Crash when compiling invalid generic instantiation

[nocturn9x]

Nim Version

Nim Compiler Version 2.2.4 [Linux: amd64]
Compiled at 2025-04-22
Copyright (c) 2006-2025 by Andreas Rumpf

git hash: f7145dd
active boot switches: -d:release

Description

The compiler crashes when compiling code such as SomeType[] instead of reporting an error.

Example:

type Test[T: auto] = object

discard Test[]

Current Output

Error: internal error: expr(nkBracketExpr, tyGenericBody)
No stack traceback available
To create a stacktrace, rerun compilation with './koch temp compile <file>', see https://nim-lang.github.io/Nim/intern.html#debugging-the-compiler for details

Expected Output

A compilation error

Known Workarounds

No response

Additional Information

No response

[litlighilit]

IMO it shall be pointed out that
discard Test[] is an invalid stmt even if generic param was filled (e.g. discard Test[int]), which results in Error: statement returns no value that can be discarded

And, as I tested, other kinds of Test[] correctly toggle compilation error, e.g. discard Test[]() and var x: Test[]

In short, this bug is subtle.

Edit: sizeof(Test[]) does cause internal Error: getTypeDescAux(tyFromExpr)

[nocturn9x]

I am well aware that it's an invalid statement, I stumbled onto this error by accident (I was doing sizeof(Atomic[T]) + sizeof(Atomic[]), forgot the type in the second one), but the point is the compiler shouldn't crash on a syntax (semantic?) error. It's lucky that the code I was working with was small, so I could trial-and-error my way to finding what the issue was, but had this happened in the larger project I was building this small piece of software for, I would've had a much harder time figuring it out. Crashing is not an acceptable behavior because it is super opaque (it would at least be helpful if the compiler reported the line and column number of what caused the crash, but I understand that if it's a panic and stack tracing is disabled that's not really possible)