80 lines
2.4 KiB
Rust
80 lines
2.4 KiB
Rust
|
use super::utils::{get_arg_name, match_var, remove_blocks, snippet, span_lint_and_sugg};
|
|||
|
|
use rustc::hir::*;
|
|||
|
|
use rustc::lint::*;
|
|||
|
|
|
|||
|
|
/// **What it does:** Checks for matches being used to destructure a single-variant enum
|
|||
|
|
/// or tuple struct where a `let` will suffice.
|
|||
|
|
///
|
|||
|
|
/// **Why is this bad?** Just readability – `let` doesn't nest, whereas a `match` does.
|
|||
|
|
///
|
|||
|
|
/// **Known problems:** None.
|
|||
|
|
///
|
|||
|
|
/// **Example:**
|
|||
|
|
/// ```rust
|
|||
|
|
/// enum Wrapper {
|
|||
|
|
/// Data(i32),
|
|||
|
|
/// }
|
|||
|
|
///
|
|||
|
|
/// let wrapper = Wrapper::Data(42);
|
|||
|
|
///
|
|||
|
|
/// let data = match wrapper {
|
|||
|
|
/// Wrapper::Data(i) => i,
|
|||
|
|
/// };
|
|||
|
|
/// ```
|
|||
|
|
///
|
|||
|
|
/// The correct use would be:
|
|||
|
|
/// ```rust
|
|||
|
|
/// enum Wrapper {
|
|||
|
|
/// Data(i32),
|
|||
|
|
/// }
|
|||
|
|
///
|
|||
|
|
/// let wrapper = Wrapper::Data(42);
|
|||
|
|
/// let Wrapper::Data(data) = wrapper;
|
|||
|
|
/// ```
|
|||
|
|
declare_clippy_lint! {
|
|||
|
|
pub INFALLIBLE_DESTRUCTURING_MATCH,
|
|||
|
|
style,
|
|||
|
|
"a match statement with a single infallible arm instead of a `let`"
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
#[derive(Copy, Clone, Default)]
|
|||
|
|
pub struct Pass;
|
|||
|
|
|
|||
|
|
impl LintPass for Pass {
|
|||
|
|
fn get_lints(&self) -> LintArray {
|
|||
|
|
lint_array!(INFALLIBLE_DESTRUCTURING_MATCH)
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
|
|||
|
|
fn check_local(&mut self, cx: &LateContext<'a, 'tcx>, local: &'tcx Local) {
|
|||
|
|
if_chain! {
|
|||
|
|
if let Some(ref expr) = local.init;
|
|||
|
|
if let Expr_::ExprMatch(ref target, ref arms, MatchSource::Normal) = expr.node;
|
|||
|
|
if arms.len() == 1 && arms[0].pats.len() == 1 && arms[0].guard.is_none();
|
|||
|
|
if let PatKind::TupleStruct(QPath::Resolved(None, ref variant_name), ref args, _) = arms[0].pats[0].node;
|
|||
|
|
if args.len() == 1;
|
|||
|
|
if let Some(arg) = get_arg_name(&args[0]);
|
|||
|
|
let body = remove_blocks(&arms[0].body);
|
|||
|
|
if match_var(body, arg);
|
|||
|
|
|
|||
|
|
then {
|
|||
|
|
span_lint_and_sugg(
|
|||
|
|
cx,
|
|||
|
|
INFALLIBLE_DESTRUCTURING_MATCH,
|
|||
|
|
local.span,
|
|||
|
|
"you seem to be trying to use match to destructure a single infallible pattern. \
|
|||
|
|
Consider using `let`",
|
|||
|
|
"try this",
|
|||
|
|
format!(
|
|||
|
|
"let {}({}) = {};",
|
|||
|
|
snippet(cx, variant_name.span, ".."),
|
|||
|
|
snippet(cx, local.pat.span, ".."),
|
|||
|
|
snippet(cx, target.span, ".."),
|
|||
|
|
),
|
|||
|
|
);
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|