parser: auto-import `sync` when `shared` objects are used (#8294)

vlib/v/parser/parser.v

@@ -1034,6 +1034,9 @@ pub fn (mut p Parser) parse_ident(language table.Language) ast.Ident {
 	// p.warn('name ')
 	is_shared := p.tok.kind == .key_shared
 	is_atomic := p.tok.kind == .key_atomic
+	if is_shared {
+		p.register_auto_import('sync')
+	}
 	mut_pos := p.tok.position()
 	is_mut := p.tok.kind == .key_mut || is_shared || is_atomic
 	if is_mut {

vlib/v/tests/shared_autolock_test.v

@@ -0,0 +1,34 @@
+const iterations = 100000
+
+fn inc_array_elem(shared b []int, i int) {
+	for _ in 0 .. iterations {
+		b[i]++
+	}
+}
+
+fn test_autolock_array() {
+	shared a := &[1, 2, 7, 5]
+	t := go inc_array_elem(shared a, 2)
+	for _ in 0 .. iterations {
+		a[2]++
+	}
+	t.wait()
+	assert a[2] == 2 * iterations + 7
+}
+
+fn inc_map_elem(shared b map[string]int, k string) {
+	for _ in 0 .. iterations {
+		b[k]++
+	}
+}
+
+fn test_autolock_map() {
+	shared m := &{'xy': 1, 'qwe': 2, 'asd': 7, 'iop': 5}
+	t := go inc_map_elem(shared m, 'asd')
+	for _ in 0 .. iterations {
+		m['asd']++
+	}
+	t.wait()
+	assert m['asd'] == 2 * iterations + 7
+}
+