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Merge pull request #524 from devonhollowood/iterator-suggestions

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Iterator suggestions
This commit is contained in:
Manish Goregaokar 2015-12-31 14:16:15 +05:30
commit 261bed1f8e
4 changed files with 184 additions and 14 deletions
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8
README.md
View file

@ -6,7 +6,7 @@ A collection of lints to catch common mistakes and improve your Rust code.
[Jump to usage instructions](#usage)
##Lints
There are 86 lints included in this crate:
There are 88 lints included in this crate:
name | default | meaning
---------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
@ -28,6 +28,7 @@ name
[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
[filter_next](https://github.com/Manishearth/rust-clippy/wiki#filter_next) | warn | using `filter(p).next()`, which is more succinctly expressed as `.find(p)`
[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`
@ -55,8 +56,8 @@ name
[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
[ok_expect](https://github.com/Manishearth/rust-clippy/wiki#ok_expect) | warn | using `ok().expect()`, which gives worse error messages than calling `expect` directly on the Result
[option_map_unwrap_or](https://github.com/Manishearth/rust-clippy/wiki#option_map_unwrap_or) | warn | using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as `map_or(a, f)`)
[option_map_unwrap_or_else](https://github.com/Manishearth/rust-clippy/wiki#option_map_unwrap_or_else) | warn | using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `map_or_else(g, f)`)
[option_map_unwrap_or](https://github.com/Manishearth/rust-clippy/wiki#option_map_unwrap_or) | warn | using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as `map_or(a, f)`
[option_map_unwrap_or_else](https://github.com/Manishearth/rust-clippy/wiki#option_map_unwrap_or_else) | warn | using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as `map_or_else(g, f)`
[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()`
[out_of_bounds_indexing](https://github.com/Manishearth/rust-clippy/wiki#out_of_bounds_indexing) | deny | out of bound constant indexing
[panic_params](https://github.com/Manishearth/rust-clippy/wiki#panic_params) | warn | missing parameters in `panic!`
@ -68,6 +69,7 @@ name
[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`
[search_is_some](https://github.com/Manishearth/rust-clippy/wiki#search_is_some) | warn | using an iterator search followed by `is_some()`, which is more succinctly expressed as a call to `any()`
[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

2
src/lib.rs
View file

@ -176,9 +176,11 @@ pub fn plugin_registrar(reg: &mut Registry) {
matches::MATCH_BOOL,
matches::MATCH_REF_PATS,
matches::SINGLE_MATCH,
methods::FILTER_NEXT,
methods::OK_EXPECT,
methods::OPTION_MAP_UNWRAP_OR,
methods::OPTION_MAP_UNWRAP_OR_ELSE,
methods::SEARCH_IS_SOME,
methods::SHOULD_IMPLEMENT_TRAIT,
methods::STR_TO_STRING,
methods::STRING_TO_STRING,

