diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs index 612cde8a6..70adaa273 100644 --- a/clippy_lints/src/lib.rs +++ b/clippy_lints/src/lib.rs @@ -590,6 +590,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) { methods::OK_EXPECT, methods::OPTION_MAP_OR_NONE, methods::OR_FUN_CALL, + methods::EXPECT_FUN_CALL, methods::SEARCH_IS_SOME, methods::SHOULD_IMPLEMENT_TRAIT, methods::SINGLE_CHAR_PATTERN, @@ -899,6 +900,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) { loops::UNUSED_COLLECT, methods::ITER_NTH, methods::OR_FUN_CALL, + methods::EXPECT_FUN_CALL, methods::SINGLE_CHAR_PATTERN, misc::CMP_OWNED, mutex_atomic::MUTEX_ATOMIC, diff --git a/clippy_lints/src/methods.rs b/clippy_lints/src/methods.rs index 461efb27f..553198ae4 100644 --- a/clippy_lints/src/methods.rs +++ b/clippy_lints/src/methods.rs @@ -329,6 +329,32 @@ declare_clippy_lint! { "using any `*or` method with a function call, which suggests `*or_else`" } +/// **What it does:** Checks for calls to `.expect(&format!(...))`, `.expect(foo(..))`, +/// etc., and suggests to use `unwrap_or_else` instead +/// +/// **Why is this bad?** The function will always be called. +/// +/// **Known problems:** If the function has side-effects, not calling it will +/// change the semantic of the program, but you shouldn't rely on that anyway. +/// +/// **Example:** +/// ```rust +/// foo.expect(&format("Err {}: {}", err_code, err_msg)) +/// ``` +/// or +/// ```rust +/// foo.expect(format("Err {}: {}", err_code, err_msg).as_str()) +/// ``` +/// this can instead be written: +/// ```rust +/// foo.unwrap_or_else(|_| panic!(&format("Err {}: {}", err_code, err_msg))) +/// ``` +declare_clippy_lint! { + pub EXPECT_FUN_CALL, + perf, + "using any `expect` method with a function call" +} + /// **What it does:** Checks for usage of `.clone()` on a `Copy` type. /// /// **Why is this bad?** The only reason `Copy` types implement `Clone` is for @@ -657,6 +683,7 @@ impl LintPass for Pass { RESULT_MAP_UNWRAP_OR_ELSE, OPTION_MAP_OR_NONE, OR_FUN_CALL, + EXPECT_FUN_CALL, CHARS_NEXT_CMP, CHARS_LAST_CMP, CLONE_ON_COPY, @@ -741,6 +768,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass { } lint_or_fun_call(cx, expr, *method_span, &method_call.name.as_str(), args); + lint_expect_fun_call(cx, expr, *method_span, &method_call.name.as_str(), args); let self_ty = cx.tables.expr_ty_adjusted(&args[0]); if args.len() == 1 && method_call.name == "clone" { @@ -964,6 +992,48 @@ fn lint_or_fun_call(cx: &LateContext, expr: &hir::Expr, method_span: Span, name: } } +/// Checks for the `EXPECT_FUN_CALL` lint. +fn lint_expect_fun_call(cx: &LateContext, expr: &hir::Expr, method_span: Span, name: &str, args: &[hir::Expr]) { + #[allow(too_many_arguments)] + fn check_general_case( + cx: &LateContext, + name: &str, + method_span: Span, + arg: &hir::Expr, + span: Span, + ) { + if name != "expect" { + return; + } + + // don't lint for constant values + let owner_def = cx.tcx.hir.get_parent_did(arg.id); + let promotable = cx.tcx.rvalue_promotable_map(owner_def).contains(&arg.hir_id.local_id); + if promotable { + return; + } + + let sugg: Cow<_> = snippet(cx, arg.span, ".."); + let span_replace_word = method_span.with_hi(span.hi()); + + span_lint_and_sugg( + cx, + EXPECT_FUN_CALL, + span_replace_word, + &format!("use of `{}` followed by a function call", name), + "try this", + format!("unwrap_or_else(|_| panic!