From 3647fc6633fd28f1c97721c0072bc309c8a1996b Mon Sep 17 00:00:00 2001
From: ChAoS_UnItY <43753315+ChAoSUnItY@users.noreply.github.com>
Date: Sun, 10 Oct 2021 06:55:25 +0800
Subject: [PATCH] parser: perform constant folding before checking size of
 fixed array (#12126)

---
 vlib/v/parser/parse_type.v              | 14 +++++++++++++-
 vlib/v/tests/constant_array_size_test.v | 12 ++++++++++++
 vlib/v/transformer/transformer.v        |  6 +++---
 3 files changed, 28 insertions(+), 4 deletions(-)
 create mode 100644 vlib/v/tests/constant_array_size_test.v

diff --git a/vlib/v/parser/parse_type.v b/vlib/v/parser/parse_type.v
index c1a30f001d..201ac927fc 100644
--- a/vlib/v/parser/parse_type.v
+++ b/vlib/v/parser/parse_type.v
@@ -3,6 +3,7 @@
 // that can be found in the LICENSE file.
 module parser
 
+import v.transformer
 import v.ast
 import v.util
 import v.token
@@ -26,7 +27,18 @@ pub fn (mut p Parser) parse_array_type() ast.Type {
 						if const_field.expr is ast.IntegerLiteral {
 							fixed_size = const_field.expr.val.int()
 						} else {
-							show_non_const_error = true
+							if const_field.expr is ast.InfixExpr {
+								t := transformer.new_transformer(p.pref)
+								folded_expr := t.infix_expr(const_field.expr)
+
+								if folded_expr is ast.IntegerLiteral {
+									fixed_size = folded_expr.val.int()
+								} else {
+									show_non_const_error = true
+								}
+							} else {
+								show_non_const_error = true
+							}
 						}
 					} else {
 						if p.pref.is_fmt {
diff --git a/vlib/v/tests/constant_array_size_test.v b/vlib/v/tests/constant_array_size_test.v
new file mode 100644
index 0000000000..9b575ba1e7
--- /dev/null
+++ b/vlib/v/tests/constant_array_size_test.v
@@ -0,0 +1,12 @@
+const (
+	c_a_s = 1
+	c_b_s = 1 + 1
+	c_c_s = c_b_s + 1 // this should be also fold by transformer since it's a constant
+)
+
+fn test_consant_array_size() {
+	mut a := [c_a_s]int{}
+	a = [1]!
+	mut b := [c_b_s]int{}
+	b = [1, 2]!
+}
diff --git a/vlib/v/transformer/transformer.v b/vlib/v/transformer/transformer.v
index 61a2d915ee..a91a3a2776 100644
--- a/vlib/v/transformer/transformer.v
+++ b/vlib/v/transformer/transformer.v
@@ -26,7 +26,7 @@ pub fn (t Transformer) transform(ast_file &ast.File) {
 	}
 }
 
-fn (t Transformer) stmt(mut node ast.Stmt) {
+pub fn (t Transformer) stmt(mut node ast.Stmt) {
 	match mut node {
 		ast.EmptyStmt {}
 		ast.NodeError {}
@@ -88,14 +88,14 @@ fn (t Transformer) stmt(mut node ast.Stmt) {
 	}
 }
 
-fn (t Transformer) expr(node ast.Expr) ast.Expr {
+pub fn (t Transformer) expr(node ast.Expr) ast.Expr {
 	match node {
 		ast.InfixExpr { return t.infix_expr(node) }
 		else { return node }
 	}
 }
 
-fn (t Transformer) infix_expr(original ast.InfixExpr) ast.Expr {
+pub fn (t Transformer) infix_expr(original ast.InfixExpr) ast.Expr {
 	mut node := original
 	node.left = t.expr(node.left)
 	node.right = t.expr(node.right)