Itroduce gen declaration

[taichi-ishitani]

close #2349

gen declaration is a new declaration like const declaration for generics feature. This is used to define genreic const which can be given as generic asg.

By using gen declaration, you can provide result of expression and variable type declaratoin to generic arg like below.

module ModuleA::<W: u32, T: type) (
    a: output logic<W>,
    b: output T       ,
) {}
module ModuleB::<A: u32, B: u32, C: u32, D: u32> {
    gen W: u32  = A + B;
    gen T: type = logic<C, D>;
    inst u: ModuleA::<W, T> (a: _, b: _);
}

Expression in gen declaration has the same limitation with generic arg becuase generic consts are used as gneric arg. Therefore, the given expression can include following factors:

• Literal
• Symbol defined in package
• Genreic parameter
• Generic const

[codspeed-hq]

Merging this PR will not alter performance

✅ 6 untouched benchmarks

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_{Comparing taichi-ishitani:gen_declaration (8613234) with master (8fa3ede)}

[taichi-ishitani]

Checker for generic reference (check_generic_reference) is rewritten based on IR evaluation.
This is to share the checker routines with generic expression checker.

To implement this, IR evaluation needs to handle component reference and component instnace because they are given as generic args.
Module, Package and Instance are added as new enum variants of ir::TypeKind for this purpose.
https://github.com/taichi-ishitani/veryl/blob/75a985f958a8b18094cc291703a3f768cd49d88a/crates/analyzer/src/ir/comptime.rs#L757-L761
Component referecne and instance are converted into ir::Factor::Value if the expression is in gen declaration.

[taichi-ishitani]

Generic consts are evaluated when resolving generic params of the generic component.
The evaluated result is converted to GenericSymbolPath and added to the resolved generic map.
Resolved generic consts acts like generic args.

[taichi-ishitani]

VariableType handles variable type declaration (e.g. logic<8>).

[taichi-ishitani]

Type kind of enum member should be its parent enum. The replacement below is for this.

[taichi-ishitani]

struct member is typed so type of evaluation result should be restored with the struct member type.

[taichi-ishitani]

Identifiers in the given expression are collected by iterating factors in the expression.
They are converted into generic symbol pashs and used to check if the expression is referable from the generic context.
At first, I implmented this check by adding a flag showing a factor can be used as generic arg to Comptime and propagting the flag during IR evaluation.
However, value of the flag is incorrect when processing the check because namespace used for the check is not provided when creating IR.
Therefore, I implemented the check based on iterating identifiers.