({}))", sugg), + ); + } + + if args.len() == 2 { + match args[1].node { + hir::ExprLit(_) => {}, + _ => check_general_case(cx, name, method_span, &args[1], expr.span), + } + } +} + /// Checks for the `CLONE_ON_COPY` lint. fn lint_clone_on_copy(cx: &LateContext, expr: &hir::Expr, arg: &hir::Expr, arg_ty: Ty) { let ty = cx.tables.expr_ty(expr); diff --git a/tests/ui/methods.rs b/tests/ui/methods.rs index 9e2536558..04e3ec13b 100644 --- a/tests/ui/methods.rs +++ b/tests/ui/methods.rs @@ -342,6 +342,35 @@ fn or_fun_call() { let _ = stringy.unwrap_or("".to_owned()); } +/// Checks implementation of the `EXPECT_FUN_CALL` lint +fn expect_fun_call() { + let with_some = Some("value"); + with_some.expect("error"); + + let with_none: Option = None; + with_none.expect("error"); + + let error_code = 123_i32; + let with_none_and_format: Option = None; + with_none_and_format.expect(&format!("Error {}: fake error", error_code)); + + let with_none_and_as_str: Option = None; + with_none_and_as_str.expect(format!("Error {}: fake error", error_code).as_str()); + + let with_ok: Result<(), ()> = Ok(()); + with_ok.expect("error"); + + let with_err: Result<(), ()> = Err(()); + with_err.expect("error"); + + let error_code = 123_i32; + let with_err_and_format: Result<(), ()> = Err(()); + with_err_and_format.expect(&format!("Error {}: fake error", error_code)); + + let with_err_and_as_str: Result<(), ()> = Err(()); + with_err_and_as_str.expect(format!("Error {}: fake error", error_code).as_str()); +} + /// Checks implementation of `ITER_NTH` lint fn iter_nth() { let mut some_vec = vec![0, 1, 2, 3]; diff --git a/tests/ui/methods.stderr b/tests/ui/methods.stderr index 1dd1ddc3c..2fe374f35 100644 --- a/tests/ui/methods.stderr +++ b/tests/ui/methods.stderr @@ -423,83 +423,109 @@ error: use of `unwrap_or` followed by a function call 342 | let _ = stringy.unwrap_or("".to_owned()); | ^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|| "".to_owned())` -error: called `.iter().nth()` on a Vec. Calling `.get()` is both faster and more readable - --> $DIR/methods.rs:353:23 +error: use of `expect` followed by a function call + --> $DIR/methods.rs:355:26 | -353 | let bad_vec = some_vec.iter().nth(3); +355 | with_none_and_format.expect(&format!("Error {}: fake error", error_code)); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|_| panic!(&format!("Error {}: fake error", error_code)))` + | + = note: `-D expect-fun-call` implied by `-D warnings` + +error: use of `expect` followed by a function call + --> $DIR/methods.rs:358:26 + | +358 | with_none_and_as_str.expect(format!("Error {}: fake error", error_code).as_str()); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|_| panic!(format!("Error {}: fake error", error_code).as_str()))` + +error: use of `expect` followed by a function call + --> $DIR/methods.rs:368:25 + | +368 | with_err_and_format.expect(&format!("Error {}: fake error", error_code)); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|_| panic!(&format!("Error {}: fake error", error_code)))` + +error: use of `expect` followed by a function call + --> $DIR/methods.rs:371:25 + | +371 | with_err_and_as_str.expect(format!("Error {}: fake error", error_code).as_str()); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try this: `unwrap_or_else(|_| panic!(format!