syn 3.0.3: syn::ExprClosure

# This file is automatically @generated by Cargo.
# It is not intended for manual editing.
version = 4

[[package]]
name = "proc-macro2"
version = "1.0.107"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "985e7ec9bb745e6ce6535b544d84d6cd6f7ad8bd711c398938ae983b91a766d9"
dependencies = [
 "unicode-ident",
]

[[package]]
name = "quote"
version = "1.0.47"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "1fbf4db142a473a8d80c26bbf18454ed458bf8d26c8219c331daecfdbd079001"
dependencies = [
 "proc-macro2",
]

[[package]]
name = "sample-syn-expr-closure"
version = "1.0.0"
dependencies = [
 "syn",
]

[[package]]
name = "syn"
version = "3.0.3"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "53e9bae58849f64dfa4f5d5ae372c8341f7305f82a3868709269343628b659a3"
dependencies = [
 "proc-macro2",
 "quote",
 "unicode-ident",
]

[[package]]
name = "unicode-ident"
version = "1.0.26"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "d245f478577f809a851594d02313b640fb437e0bb33866753cff937863096954"

[package]
name = "sample-syn-expr-closure"
version = "1.0.0"
edition = "2021"
publish = false

[dependencies]
syn = { version = "=3.0.3", features = ["full", "extra-traits"] }

[[bin]]
name = "contract"
path = "test/contract.rs"

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::ExprClosure 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::ExprClosure

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:sha256:94525718de98c993202d1ce95fb087a91c6b7103500e353ebf12c31d80de9e2b","contract":["syn::ExprClosure parses closure with typed parameters and expression body","syn::ExprClosure parses move closure with capture token","syn::ExprClosure parses async closure with async token","syn::ExprClosure parses closure with explicit return type and block body","syn::ExprClosure parses closure with higher-ranked lifetime bounds","syn::ExprClosure rejects invalid closure syntax"],"goal":"verify syn::ExprClosure in pkg:cargo/syn@3.0.3","kind":"HOW","packages":["pkg:cargo/syn@3.0.3"],"schemaVersion":1,"symbols":["syn::ExprClosure"]},"contractCommand":["cargo","run","--offline"],"environment":{"arch":"x64","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::ExprClosure"],"verifierAdapter":"cargo@1"}

{
  "schemaVersion": 1,
  "goal": "verify syn::ExprClosure in pkg:cargo/syn@3.0.3",
  "kind": "HOW",
  "packages": [
    "pkg:cargo/syn@3.0.3"
  ],
  "symbols": [
    "syn::ExprClosure"
  ]
}

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

pub use syn::ExprClosure;

use syn::{parse_str, Expr, ExprClosure, ReturnType};

fn main() {
    // 1. syn::ExprClosure parses closure with typed parameters and expression body
    let code1 = "|x: i32| x + 1";
    let closure1: ExprClosure = parse_str(code1).expect("failed to parse basic closure");
    assert_eq!(closure1.inputs.len(), 1);
    assert!(closure1.capture.is_none());
    assert!(closure1.asyncness.is_none());
    assert!(closure1.constness.is_none());
    assert!(closure1.lifetimes.is_none());
    assert!(matches!(closure1.output, ReturnType::Default));
    assert!(matches!(*closure1.body, Expr::Binary(_)));

    // 2. syn::ExprClosure parses move closure with capture token
    let code2 = "move |a, b| a + b";
    let closure2: ExprClosure = parse_str(code2).expect("failed to parse move closure");
    assert_eq!(closure2.inputs.len(), 2);
    assert!(closure2.capture.is_some());
    assert!(closure2.asyncness.is_none());

    // 3. syn::ExprClosure parses async closure with async token
    let code3 = "async || 42";
    let closure3: ExprClosure = parse_str(code3).expect("failed to parse async closure");
    assert!(closure3.inputs.is_empty());
    assert!(closure3.asyncness.is_some());
    assert!(closure3.capture.is_none());

    // 4. syn::ExprClosure parses closure with explicit return type and block body
    let code4 = "|x: i32| -> i32 { x * 2 }";
    let closure4: ExprClosure = parse_str(code4).expect("failed to parse closure with return type");
    assert_eq!(closure4.inputs.len(), 1);
    assert!(matches!(closure4.output, ReturnType::Type(_, _)));
    assert!(matches!(*closure4.body, Expr::Block(_)));

    // 5. syn::ExprClosure parses closure with higher-ranked lifetime bounds
    let code5 = "for<'a> |x: &'a i32| *x";
    let closure5: ExprClosure = parse_str(code5).expect("failed to parse closure with lifetimes");
    assert!(closure5.lifetimes.is_some());
    assert_eq!(closure5.inputs.len(), 1);

    // 6. syn::ExprClosure rejects invalid closure syntax
    assert!(parse_str::<ExprClosure>("fn not_a_closure() {}").is_err());
    assert!(parse_str::<ExprClosure>("let x = 1;").is_err());

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