fix: replace comparison

[dnalborczyk]

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:

Description

@lukastaegert jus a follow-up from: #4302 (comment).

let me know if you have any questions. I can explain it a bit more (it's a bit late right now 😄 ) I'm trying to achieve that the types can eventually be trusted. 😉 although, someone might have to start likely with acorn to achieve that: acornjs/acorn#946

[codecov]

Codecov Report

Merging #4321 (665a837) into master (2a899d5) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #4321   +/-   ##
=======================================
  Coverage   98.44%   98.44%           
=======================================
  Files         205      205           
  Lines        7314     7314           
  Branches     2084     2084           
=======================================
  Hits         7200     7200           
  Misses         55       55           
  Partials       59       59           

Impacted Files	Coverage Δ
src/utils/getOriginalLocation.ts	82.35% <100.00%> (ø)

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[lukastaegert]

I am sorry but I do not see how this improves anything. The types have been working before, the previous check for truthiness was correct as in all cases where .mappings was falsy, it was definitely not a valid SourceMap. So why are you so determine to add this? Sure, the TypeScript types say it should be enough to compare against undefined, but in the end, source maps are generated by plugins and may have been generated completely without any types. TypeScript cannot give any guarantees here. And at this point, maybe some build setup was relying on this, who knows. The more general check we had was basically for free, so I would prefer to keep it.