Fix regressions when handling assignments and expression statements with side effects #1591
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declaration handling * Resolves rollup#1589
* Except for certain white-listed nodes, assume that a side-effect is expected when an expression is called as a statement
lukastaegert
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This will resolve #1589 and #1592.
For #1589: In Identifier.js, I assumed that all declarations have assignedExpressions, which is certainly not true for SyntheticNamespaceDeclarations. To be cautious, for now we assume that those always have effects when mutated.
For #1592: It seems that people are calling getters for side-effects and this is something that rollup is not (and was never) prepared for yet. The better solution, as suggested by @kzc , is probably to start adding flags for certain more aggressive aspects of tree-shaking such as assuming that all getters are pure. Until then with this PR, rollup will keep all expression statements that are not usually called as statements because we assume that they are called for side-effects. That seems to cover the cases listed in #1592 and also keep things like 'use strict'.