syn 3.0.3: syn::Item

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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::Item 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::Item

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:c872bfef429ee069748c13ba330db2fc535c228e8b8ff809848abf65c0844842","contract":["syn::parse_str parses a function declaration into Item::Fn","syn::parse_str parses a struct definition into Item::Struct","syn::parse_str parses an enum definition into Item::Enum","syn::parse_str parses a const declaration into Item::Const","syn::parse_str parses a trait definition into Item::Trait","syn::parse_str rejects invalid item syntax with a parse error"],"goal":"verify syn::Item in pkg:cargo/syn@3.0.3","kind":"HOW","packages":["pkg:cargo/syn@3.0.3"],"schemaVersion":1,"symbols":["syn::Item"]},"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::Item"],"verifierAdapter":"cargo@1"}

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  "kind": "HOW",
  "packages": [
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  ],
  "symbols": [
    "syn::Item"
  ]
}

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

pub use syn::*;

use syn::{parse_str, Item, ItemConst, ItemEnum, ItemFn, ItemStruct, ItemTrait};

fn main() {
    // 1. syn::parse_str parses a function declaration into Item::Fn
    let item_fn: Item = parse_str("fn compute(x: i32) -> i32 { x + 1 }").expect("valid fn item");
    match item_fn {
        Item::Fn(ItemFn { sig, .. }) => {
            assert_eq!(sig.ident.to_string(), "compute");
            assert_eq!(sig.inputs.len(), 1);
        }
        _ => panic!("expected Item::Fn"),
    }

    // 2. syn::parse_str parses a struct definition into Item::Struct
    let item_struct: Item = parse_str("pub struct Config { pub timeout: u64 }").expect("valid struct item");
    match item_struct {
        Item::Struct(ItemStruct { ident, .. }) => {
            assert_eq!(ident.to_string(), "Config");
        }
        _ => panic!("expected Item::Struct"),
    }

    // 3. syn::parse_str parses an enum definition into Item::Enum
    let item_enum: Item = parse_str("enum Status { Active, Inactive }").expect("valid enum item");
    match item_enum {
        Item::Enum(ItemEnum { ident, variants, .. }) => {
            assert_eq!(ident.to_string(), "Status");
            assert_eq!(variants.len(), 2);
        }
        _ => panic!("expected Item::Enum"),
    }

    // 4. syn::parse_str parses a const declaration into Item::Const
    let item_const: Item = parse_str("const MAX_RETRIES: usize = 5;").expect("valid const item");
    match item_const {
        Item::Const(ItemConst { ident, .. }) => {
            assert_eq!(ident.to_string(), "MAX_RETRIES");
        }
        _ => panic!("expected Item::Const"),
    }

    // 5. syn::parse_str parses a trait definition into Item::Trait
    let item_trait: Item = parse_str("pub trait Handler { fn handle(&self); }").expect("valid trait item");
    match item_trait {
        Item::Trait(ItemTrait { ident, .. }) => {
            assert_eq!(ident.to_string(), "Handler");
        }
        _ => panic!("expected Item::Trait"),
    }

    // 6. syn::parse_str rejects invalid item syntax with a parse error
    let invalid = parse_str::<Item>("let x = 10;");
    assert!(invalid.is_err());

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