92
src/methods.rs
View file

@ -6,7 +6,7 @@ use std::iter;
use std::borrow::Cow;
use utils::{snippet, span_lint, span_note_and_lint, match_path, match_type, method_chain_args,
walk_ptrs_ty_depth, walk_ptrs_ty};
match_trait_method, walk_ptrs_ty_depth, walk_ptrs_ty};
use utils::{OPTION_PATH, RESULT_PATH, STRING_PATH};
use utils::MethodArgs;
@ -135,7 +135,7 @@ declare_lint!(pub OK_EXPECT, Warn,
/// **Example:** `x.map(|a| a + 1).unwrap_or(0)`
declare_lint!(pub OPTION_MAP_UNWRAP_OR, Warn,
"using `Option.map(f).unwrap_or(a)`, which is more succinctly expressed as \
`map_or(a, f)`)");
`map_or(a, f)`");
/// **What it does:** This lint `Warn`s on `_.map(_).unwrap_or_else(_)`.
///
@ -146,7 +146,29 @@ declare_lint!(pub OPTION_MAP_UNWRAP_OR, Warn,
/// **Example:** `x.map(|a| a + 1).unwrap_or_else(some_function)`
declare_lint!(pub OPTION_MAP_UNWRAP_OR_ELSE, Warn,
"using `Option.map(f).unwrap_or_else(g)`, which is more succinctly expressed as \
`map_or_else(g, f)`)");
`map_or_else(g, f)`");
/// **What it does:** This lint `Warn`s on `_.filter(_).next()`.
///
/// **Why is this bad?** Readability, this can be written more concisely as `_.find(_)`.
///
/// **Known problems:** None.
///
/// **Example:** `iter.filter(|x| x == 0).next()`
declare_lint!(pub FILTER_NEXT, Warn,
"using `filter(p).next()`, which is more succinctly expressed as `.find(p)`");
/// **What it does:** This lint `Warn`s on an iterator search (such as `find()`, `position()`, or
/// `rposition()`) followed by a call to `is_some()`.
///
/// **Why is this bad?** Readability, this can be written more concisely as `_.any(_)`.
///
/// **Known problems:** None.
///
/// **Example:** `iter.find(|x| x == 0).is_some()`
declare_lint!(pub SEARCH_IS_SOME, Warn,
"using an iterator search followed by `is_some()`, which is more succinctly \
expressed as a call to `any()`");
impl LintPass for MethodsPass {
fn get_lints(&self) -> LintArray {
@ -174,6 +196,18 @@ impl LateLintPass for MethodsPass {
else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or_else"]) {
lint_map_unwrap_or_else(cx, expr, arglists[0], arglists[1]);
}
else if let Some(arglists) = method_chain_args(expr, &["filter", "next"]) {
lint_filter_next(cx, expr, arglists[0]);
}
else if let Some(arglists) = method_chain_args(expr, &["find", "is_some"]) {
lint_search_is_some(cx, expr, "find", arglists[0], arglists[1]);
}
else if let Some(arglists) = method_chain_args(expr, &["position", "is_some"]) {
lint_search_is_some(cx, expr, "position", arglists[0], arglists[1]);
}
else if let Some(arglists) = method_chain_args(expr, &["rposition", "is_some"]) {
lint_search_is_some(cx, expr, "rposition", arglists[0], arglists[1]);
}
}
}
@ -275,8 +309,8 @@ fn lint_ok_expect(cx: &LateContext, expr: &Expr, ok_args: &MethodArgs) {
#[allow(ptr_arg)] // Type of MethodArgs is potentially a Vec
/// lint use of `map().unwrap_or()` for `Option`s
fn lint_map_unwrap_or(cx: &LateContext, expr: &Expr, unwrap_args: &MethodArgs,
map_args: &MethodArgs) {
fn lint_map_unwrap_or(cx: &LateContext, expr: &Expr, map_args: &MethodArgs,
unwrap_args: &MethodArgs) {
// lint if the caller of `map()` is an `Option`
if match_type(cx, cx.tcx.expr_ty(&map_args[0]), &OPTION_PATH) {
// lint message
@ -293,7 +327,8 @@ fn lint_map_unwrap_or(cx: &LateContext, expr: &Expr, unwrap_args: &MethodArgs,
if same_span && !multiline {
span_note_and_lint(
cx, OPTION_MAP_UNWRAP_OR, expr.span, msg, expr.span,
&format!("replace this with map_or({1}, {0})", map_snippet, unwrap_snippet)
&format!("replace `map({0}).unwrap_or({1})` with `map_or({1}, {0})`", map_snippet,
unwrap_snippet)
);
}
else if same_span && multiline {
@ -304,8 +339,8 @@ fn lint_map_unwrap_or(cx: &LateContext, expr: &Expr, unwrap_args: &MethodArgs,
#[allow(ptr_arg)] // Type of MethodArgs is potentially a Vec
/// lint use of `map().unwrap_or_else()` for `Option`s
fn lint_map_unwrap_or_else(cx: &LateContext, expr: &Expr, unwrap_args: &MethodArgs,
map_args: &MethodArgs) {
fn lint_map_unwrap_or_else(cx: &LateContext, expr: &Expr, map_args: &MethodArgs,
unwrap_args: &MethodArgs) {
// lint if the caller of `map()` is an `Option`
if match_type(cx, cx.tcx.expr_ty(&map_args[0]), &OPTION_PATH) {
// lint message
@ -322,7 +357,8 @@ fn lint_map_unwrap_or_else(cx: &LateContext, expr: &Expr, unwrap_args: &MethodAr
if same_span && !multiline {
span_note_and_lint(
cx, OPTION_MAP_UNWRAP_OR_ELSE, expr.span, msg, expr.span,
&format!("replace this with map_or_else({1}, {0})", map_snippet, unwrap_snippet)
&format!("replace `map({0}).unwrap_or_else({1})` with `with map_or_else({1}, {0})`",
map_snippet, unwrap_snippet)
);
}
else if same_span && multiline {
@ -331,6 +367,44 @@ fn lint_map_unwrap_or_else(cx: &LateContext, expr: &Expr, unwrap_args: &MethodAr
}
}
#[allow(ptr_arg)] // Type of MethodArgs is potentially a Vec
/// lint use of `filter().next() for Iterators`
fn lint_filter_next(cx: &LateContext, expr: &Expr, filter_args: &MethodArgs) {
// lint if caller of `.filter().next()` is an Iterator
if match_trait_method(cx, expr, &["core", "iter", "Iterator"]) {
let msg = "called `filter(p).next()` on an Iterator. This is more succinctly expressed by \
calling `.find(p)` instead.";
let filter_snippet = snippet(cx, filter_args[1].span, "..");
if filter_snippet.lines().count() <= 1 { // add note if not multi-line
span_note_and_lint(cx, FILTER_NEXT, expr.span, msg, expr.span,
&format!("replace `filter({0}).next()` with `find({0})`", filter_snippet));
}
else {
span_lint(cx, FILTER_NEXT, expr.span, msg);
}
}
}
#[allow(ptr_arg)] // Type of MethodArgs is potentially a Vec
/// lint searching an Iterator followed by `is_some()`
fn lint_search_is_some(cx: &LateContext, expr: &Expr, search_method: &str, search_args: &MethodArgs,
is_some_args: &MethodArgs) {
// lint if caller of search is an Iterator
if match_trait_method(cx, &*is_some_args[0], &["core", "iter", "Iterator"]) {
let msg = format!("called `is_some()` after searching an iterator with {}. This is more \
succinctly expressed by calling `any()`.", search_method);
let search_snippet = snippet(cx, search_args[1].span, "..");
if search_snippet.lines().count() <= 1 { // add note if not multi-line
span_note_and_lint(cx, SEARCH_IS_SOME, expr.span, &msg, expr.span,
&format!("replace `{0}({1}).is_some()` with `any({1})`", search_method,
search_snippet));
}
else {
span_lint(cx, SEARCH_IS_SOME, expr.span, &msg);
}
}
}
// Given a `Result<T, E>` type, return its error type (`E`)
fn get_error_type<'a>(cx: &LateContext, ty: ty::Ty<'a>) -> Option<ty::Ty<'a>> {
if !match_type(cx, ty, &RESULT_PATH) {

