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Add block_in_if lint, #434

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John Quigley 2015-11-20 00:22:52 -05:00 committed by Manish Goregaokar
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@ -6,84 +6,86 @@ A collection of lints to catch common mistakes and improve your Rust code.
[Jump to usage instructions](#usage)
##Lints
There are 74 lints included in this crate:
There are 76 lints included in this crate:
name | default | meaning
-------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[approx_constant](https://github.com/Manishearth/rust-clippy/wiki#approx_constant) | warn | the approximate of a known float constant (in `std::f64::consts` or `std::f32::consts`) is found; suggests to use the constant
[bad_bit_mask](https://github.com/Manishearth/rust-clippy/wiki#bad_bit_mask) | warn | expressions of the form `_ & mask == select` that will only ever return `true` or `false` (because in the example `select` containing bits that `mask` doesn't have)
[box_vec](https://github.com/Manishearth/rust-clippy/wiki#box_vec) | warn | usage of `Box<Vec<T>>`, vector elements are already on the heap
[cast_possible_truncation](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_truncation) | allow | casts that may cause truncation of the value, e.g `x as u8` where `x: u32`, or `x as i32` where `x: f32`
[cast_possible_wrap](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_wrap) | allow | casts that may cause wrapping around the value, e.g `x as i32` where `x: u32` and `x > i32::MAX`
[cast_precision_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_precision_loss) | allow | casts that cause loss of precision, e.g `x as f32` where `x: u64`
[cast_sign_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_sign_loss) | allow | casts from signed types to unsigned types, e.g `x as u32` where `x: i32`
[cmp_nan](https://github.com/Manishearth/rust-clippy/wiki#cmp_nan) | deny | comparisons to NAN (which will always return false, which is probably not intended)
[cmp_owned](https://github.com/Manishearth/rust-clippy/wiki#cmp_owned) | warn | creating owned instances for comparing with others, e.g. `x == "foo".to_string()`
[collapsible_if](https://github.com/Manishearth/rust-clippy/wiki#collapsible_if) | warn | two nested `if`-expressions can be collapsed into one, e.g. `if x { if y { foo() } }` can be written as `if x && y { foo() }`
[empty_loop](https://github.com/Manishearth/rust-clippy/wiki#empty_loop) | warn | empty `loop {}` detected
[eq_op](https://github.com/Manishearth/rust-clippy/wiki#eq_op) | warn | equal operands on both sides of a comparison or bitwise combination (e.g. `x == x`)
[explicit_counter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_counter_loop) | warn | for-looping with an explicit counter when `_.enumerate()` would do
[explicit_iter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_iter_loop) | warn | for-looping over `_.iter()` or `_.iter_mut()` when `&_` or `&mut _` would do
[float_cmp](https://github.com/Manishearth/rust-clippy/wiki#float_cmp) | warn | using `==` or `!=` on float values (as floating-point operations usually involve rounding errors, it is always better to check for approximate equality within small bounds)
[identity_op](https://github.com/Manishearth/rust-clippy/wiki#identity_op) | warn | using identity operations, e.g. `x + 0` or `y / 1`
[ineffective_bit_mask](https://github.com/Manishearth/rust-clippy/wiki#ineffective_bit_mask) | warn | expressions where a bit mask will be rendered useless by a comparison, e.g. `(x | 1) > 2`
[inline_always](https://github.com/Manishearth/rust-clippy/wiki#inline_always) | warn | `#[inline(always)]` is a bad idea in most cases
[iter_next_loop](https://github.com/Manishearth/rust-clippy/wiki#iter_next_loop) | warn | for-looping over `_.next()` which is probably not intended
