TypeScript import pruning does not respect shadowed usages

[alangpierce]

This code in the TypeScript transform should NOT import the ./a module since it's not used (meaning "it's only used as a type" is vacuously true).

import a from './a';

function foo() {
  let a;
  a();
}

Instead, Sucrase gives this output:

"use strict"; function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { default: obj }; }
var _a = require('./a'); var _a2 = _interopRequireDefault(_a);

function foo() {
  let a;
  a();
}

Playground link

Sucrase should notice that the a() usage refers to the shadowed a declaration and not to the import, and thus not count it as a runtime usage of a.