96
tests/compile-fail/methods.rs
View file

@ -50,7 +50,7 @@ fn option_methods() {
// Check OPTION_MAP_UNWRAP_OR
// single line case
let _ = opt.map(|x| x + 1) //~ ERROR called `map(f).unwrap_or(a)`
//~| NOTE replace this
//~| NOTE replace `map(|x| x + 1).unwrap_or(0)`
.unwrap_or(0); // should lint even though this call is on a separate line
// multi line cases
let _ = opt.map(|x| { //~ ERROR called `map(f).unwrap_or(a)`
@ -67,7 +67,7 @@ fn option_methods() {
// Check OPTION_MAP_UNWRAP_OR_ELSE
// single line case
let _ = opt.map(|x| x + 1) //~ ERROR called `map(f).unwrap_or_else(g)`
//~| NOTE replace this
//~| NOTE replace `map(|x| x + 1).unwrap_or_else(|| 0)`
.unwrap_or_else(|| 0); // should lint even though this call is on a separate line
// multi line cases
let _ = opt.map(|x| { //~ ERROR called `map(f).unwrap_or_else(g)`
@ -83,6 +83,98 @@ fn option_methods() {
}
/// Struct to generate false positive for Iterator-based lints
#[derive(Copy, Clone)]
struct IteratorFalsePositives {
foo: u32,
}
impl IteratorFalsePositives {
fn filter(self) -> IteratorFalsePositives {
self
}
fn next(self) -> IteratorFalsePositives {
self
}
fn find(self) -> Option<u32> {
Some(self.foo)
}
fn position(self) -> Option<u32> {
Some(self.foo)
}
fn rposition(self) -> Option<u32> {
Some(self.foo)
}
}
/// Checks implementation of FILTER_NEXT lint
fn filter_next() {
let v = vec![3, 2, 1, 0, -1, -2, -3];
// check single-line case
let _ = v.iter().filter(|&x| *x < 0).next();
//~^ ERROR called `filter(p).next()` on an Iterator.
//~| NOTE replace `filter(|&x| *x < 0).next()`
// check multi-line case
let _ = v.iter().filter(|&x| { //~ERROR called `filter(p).next()` on an Iterator.
*x < 0
}
).next();
// check that we don't lint if the caller is not an Iterator
let foo = IteratorFalsePositives { foo: 0 };
let _ = foo.filter().next();
}
/// Checks implementation of SEARCH_IS_SOME lint
fn search_is_some() {
let v = vec![3, 2, 1, 0, -1, -2, -3];
// check `find().is_some()`, single-line
let _ = v.iter().find(|&x| *x < 0).is_some();
//~^ ERROR called `is_some()` after searching
//~| NOTE replace `find(|&x| *x < 0).is_some()`
// check `find().is_some()`, multi-line
let _ = v.iter().find(|&x| { //~ERROR called `is_some()` after searching
*x < 0
}
).is_some();
// check `position().is_some()`, single-line
let _ = v.iter().position(|&x| x < 0).is_some();
//~^ ERROR called `is_some()` after searching
//~| NOTE replace `position(|&x| x < 0).is_some()`
// check `position().is_some()`, multi-line
let _ = v.iter().position(|&x| { //~ERROR called `is_some()` after searching
x < 0
}
).is_some();
// check `rposition().is_some()`, single-line
let _ = v.iter().rposition(|&x| x < 0).is_some();
//~^ ERROR called `is_some()` after searching
//~| NOTE replace `rposition(|&x| x < 0).is_some()`
// check `rposition().is_some()`, multi-line
let _ = v.iter().rposition(|&x| { //~ERROR called `is_some()` after searching
x < 0
}
).is_some();
// check that we don't lint if the caller is not an Iterator
let foo = IteratorFalsePositives { foo: 0 };
let _ = foo.find().is_some();
let _ = foo.position().is_some();
let _ = foo.rposition().is_some();
}
fn main() {
use std::io;