --git a/vlib/v/util/diff/diff.v b/vlib/v/util/diff/diff.v
index 8d12c0c45f..195cec774f 100644
--- a/vlib/v/util/diff/diff.v
+++ b/vlib/v/util/diff/diff.v
@@ -5,7 +5,7 @@ import time
 
 // iterates through a list of known diff cli commands
 // and returns it with basic options
-pub fn find_working_diff_command() ?string {
+pub fn find_working_diff_command() !string {
 	env_difftool := os.getenv('VDIFF_TOOL')
 	env_diffopts := os.getenv('VDIFF_OPTIONS')
 	if env_difftool != '' {
diff --git a/vlib/v/util/module.v b/vlib/v/util/module.v
index 0454878a4b..555a6eab8a 100644
--- a/vlib/v/util/module.v
+++ b/vlib/v/util/module.v
@@ -96,7 +96,7 @@ pub fn qualify_module(pref &pref.Preferences, mod string, file_path string) stri
 // 2022-01-30 just on windows, because while `vlib\v\checker\tests\modules\deprecated_module` works,
 // 2022-01-30 it leads to path differences, and the / version on windows triggers a module lookip bug,
 // 2022-01-30 leading to completely different errors)
-fn mod_path_to_full_name(pref &pref.Preferences, mod string, path string) ?string {
+fn mod_path_to_full_name(pref &pref.Preferences, mod string, path string) !string {
 	// TODO: explore using `pref.lookup_path` & `os.vmodules_paths()`
 	// absolute paths instead of 'vlib' & '.vmodules'
 	mut vmod_folders := ['vlib', '.vmodules', 'modules']
diff --git a/vlib/v/util/util.v b/vlib/v/util/util.v
index 7c148d276c..5e69155e43 100644
--- a/vlib/v/util/util.v
+++ b/vlib/v/util/util.v
@@ -62,7 +62,7 @@ pub fn set_vroot_folder(vroot_path string) {
 	os.setenv('VCHILD', 'true', true)
 }
 
-pub fn resolve_vmodroot(str string, dir string) ?string {
+pub fn resolve_vmodroot(str string, dir string) !string {
 	mut mcache := vmod.get_cache()
 	vmod_file_location := mcache.get_by_folder(dir)
 	if vmod_file_location.vmod_file.len == 0 {
@@ -75,7 +75,7 @@ pub fn resolve_vmodroot(str string, dir string) ?string {
 
 // resolve_env_value replaces all occurrences of `$env('ENV_VAR_NAME')`
 // in `str` with the value of the env variable `$ENV_VAR_NAME`.
-pub fn resolve_env_value(str string, check_for_presence bool) ?string {
+pub fn resolve_env_value(str string, check_for_presence bool) !string {
 	env_ident := "\$env('"
 	at := str.index(env_ident) or {
 		return error('no "$env_ident' + '...\')" could be found in "$str".')
@@ -296,7 +296,7 @@ mut:
 }
 
 [unsafe]
-pub fn cached_read_source_file(path string) ?string {
+pub fn cached_read_source_file(path string) !string {
 	mut static cache := &SourceCache(0)
 	if cache == unsafe { nil } {
 		cache = &SourceCache{}
@@ -366,7 +366,7 @@ fn non_empty(arg []string) []string {
 	return arg.filter(it != '')
 }
 
-pub fn check_module_is_installed(modulename string, is_verbose bool) ?bool {
+pub fn check_module_is_installed(modulename string, is_verbose bool) !bool {
 	mpath := os.join_path_single(os.vmodules_dir(), modulename)
 	mod_v_file := os.join_path_single(mpath, 'v.mod')
 	murl := 'https://github.com/vlang/$modulename'
@@ -510,7 +510,7 @@ pub fn should_bundle_module(mod string) bool {
 // find_all_v_files - given a list of files/folders, finds all .v/.vsh files
 // if some of the files/folders on the list does not exist, or a file is not
 // a .v or .vsh file, returns an error instead.
-pub fn find_all_v_files(roots []string) ?[]string {
+pub fn find_all_v_files(roots []string) ![]string {
 	mut files := []string{}
 	for file in roots {
 		if os.is_dir(file) {
@@ -539,6 +539,6 @@ pub fn free_caches() {
 	}
 }
 
-pub fn read_file(file_path string) ?string {
+pub fn read_file(file_path string) !string {
 	return unsafe { cached_read_source_file(file_path) }
 }
diff --git a/vlib/v/vmod/parser.v b/vlib/v/vmod/parser.v
index e59d09b90e..6e7883b3f7 100644
--- a/vlib/v/vmod/parser.v
+++ b/vlib/v/vmod/parser.v
@@ -52,7 +52,7 @@ struct Token {
 	line int
 }
 
-pub fn from_file(vmod_path string) ?Manifest {
+pub fn from_file(vmod_path string) !Manifest {
 	if !os.exists(vmod_path) {
 		return error('v.mod: v.mod file not found.')
 	}
@@ -60,7 +60,7 @@ pub fn from_file(vmod_path string) ?Manifest {
 	return decode(contents)
 }
 
-pub fn decode(contents string) ?Manifest {
+pub fn decode(contents string) !Manifest {
 	mut parser := Parser{
 		scanner: Scanner{
 			pos: 0
@@ -158,7 +158,7 @@ fn (mut s Scanner) scan_all() {
 	s.tokenize(.eof, 'eof')
 }
 
-fn get_array_content(tokens []Token, st_idx int) ?([]string, int) {
+fn get_array_content(tokens []Token, st_idx int) !([]string, int) {
 	mut vals := []string{}
 	mut idx := st_idx
 	if tokens[idx].typ != .labr {
@@ -187,7 +187,7 @@ fn get_array_content(tokens []Token, st_idx int) ?([]string, int) {
 	return vals, idx
 }
 
-fn (mut p Parser) parse() ?Manifest {
+fn (mut p Parser) parse() !Manifest {
 	if p.scanner.text.len == 0 {
 		return error('$vmod.err_label no content.')
 	}
@@ -237,14 +237,14 @@ fn (mut p Parser) parse() ?Manifest {
 						mn.author = field_value
 					}
 					'dependencies' {
-						deps, idx := get_array_content(tokens, i + 1)?
+						deps, idx := get_array_content(tokens, i + 1)!
 						mn.dependencies = deps
 						i = idx
 						continue
 					}
 					else {
 						if tokens[i + 1].typ == .labr {
-							vals, idx := get_array_content(tokens, i + 1)?
+							vals, idx := get_array_content(tokens, i + 1)!
 							mn.unknown[field_name] = vals
 							i = idx
 							continue