From f55646746c6bc423084d1e2bfcfb8199247cd359 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Fri, 24 Jan 2020 18:57:32 +0100
Subject: [PATCH] handle empty config structs

---
 vlib/compiler/expression.v        |  2 +-
 vlib/compiler/gen_c.v             |  9 +++++++++
 vlib/compiler/tests/struct_test.v | 15 +++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/vlib/compiler/expression.v b/vlib/compiler/expression.v
index f1a41db9d6..bdf423678d 100644
--- a/vlib/compiler/expression.v
+++ b/vlib/compiler/expression.v
@@ -903,7 +903,7 @@ fn (p mut Parser) factor() string {
 				return p.map_init()
 			}
 			peek2 := p.tokens[p.token_idx + 1]
-			if p.peek() == .name && peek2.tok == .colon {
+			if p.peek() == .rcbr || (p.peek() == .name && peek2.tok == .colon) {
 				if !p.expected_type.ends_with('Config') {
 					p.error('short struct initialization syntax only works with structs that end with `Config`')
 				}
diff --git a/vlib/compiler/gen_c.v b/vlib/compiler/gen_c.v
index 901e0d3698..ebe0a68c6a 100644
--- a/vlib/compiler/gen_c.v
+++ b/vlib/compiler/gen_c.v
@@ -493,10 +493,19 @@ fn (p mut Parser) gen_struct_init(typ string, t &Type) bool {
 	if typ == 'tm' {
 		p.cgen.lines[p.cgen.lines.len - 1] = ''
 	}
+	mut is_config := false
 	if p.tok != .lcbr {
 		p.next()
+	} else {
+		is_config = true
 	}
 	p.check(.lcbr)
+	// Handle empty config ({})
+	if is_config && p.tok == .rcbr {
+		p.check(.rcbr)
+		p.gen('($typ) {}')
+		return true
+	}
 	ptr := typ.contains('*')
 	// `user := User{foo:bar}` => `User user = (User){ .foo = bar}`
 	if !ptr {
diff --git a/vlib/compiler/tests/struct_test.v b/vlib/compiler/tests/struct_test.v
index 1654a64094..879e8c2f86 100644
--- a/vlib/compiler/tests/struct_test.v
+++ b/vlib/compiler/tests/struct_test.v
@@ -194,3 +194,18 @@ fn test_fixed_field() {
 }
 */
 
+
+struct Config {
+	n int
+	def int = 10
+}
+
+fn foo_config(c Config) {
+}
+
+fn test_config() {
+	foo_config({n: 10, def: 20})
+	foo_config({})
+}
+
+