Fix incomplete computed property deoptimization

[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 #3264

Description

I am aware that #3266 already provides a fix for #3264 and I hope there is no ill thought from the author (the other fix in the PR is still welcome), but this PR will actually fix the root cause of the issue, which is that when the key of a computed property is later deoptimized, and the involved member expression had a deoptimized path, then ALL paths of the member expression need to be deoptimized (I know this may sound VERY confusing. I really hope to find some time soon to improve the names of the concepts around this).

So the result is that

const obj1 = {};
let prop = 'x';

updateProp();

obj1[prop] = true;

assert.strictEqual(obj1.y ? 'WORKING' : 'BUG', 'WORKING');

function updateProp() {
	prop = 'y';
}

is completely retained, while

const obj1 = {};
let prop = 'x';

obj1[prop] = true;

assert.strictEqual(obj1.y ? 'BUG' : 'WORKING', 'WORKING');

is correctly optimized to

assert.strictEqual( 'WORKING', 'WORKING');

[codecov]

Codecov Report

Merging #3267 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3267      +/-   ##
==========================================
+ Coverage   92.83%   92.84%   +<.01%     
==========================================
  Files         170      170              
  Lines        5934     5941       +7     
  Branches     1793     1795       +2     
==========================================
+ Hits         5509     5516       +7     
  Misses        223      223              
  Partials      202      202

Impacted Files	Coverage Δ
src/ast/nodes/ObjectExpression.ts	90.41% <ø> (ø)	⬆️
src/ast/nodes/MemberExpression.ts	95.61% <100%> (+0.28%)	⬆️

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