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emitter(v1-seed): derive Debug/PartialEq/serde on phantom type-tag markers #5400

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emitter(v1-seed): derive Debug/PartialEq/serde on phantom type-tag markers #5400

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16 changes: 14 additions & 2 deletions src/v1/05_emit_rust.dag
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Original file line number Diff line number Diff line change
Expand Up @@ -1224,13 +1224,25 @@ fn rust_render_type_leaf_name(name: String, variant_to_enum: Map<String, String>
}
}

// Phantom ZST type-tag markers (enum variants used as type-level kinds, e.g. the
// Quantity/Scale tags Memory/One/Power in Measure<Memory, One, Nat>) must derive the
// same trait set as the carriers that mention them (Measure derives Debug/Clone/
// PartialEq + serde), or those derives fail closed (E0277 Memory: !Debug, E0369 == on
// Measure, E0392 unused param). Single authority for the marker definition.
fn rust_phantom_zst_marker_def(vname: String) -> String {
concat(
"#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]\n",
rust_visibility_prefix(), rust_items().struct_keyword, " ", vname, ";"
)
}

fn emit_phantom_zst_markers_for_enum(children: List<Node>, env: TypeEnv) -> String {
let markers = children
|> filter(child => child.children |> count == 0)
|> filter(child => is_phantom_unit_variant_type_arg(env: env, variant_name: authored_name(env: env, node: child)))
|> map(child =>
let vname = authored_name(env: env, node: child)
concat(rust_visibility_prefix(), rust_items().struct_keyword, " ", vname, ";")
rust_phantom_zst_marker_def(vname: vname)
)
|> join(separator: "\n")
markers
Expand All @@ -1253,7 +1265,7 @@ fn collect_phantom_zst_marker_names(items: List<Node>, env: TypeEnv) -> List<Str

fn emit_module_phantom_zst_markers(items: List<Node>, env: TypeEnv) -> String {
collect_phantom_zst_marker_names(items: items, env: env)
|> map(vname => concat(rust_visibility_prefix(), rust_items().struct_keyword, " ", vname, ";"))
|> map(vname => rust_phantom_zst_marker_def(vname: vname))
|> join(separator: "\n")
}

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