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Extend iter_nth lint to work with iter_mut() and VecDeque

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This commit is contained in:
Devon Hollowood 2016-06-16 14:46:29 -07:00
parent 12bc90d457
commit cfa0c5782e
2 changed files with 27 additions and 14 deletions
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2
README.md
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@ -78,7 +78,7 @@ name
[invalid_upcast_comparisons](https://github.com/Manishearth/rust-clippy/wiki#invalid_upcast_comparisons) | allow | a comparison involving an upcast which is always true or false
[items_after_statements](https://github.com/Manishearth/rust-clippy/wiki#items_after_statements) | allow | finds blocks where an item comes after a statement
[iter_next_loop](https://github.com/Manishearth/rust-clippy/wiki#iter_next_loop) | warn | for-looping over `_.next()` which is probably not intended
[iter_nth](https://github.com/Manishearth/rust-clippy/wiki#iter_nth) | warn | using `.iter().nth()` on a slice or Vec
[iter_nth](https://github.com/Manishearth/rust-clippy/wiki#iter_nth) | warn | using `.iter().nth()` on a standard library type with O(1) element access
[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

39
clippy_lints/src/methods.rs
View file

@ -312,9 +312,10 @@ declare_lint! {
"getting the inner pointer of a temporary `CString`"
}
/// **What it does:** This lint checks for use of `.iter().nth()` on a slice or Vec.
/// **What it does:** This lint checks for use of `.iter().nth()` (and the related
/// `.iter_mut().nth()`) on standard library types with O(1) element access.
///
/// **Why is this bad?** `.get()` is more efficient and more readable.
/// **Why is this bad?** `.get()` and `.get_mut()` are more efficient and more readable.
///
/// **Known problems:** None.
///
@ -333,7 +334,7 @@ declare_lint! {
declare_lint! {
pub ITER_NTH,
Warn,
"using `.iter().nth()` on a slice or Vec"
"using `.iter().nth()` on a standard library type with O(1) element access"
}
impl LintPass for Pass {
@ -389,7 +390,9 @@ impl LateLintPass for Pass {
} else if let Some(arglists) = method_chain_args(expr, &["unwrap", "as_ptr"]) {
lint_cstring_as_ptr(cx, expr, &arglists[0][0], &arglists[1][0]);
} else if let Some(arglists) = method_chain_args(expr, &["iter", "nth"]) {
lint_iter_nth(cx, expr, arglists[0]);
lint_iter_nth(cx, expr, arglists[0], false);
} else if let Some(arglists) = method_chain_args(expr, &["iter_mut", "nth"]) {
lint_iter_nth(cx, expr, arglists[0], true);
}
lint_or_fun_call(cx, expr, &name.node.as_str(), args);
@ -645,21 +648,31 @@ fn lint_cstring_as_ptr(cx: &LateContext, expr: &hir::Expr, new: &hir::Expr, unwr
#[allow(ptr_arg)]
// Type of MethodArgs is potentially a Vec
fn lint_iter_nth(cx: &LateContext, expr: &hir::Expr, iter_args: &MethodArgs){
fn lint_iter_nth(cx: &LateContext, expr: &hir::Expr, iter_args: &MethodArgs, is_mut: bool){
// lint if the caller of `.iter().nth()` is a `slice`
let caller_type;
let mut_str = if is_mut { "_mut" } else {""};
if let Some(_) = derefs_to_slice(cx, &iter_args[0], &cx.tcx.expr_ty(&iter_args[0])) {
span_lint(cx,
ITER_NTH,
expr.span,
"called `.iter().nth()` on a slice. Calling `.get()` is both faster and more readable");
caller_type = "slice";
}
// lint if the caller of `.iter().nth()` is a `Vec`
else if match_type(cx, cx.tcx.expr_ty(&iter_args[0]), &paths::VEC) {
span_lint(cx,
ITER_NTH,
expr.span,
"called `.iter().nth()` on a Vec. Calling `.get()` is both faster and more readable");
caller_type = "Vec";
}
// lint if the caller of `.iter().nth()` is a `VecDeque`
else if match_type(cx, cx.tcx.expr_ty(&iter_args[0]), &paths::VEC_DEQUE) {
caller_type = "VecDeque";
}
else {
return; // caller is not a type that we want to lint
}
span_lint(
cx,
ITER_NTH,
expr.span,
&format!("called `.iter{0}().nth()` on a {1}. Calling `.get{0}()` is both faster and more readable",
mut_str, caller_type)
);
}
fn derefs_to_slice(cx: &LateContext, expr: &hir::Expr, ty: &ty::Ty) -> Option<(Span, &'static str)> {