diff --git a/CHANGELOG.md b/CHANGELOG.md index 285a2ff8060d..2aa4991488cc 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -1676,6 +1676,7 @@ Released 2018-09-13 [`many_single_char_names`]: https://rust-lang.github.io/rust-clippy/master/index.html#many_single_char_names [`map_clone`]: https://rust-lang.github.io/rust-clippy/master/index.html#map_clone [`map_entry`]: https://rust-lang.github.io/rust-clippy/master/index.html#map_entry +[`map_err_ignore`]: https://rust-lang.github.io/rust-clippy/master/index.html#map_err_ignore [`map_flatten`]: https://rust-lang.github.io/rust-clippy/master/index.html#map_flatten [`map_identity`]: https://rust-lang.github.io/rust-clippy/master/index.html#map_identity [`map_unwrap_or`]: https://rust-lang.github.io/rust-clippy/master/index.html#map_unwrap_or diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index c017c5cb5d02..44afd7e82fe7 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -231,6 +231,7 @@ mod main_recursion; mod manual_async_fn; mod manual_non_exhaustive; mod map_clone; +mod map_err_ignore; mod map_identity; mod map_unit_fn; mod match_on_vec_items; @@ -627,6 +628,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: &manual_async_fn::MANUAL_ASYNC_FN, &manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE, &map_clone::MAP_CLONE, + &map_err_ignore::MAP_ERR_IGNORE, &map_identity::MAP_IDENTITY, &map_unit_fn::OPTION_MAP_UNIT_FN, &map_unit_fn::RESULT_MAP_UNIT_FN, @@ -920,6 +922,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: store.register_late_pass(|| box implicit_saturating_sub::ImplicitSaturatingSub); store.register_late_pass(|| box methods::Methods); store.register_late_pass(|| box map_clone::MapClone); + store.register_late_pass(|| box map_err_ignore::MapErrIgnore); store.register_late_pass(|| box shadow::Shadow); store.register_late_pass(|| box types::LetUnitValue); store.register_late_pass(|| box types::UnitCmp); @@ -1186,6 +1189,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf: LintId::of(&loops::EXPLICIT_INTO_ITER_LOOP), LintId::of(&loops::EXPLICIT_ITER_LOOP), LintId::of(¯o_use::MACRO_USE_IMPORTS), + LintId::of(&map_err_ignore::MAP_ERR_IGNORE), LintId::of(&match_on_vec_items::MATCH_ON_VEC_ITEMS), LintId::of(&matches::MATCH_BOOL), LintId::of(&matches::MATCH_WILDCARD_FOR_SINGLE_VARIANTS), diff --git a/clippy_lints/src/map_err_ignore.rs b/clippy_lints/src/map_err_ignore.rs new file mode 100644 index 000000000000..5298e16a04d9 --- /dev/null +++ b/clippy_lints/src/map_err_ignore.rs @@ -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::() + /// .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::() + /// .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", + ); + } + } + } + } + } + } + } +} diff --git a/src/lintlist/mod.rs b/src/lintlist/mod.rs index a7d38c93433d..a386cba8fba3 100644 --- a/src/lintlist/mod.rs +++ b/src/lintlist/mod.rs @@ -1172,6 +1172,13 @@ pub static ref ALL_LINTS: Vec = vec![ deprecation: None, module: "entry", }, + Lint { + name: "map_err_ignore", + group: "pedantic", + desc: "`map_err` should not ignore the original error", + deprecation: None, + module: "map_err_ignore", + }, Lint { name: "map_flatten", group: "pedantic", diff --git a/tests/ui/drop_ref.rs b/tests/ui/drop_ref.rs index 9181d789d4fb..6b5bcdaa78e2 100644 --- a/tests/ui/drop_ref.rs +++ b/tests/ui/drop_ref.rs @@ -1,5 +1,6 @@ #![warn(clippy::drop_ref)] #![allow(clippy::toplevel_ref_arg)] +#![allow(clippy::map_err_ignore)] use std::mem::drop; diff --git a/tests/ui/drop_ref.stderr b/tests/ui/drop_ref.stderr index 35ae88b78a4c..7974bf56d44c 100644 --- a/tests/ui/drop_ref.stderr +++ b/tests/ui/drop_ref.stderr @@ -1,108 +1,108 @@ error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing. - --> $DIR/drop_ref.rs:9:5 + --> $DIR/drop_ref.rs:10:5 | LL | drop(&SomeStruct); | ^^^^^^^^^^^^^^^^^ | = note: `-D clippy::drop-ref` implied by `-D warnings` note: argument has type `&SomeStruct` - --> $DIR/drop_ref.rs:9:10 + --> $DIR/drop_ref.rs:10:10 | LL | drop(&SomeStruct); | ^^^^^^^^^^^ error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing. - --> $DIR/drop_ref.rs:12:5 + --> $DIR/drop_ref.rs:13:5 | LL | drop(&owned1); | ^^^^^^^^^^^^^ | note: argument has type `&SomeStruct` - --> $DIR/drop_ref.rs:12:10 + --> $DIR/drop_ref.rs:13:10 | LL | drop(&owned1); | ^^^^^^^ error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing. - --> $DIR/drop_ref.rs:13:5 + --> $DIR/drop_ref.rs:14:5 | LL | drop(&&owned1); | ^^^^^^^^^^^^^^ | note: argument has type `&&SomeStruct` - --> $DIR/drop_ref.rs:13:10 + --> $DIR/drop_ref.rs:14:10 | LL | drop(&&owned1); | ^^^^^^^^ error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing. - --> $DIR/drop_ref.rs:14:5 + --> $DIR/drop_ref.rs:15:5 | LL | drop(&mut owned1); | ^^^^^^^^^^^^^^^^^ | note: argument has type `&mut SomeStruct` - --> $DIR/drop_ref.rs:14:10 + --> $DIR/drop_ref.rs:15:10 | LL | drop(&mut owned1); | ^^^^^^^^^^^ error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing. - --> $DIR/drop_ref.rs:18:5 + --> $DIR/drop_ref.rs:19:5 | LL | drop(reference1); | ^^^^^^^^^^^^^^^^ | note: argument has type `&SomeStruct` - --> $DIR/drop_ref.rs:18:10 + --> $DIR/drop_ref.rs:19:10 | LL | drop(reference1); | ^^^^^^^^^^ error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing. - --> $DIR/drop_ref.rs:21:5 + --> $DIR/drop_ref.rs:22:5 | LL | drop(reference2); | ^^^^^^^^^^^^^^^^ | note: argument has type `&mut SomeStruct` - --> $DIR/drop_ref.rs:21:10 + --> $DIR/drop_ref.rs:22:10 | LL | drop(reference2); | ^^^^^^^^^^ error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing. - --> $DIR/drop_ref.rs:24:5 + --> $DIR/drop_ref.rs:25:5 | LL | drop(reference3); | ^^^^^^^^^^^^^^^^ | note: argument has type `&SomeStruct` - --> $DIR/drop_ref.rs:24:10 + --> $DIR/drop_ref.rs:25:10 | LL | drop(reference3); | ^^^^^^^^^^ error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing. - --> $DIR/drop_ref.rs:29:5 + --> $DIR/drop_ref.rs:30:5 | LL | drop(&val); | ^^^^^^^^^^ | note: argument has type `&T` - --> $DIR/drop_ref.rs:29:10 + --> $DIR/drop_ref.rs:30:10 | LL | drop(&val); | ^^^^ error: calls to `std::mem::drop` with a reference instead of an owned value. Dropping a reference does nothing. - --> $DIR/drop_ref.rs:37:5 + --> $DIR/drop_ref.rs:38:5 | LL | std::mem::drop(&SomeStruct); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ | note: argument has type `&SomeStruct` - --> $DIR/drop_ref.rs:37:20 + --> $DIR/drop_ref.rs:38:20 | LL | std::mem::drop(&SomeStruct); | ^^^^^^^^^^^ diff --git a/tests/ui/map_err.rs b/tests/ui/map_err.rs new file mode 100644 index 000000000000..617b64228726 --- /dev/null +++ b/tests/ui/map_err.rs @@ -0,0 +1,25 @@ +#![warn(clippy::map_err_ignore)] +use std::convert::TryFrom; +use std::error::Error; +use std::fmt; + +#[derive(Debug)] +enum Errors { + Ignored, +} + +impl Error for Errors {} + +impl fmt::Display for Errors { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "Error") + } +} + +fn main() -> Result<(), Errors> { + let x = u32::try_from(-123_i32); + + println!("{:?}", x.map_err(|_| Errors::Ignored)); + + Ok(()) +} diff --git a/tests/ui/map_err.stderr b/tests/ui/map_err.stderr new file mode 100644 index 000000000000..7273f4603807 --- /dev/null +++ b/tests/ui/map_err.stderr @@ -0,0 +1,11 @@ +error: `map_err(|_|...` ignores the original error + --> $DIR/map_err.rs:22:32 + | +LL | println!("{:?}", x.map_err(|_| Errors::Ignored)); + | ^^^ + | + = note: `-D clippy::map-err-ignore` implied by `-D warnings` + = help: Consider wrapping the error in an enum variant + +error: aborting due to previous error +