From 78948ef7af8fd7246d2c9c8536499787d0620a63 Mon Sep 17 00:00:00 2001
From: Evgenii Stratonikov <evgeniy@nspcc.ru>
Date: Tue, 15 Sep 2020 09:52:56 +0300
Subject: [PATCH] compiler: emit error for non-byte subslices

They are not supported for now, as VM has only
`SUBSTR` opcode for Buffers (`[]byte` in Go).
---
 pkg/compiler/codegen.go    |  4 ++++
 pkg/compiler/slice_test.go | 11 +++++++++++
 2 files changed, 15 insertions(+)

diff --git a/pkg/compiler/codegen.go b/pkg/compiler/codegen.go
index be9e8ec2c..7aa889e0a 100644
--- a/pkg/compiler/codegen.go
+++ b/pkg/compiler/codegen.go
@@ -517,6 +517,10 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 		return nil
 
 	case *ast.SliceExpr:
+		if isCompoundSlice(c.typeOf(n.X.(*ast.Ident)).Underlying()) {
+			c.prog.Err = errors.New("subslices are supported only for []byte")
+			return nil
+		}
 		name := n.X.(*ast.Ident).Name
 		c.emitLoadVar("", name)
 
diff --git a/pkg/compiler/slice_test.go b/pkg/compiler/slice_test.go
index ee776407f..7d14650d5 100644
--- a/pkg/compiler/slice_test.go
+++ b/pkg/compiler/slice_test.go
@@ -316,6 +316,17 @@ func TestSliceOperations(t *testing.T) {
 	runTestCases(t, sliceTestCases)
 }
 
+func TestSubsliceCompound(t *testing.T) {
+	src := `package foo
+	func Main() []int {
+		a := []int{0, 1, 2, 3}
+		b := a[1:3]
+		return b
+	}`
+	_, err := compiler.Compile("", strings.NewReader(src))
+	require.Error(t, err)
+}
+
 func TestJumps(t *testing.T) {
 	src := `
 	package foo