Fix accessing nested properties of namespaces

[lukastaegert]

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:
Resolves #3642

Description

As part of a refactoring in #3637, accessing properties of namespace members was no longer working correctly, which is fixed here.

[rollup-bot]

Thank you for your contribution! ❤️

You can try out this pull request locally by installing Rollup via

npm install rollup/rollup#gh-3642-namespace-member-access

or load it into the REPL:
https://rollupjs.org/repl/?circleci=12026

[codecov]

Codecov Report

Merging #3643 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3643   +/-   ##
=======================================
  Coverage   96.54%   96.54%           
=======================================
  Files         183      183           
  Lines        6244     6245    +1     
  Branches     1832     1832           
=======================================
+ Hits         6028     6029    +1     
  Misses        107      107           
  Partials      109      109           

Impacted Files	Coverage Δ
src/ast/nodes/MemberExpression.ts	98.31% <100.00%> (+0.01%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 3fabc1b...2223a52. Read the comment docs.