fix: composite map assign (#683)

* fix: composite map assign

* reword comment

Co-authored-by: Marc Vertes <mvertes@free.fr>

_test/map29.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"fmt"
+	"time"
+)
+
+type Item struct {
+	Object interface{}
+	Expiry time.Duration
+}
+
+func main() {
+	items := map[string]Item{}
+
+	items["test"] = Item{
+		Object: "test",
+		Expiry: time.Second,
+	}
+
+	item := items["test"]
+	fmt.Println(item)
+}
+
+// Output:
+// {test 1s}

interp/cfg.go

@@ -523,9 +523,10 @@ func (interp *Interpreter) cfg(root *node, pkgID string) ([]*node, error) {
 					n.gen = nop
 					src.findex = dest.findex // Set recv address to LHS
 					dest.typ = src.typ
-				case n.action == aAssign && src.action == aCompositeLit:
+				case n.action == aAssign && src.action == aCompositeLit && !isMapEntry(dest):
 					if dest.typ.cat == valueT && dest.typ.rtype.Kind() == reflect.Interface {
-						// No optimisation attempt for assigned binary interface
+						// Skip optimisation for assigned binary interface or map entry
+						// which require and additional operation to set the value
 						break
 					}
 					// Skip the assign operation entirely, the source frame index is set