Slow auto completion for Grails app

#### What steps will reproduce the issue?

See the attached project and CPU profile

1. Open VenueController
2. Edit the index() action
3. Type `[venues: v]`
4. Wait for autocompletion to fill in `[venues: venues]`

#### What is the expected result?

The auto completion should happen quite quickly as I'm referencing a local variable

#### What happens instead?

It takes around a second for the completion to kick in

#### Notes

1. This ticket was created after a comment from @ on a [related ticket][1]
2. I also switched the runtime based on [this ticket][2]

#### Environment

* IntelliJ IDEA 2020.1.2 (Ultimate Edition)
* Build #IU-201.7846.76, built on June 1, 2020
* Runtime version: 11.0.6+8-b765.40 x86_64
* VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
* macOS 10.15.5
* GC: ParNew, ConcurrentMarkSweep
* Memory: 1979M
* Cores: 16 (actually 8)
* Non-Bundled Plugins: com.daynight.plugin, org.jetbrains.plugins.hocon, com.jetbrains.ChooseRuntime, io.protostuff.protostuff-jetbrains-plugin, org.intellij.scala, com.github.tomasmilata.intelliroutes, com.triplequote.hydra, zio.intellij.zio-intellij, org.toml.lang

[1]: https://youtrack.jetbrains.com/issue/IDEA-244102#focus=streamItem-27-4227680.0-0
[2]: https://youtrack.jetbrains.com/issue/JBR-2475#focus=streamItem-27-4181537.0-0

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*Imported from [IDEA-244941](https://youtrack.jetbrains.com/issue/IDEA-244941) · Type: Bug · Votes: 0*
*Comments, attachments, dates and reporter are not part of the export — follow the link above for the full history.*

Reproduce the slowdown in the attached project by opening VenueController, editing the index() action, and typing `[venues: v]`; start by reviewing the attached CPU profile. Investigate the completion path for this local-variable case and verify that `[venues: venues]` appears significantly faster.

Written by the indexing model from the issue text.