[len_without_is_empty](https://github.com/Manishearth/rust-clippy/wiki#len_without_is_empty) | warn | traits and impls that have `.len()` but not `.is_empty()`
[len_zero](https://github.com/Manishearth/rust-clippy/wiki#len_zero) | warn | checking `.len() == 0` or `.len() > 0` (or similar) when `.is_empty()` could be used instead
[let_and_return](https://github.com/Manishearth/rust-clippy/wiki#let_and_return) | warn | creating a let-binding and then immediately returning it like `let x = expr; x` at the end of a block
[let_unit_value](https://github.com/Manishearth/rust-clippy/wiki#let_unit_value) | warn | creating a let binding to a value of unit type, which usually can't be used afterwards
[linkedlist](https://github.com/Manishearth/rust-clippy/wiki#linkedlist) | warn | usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque
[map_clone](https://github.com/Manishearth/rust-clippy/wiki#map_clone) | warn | using `.map(|x| x.clone())` to clone an iterator or option's contents (recommends `.cloned()` instead)
[match_bool](https://github.com/Manishearth/rust-clippy/wiki#match_bool) | warn | a match on boolean expression; recommends `if..else` block instead
[match_ref_pats](https://github.com/Manishearth/rust-clippy/wiki#match_ref_pats) | warn | a match has all arms prefixed with `&`; the match expression can be dereferenced instead
[min_max](https://github.com/Manishearth/rust-clippy/wiki#min_max) | warn | `min(_, max(_, _))` (or vice versa) with bounds clamping the result to a constant
[modulo_one](https://github.com/Manishearth/rust-clippy/wiki#modulo_one) | warn | taking a number modulo 1, which always returns 0
[mut_mut](https://github.com/Manishearth/rust-clippy/wiki#mut_mut) | allow | usage of double-mut refs, e.g. `&mut &mut ...` (either copy'n'paste error, or shows a fundamental misunderstanding of references)
[mutex_atomic](https://github.com/Manishearth/rust-clippy/wiki#mutex_atomic) | warn | using a Mutex where an atomic value could be used instead
[mutex_integer](https://github.com/Manishearth/rust-clippy/wiki#mutex_integer) | allow | using a Mutex for an integer type
[needless_bool](https://github.com/Manishearth/rust-clippy/wiki#needless_bool) | warn | if-statements with plain booleans in the then- and else-clause, e.g. `if p { true } else { false }`
[needless_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#needless_lifetimes) | warn | using explicit lifetimes for references in function arguments when elision rules would allow omitting them
[needless_range_loop](https://github.com/Manishearth/rust-clippy/wiki#needless_range_loop) | warn | for-looping over a range of indices where an iterator over items would do
[needless_return](https://github.com/Manishearth/rust-clippy/wiki#needless_return) | warn | using a return statement like `return expr;` where an expression would suffice
[needless_update](https://github.com/Manishearth/rust-clippy/wiki#needless_update) | warn | using `{ ..base }` when there are no missing fields
[no_effect](https://github.com/Manishearth/rust-clippy/wiki#no_effect) | warn | statements with no effect
[non_ascii_literal](https://github.com/Manishearth/rust-clippy/wiki#non_ascii_literal) | allow | using any literal non-ASCII chars in a string literal; suggests using the \\u escape instead
[nonsensical_open_options](https://github.com/Manishearth/rust-clippy/wiki#nonsensical_open_options) | warn | nonsensical combination of options for opening a file
[option_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#option_unwrap_used) | allow | using `Option.unwrap()`, which should at least get a better message using `expect()`
[precedence](https://github.com/Manishearth/rust-clippy/wiki#precedence) | warn | catches operations where precedence may be unclear. See the wiki for a list of cases caught
[ptr_arg](https://github.com/Manishearth/rust-clippy/wiki#ptr_arg) | warn | fn arguments of the type `&Vec<...>` or `&String`, suggesting to use `&[...]` or `&str` instead, respectively
[range_step_by_zero](https://github.com/Manishearth/rust-clippy/wiki#range_step_by_zero) | warn | using Range::step_by(0), which produces an infinite iterator
[range_zip_with_len](https://github.com/Manishearth/rust-clippy/wiki#range_zip_with_len) | warn | zipping iterator with a range when enumerate() would do
[redundant_closure](https://github.com/Manishearth/rust-clippy/wiki#redundant_closure) | warn | using redundant closures, i.e. `|a| foo(a)` (which can be written as just `foo`)
[redundant_pattern](https://github.com/Manishearth/rust-clippy/wiki#redundant_pattern) | warn | using `name @ _` in a pattern
[result_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#result_unwrap_used) | allow | using `Result.unwrap()`, which might be better handled
[reverse_range_loop](https://github.com/Manishearth/rust-clippy/wiki#reverse_range_loop) | warn | Iterating over an empty range, such as `10..0` or `5..5`
[shadow_reuse](https://github.com/Manishearth/rust-clippy/wiki#shadow_reuse) | allow | rebinding a name to an expression that re-uses the original value, e.g. `let x = x + 1`
[shadow_same](https://github.com/Manishearth/rust-clippy/wiki#shadow_same) | allow | rebinding a name to itself, e.g. `let mut x = &mut x`
[shadow_unrelated](https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated) | allow | The name is re-bound without even using the original value
[should_implement_trait](https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait) | warn | defining a method that should be implementing a std trait
[single_match](https://github.com/Manishearth/rust-clippy/wiki#single_match) | warn | a match statement with a single nontrivial arm (i.e, where the other arm is `_ => {}`) is used; recommends `if let` instead
[str_to_string](https://github.com/Manishearth/rust-clippy/wiki#str_to_string) | warn | using `to_string()` on a str, which should be `to_owned()`
[string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add) | allow | using `x + ..` where x is a `String`; suggests using `push_str()` instead
[string_add_assign](https://github.com/Manishearth/rust-clippy/wiki#string_add_assign) | allow | using `x = x + ..` where x is a `String`; suggests using `push_str()` instead
[string_to_string](https://github.com/Manishearth/rust-clippy/wiki#string_to_string) | warn | calling `String.to_string()` which is a no-op
[temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment) | warn | assignments to temporaries
[toplevel_ref_arg](https://github.com/Manishearth/rust-clippy/wiki#toplevel_ref_arg) | warn | An entire binding was declared as `ref`, in a function argument (`fn foo(ref x: Bar)`), or a `let` statement (`let ref x = foo()`). In such cases, it is preferred to take references with `&`.
[type_complexity](https://github.com/Manishearth/rust-clippy/wiki#type_complexity) | warn | usage of very complex types; recommends factoring out parts into `type` definitions
[unicode_not_nfc](https://github.com/Manishearth/rust-clippy/wiki#unicode_not_nfc) | allow | using a unicode literal not in NFC normal form (see http://www.unicode.org/reports/tr15/ for further information)
[unit_cmp](https://github.com/Manishearth/rust-clippy/wiki#unit_cmp) | warn | comparing unit values (which is always `true` or `false`, respectively)
[unnecessary_mut_passed](https://github.com/Manishearth/rust-clippy/wiki#unnecessary_mut_passed) | warn | an argument is passed as a mutable reference although the function/method only demands an immutable reference
[unstable_as_mut_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_mut_slice) | warn | as_mut_slice is not stable and can be replaced by &mut v[..]see https://github.com/rust-lang/rust/issues/27729
[unstable_as_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_slice) | warn | as_slice is not stable and can be replaced by & v[..]see https://github.com/rust-lang/rust/issues/27729
[unused_collect](https://github.com/Manishearth/rust-clippy/wiki#unused_collect) | warn | `collect()`ing an iterator without using the result; this is usually better written as a for loop
[useless_transmute](https://github.com/Manishearth/rust-clippy/wiki#useless_transmute) | warn | transmutes that have the same to and from types
[while_let_loop](https://github.com/Manishearth/rust-clippy/wiki#while_let_loop) | warn | `loop { if let { ... } else break }` can be written as a `while let` loop
[while_let_on_iterator](https://github.com/Manishearth/rust-clippy/wiki#while_let_on_iterator) | warn | using a while-let loop instead of a for loop on an iterator
[wrong_pub_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_pub_self_convention) | allow | defining a public method named with an established prefix (like "into_") that takes `self` with the wrong convention
[wrong_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_self_convention) | warn | defining a method named with an established prefix (like "into_") that takes `self` with the wrong convention
[zero_divided_by_zero](https://github.com/Manishearth/rust-clippy/wiki#zero_divided_by_zero) | warn | usage of `0.0 / 0.0` to obtain NaN instead of std::f32::NaN or std::f64::NaN
[zero_width_space](https://github.com/Manishearth/rust-clippy/wiki#zero_width_space) | deny | using a zero-width space in a string literal, which is confusing
name | default | meaning
---------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[approx_constant](https://github.com/Manishearth/rust-clippy/wiki#approx_constant) | warn | the approximate of a known float constant (in `std::f64::consts` or `std::f32::consts`) is found; suggests to use the constant
[bad_bit_mask](https://github.com/Manishearth/rust-clippy/wiki#bad_bit_mask) | warn | expressions of the form `_ & mask == select` that will only ever return `true` or `false` (because in the example `select` containing bits that `mask` doesn't have)
[block_in_if_condition_expr](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_expr) | warn | braces can be eliminated in conditions that are expressions, e.g `if { true } ...`
[block_in_if_condition_stmt](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_stmt) | warn | avoid complex blocks in conditions, instead move the block higher and bind it with 'let'; e.g: `if { let x = true; x } ...`
[box_vec](https://github.com/Manishearth/rust-clippy/wiki#box_vec) | warn | usage of `Box<Vec<T>>`, vector elements are already on the heap
[cast_possible_truncation](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_truncation) | allow | casts that may cause truncation of the value, e.g `x as u8` where `x: u32`, or `x as i32` where `x: f32`
[cast_possible_wrap](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_wrap) | allow | casts that may cause wrapping around the value, e.g `x as i32` where `x: u32` and `x > i32::MAX`
[cast_precision_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_precision_loss) | allow | casts that cause loss of precision, e.g `x as f32` where `x: u64`
[cast_sign_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_sign_loss) | allow | casts from signed types to unsigned types, e.g `x as u32` where `x: i32`
[cmp_nan](https://github.com/Manishearth/rust-clippy/wiki#cmp_nan) | deny | comparisons to NAN (which will always return false, which is probably not intended)
[cmp_owned](https://github.com/Manishearth/rust-clippy/wiki#cmp_owned) | warn | creating owned instances for comparing with others, e.g. `x == "foo".to_string()`
[collapsible_if](https://github.com/Manishearth/rust-clippy/wiki#collapsible_if) | warn | two nested `if`-expressions can be collapsed into one, e.g. `if x { if y { foo() } }` can be written as `if x && y { foo() }`
[empty_loop](https://github.com/Manishearth/rust-clippy/wiki#empty_loop) | warn | empty `loop {}` detected
[eq_op](https://github.com/Manishearth/rust-clippy/wiki#eq_op) | warn | equal operands on both sides of a comparison or bitwise combination (e.g. `x == x`)
[explicit_counter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_counter_loop) | warn | for-looping with an explicit counter when `_.enumerate()` would do
[explicit_iter_loop](https://github.com/Manishearth/rust-clippy/wiki#explicit_iter_loop) | warn | for-looping over `_.iter()` or `_.iter_mut()` when `&_` or `&mut _` would do
[float_cmp](https://github.com/Manishearth/rust-clippy/wiki#float_cmp) | warn | using `==` or `!=` on float values (as floating-point operations usually involve rounding errors, it is always better to check for approximate equality within small bounds)
[identity_op](https://github.com/Manishearth/rust-clippy/wiki#identity_op) | warn | using identity operations, e.g. `x + 0` or `y / 1`
[ineffective_bit_mask](https://github.com/Manishearth/rust-clippy/wiki#ineffective_bit_mask) | warn | expressions where a bit mask will be rendered useless by a comparison, e.g. `(x | 1) > 2`
[inline_always](https://github.com/Manishearth/rust-clippy/wiki#inline_always) | warn | `#[inline(always)]` is a bad idea in most cases
[iter_next_loop](https://github.com/Manishearth/rust-clippy/wiki#iter_next_loop) | warn | for-looping over `_.next()` which is probably not intended
[len_without_is_empty](https://github.com/Manishearth/rust-clippy/wiki#len_without_is_empty) | warn | traits and impls that have `.len()` but not `.is_empty()`
[len_zero](https://github.com/Manishearth/rust-clippy/wiki#len_zero) | warn | checking `.len() == 0` or `.len() > 0` (or similar) when `.is_empty()` could be used instead
[let_and_return](https://github.com/Manishearth/rust-clippy/wiki#let_and_return) | warn | creating a let-binding and then immediately returning it like `let x = expr; x` at the end of a block
[let_unit_value](https://github.com/Manishearth/rust-clippy/wiki#let_unit_value) | warn | creating a let binding to a value of unit type, which usually can't be used afterwards
[linkedlist](https://github.com/Manishearth/rust-clippy/wiki#linkedlist) | warn | usage of LinkedList, usually a vector is faster, or a more specialized data structure like a VecDeque
[map_clone](https://github.com/Manishearth/rust-clippy/wiki#map_clone) | warn | using `.map(|x| x.clone())` to clone an iterator or option's contents (recommends `.cloned()` instead)
[match_bool](https://github.com/Manishearth/rust-clippy/wiki#match_bool) | warn | a match on boolean expression; recommends `if..else` block instead
[match_ref_pats](https://github.com/Manishearth/rust-clippy/wiki#match_ref_pats) | warn | a match has all arms prefixed with `&`; the match expression can be dereferenced instead
[min_max](https://github.com/Manishearth/rust-clippy/wiki#min_max) | warn | `min(_, max(_, _))` (or vice versa) with bounds clamping the result to a constant
[modulo_one](https://github.com/Manishearth/rust-clippy/wiki#modulo_one) | warn | taking a number modulo 1, which always returns 0
[mut_mut](https://github.com/Manishearth/rust-clippy/wiki#mut_mut) | allow | usage of double-mut refs, e.g. `&mut &mut ...` (either copy'n'paste error, or shows a fundamental misunderstanding of references)
[mutex_atomic](https://github.com/Manishearth/rust-clippy/wiki#mutex_atomic) | warn | using a Mutex where an atomic value could be used instead
[mutex_integer](https://github.com/Manishearth/rust-clippy/wiki#mutex_integer) | allow | using a Mutex for an integer type
[needless_bool](https://github.com/Manishearth/rust-clippy/wiki#needless_bool) | warn | if-statements with plain booleans in the then- and else-clause, e.g. `if p { true } else { false }`
[needless_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#needless_lifetimes) | warn | using explicit lifetimes for references in function arguments when elision rules would allow omitting them
[needless_range_loop](https://github.com/Manishearth/rust-clippy/wiki#needless_range_loop) | warn | for-looping over a range of indices where an iterator over items would do
[needless_return](https://github.com/Manishearth/rust-clippy/wiki#needless_return) | warn | using a return statement like `return expr;` where an expression would suffice
