The problem results in broken import quick fix and import optimizer on
the IDE side [1].
`AssignResolutionAltererExtension` introduced a possibility to override
resolution of assignment statements. The inconsistency though is
that `KtSimpleNameReference.getResolvesByNames` doesn't return a name
for the overridden `=`. Kotlin as a language doesn't support this [2].
This commit eliminates the drawback above:
1. It fixes the name `assign` the `=` can be resolved to [3].
This eliminates the need to search for the name, bypassing the
plugins.
2. `KtSimpleNameReference.getResolvesByNames` returns `assign` among
other names in case it deals with binary `=` and assignment is
resolved.
3. `KtCompilerPluginsProvider` was extended to check plugins' presence.
K1 implementation added.
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[1]: https://youtrack.jetbrains.com/issue/KTIJ-24390
[2]: OperatorConventions.getNameForOperationSymbol
https://kotlinlang.org/docs/operator-overloading.html#augmented-assignments
[3]: OperatorConventions#ASSIGN_METHOD + AssignmentPluginNames
Andrei Klunnyi