From 576192949dbc185ba478070587a6db6786288ca5 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Sun, 4 Aug 2019 03:59:12 +0200
Subject: [PATCH] fixed size array with const size: `numbers := [N]int`

---
 compiler/parser.v         | 14 +++++++++++++-
 vlib/builtin/array_test.v | 17 +++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/compiler/parser.v b/compiler/parser.v
index a7d2129b8f..c5e686ffb6 100644
--- a/compiler/parser.v
+++ b/compiler/parser.v
@@ -2482,7 +2482,16 @@ fn (p mut Parser) map_init() string {
 fn (p mut Parser) array_init() string {
 	p.is_alloc = true 
 	p.check(.lsbr)
-	is_integer := p.tok == .number
+	mut is_integer := p.tok == .number  // for `[10]int` 
+	// fixed length arrays with a const len: `nums := [N]int`, same as `[10]int` basically 
+	mut is_const_len := false 
+	if p.tok == .name {
+		c := p.table.find_const(p.prepend_pkg(p.lit)) 
+		if c.name != '' && c.typ == 'int' && p.peek() == .rsbr && !p.inside_const {
+			is_integer = true 
+			is_const_len = true 
+		} 
+	} 
 	lit := p.lit
 	mut typ := ''
 	new_arr_ph := p.cgen.add_placeholder()
@@ -2504,6 +2513,9 @@ fn (p mut Parser) array_init() string {
 					if p.table.known_type(name) {
 						p.cgen.resetln('')
 						p.gen('STRUCT_DEFAULT_VALUE')
+						if is_const_len { 
+							return '[${p.mod}__$lit]$name' 
+						} 
 						return '[$lit]$name'
 					}
 					else {
diff --git a/vlib/builtin/array_test.v b/vlib/builtin/array_test.v
index efa9a6c77f..482e794d90 100644
--- a/vlib/builtin/array_test.v
+++ b/vlib/builtin/array_test.v
@@ -160,3 +160,20 @@ fn test_reverse() {
 		assert d[i] == b[b.len-i-1]
 	}
 }
+
+const (
+	N = 5
+) 
+
+fn test_fixed() {
+	mut nums := [4]int 
+	assert nums[0] == 0 
+	assert nums[1] == 0 
+	assert nums[2] == 0 
+	assert nums[3] == 0 
+	nums[1] = 7 
+	assert nums[1] == 7 
+	///////
+	nums2 := [N]int 
+	assert nums2[N - 1] == 0 
+}