Avoid multi edges for gvars

lib/typeprof/core/ast/variable.rb

@@ -192,6 +192,7 @@ def undefine0(genv)
 
       def install0(genv)
         val = @rhs.install(genv)
+        val = val.new_vertex(genv, self) # avoid multi-edge from val to static_ret.vtx
         @changes.add_edge(genv, val, @static_ret.vtx)
         val
       end

scenario/regressions/multi_edge_to_gvar.rb

@@ -0,0 +1,16 @@
+## update
+def check
+  while true
+    opt = 1
+    if cond
+      $foo = opt
+    else
+      $foo = opt
+    end
+  end
+end
+
+## assert
+class Object
+  def check: -> nil
+end