[needless_update](https://github.com/Manishearth/rust-clippy/wiki#needless_update) | warn | using `{ ..base }` when there are no missing fields
[no_effect](https://github.com/Manishearth/rust-clippy/wiki#no_effect) | warn | statements with no effect
[non_ascii_literal](https://github.com/Manishearth/rust-clippy/wiki#non_ascii_literal) | allow | using any literal non-ASCII chars in a string literal; suggests using the \\u escape instead
[nonsensical_open_options](https://github.com/Manishearth/rust-clippy/wiki#nonsensical_open_options) | warn | nonsensical combination of options for opening a file
[option_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#option_unwrap_used) | allow | using `Option.unwrap()`, which should at least get a better message using `expect()`
[precedence](https://github.com/Manishearth/rust-clippy/wiki#precedence) | warn | catches operations where precedence may be unclear. See the wiki for a list of cases caught
[ptr_arg](https://github.com/Manishearth/rust-clippy/wiki#ptr_arg) | warn | fn arguments of the type `&Vec<...>` or `&String`, suggesting to use `&[...]` or `&str` instead, respectively
[range_step_by_zero](https://github.com/Manishearth/rust-clippy/wiki#range_step_by_zero) | warn | using Range::step_by(0), which produces an infinite iterator
[range_zip_with_len](https://github.com/Manishearth/rust-clippy/wiki#range_zip_with_len) | warn | zipping iterator with a range when enumerate() would do
[redundant_closure](https://github.com/Manishearth/rust-clippy/wiki#redundant_closure) | warn | using redundant closures, i.e. `|a| foo(a)` (which can be written as just `foo`)
[redundant_pattern](https://github.com/Manishearth/rust-clippy/wiki#redundant_pattern) | warn | using `name @ _` in a pattern
[result_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#result_unwrap_used) | allow | using `Result.unwrap()`, which might be better handled
[reverse_range_loop](https://github.com/Manishearth/rust-clippy/wiki#reverse_range_loop) | warn | Iterating over an empty range, such as `10..0` or `5..5`
[shadow_reuse](https://github.com/Manishearth/rust-clippy/wiki#shadow_reuse) | allow | rebinding a name to an expression that re-uses the original value, e.g. `let x = x + 1`
[shadow_same](https://github.com/Manishearth/rust-clippy/wiki#shadow_same) | allow | rebinding a name to itself, e.g. `let mut x = &mut x`
[shadow_unrelated](https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated) | allow | The name is re-bound without even using the original value
[should_implement_trait](https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait) | warn | defining a method that should be implementing a std trait
[single_match](https://github.com/Manishearth/rust-clippy/wiki#single_match) | warn | a match statement with a single nontrivial arm (i.e, where the other arm is `_ => {}`) is used; recommends `if let` instead
[str_to_string](https://github.com/Manishearth/rust-clippy/wiki#str_to_string) | warn | using `to_string()` on a str, which should be `to_owned()`
[string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add) | allow | using `x + ..` where x is a `String`; suggests using `push_str()` instead
[string_add_assign](https://github.com/Manishearth/rust-clippy/wiki#string_add_assign) | allow | using `x = x + ..` where x is a `String`; suggests using `push_str()` instead
[string_to_string](https://github.com/Manishearth/rust-clippy/wiki#string_to_string) | warn | calling `String.to_string()` which is a no-op
[temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment) | warn | assignments to temporaries
[toplevel_ref_arg](https://github.com/Manishearth/rust-clippy/wiki#toplevel_ref_arg) | warn | An entire binding was declared as `ref`, in a function argument (`fn foo(ref x: Bar)`), or a `let` statement (`let ref x = foo()`). In such cases, it is preferred to take references with `&`.
