From fdfcb9c1df4e928cba5a70c3344ec3bf16bf2fd9 Mon Sep 17 00:00:00 2001
From: Marc Vertes <mvertes@free.fr>
Date: Tue, 9 Mar 2021 11:58:04 +0100
Subject: [PATCH] interp: do not check properties of incomplete types

Fixes #1042.
---
 _test/const25.go | 11 +++++++++++
 interp/cfg.go    | 11 +++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)
 create mode 100644 _test/const25.go

diff --git a/_test/const25.go b/_test/const25.go
new file mode 100644
index 00000000..7cb053da
--- /dev/null
+++ b/_test/const25.go
@@ -0,0 +1,11 @@
+package main
+
+const (
+	FGBlack Attribute = iota + 30
+)
+
+type Attribute int
+
+func main() {
+	println(FGBlack)
+}
diff --git a/interp/cfg.go b/interp/cfg.go
index d9a7d015..67a79caa 100644
--- a/interp/cfg.go
+++ b/interp/cfg.go
@@ -82,8 +82,15 @@ func (interp *Interpreter) cfg(root *node, importPath string) ([]*node, error) {
 					i--
 				}
 				dest := a.child[i]
-				if dest.typ != nil && !isInterface(dest.typ) {
-					// Interface type are not propagated, and will be resolved at post-order.
+				if dest.typ == nil {
+					break
+				}
+				if dest.typ.incomplete {
+					err = n.cfgErrorf("invalid type declaration")
+					return false
+				}
+				if !isInterface(dest.typ) {
+					// Interface types are not propagated, and will be resolved at post-order.
 					n.typ = dest.typ
 				}
 			case binaryExpr, unaryExpr, parenExpr: