From 1a9dba0005898f16ac4b4e8ef0effe629c98c0e5 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@vlang.io>
Date: Tue, 11 Aug 2020 01:05:34 +0200
Subject: [PATCH] checker: make << shifts work with custom number types

---
 vlib/v/checker/check_types.v | 8 ++++++--
 vlib/v/tests/shift_test.v    | 5 +++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/vlib/v/checker/check_types.v b/vlib/v/checker/check_types.v
index 795348f87f..6c7a15bfda 100644
--- a/vlib/v/checker/check_types.v
+++ b/vlib/v/checker/check_types.v
@@ -144,8 +144,12 @@ pub fn (mut c Checker) check_matching_function_symbols(got_type_sym, exp_type_sy
 [inline]
 fn (mut c Checker) check_shift(left_type, right_type table.Type, left_pos, right_pos token.Position) table.Type {
 	if !left_type.is_int() {
-		c.error('invalid operation: shift of type `${c.table.get_type_symbol(left_type).name}`',
-			left_pos)
+		// maybe it's an int alias? TODO move this to is_int() ?
+		sym := c.table.get_type_symbol(left_type)
+		if sym.kind == .alias && (sym.info as table.Alias).parent_type.is_int() {
+			return left_type
+		}
+		c.error('invalid operation: shift of type `$sym.name`', left_pos)
 		return table.void_type
 	} else if !right_type.is_int() {
 		c.error('cannot shift non-integer type ${c.table.get_type_symbol(right_type).name} into type ${c.table.get_type_symbol(left_type).name}',
diff --git a/vlib/v/tests/shift_test.v b/vlib/v/tests/shift_test.v
index 597e8389a0..f5ef181685 100644
--- a/vlib/v/tests/shift_test.v
+++ b/vlib/v/tests/shift_test.v
@@ -1,3 +1,5 @@
+type MyInt int
+
 fn test_shift_operators() {
 	// check that shift works with all integer types
 	// as the right-hand side operand
@@ -63,4 +65,7 @@ fn test_shift_operators() {
 	assert e3 == b
 	e3 >>= u64(i)
 	assert e3 == a
+	// Test shifts with custom int types
+	x := MyInt(2)
+	assert x << 2 == 8
 }