From b1ef9251d41488d4ef4f7daee26ede712f7058a6 Mon Sep 17 00:00:00 2001
From: Marc Vertes <mvertes@free.fr>
Date: Fri, 11 Jun 2021 17:58:11 +0200
Subject: [PATCH] interp: fix detection of binary types implementing interfaces

Fixes #1136.
---
 _test/issue-1136.go | 12 ++++++++++++
 interp/type.go      | 13 ++++++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 _test/issue-1136.go

diff --git a/_test/issue-1136.go b/_test/issue-1136.go
new file mode 100644
index 00000000..a3d729c9
--- /dev/null
+++ b/_test/issue-1136.go
@@ -0,0 +1,12 @@
+package main
+
+import (
+	"fmt"
+	"io"
+)
+
+func main() {
+	x := io.LimitedReader{}
+	y := io.Reader(&x)
+	fmt.Println(y)
+}
diff --git a/interp/type.go b/interp/type.go
index a7e8a0f1..7fb6792c 100644
--- a/interp/type.go
+++ b/interp/type.go
@@ -1558,7 +1558,7 @@ func (t *itype) frameType() (r reflect.Type) {
 }
 
 func (t *itype) implements(it *itype) bool {
-	if t.cat == valueT {
+	if isBin(t) {
 		return t.TypeOf().Implements(it.TypeOf())
 	}
 	return t.methods().contains(it.methods())
@@ -1730,6 +1730,17 @@ func isInterface(t *itype) bool {
 	return isInterfaceSrc(t) || t.TypeOf() != nil && t.TypeOf().Kind() == reflect.Interface
 }
 
+func isBin(t *itype) bool {
+	switch t.cat {
+	case valueT:
+		return true
+	case aliasT, ptrT:
+		return isBin(t.val)
+	default:
+		return false
+	}
+}
+
 func isStruct(t *itype) bool {
 	// Test first for a struct category, because a recursive interpreter struct may be
 	// represented by an interface{} at reflect level.