[type_complexity](https://github.com/Manishearth/rust-clippy/wiki#type_complexity) | warn | usage of very complex types; recommends factoring out parts into `type` definitions
[unicode_not_nfc](https://github.com/Manishearth/rust-clippy/wiki#unicode_not_nfc) | allow | using a unicode literal not in NFC normal form (see http://www.unicode.org/reports/tr15/ for further information)
[unit_cmp](https://github.com/Manishearth/rust-clippy/wiki#unit_cmp) | warn | comparing unit values (which is always `true` or `false`, respectively)
[unnecessary_mut_passed](https://github.com/Manishearth/rust-clippy/wiki#unnecessary_mut_passed) | warn | an argument is passed as a mutable reference although the function/method only demands an immutable reference
[unstable_as_mut_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_mut_slice) | warn | as_mut_slice is not stable and can be replaced by &mut v[..]see https://github.com/rust-lang/rust/issues/27729
[unstable_as_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_slice) | warn | as_slice is not stable and can be replaced by & v[..]see https://github.com/rust-lang/rust/issues/27729
[unused_collect](https://github.com/Manishearth/rust-clippy/wiki#unused_collect) | warn | `collect()`ing an iterator without using the result; this is usually better written as a for loop
[useless_transmute](https://github.com/Manishearth/rust-clippy/wiki#useless_transmute) | warn | transmutes that have the same to and from types
[while_let_loop](https://github.com/Manishearth/rust-clippy/wiki#while_let_loop) | warn | `loop { if let { ... } else break }` can be written as a `while let` loop
[while_let_on_iterator](https://github.com/Manishearth/rust-clippy/wiki#while_let_on_iterator) | warn | using a while-let loop instead of a for loop on an iterator
[wrong_pub_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_pub_self_convention) | allow | defining a public method named with an established prefix (like "into_") that takes `self` with the wrong convention
[wrong_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_self_convention) | warn | defining a method named with an established prefix (like "into_") that takes `self` with the wrong convention
[zero_divided_by_zero](https://github.com/Manishearth/rust-clippy/wiki#zero_divided_by_zero) | warn | usage of `0.0 / 0.0` to obtain NaN instead of std::f32::NaN or std::f64::NaN
[zero_width_space](https://github.com/Manishearth/rust-clippy/wiki#zero_width_space) | deny | using a zero-width space in a string literal, which is confusing
More to come, please [file an issue](https://github.com/Manishearth/rust-clippy/issues) if you have ideas!

91
src/block_in_if_condition.rs Normal file
View file

@ -0,0 +1,91 @@
use rustc_front::hir::*;
use rustc::lint::{LateLintPass, LateContext, LintArray, LintPass};
use rustc_front::intravisit::{Visitor, walk_expr};
use utils::*;
declare_lint! {
pub BLOCK_IN_IF_CONDITION_EXPR, Warn,
"braces can be eliminated in conditions that are expressions, e.g `if { true } ...`"
}
declare_lint! {
pub BLOCK_IN_IF_CONDITION_STMT, Warn,
"avoid complex blocks in conditions, instead move the block higher and bind it \
with 'let'; e.g: `if { let x = true; x } ...`"
}
#[derive(Copy,Clone)]
pub struct BlockInIfCondition;
impl LintPass for BlockInIfCondition {
fn get_lints(&self) -> LintArray {
lint_array!(BLOCK_IN_IF_CONDITION_EXPR, BLOCK_IN_IF_CONDITION_STMT)
}
}
struct ExVisitor<'v> {
found_block: Option<&'v Expr>
}
impl<'v> Visitor<'v> for ExVisitor<'v> {
fn visit_expr(&mut self, expr: &'v Expr) {
if let ExprClosure(_, _, ref block) = expr.node {
let complex = {
if !block.stmts.is_empty() {
true
} else {
if let Some(ref ex) = block.expr {
match ex.node {
ExprBlock(_) => true,
_ => false
}
} else {
false
}
}
};
if complex {
self.found_block = Some(& expr);
return;
}
}
