Imports as completion candidates for hash-langs

General
27

Here's probably a better example to start from. This highlights/links to documentation for both sqr and pi, and shows arrows for math, but doesn't show arrows or offer to go to the definition of either sqr or pi. I think if that can be fixed then Rhombus can be adjusted pretty easily.

#lang racket

(define-syntax math (syntax-rules ()))

(require racket/math)

(define-for-syntax tbl (hash 'pi #'pi
			     'sqr #'sqr))

(define-syntax (scope stx)
  (syntax-case stx ()
    [(_ mth id)
     (free-identifier=? #'mth #'math)
     (syntax-property (hash-ref tbl (syntax-e #'id))
                      'disappeared-use
                      (cons
                       (datum->syntax #'here
                                      'math
                                      #'mth
                                      #'mth)
                       (datum->syntax #'here
                                      (syntax-e #'id)
                                      #'id
                                      #'id)))]))
(provide scope math)

#lang racket/base

(require "a.rkt")

(scope math sqr)

(scope math pi)