### Describe the problem
The features that rely on the language server (autoc…omplete, editor hover, "Go To Definition", "Go To Symbol", "Peek Definition") don't work when a board from the Arduino "megaAVR" architecture (megaAVR 0-series, ~~tinyAVR 0-series and 1-series~~) (e.g., Nano Every, Uno WiFi Rev2) is selected.
### To reproduce
1. Use the Arduino IDE "**Boards Manager**" to install the "**Arduino megaAVR Boards**" platform, if not already installed.
1. Select **File > New** from the Arduino IDE menus.
1. Select **Tools > Board > Arduino megaAVR Boards > Nano Every** from the Arduino IDE menus.
1. Hover the mouse pointer over `setup` in the sketch code code
🐛 No "hover" popup appears.
1. Right click on `setup()`
1. Select "**Go To Definition**" from the context menu.
🐛 A "**No definition found for 'setup'**" tooltip appears.
1. Right click on `setup()`
1. Select "**Go To Symbol**" from the context menu.
🐛 The command palette shows "**No editor symbols**"
1. Right click on `setup()`
1. Select "**Peek > Peek Definition**" from the context menu.
🐛 A "**No definition found for 'setup'**" tooltip appears.
1. Type the following code inside the `setup` function:
```cpp
pinMo
```
1. Press <kbd>**Ctrl**</kbd>+<kbd>**Space**</kbd>
🐛 The "suggest" interface shows "**No suggestions.**"
### Expected behavior
Language server features to work on megaAVR boards just like on boards of other architectures.
### Arduino IDE version
#### Original report
2.0.0-beta.2-snapshot.f9730ab
#### Last verified with
2.0.0-rc9.3
### Operating system
Windows, Linux
### Operating system version
Windows 10, Ubuntu 20.04
### Additional context
From `inols-clangd-err.log`:
```
V[12:54:19.163] Ignored diagnostic. unknown target CPU 'atmega4809'
V[12:54:19.163] Ignored diagnostic. valid target CPU values are: avr1, avr2, avr25, avr3, avr31, avr35, avr4, avr5, avr51, avr6, avrxmega1, avrxmega2, avrxmega3, avrxmega4, avrxmega5, avrxmega6, avrxmega7, avrtiny, at90s1200, attiny11, attiny12, attiny15, attiny28, at90s2313, at90s2323, at90s2333, at90s2343, attiny22, attiny26, at86rf401, at90s4414, at90s4433, at90s4434, at90s8515, at90c8534, at90s8535, ata5272, attiny13, attiny13a, attiny2313, attiny2313a, attiny24, attiny24a, attiny4313, attiny44, attiny44a, attiny84, attiny84a, attiny25, attiny45, attiny85, attiny261, attiny261a, attiny441, attiny461, attiny461a, attiny841, attiny861, attiny861a, attiny87, attiny43u, attiny48, attiny88, attiny828, at43usb355, at76c711, atmega103, at43usb320, attiny167, at90usb82, at90usb162, ata5505, atmega8u2, atmega16u2, atmega32u2, attiny1634, atmega8, ata6289, atmega8a, ata6285, ata6286, atmega48, atmega48a, atmega48pa, atmega48pb, atmega48p, atmega88, atmega88a, atmega88p, atmega88pa, atmega88pb, atmega8515, atmega8535, atmega8hva, at90pwm1, at90pwm2, at90pwm2b, at90pwm3, at90pwm3b, at90pwm81, ata5790, ata5795, atmega16, atmega16a, atmega161, atmega162, atmega163, atmega164a, atmega164p, atmega164pa, atmega165, atmega165a, atmega165p, atmega165pa, atmega168, atmega168a, atmega168p, atmega168pa, atmega168pb, atmega169, atmega169a, atmega169p, atmega169pa, atmega32, atmega32a, atmega323, atmega324a, atmega324p, atmega324pa, atmega324pb, atmega325, atmega325a, atmega325p, atmega325pa, atmega3250, atmega3250a, atmega3250p, atmega3250pa, atmega328, atmega328p, atmega328pb, atmega329, atmega329a, atmega329p, atmega329pa, atmega3290, atmega3290a, atmega3290p, atmega3290pa, atmega406, atmega64, atmega64a, atmega640, atmega644, atmega644a, atmega644p, atmega644pa, atmega645, atmega645a, atmega645p, atmega649, atmega649a, atmega649p, atmega6450, atmega6450a, atmega6450p, atmega6490, atmega6490a, atmega6490p, atmega64rfr2, atmega644rfr2, atmega16hva, atmega16hva2, atmega16hvb, atmega16hvbrevb, atmega32hvb, atmega32hvbrevb, atmega64hve, at90can32, at90can64, at90pwm161, at90pwm216, at90pwm316, atmega32c1, atmega64c1, atmega16m1, atmega32m1, atmega64m1, atmega16u4, atmega32u4, atmega32u6, at90usb646, at90usb647, at90scr100, at94k, m3000, atmega128, atmega128a, atmega1280, atmega1281, atmega1284, atmega1284p, atmega128rfa1, atmega128rfr2, atmega1284rfr2, at90can128, at90usb1286, at90usb1287, atmega2560, atmega2561, atmega256rfr2, atmega2564rfr2, atxmega16a4, atxmega16a4u, atxmega16c4, atxmega16d4, atxmega32a4, atxmega32a4u, atxmega32c4, atxmega32d4, atxmega32e5, atxmega16e5, atxmega8e5, atxmega32x1, atxmega64a3, atxmega64a3u, atxmega64a4u, atxmega64b1, atxmega64b3, atxmega64c3, atxmega64d3, atxmega64d4, atxmega64a1, atxmega64a1u, atxmega128a3, atxmega128a3u, atxmega128b1, atxmega128b3, atxmega128c3, atxmega128d3, atxmega128d4, atxmega192a3, atxmega192a3u, atxmega192c3, atxmega192d3, atxmega256a3, atxmega256a3u, atxmega256a3b, atxmega256a3bu, atxmega256c3, atxmega256d3, atxmega384c3, atxmega384d3, atxmega128a1, atxmega128a1u, atxmega128a4u, attiny4, attiny5, attiny9, attiny10, attiny20, attiny40, attiny102, attiny104
E[12:54:19.163] Indexing C:\Users\per\AppData\Local\Arduino15\packages\arduino\hardware\megaavr\1.8.7\cores\arduino\WInterrupts.cpp failed: Couldn't build compiler instance
```
---
The equivalent error occurs when using boards with other microcontrollers in this architecture family.
---
This is actually a deficiency in lower level tools ([clangd](https://clangd.llvm.org/) via [Arduino Language Server](https://github.com/arduino/arduino-language-server)), and not actually anything to do with the Arduino IDE 2.x code base. So in fact the issue is off topic for this repository, but it was decided that an issue should be created here for the sake of documenting it in a place that would be easily found by Arduino IDE 2.x users.
The deficiency is also tracked in the Arduino Language Server repository at https://github.com/arduino/arduino-language-server/issues/112
#### Updates
- tinyAVR 0-series and 1-series was added by https://github.com/llvm/llvm-project/commit/b0d4d969e22efd282047e51b7927c1ab53eccf32
- Arduino IDE was updated to use the **clangd** version with support via https://github.com/arduino/arduino-ide/commit/a59e0da2afe766568ecff4f1335e45a6d7022d3a
- megaAVR 0-series support appears to have been added to clangd, released in LLVM 15.0.0: https://github.com/llvm/llvm-project/commit/b62ea9b38b627ce2a96f66242c15250d59a9b134
- Arduino IDE has not yet been updated to use the **clangd** version with support.
#### Additional reports
- https://forum.arduino.cc/t/ide-2-0-3-editor-discover-like-feature-name-and-usage-questions/1072796
- https://forum.arduino.cc/t/windows-10-suggestions-dont-work/1071229
- https://forum.arduino.cc/t/go-to-definition-not-working/1020673
- https://forum.arduino.cc/t/known-bug-arduino-ide-2-0-different-rcs-autocomplete-not-working-for-specific-targets/1007394
- https://forum.arduino.cc/t/where-to-locate-h-files-in-ide-2/1138746/9
- https://forum.arduino.cc/t/intellisense-autocomplete-problems-and-other-things-i-miss/698272
- https://forum.arduino.cc/t/intellisense-in-ide-20-beta-solved/847876/3
