Correctly handle catch declarations

[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 #4096
Resolves #4106

Description

There was a scoping issue in catch scopes that could lead to incorrect variable associations, see the linked issues. The implemented logic now works like this:

• The body of a catch clause now receives a block scope so that block scoped declarations do not seep into surrounding scopes, including the parameter scope
• Hoisted declarations inside the catch clause that do not match a parameter name will be hoisted to the surrounding scope (as before)
• Hoisted declarations that DO match a parameter will instead be associated with the parameter and are not hoisted to the outside (this is new and indeed correct)

[github-actions]

Thank you for your contribution! ❤️

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

npm install rollup/rollup#gh-4096-catch-block-scoping

or load it into the REPL:
https://rollupjs.org/repl/?pr=4108

[codecov]

Codecov Report

Merging #4108 (c5bae30) into master (8308279) will decrease coverage by 0.01%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##           master    #4108      +/-   ##
==========================================
- Coverage   98.02%   98.01%   -0.02%     
==========================================
  Files         201      201              
  Lines        7038     7040       +2     
  Branches     2064     2065       +1     
==========================================
+ Hits         6899     6900       +1     
  Misses         66       66              
- Partials       73       74       +1     

Impacted Files	Coverage Δ
src/ast/nodes/CatchClause.ts	83.33% <75.00%> (-16.67%)	⬇️
src/ast/scopes/CatchScope.ts	100.00% <100.00%> (ø)

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