compiler: process empty []byte{} literals as ByteArrays

It is wrong to count an empty byte slice as an Array.

pkg/compiler/analysis.go

@@ -189,6 +189,12 @@ func isBuiltin(expr ast.Expr) bool {
 
 func isByteArray(lit *ast.CompositeLit, tInfo *types.Info) bool {
 	if len(lit.Elts) == 0 {
+		if typ, ok := lit.Type.(*ast.ArrayType); ok {
+			if name, ok := typ.Elt.(*ast.Ident); ok {
+				return name.Name == "byte" || name.Name == "uint8"
+			}
+		}
+
 		return false
 	}
 

pkg/compiler/for_test.go

@@ -293,6 +293,18 @@ func TestAppendByte(t *testing.T) {
 	eval(t, src, []uint8{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06})
 }
 
+func TestAppendByteToEmpty(t *testing.T) {
+	src := `
+	package foo
+	func Main() []byte {
+		out := []byte{}
+		out = append(out, 1)
+		out = append(out, 2)
+		return out
+	}`
+	eval(t, src, []byte{1, 2})
+}
+
 func TestAppendString(t *testing.T) {
 	src := `
 	package foo