cgen: fix $tmpl() in returning match expr (fix #16109, fix #16124) (#16229)

vlib/v/gen/c/cgen.v

@@ -126,6 +126,7 @@ mut:
 	inside_match_result       bool
 	inside_vweb_tmpl          bool
 	inside_return             bool
+	inside_return_tmpl        bool
 	inside_struct_init        bool
 	inside_or_block           bool
 	inside_call               bool
@@ -4281,7 +4282,9 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 	if node.exprs.len > 0 {
 		// skip `return $vweb.html()`
 		if node.exprs[0] is ast.ComptimeCall && (node.exprs[0] as ast.ComptimeCall).is_vweb {
+			g.inside_return_tmpl = true
 			g.expr(node.exprs[0])
+			g.inside_return_tmpl = false
 			g.writeln(';')
 			return
 		}

vlib/v/gen/c/comptime.v

@@ -75,7 +75,7 @@ fn (mut g Gen) comptime_call(mut node ast.ComptimeCall) {
 		} else {
 			// return $tmpl string
 			g.write(cur_line)
-			if g.inside_return {
+			if g.inside_return_tmpl {
 				g.write('return ')
 			}
 			g.write('_tmpl_res_$fn_name')

vlib/v/tests/tmpl/template.txt

@@ -0,0 +1 @@
+@name

vlib/v/tests/tmpl_in_return_match_expr_test.v

@@ -0,0 +1,51 @@
+fn foo1() string {
+	return match true {
+		true {
+			name := 'abc'
+			$tmpl('tmpl/template.txt')
+		}
+		else {
+			'else'
+		}
+	}
+}
+
+fn foo2() string {
+	return if true {
+		name := 'abc'
+		$tmpl('tmpl/template.txt')
+	} else {
+		'else'
+	}
+}
+
+struct Res {
+mut:
+	str string
+}
+
+fn foo3() Res {
+	name := 'abc'
+	return Res{
+		str: $tmpl('tmpl/template.txt')
+	}
+}
+
+fn new_res(str string) Res {
+	mut res := Res{}
+	res.str = str
+	return res
+}
+
+fn foo4() Res {
+	name := 'abc'
+	return new_res($tmpl('tmpl/template.txt'))
+}
+
+fn test_tmpl_in_return_match_expr() {
+	println(foo1())
+	println(foo2())
+	println(foo3())
+	println(foo4())
+	assert true
+}