walk_expr(self, expr);
}
}
const BRACED_EXPR_MESSAGE:&'static str = "omit braces around single expression condition";
const COMPLEX_BLOCK_MESSAGE:&'static str = "in an 'if' condition, avoid complex blocks or closures with blocks; instead, move the block or closure higher and bind it with a 'let'";
impl LateLintPass for BlockInIfCondition {
fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if let ExprIf(ref check, ref then, _) = expr.node {
if let ExprBlock(ref block) = check.node {
if block.stmts.is_empty() {
if let Some(ref ex) = block.expr {
// don't dig into the expression here, just suggest that they remove
// the block
span_help_and_lint(cx, BLOCK_IN_IF_CONDITION_EXPR, check.span,
BRACED_EXPR_MESSAGE,
&format!("try\nif {} {} ... ", snippet_block(cx, ex.span, ".."),
snippet_block(cx, then.span, "..")));
}
} else {
// move block higher
span_help_and_lint(cx, BLOCK_IN_IF_CONDITION_STMT, check.span,
COMPLEX_BLOCK_MESSAGE,
&format!("try\nlet res = {};\nif res {} ... ",
snippet_block(cx, block.span, ".."),
snippet_block(cx, then.span, "..")));
}
} else {
let mut visitor = ExVisitor { found_block: None };
walk_expr(&mut visitor, check);
if let Some(ref block) = visitor.found_block {
span_help_and_lint(cx, BLOCK_IN_IF_CONDITION_STMT, block.span,
COMPLEX_BLOCK_MESSAGE, "");
}
}
}
}
}

4
src/lib.rs
View file

@ -37,6 +37,7 @@ pub mod mut_reference;
pub mod len_zero;
pub mod attrs;
pub mod collapsible_if;
pub mod block_in_if_condition;
pub mod unicode;
pub mod shadow;
pub mod strings;
@ -81,6 +82,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
reg.register_late_lint_pass(box misc::CmpOwned);
reg.register_late_lint_pass(box attrs::AttrPass);
reg.register_late_lint_pass(box collapsible_if::CollapsibleIf);
reg.register_late_lint_pass(box block_in_if_condition::BlockInIfCondition);
reg.register_late_lint_pass(box misc::ModuloOne);
reg.register_late_lint_pass(box unicode::Unicode);
reg.register_late_lint_pass(box strings::StringAdd);
@ -131,6 +133,8 @@ pub fn plugin_registrar(reg: &mut Registry) {
attrs::INLINE_ALWAYS,
bit_mask::BAD_BIT_MASK,
bit_mask::INEFFECTIVE_BIT_MASK,
block_in_if_condition::BLOCK_IN_IF_CONDITION_EXPR,
block_in_if_condition::BLOCK_IN_IF_CONDITION_STMT,
collapsible_if::COLLAPSIBLE_IF,
eq_op::EQ_OP,
eta_reduction::REDUNDANT_CLOSURE,

64
tests/compile-fail/block_in_if_condition.rs Normal file
View file

@ -0,0 +1,64 @@
#![feature(plugin)]
#![plugin(clippy)]
#![deny(block_in_if_condition_expr)]
#![deny(block_in_if_condition_stmt)]
#![allow(unused)]
fn condition_has_block() -> i32 {
if { //~ERROR in an 'if' condition, avoid complex blocks or closures with blocks; instead, move the block or closure higher and bind it with a 'let'
let x = 3;
x == 3
} {
6
} else {
10
}
}
fn condition_has_block_with_single_expression() -> i32 {
if { true } { //~ERROR omit braces around single expression condition
6
} else {
10
}
}
fn predicate<F: FnOnce(T) -> bool, T>(pfn: F, val:T) -> bool {
pfn(val)
}
fn pred_test() {
let v = 3;
let sky = "blue";
// this is a sneaky case, where the block isn't directly in the condition, but is actually
// inside a closure that the condition is using. same principle applies. add some extra
// expressions to make sure linter isn't confused by them.
if v == 3 && sky == "blue" && predicate(|x| { let target = 3; x == target }, v) { //~ERROR in an 'if' condition, avoid complex blocks or closures with blocks; instead, move the block or closure higher and bind it with a 'let'
}
if predicate(|x| { let target = 3; x == target }, v) { //~ERROR in an 'if' condition, avoid complex blocks or closures with blocks; instead, move the block or closure higher and bind it with a 'let'
}
}
fn condition_is_normal() -> i32 {
let x = 3;
if true && x == 3 {
6
} else {
10
}
}
fn closure_without_block() {
if predicate(|x| x == 3, 6) {
}
}
fn main() {
}