Tree-shake pure call expressions with optional chaining

[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 #4006

Description

Not really a bug fix but rather an oversight: Since optional chaining call expressions are wrapped in a "ChainExpression" node, the existing logic for marking pure call expressions was skipping it. This is fixed now.

[rollup-bot]

Thank you for your contribution! ❤️

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

npm install rollup/rollup#gh-4006_treeshake_pure_optional_chaining_call

or load it into the REPL:
https://rollupjs.org/repl/?circleci=14651

[codecov]

Codecov Report

Merging #4007 (6155b4f) into master (b8db675) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #4007   +/-   ##
=======================================
  Coverage   97.24%   97.24%           
=======================================
  Files         192      192           
  Lines        6759     6760    +1     
  Branches     1973     1973           
=======================================
+ Hits         6573     6574    +1     
  Misses         99       99           
  Partials       87       87           

Impacted Files	Coverage Δ
src/utils/pureComments.ts	100.00% <100.00%> (ø)
src/ast/nodes/NodeType.ts	100.00% <0.00%> (ø)

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