fix: correct handling of methods on binary interface types (#218)

_test/bin1.go

@@ -0,0 +1,16 @@
+package main
+
+import (
+	"crypto/sha1"
+	"fmt"
+)
+
+func main() {
+	d := sha1.New()
+	d.Write([]byte("password"))
+	a := d.Sum(nil)
+	fmt.Println(a)
+}
+
+// Output:
+// [91 170 97 228 201 185 63 63 6 130 37 11 108 248 51 27 126 230 143 216]

interp/cfg.go

@@ -1042,8 +1042,8 @@ func (interp *Interpreter) Cfg(root *Node) ([]*Node, error) {
 				case ok:
 					n.val = method.Index
 					n.gen = getIndexBinMethod
-					n.typ = &Type{cat: ValueT, rtype: method.Type}
 					n.recv = &Receiver{node: n.child[0]}
+					n.typ = &Type{cat: ValueT, rtype: method.Type}
 				case n.typ.rtype.Kind() == reflect.Ptr:
 					if field, ok := n.typ.rtype.Elem().FieldByName(n.child[1].ident); ok {
 						n.typ = &Type{cat: ValueT, rtype: field.Type}

interp/run.go

@@ -727,8 +727,9 @@ func callBin(n *Node) {
 	if funcType.IsVariadic() {
 		variadic = funcType.NumIn() - 1
 	}
+	// method signature obtained from reflect.Type include receiver as 1st arg, except for interface types
 	receiverOffset := 0
-	if n.child[0].recv != nil {
+	if recv := n.child[0].recv; recv != nil && recv.node.typ.TypeOf().Kind() != reflect.Interface {
 		receiverOffset = 1
 	}