{
  "id": "rust/e0080-unable-to-infer-closure-type",
  "signature": "error[E0080]: unable to infer closure type; the closure requires a type annotation due to ambiguous return type",
  "signature_zh": "错误[E0080]：无法推断闭包类型；由于返回类型不明确，闭包需要类型注解",
  "regex": "error\\[E0080\\]: unable to infer closure type",
  "domain": "rust",
  "category": "type_error",
  "subcategory": null,
  "root_cause": "The compiler cannot infer the return type of a closure because it is used in multiple contexts with conflicting expectations, or the closure body is too complex for inference.",
  "root_cause_type": "generic",
  "root_cause_zh": "编译器无法推断闭包的返回类型，因为它在多个上下文中使用且期望冲突，或者闭包体过于复杂导致无法推断。",
  "versions": [
    {
      "version": "rustc 1.76.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "rustc 1.78.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "rustc 1.81.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "",
      "why_fails": "The error is about the closure's return type, not local variables; annotating locals doesn't help the compiler infer the overall return type.",
      "fail_rate": 0.7,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Adding a semicolon turns the closure into a statement, making it return (), which likely conflicts with the expected return type.",
      "fail_rate": 0.6,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Explicitly annotate the closure's return type using `|| -> ReturnType { ... }` syntax.",
      "success_rate": 0.9,
      "how": "Explicitly annotate the closure's return type using `|| -> ReturnType { ... }` syntax.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Assign the closure to a variable with a type hint, e.g., `let f: fn() -> i32 = || 5;`.",
      "success_rate": 0.85,
      "how": "Assign the closure to a variable with a type hint, e.g., `let f: fn() -> i32 = || 5;`.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Simplify the closure body to a single expression so the compiler can infer the type more easily.",
      "success_rate": 0.8,
      "how": "Simplify the closure body to a single expression so the compiler can infer the type more easily.",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "Explicitly annotate the closure's return type using `|| -> ReturnType { ... }` syntax.",
    "Assign the closure to a variable with a type hint, e.g., `let f: fn() -> i32 = || 5;`.",
    "Simplify the closure body to a single expression so the compiler can infer the type more easily."
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": "https://doc.rust-lang.org/error_codes/E0080.html",
  "official_doc_section": null,
  "error_code": "E0080",
  "verification_tier": "ai_generated",
  "confidence": 0.88,
  "fix_success_rate": 0.82,
  "resolvable": "true",
  "first_seen": "2024-01-10",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [],
  "locale": "en",
  "aliases": []
}