Patch! :D

gistfile1.txt

diff --git a/src/cmd/compile/internal/gc/subr.go b/src/cmd/compile/internal/gc/subr.go
index 629186829a..fabae194be 100644
--- a/src/cmd/compile/internal/gc/subr.go
+++ b/src/cmd/compile/internal/gc/subr.go
@@ -1710,6 +1710,23 @@ func implements(t, iface *types.Type, m, samename **types.Field, ptr *int) bool
                        return false
                }
                tm := tms[i]
+
+               for _, f := range types.ParamsResults {
+                       // Loop over fields in structs, ignoring argument names.
+                       fs1, fs2 := f(tm.Type).FieldSlice(), f(im.Type).FieldSlice()
+                       if len(fs1) != len(fs2) {
+                               return false
+                       }
+                       for i, f1 := range fs1 {
+                               f2 := fs2[i]
+                               if f2.Type.IsInterface() {
+                                       return implements(f1.Type, f2.Type, m, samename, ptr)
+                               }
+                               if f1.IsDDD() != f2.IsDDD() || !types.Identical(f1.Type, f2.Type) {
+                                       return false
+                               }
+                       }
+               }
                if tm.Nointerface() || !types.Identical(tm.Type, im.Type) {
                        *m = im
                        *samename = tm