("Error {}: fake error", error_code).as_str()))` + +error: called `.iter().nth()` on a Vec. Calling `.get()` is both faster and more readable + --> $DIR/methods.rs:382:23 + | +382 | let bad_vec = some_vec.iter().nth(3); | ^^^^^^^^^^^^^^^^^^^^^^ | = note: `-D iter-nth` implied by `-D warnings` error: called `.iter().nth()` on a slice. Calling `.get()` is both faster and more readable - --> $DIR/methods.rs:354:26 + --> $DIR/methods.rs:383:26 | -354 | let bad_slice = &some_vec[..].iter().nth(3); +383 | let bad_slice = &some_vec[..].iter().nth(3); | ^^^^^^^^^^^^^^^^^^^^^^^^^^ error: called `.iter().nth()` on a slice. Calling `.get()` is both faster and more readable - --> $DIR/methods.rs:355:31 + --> $DIR/methods.rs:384:31 | -355 | let bad_boxed_slice = boxed_slice.iter().nth(3); +384 | let bad_boxed_slice = boxed_slice.iter().nth(3); | ^^^^^^^^^^^^^^^^^^^^^^^^^ error: called `.iter().nth()` on a VecDeque. Calling `.get()` is both faster and more readable - --> $DIR/methods.rs:356:29 + --> $DIR/methods.rs:385:29 | -356 | let bad_vec_deque = some_vec_deque.iter().nth(3); +385 | let bad_vec_deque = some_vec_deque.iter().nth(3); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: called `.iter_mut().nth()` on a Vec. Calling `.get_mut()` is both faster and more readable - --> $DIR/methods.rs:361:23 + --> $DIR/methods.rs:390:23 | -361 | let bad_vec = some_vec.iter_mut().nth(3); +390 | let bad_vec = some_vec.iter_mut().nth(3); | ^^^^^^^^^^^^^^^^^^^^^^^^^^ error: called `.iter_mut().nth()` on a slice. Calling `.get_mut()` is both faster and more readable - --> $DIR/methods.rs:364:26 + --> $DIR/methods.rs:393:26 | -364 | let bad_slice = &some_vec[..].iter_mut().nth(3); +393 | let bad_slice = &some_vec[..].iter_mut().nth(3); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: called `.iter_mut().nth()` on a VecDeque. Calling `.get_mut()` is both faster and more readable - --> $DIR/methods.rs:367:29 + --> $DIR/methods.rs:396:29 | -367 | let bad_vec_deque = some_vec_deque.iter_mut().nth(3); +396 | let bad_vec_deque = some_vec_deque.iter_mut().nth(3); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)` - --> $DIR/methods.rs:379:13 + --> $DIR/methods.rs:408:13 | -379 | let _ = some_vec.iter().skip(42).next(); +408 | let _ = some_vec.iter().skip(42).next(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: `-D iter-skip-next` implied by `-D warnings` error: called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)` - --> $DIR/methods.rs:380:13 + --> $DIR/methods.rs:409:13 | -380 | let _ = some_vec.iter().cycle().skip(42).next(); +409 | let _ = some_vec.iter().cycle().skip(42).next(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)` - --> $DIR/methods.rs:381:13 + --> $DIR/methods.rs:410:13 | -381 | let _ = (1..10).skip(10).next(); +410 | let _ = (1..10).skip(10).next(); | ^^^^^^^^^^^^^^^^^^^^^^^ error: called `skip(x).next()` on an iterator. This is more succinctly expressed by calling `nth(x)` - --> $DIR/methods.rs:382:14 + --> $DIR/methods.rs:411:14 | -382 | let _ = &some_vec[..].iter().skip(3).next(); +411 | let _ = &some_vec[..].iter().skip(3).next(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: used unwrap() on an Option value. If you don't want to handle the None case gracefully, consider using expect() to provide a better panic message - --> $DIR/methods.rs:391:13 + --> $DIR/methods.rs:420:13 | -391 | let _ = opt.unwrap(); +420 | let _ = opt.unwrap(); | ^^^^^^^^^^^^ | = note: `-D option-unwrap-used` implied by `-D warnings` -error: aborting due to 66 previous errors +error: aborting due to 70 previous errors