parser: fix $tmpl with single quotes (fix #16154) (#16216)

vlib/v/parser/tmpl.v

@@ -80,7 +80,10 @@ fn insert_template_code(fn_name string, tmpl_str_start string, line string) stri
 	round1 := ['\\', '\\\\', r"'", "\\'", r'@', r'$']
 	round2 := [r'$$', r'\@', r'.$', r'.@']
 	mut rline := line.replace_each(round1).replace_each(round2)
-
+	comptime_call_str := rline.find_between('\${', '}')
+	if comptime_call_str.contains("\\'") {
+		rline = rline.replace(comptime_call_str, comptime_call_str.replace("\\'", r"'"))
+	}
 	if rline.ends_with('\\') {
 		rline = rline[0..rline.len - 2] + trailing_bs
 	}

vlib/v/tests/tmpl/template.in

@@ -0,0 +1,3 @@
+someval: @{s.someval('huh')}
+
+someotherval: @{s.m['hah']}

vlib/v/tests/tmpl_with_single_quotes_test.v

@@ -0,0 +1,27 @@
+module main
+
+pub struct SomeThing {
+pub:
+	m map[string]string
+}
+
+fn (s SomeThing) someval(what string) string {
+	return s.m[what]
+}
+
+fn (s SomeThing) template() string {
+	return $tmpl('tmpl/template.in')
+}
+
+fn test_tmpl_with_single_quotes() {
+	mut sm := map[string]string{}
+	sm['huh'] = 'monkey'
+	sm['hah'] = 'parrot'
+
+	s := SomeThing{sm}
+	result := s.template()
+	println(result)
+	assert result.trim_space() == 'someval: monkey
+
+someotherval: parrot'
+}