From e5839effbca36d777fc4eb241ad698281b9c54fb Mon Sep 17 00:00:00 2001
From: zakuro <z@kuro.red>
Date: Mon, 8 Feb 2021 09:41:47 +0900
Subject: [PATCH] checker/cgen: allow `<<` operator for aliases (#8561)

---
 vlib/v/checker/checker.v             | 10 ++++++----
 vlib/v/gen/c/cgen.v                  |  8 +++++---
 vlib/v/tests/array_type_alias_test.v |  9 +++++++--
 3 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 7c08bd13f8..219586f760 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -756,7 +756,9 @@ pub fn (mut c Checker) infix_expr(mut infix_expr ast.InfixExpr) table.Type {
 	// right_type = c.unwrap_genric(c.expr(infix_expr.right))
 	infix_expr.right_type = right_type
 	mut right := c.table.get_type_symbol(right_type)
+	right_final := c.table.get_final_type_symbol(right_type)
 	mut left := c.table.get_type_symbol(left_type)
+	left_final := c.table.get_final_type_symbol(left_type)
 	left_pos := infix_expr.left.position()
 	right_pos := infix_expr.right.position()
 	if (left_type.is_ptr() || left.is_pointer()) && infix_expr.op in [.plus, .minus] {
@@ -919,17 +921,17 @@ pub fn (mut c Checker) infix_expr(mut infix_expr ast.InfixExpr) table.Type {
 			}
 		}
 		.left_shift {
-			if left.kind == .array {
+			if left_final.kind == .array {
 				// `array << elm`
 				infix_expr.auto_locked, _ = c.fail_if_immutable(infix_expr.left)
 				left_value_type := c.table.value_type(left_type)
 				left_value_sym := c.table.get_type_symbol(left_value_type)
 				if left_value_sym.kind == .interface_ {
-					if right.kind != .array {
+					if right_final.kind != .array {
 						// []Animal << Cat
 						c.type_implements(right_type, left_value_type, right_pos)
 					} else {
-						// []Animal << Cat
+						// []Animal << []Cat
 						c.type_implements(c.table.value_type(right_type), left_value_type,
 							right_pos)
 					}
@@ -940,7 +942,7 @@ pub fn (mut c Checker) infix_expr(mut infix_expr ast.InfixExpr) table.Type {
 					// []T << T
 					return table.void_type
 				}
-				if right.kind == .array
+				if right_final.kind == .array
 					&& c.check_types(left_value_type, c.table.value_type(right_type)) {
 					// []T << []T
 					return table.void_type
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 26bdef3282..82f85debdd 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -3042,6 +3042,7 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 	}
 	left_type := g.unwrap_generic(node.left_type)
 	left_sym := g.table.get_type_symbol(left_type)
+	left_final_sym := g.table.get_final_type_symbol(left_type)
 	unaliased_left := if left_sym.kind == .alias {
 		(left_sym.info as table.Alias).parent_type
 	} else {
@@ -3055,6 +3056,7 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 	op_is_key_in_or_not_in := node.op in [.key_in, .not_in]
 	op_is_eq_or_ne := node.op in [.eq, .ne]
 	right_sym := g.table.get_type_symbol(node.right_type)
+	right_final_sym := g.table.get_final_type_symbol(node.right_type)
 	has_eq_overloaded := !left_sym.has_method('==')
 	unaliased_right := if right_sym.info is table.Alias {
 		right_sym.info.parent_type
@@ -3289,11 +3291,11 @@ fn (mut g Gen) infix_expr(node ast.InfixExpr) {
 			g.expr(node.left)
 			g.write(')')
 		}
-	} else if node.op == .left_shift && left_sym.kind == .array {
+	} else if node.op == .left_shift && left_final_sym.kind == .array {
 		// arr << val
 		tmp := g.new_tmp_var()
-		info := left_sym.info as table.Array
-		if right_sym.kind == .array && info.elem_type != node.right_type {
+		info := left_final_sym.info as table.Array
+		if right_final_sym.kind == .array && info.elem_type != node.right_type {
 			// push an array => PUSH_MANY, but not if pushing an array to 2d array (`[][]int << []int`)
 			g.write('_PUSH_MANY(')
 			mut expected_push_many_atype := left_type
diff --git a/vlib/v/tests/array_type_alias_test.v b/vlib/v/tests/array_type_alias_test.v
index 17ee8d62ec..ca6b693e11 100644
--- a/vlib/v/tests/array_type_alias_test.v
+++ b/vlib/v/tests/array_type_alias_test.v
@@ -1,6 +1,11 @@
 type Test = []int
 
 fn test_index() {
-    t := Test([2,4])
-    assert t[1] == 4
+	mut t := Test([2, 4])
+	assert t[1] == 4
+	assert t == Test([2, 4])
+	t << 6
+	assert t == Test([2, 4, 6])
+	t << Test([8, 10])
+	assert t == Test([2, 4, 6, 8, 10])
 }