Problem in converting ast.Node to cue.Value using BuildExpr

[dcb1001]

Hey,
I was trying to convert ast.Comprehension.Value (of type ast.Expr) into cue.Value. I tried the method (*Context) BuildExpr. Now, this works fine for case

body:{
	a?: int
	b?: int

	if b != null {
		a !: int
	}
}

However, for nested if-else such as

body:{
	a?: int
	b?: int

	if b != null {
		if b < 10 { 
			a !: int
		}
	}
}

it gives error: -

6:4
reference "b" set to unknown node in AST; this can result from incorrect API usage or a compiler bug
7:5
{
        a!: int
}

Now, my speculation is when I try to convert the outer if's ast.Node to cue.Value the BuildExpr tries to find the reference of b used in inner if condition which is not present in the scope of outer if.
I tried the Scope buildOption, but couldn't resolve the reference (maybe I am not using it correctly). I tried making a small change to inner if but nothing changed. It now gives error reference for 'body' not found.

body:{
	a?: int
	b?: int

	if b != null {
		if body.b < 10 { 
			a !: int
		}
	}
}

Go Code : -

var arr []ast.Comprehension
for _, ele := range arr {
  fmt.Println(ele.Clauses[0].Pos())
  cueVal := ctx.BuildExpr(ele.Value, []cue.BuildOption{
	  cue.Scope(insts),
  }...)
  if (cueVal.Err() != nil){
	  fmt.Println(cueVal.Err())
	  continue
  }
  fmt.Println(cueVal)
}