From 354645fbe3a7946e1ffac12d79034817108ebd70 Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Mon, 24 Aug 2020 18:55:30 +0300
Subject: [PATCH] compiler: allow to use `switch` without tag

---
 pkg/compiler/codegen.go     | 10 +++++++---
 pkg/compiler/switch_test.go | 15 +++++++++++++++
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/pkg/compiler/codegen.go b/pkg/compiler/codegen.go
index a12a753bd..0d4445b3f 100644
--- a/pkg/compiler/codegen.go
+++ b/pkg/compiler/codegen.go
@@ -578,9 +578,13 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 		return nil
 
 	case *ast.SwitchStmt:
-		ast.Walk(c, n.Tag)
-
-		eqOpcode, _ := convertToken(token.EQL, c.typeOf(n.Tag))
+		eqOpcode := opcode.EQUAL
+		if n.Tag != nil {
+			ast.Walk(c, n.Tag)
+			eqOpcode, _ = convertToken(token.EQL, c.typeOf(n.Tag))
+		} else {
+			emit.Bool(c.prog.BinWriter, true)
+		}
 		switchEnd, label := c.generateLabel(labelEnd)
 
 		lastSwitch := c.currentSwitch
diff --git a/pkg/compiler/switch_test.go b/pkg/compiler/switch_test.go
index 7a34e3174..ce90ee0c2 100644
--- a/pkg/compiler/switch_test.go
+++ b/pkg/compiler/switch_test.go
@@ -18,6 +18,21 @@ var switchTestCases = []testCase{
 		}`,
 		big.NewInt(2),
 	},
+	{
+		"switch with no tag",
+		`package main
+		func f() bool { return false }
+		func Main() int {
+			switch {
+			case f():
+				return 1
+			case true:
+				return 2
+			}
+			return 3
+		}`,
+		big.NewInt(2),
+	},
 	{
 		"simple switch fail",
 		`package main