From 097d35b9d50d6dc7c165a2680fd985d70ddb02f2 Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Mon, 27 Jan 2020 11:53:47 +0300
Subject: [PATCH] compiler: fix a bug with FromAddress handling

Conversion of string to address with FromAddress is performed
at compile time so there is no need to push parameters on stack.
---
 pkg/compiler/analysis.go     |  5 +++++
 pkg/compiler/codegen.go      | 10 ++++++---
 pkg/compiler/interop_test.go | 40 ++++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/pkg/compiler/analysis.go b/pkg/compiler/analysis.go
index d29348b8d..c1b01e2ee 100644
--- a/pkg/compiler/analysis.go
+++ b/pkg/compiler/analysis.go
@@ -185,6 +185,11 @@ func isAppCall(expr ast.Expr) bool {
 	return ok && t.Sel.Name == "AppCall"
 }
 
+func isFromAddress(expr ast.Expr) bool {
+	t, ok := expr.(*ast.SelectorExpr)
+	return ok && t.Sel.Name == "FromAddress"
+}
+
 func isByteArray(lit *ast.CompositeLit, tInfo *types.Info) bool {
 	if len(lit.Elts) == 0 {
 		return false
diff --git a/pkg/compiler/codegen.go b/pkg/compiler/codegen.go
index 95695e98b..1023bd142 100644
--- a/pkg/compiler/codegen.go
+++ b/pkg/compiler/codegen.go
@@ -491,9 +491,13 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 
 		args := n.Args
 		isAppCall := isAppCall(n.Fun)
-		// When using APPCALL, script hash is a part of the instruction so
-		// script hash should be emitted after APPCALL.
-		if isAppCall {
+		isFromAddress := isFromAddress(n.Fun)
+		// There are 2 special cases:
+		// 1. When using APPCALL, script hash is a part of the instruction so
+		//    script hash should be emitted after APPCALL.
+		// 2. With FromAddress, parameter conversion is happening at compile-time
+		//    so there is no need to push parameters on stack and perform an actual call
+		if isAppCall || isFromAddress {
 			args = n.Args[1:]
 		}
 
diff --git a/pkg/compiler/interop_test.go b/pkg/compiler/interop_test.go
index bd86c4e4f..f1e0e1748 100644
--- a/pkg/compiler/interop_test.go
+++ b/pkg/compiler/interop_test.go
@@ -8,10 +8,50 @@ import (
 
 	"github.com/CityOfZion/neo-go/pkg/compiler"
 	"github.com/CityOfZion/neo-go/pkg/crypto/hash"
+	"github.com/CityOfZion/neo-go/pkg/encoding/address"
 	"github.com/CityOfZion/neo-go/pkg/util"
 	"github.com/stretchr/testify/require"
 )
 
+func TestFromAddress(t *testing.T) {
+	as1 := "Aej1fe4mUgou48Zzup5j8sPrE3973cJ5oz"
+	addr1, err := address.StringToUint160(as1)
+	require.NoError(t, err)
+
+	as2 := "AK2nJJpJr6o664CWJKi1QRXjqeic2zRp8y"
+	addr2, err := address.StringToUint160(as2)
+	require.NoError(t, err)
+
+	t.Run("append 2 addresses", func(t *testing.T) {
+		src := `
+		package foo
+ 		import "github.com/CityOfZion/neo-go/pkg/interop/util"
+		func Main() []byte {
+			addr1 := util.FromAddress("` + as1 + `")
+			addr2 := util.FromAddress("` + as2 + `")
+			sum := append(addr1, addr2...)
+			return sum
+		}
+		`
+
+		eval(t, src, append(addr1.BytesBE(), addr2.BytesBE()...))
+	})
+
+	t.Run("append 2 addresses inline", func(t *testing.T) {
+		src := `
+		package foo
+ 		import "github.com/CityOfZion/neo-go/pkg/interop/util"
+		func Main() []byte {
+			addr1 := util.FromAddress("` + as1 + `")
+			sum := append(addr1, util.FromAddress("` + as2 + `")...)
+			return sum
+		}
+		`
+
+		eval(t, src, append(addr1.BytesBE(), addr2.BytesBE()...))
+	})
+}
+
 func TestAppCall(t *testing.T) {
 	srcInner := `
 	package foo