Fix reassignment tracking

[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 #4468

Description

This one seemed quite the mystery bug. It seemed code was removed when you arranged things "just the right way". Turns out, the logic to prevent infinite recursions for assignment tracking was accidentally sharing an object with the same logic for property accesses, with the effect that an earlier property access could tell the system that an assignment had no effect even though it had.

[github-actions]

Thank you for your contribution! ❤️

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

npm install rollup/rollup#gh-4468-unexpected-dce

or load it into the REPL:
https://rollupjs.org/repl/?pr=4486

[codecov]

Codecov Report

Merging #4486 (e19adf3) into master (f44a3a3) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4486   +/-   ##
=======================================
  Coverage   98.75%   98.75%           
=======================================
  Files         205      205           
  Lines        7331     7331           
  Branches     2082     2082           
=======================================
  Hits         7240     7240           
  Misses         33       33           
  Partials       58       58           

Impacted Files	Coverage Δ
src/ast/variables/LocalVariable.ts	93.15% <ø> (ø)

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