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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,147 @@ | ||
| use crate::utils::span_lint_and_help; | ||
|
|
||
| use rustc_hir::{CaptureBy, Expr, ExprKind, PatKind}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// **What it does:** Checks for instances of `map_err(|_| Some::Enum)` | ||
| /// | ||
| /// **Why is this bad?** This map_err throws away the original error rather than allowing the enum to contain and report the cause of the error | ||
| /// | ||
| /// **Known problems:** None. | ||
| /// | ||
| /// **Example:** | ||
| /// Before: | ||
| /// ```rust | ||
| /// use std::fmt; | ||
| /// | ||
| /// #[derive(Debug)] | ||
| /// enum Error { | ||
| /// Indivisible, | ||
| /// Remainder(u8), | ||
| /// } | ||
| /// | ||
| /// impl fmt::Display for Error { | ||
| /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
| /// match self { | ||
| /// Error::Indivisible => write!(f, "could not divide input by three"), | ||
| /// Error::Remainder(remainder) => write!( | ||
| /// f, | ||
| /// "input is not divisible by three, remainder = {}", | ||
| /// remainder | ||
| /// ), | ||
| /// } | ||
| /// } | ||
| /// } | ||
| /// | ||
| /// impl std::error::Error for Error {} | ||
| /// | ||
| /// fn divisible_by_3(input: &str) -> Result<(), Error> { | ||
| /// input | ||
| /// .parse::<i32>() | ||
| /// .map_err(|_| Error::Indivisible) | ||
| /// .map(|v| v % 3) | ||
| /// .and_then(|remainder| { | ||
| /// if remainder == 0 { | ||
| /// Ok(()) | ||
| /// } else { | ||
| /// Err(Error::Remainder(remainder as u8)) | ||
| /// } | ||
| /// }) | ||
| /// } | ||
| /// ``` | ||
| /// | ||
| /// After: | ||
| /// ```rust | ||
| /// use std::{fmt, num::ParseIntError}; | ||
| /// | ||
| /// #[derive(Debug)] | ||
| /// enum Error { | ||
| /// Indivisible(ParseIntError), | ||
| /// Remainder(u8), | ||
| /// } | ||
| /// | ||
| /// impl fmt::Display for Error { | ||
| /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
| /// match self { | ||
| /// Error::Indivisible(_) => write!(f, "could not divide input by three"), | ||
| /// Error::Remainder(remainder) => write!( | ||
| /// f, | ||
| /// "input is not divisible by three, remainder = {}", | ||
| /// remainder | ||
| /// ), | ||
| /// } | ||
| /// } | ||
| /// } | ||
| /// | ||
| /// impl std::error::Error for Error { | ||
| /// fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { | ||
| /// match self { | ||
| /// Error::Indivisible(source) => Some(source), | ||
| /// _ => None, | ||
| /// } | ||
| /// } | ||
| /// } | ||
| /// | ||
| /// fn divisible_by_3(input: &str) -> Result<(), Error> { | ||
| /// input | ||
| /// .parse::<i32>() | ||
| /// .map_err(Error::Indivisible) | ||
| /// .map(|v| v % 3) | ||
| /// .and_then(|remainder| { | ||
| /// if remainder == 0 { | ||
| /// Ok(()) | ||
| /// } else { | ||
| /// Err(Error::Remainder(remainder as u8)) | ||
| /// } | ||
| /// }) | ||
| /// } | ||
| /// ``` | ||
| pub MAP_ERR_IGNORE, | ||
| pedantic, | ||
| "`map_err` should not ignore the original error" | ||
| } | ||
|
|
||
| declare_lint_pass!(MapErrIgnore => [MAP_ERR_IGNORE]); | ||
|
|
||
| impl<'tcx> LateLintPass<'tcx> for MapErrIgnore { | ||
| // do not try to lint if this is from a macro or desugaring | ||
| fn check_expr(&mut self, cx: &LateContext<'_>, e: &Expr<'_>) { | ||
| if e.span.from_expansion() { | ||
| return; | ||
| } | ||
|
|
||
| // check if this is a method call (e.g. x.foo()) | ||
| if let ExprKind::MethodCall(ref method, _t_span, ref args, _) = e.kind { | ||
| // only work if the method name is `map_err` and there are only 2 arguments (e.g. x.map_err(|_|[1] | ||
| // Enum::Variant[2])) | ||
| if method.ident.as_str() == "map_err" && args.len() == 2 { | ||
| // make sure the first argument is a closure, and grab the CaptureRef, body_id, and body_span fields | ||
| if let ExprKind::Closure(capture, _, body_id, body_span, _) = args[1].kind { | ||
| // check if this is by Reference (meaning there's no move statement) | ||
| if capture == CaptureBy::Ref { | ||
| // Get the closure body to check the parameters and values | ||
| let closure_body = cx.tcx.hir().body(body_id); | ||
| // make sure there's only one parameter (`|_|`) | ||
| if closure_body.params.len() == 1 { | ||
| // make sure that parameter is the wild token (`_`) | ||
| if let PatKind::Wild = closure_body.params[0].pat.kind { | ||
| // span the area of the closure capture and warn that the | ||
| // original error will be thrown away | ||
| span_lint_and_help( | ||
| cx, | ||
| MAP_ERR_IGNORE, | ||
| body_span, | ||
| "`map_err(|_|...` ignores the original error", | ||
| None, | ||
| "Consider wrapping the error in an enum variant", | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |
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