From 2b1d6f0e7a453d18fec5c6043287f73010ba222f Mon Sep 17 00:00:00 2001
From: Marc Vertes <mvertes@free.fr>
Date: Fri, 26 Mar 2021 09:34:03 +0100
Subject: [PATCH] interp: fix append on variadic recursive struct

Fixes #1065. Improves #1058.
---
 _test/issue-1065.go | 20 ++++++++++++++++++++
 interp/run.go       |  2 +-
 interp/typecheck.go |  4 ++++
 3 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 _test/issue-1065.go

diff --git a/_test/issue-1065.go b/_test/issue-1065.go
new file mode 100644
index 000000000..e65a83f9a
--- /dev/null
+++ b/_test/issue-1065.go
@@ -0,0 +1,20 @@
+package main
+
+import "fmt"
+
+type AST struct {
+	Num      int
+	Children []AST
+}
+
+func newAST(num int, root AST, children ...AST) AST {
+	return AST{num, append([]AST{root}, children...)}
+}
+
+func main() {
+	ast := newAST(1, AST{}, AST{})
+	fmt.Println(ast)
+}
+
+// Output:
+// {1 [{0 []} {0 []}]}
diff --git a/interp/run.go b/interp/run.go
index 0c006ba1a..24b71db53 100644
--- a/interp/run.go
+++ b/interp/run.go
@@ -2947,7 +2947,7 @@ func _append(n *node) {
 	if len(n.child) == 3 {
 		c1, c2 := n.child[1], n.child[2]
 		if (c1.typ.cat == valueT || c2.typ.cat == valueT) && c1.typ.rtype == c2.typ.rtype ||
-			c2.typ.cat == arrayT && c2.typ.val.id() == n.typ.val.id() ||
+			(c2.typ.cat == arrayT || c2.typ.cat == variadicT) && c2.typ.val.id() == n.typ.val.id() ||
 			isByteArray(c1.typ.TypeOf()) && isString(c2.typ.TypeOf()) {
 			appendSlice(n)
 			return
diff --git a/interp/typecheck.go b/interp/typecheck.go
index b05080fb4..1fa7b0c76 100644
--- a/interp/typecheck.go
+++ b/interp/typecheck.go
@@ -48,6 +48,10 @@ func (check typecheck) assignment(n *node, typ *itype, context string) error {
 		return nil
 	}
 
+	if typ.isRecursive() || typ.val != nil && typ.val.isRecursive() {
+		return nil
+	}
+
 	if !n.typ.assignableTo(typ) {
 		if context == "" {
 			return n.cfgErrorf("cannot use type %s as type %s", n.typ.id(), typ.id())