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use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::ty::is_type_diagnostic_item;
use clippy_utils::visitors::for_each_expr;
use clippy_utils::{method_chain_args, return_ty};
use core::ops::ControlFlow;
use if_chain::if_chain;
use rustc_hir as hir;
use rustc_hir::ImplItemKind;
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::{sym, Span};
declare_clippy_lint! {
/// ### What it does
/// Checks for functions of type `Result` that contain `expect()` or `unwrap()`
///
/// ### Why is this bad?
/// These functions promote recoverable errors to non-recoverable errors which may be undesirable in code bases which wish to avoid panics.
///
/// ### Known problems
/// This can cause false positives in functions that handle both recoverable and non recoverable errors.
///
/// ### Example
/// Before:
/// ```rust
/// fn divisible_by_3(i_str: String) -> Result<(), String> {
/// let i = i_str
/// .parse::<i32>()
/// .expect("cannot divide the input by three");
///
/// if i % 3 != 0 {
/// Err("Number is not divisible by 3")?
/// }
///
/// Ok(())
/// }
/// ```
///
/// After:
/// ```rust
/// fn divisible_by_3(i_str: String) -> Result<(), String> {
/// let i = i_str
/// .parse::<i32>()
/// .map_err(|e| format!("cannot divide the input by three: {}", e))?;
///
/// if i % 3 != 0 {
/// Err("Number is not divisible by 3")?
/// }
///
/// Ok(())
/// }
/// ```
#[clippy::version = "1.48.0"]
pub UNWRAP_IN_RESULT,
restriction,
"functions of type `Result<..>` or `Option`<...> that contain `expect()` or `unwrap()`"
}
declare_lint_pass!(UnwrapInResult=> [UNWRAP_IN_RESULT]);
impl<'tcx> LateLintPass<'tcx> for UnwrapInResult {
fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
if_chain! {
// first check if it's a method or function
if let hir::ImplItemKind::Fn(ref _signature, _) = impl_item.kind;
// checking if its return type is `result` or `option`
if is_type_diagnostic_item(cx, return_ty(cx, impl_item.owner_id), sym::Result)
|| is_type_diagnostic_item(cx, return_ty(cx, impl_item.owner_id), sym::Option);
then {
lint_impl_body(cx, impl_item.span, impl_item);
}
}
}
}
fn lint_impl_body<'tcx>(cx: &LateContext<'tcx>, impl_span: Span, impl_item: &'tcx hir::ImplItem<'_>) {
if let ImplItemKind::Fn(_, body_id) = impl_item.kind {
let body = cx.tcx.hir().body(body_id);
let typeck = cx.tcx.typeck(impl_item.owner_id.def_id);
let mut result = Vec::new();
let _: Option<!> = for_each_expr(body.value, |e| {
// check for `expect`
if let Some(arglists) = method_chain_args(e, &["expect"]) {
let receiver_ty = typeck.expr_ty(arglists[0].0).peel_refs();
if is_type_diagnostic_item(cx, receiver_ty, sym::Option)
|| is_type_diagnostic_item(cx, receiver_ty, sym::Result)
{
result.push(e.span);
}
}
// check for `unwrap`
if let Some(arglists) = method_chain_args(e, &["unwrap"]) {
let receiver_ty = typeck.expr_ty(arglists[0].0).peel_refs();
if is_type_diagnostic_item(cx, receiver_ty, sym::Option)
|| is_type_diagnostic_item(cx, receiver_ty, sym::Result)
{
result.push(e.span);
}
}
ControlFlow::Continue(())
});
// if we've found one, lint
if !result.is_empty() {
span_lint_and_then(
cx,
UNWRAP_IN_RESULT,
impl_span,
"used unwrap or expect in a function that returns result or option",
move |diag| {
diag.help("unwrap and expect should not be used in a function that returns result or option");
diag.span_note(result, "potential non-recoverable error(s)");
},
);
}
}
}
|
