Fix mismatch_assignment error reported for generic arguments using items imported at an enclosing scope

[taichi-ishitani]

fix #3120

Cause

scope::is_imported only inspected the import / wildcard bindings declared directly in the given scope, without walking toward the enclosing scopes. Its two helpers are documented as such:

• imports_get: "Returns the explicit import bindings of name directly in scope."
• wildcards_get: "Returns the wildcard imports declared directly in scope."

So a reference made from inside a generate block asked the wrong scope:

module Module25H {
    import Pacakge25G::baz_1_2;                                        // bound in `Module25H`

    alias package baz_1_3 = veryl_sample4::baz_pkg::<baz_1_2::BAZ_0, 3>;

    inst baz: veryl_sample4::baz_if::<baz_1_3>;                        // scope: Module25H     -> OK
    :g {
        inst u: veryl_sample4::baz_module::<baz_1_3> (                 // scope: Module25H::g  -> NG
            baz: baz,
        );
    }
}

reference site	scope asked	is_imported	head_already_qualified	qualification
inst baz	Module25H	true	false	runs
inst u	Module25H::g	false	true	skipped

Once the qualification is skipped, baz_1_2 stays unqualified. In unalias_inner the loop then starts at the alias itself instead of its containing package, so Pacakge25G is never visited and its gen-const map {BAZ_0_VALUE: 1, BAZ_1_VALUE: 2} is never pushed onto generic_maps. apply_map runs with an empty map, BAZ_0_VALUE is left unsubstituted, and GenericSymbol::mangled() drops the arguments altogether because one of them still refers to a GenericConst:

inst baz : baz_pkg::<baz_pkg::<1,2>::BAZ_0, 3>
inst u   : baz_pkg::<baz_pkg::BAZ_0, 3>          // arguments lost

The two baz_if signatures then disagree, Signature::is_compatible fails on generic_parameters, and mismatch_assignment is reported for the port connection:

dst: sym=.. full_path=["veryl_sample4", "baz_if"] gparams=[]
src: sym=.. full_path=["veryl_sample4", "__baz_if__veryl_sample4___baz_pkg__veryl_sample4___baz_pkg__1__2_BAZ_0__3"]
     gparams=["PKG=veryl_sample4 __baz_pkg__veryl_sample4___baz_pkg__1__2_BAZ_0__3"]

Fix

scope::is_imported now walks from the query scope toward the enclosing scopes, stopping at the module / interface / package containing it, since import is not visible across a container boundary.

let mut current = Some(intern_namespace(namespace));
while let Some(scope) = current {
    let imported = /* existing imports_get / wildcards_get checks, unchanged */;
    if imported {
        return true;
    }
    if is_import_container(scope) {
        break;
    }
    current = parent(scope);
}
false

The two ifdef-related checks are carried over verbatim. In particular b.define_context == dctx stays an equality, so a reference inside an #[ifdef]-guarded generate block still does not see an unguarded import of its container. That is unchanged from the current behaviour (the nested scope holds no bindings today either), and relaxing it would alter ifdef visibility semantics on its own, so it is left out of this fix.

[codspeed-hq]

Merging this PR will not alter performance

✅ 8 untouched benchmarks

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_{Comparing taichi-ishitani:fix_import_visibility_in_nested_scope (b6ac5ae) with master (283e237)}