syn 3.0.3: syn::DeriveInput

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[dependencies]
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Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify syn::DeriveInput in pkg:cargo/syn@3.0.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:cargo/syn@3.0.3
Demonstrate these symbols/APIs:
  - syn::DeriveInput

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:beff69e7a9b23e6e8858991638c8e3522d868178f3a65aa17aab29fb9e08b616","contract":["parse_str parses a struct definition into DeriveInput","DeriveInput identifies struct fields and field types","parse_str parses an enum definition into DeriveInput with variants","DeriveInput retains generic type parameters and where clauses","DeriveInput exposes outer doc and derive attributes"],"goal":"verify syn::DeriveInput in pkg:cargo/syn@3.0.3","kind":"HOW","packages":["pkg:cargo/syn@3.0.3"],"schemaVersion":1,"symbols":["syn::DeriveInput"]},"contractCommand":["cargo","run","--offline"],"environment":{"arch":"x64","distro":"alpine","ecosystem":"cargo","libc":"musl","os":"linux","packageManager":"cargo","schemaVersion":1},"license":"MIT-0","packages":["pkg:cargo/syn@3.0.3"],"schemaVersion":1,"subject":"pkg:cargo/syn@3.0.3","symbols":["syn::DeriveInput"],"verifierAdapter":"cargo@1"}

{
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  "goal": "verify syn::DeriveInput in pkg:cargo/syn@3.0.3",
  "kind": "HOW",
  "packages": [
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  ],
  "symbols": [
    "syn::DeriveInput"
  ]
}

//! Clean-room verification sample for syn::DeriveInput.

pub use syn::DeriveInput;

use syn::{parse_str, Data, DeriveInput, Fields};

fn main() {
    // 1. parse_str parses a struct definition into DeriveInput
    let struct_src = "pub struct Point { pub x: f64, pub y: f64 }";
    let input: DeriveInput = parse_str(struct_src).expect("parse struct DeriveInput");
    assert_eq!(input.ident.to_string(), "Point");

    // 2. DeriveInput identifies struct fields and field types
    if let Data::Struct(data_struct) = &input.data {
        if let Fields::Named(fields_named) = &data_struct.fields {
            let field_names: Vec<String> = fields_named
                .named
                .iter()
                .filter_map(|f| f.ident.as_ref().map(|i| i.to_string()))
                .collect();
            assert_eq!(field_names, vec!["x", "y"]);
        } else {
            panic!("expected named fields");
        }
    } else {
        panic!("expected Data::Struct");
    }

    // 3. parse_str parses an enum definition into DeriveInput with variants
    let enum_src = "enum Status { Active, Inactive(u32), Suspended { reason: String } }";
    let enum_input: DeriveInput = parse_str(enum_src).expect("parse enum DeriveInput");
    assert_eq!(enum_input.ident.to_string(), "Status");
    if let Data::Enum(data_enum) = &enum_input.data {
        let variant_names: Vec<String> = data_enum
            .variants
            .iter()
            .map(|v| v.ident.to_string())
            .collect();
        assert_eq!(variant_names, vec!["Active", "Inactive", "Suspended"]);
    } else {
        panic!("expected Data::Enum");
    }

    // 4. DeriveInput retains generic type parameters and where clauses
    let generic_src = "struct Container<T: Clone> where T: Send { item: T }";
    let generic_input: DeriveInput = parse_str(generic_src).expect("parse generic DeriveInput");
    assert_eq!(generic_input.ident.to_string(), "Container");
    assert_eq!(generic_input.generics.params.len(), 1);
    assert!(generic_input.generics.where_clause.is_some());

    // 5. DeriveInput exposes outer doc and derive attributes
    let attr_src = "#[derive(Debug, Clone)] #[repr(C)] struct Flagged;";
    let attr_input: DeriveInput = parse_str(attr_src).expect("parse attr DeriveInput");
    assert_eq!(attr_input.ident.to_string(), "Flagged");
    assert_eq!(attr_input.attrs.len(), 2);

    println!("All syn::DeriveInput contract assertions passed successfully.");
}