973 lines
38 KiB
Rust
973 lines
38 KiB
Rust
use reexport::*;
|
||
use rustc::front::map::Node::NodeBlock;
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use rustc::lint::*;
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use rustc::middle::const_eval::EvalHint::ExprTypeChecked;
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use rustc::middle::const_eval::{ConstVal, eval_const_expr_partial};
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use rustc::middle::def::Def;
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use rustc::middle::region::CodeExtent;
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use rustc::ty;
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use rustc_front::hir::*;
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use rustc_front::intravisit::{Visitor, walk_expr, walk_block, walk_decl};
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use std::borrow::Cow;
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use std::collections::HashMap;
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use syntax::ast;
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use utils::{snippet, span_lint, get_parent_expr, match_trait_method, match_type, in_external_macro,
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span_help_and_lint, is_integer_literal, get_enclosing_block, span_lint_and_then,
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unsugar_range, walk_ptrs_ty, recover_for_loop};
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use utils::{BTREEMAP_PATH, HASHMAP_PATH, LL_PATH, OPTION_PATH, RESULT_PATH, VEC_PATH};
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use utils::UnsugaredRange;
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/// **What it does:** This lint checks for looping over the range of `0..len` of some collection just to get the values by index.
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///
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/// **Why is this bad?** Just iterating the collection itself makes the intent more clear and is probably faster.
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///
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/// **Known problems:** None
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///
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/// **Example:**
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/// ```
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/// for i in 0..vec.len() {
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/// println!("{}", vec[i]);
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/// }
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/// ```
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declare_lint! {
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pub NEEDLESS_RANGE_LOOP,
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Warn,
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"for-looping over a range of indices where an iterator over items would do"
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}
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/// **What it does:** This lint checks for loops on `x.iter()` where `&x` will do, and suggest the latter.
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///
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/// **Why is this bad?** Readability.
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///
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/// **Known problems:** False negatives. We currently only warn on some known types.
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///
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/// **Example:** `for x in y.iter() { .. }` (where y is a `Vec` or slice)
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declare_lint! {
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pub EXPLICIT_ITER_LOOP,
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Warn,
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"for-looping over `_.iter()` or `_.iter_mut()` when `&_` or `&mut _` would do"
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}
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/// **What it does:** This lint checks for loops on `x.next()`.
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///
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/// **Why is this bad?** `next()` returns either `Some(value)` if there was a value, or `None` otherwise. The insidious thing is that `Option<_>` implements `IntoIterator`, so that possibly one value will be iterated, leading to some hard to find bugs. No one will want to write such code [except to win an Underhanded Rust Contest](https://www.reddit.com/r/rust/comments/3hb0wm/underhanded_rust_contest/cu5yuhr).
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///
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/// **Known problems:** None
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///
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/// **Example:** `for x in y.next() { .. }`
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declare_lint! {
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pub ITER_NEXT_LOOP,
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Warn,
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"for-looping over `_.next()` which is probably not intended"
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}
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/// **What it does:** This lint checks for `for` loops over `Option` values.
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///
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/// **Why is this bad?** Readability. This is more clearly expressed as an `if let`.
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///
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/// **Known problems:** None
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///
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/// **Example:** `for x in option { .. }`. This should be `if let Some(x) = option { .. }`.
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declare_lint! {
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pub FOR_LOOP_OVER_OPTION,
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Warn,
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"for-looping over an `Option`, which is more clearly expressed as an `if let`"
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}
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/// **What it does:** This lint checks for `for` loops over `Result` values.
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///
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/// **Why is this bad?** Readability. This is more clearly expressed as an `if let`.
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///
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/// **Known problems:** None
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///
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/// **Example:** `for x in result { .. }`. This should be `if let Ok(x) = result { .. }`.
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declare_lint! {
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pub FOR_LOOP_OVER_RESULT,
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Warn,
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"for-looping over a `Result`, which is more clearly expressed as an `if let`"
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}
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/// **What it does:** This lint detects `loop + match` combinations that are easier written as a `while let` loop.
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///
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/// **Why is this bad?** The `while let` loop is usually shorter and more readable
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///
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/// **Known problems:** Sometimes the wrong binding is displayed (#383)
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///
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/// **Example:**
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///
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/// ```
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/// loop {
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/// let x = match y {
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/// Some(x) => x,
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/// None => break,
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/// }
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/// // .. do something with x
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/// }
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/// // is easier written as
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/// while let Some(x) = y {
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/// // .. do something with x
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/// }
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/// ```
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declare_lint! {
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pub WHILE_LET_LOOP,
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Warn,
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"`loop { if let { ... } else break }` can be written as a `while let` loop"
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}
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/// **What it does:** This lint checks for using `collect()` on an iterator without using the result.
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///
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/// **Why is this bad?** It is more idiomatic to use a `for` loop over the iterator instead.
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///
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/// **Known problems:** None
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///
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/// **Example:** `vec.iter().map(|x| /* some operation returning () */).collect::<Vec<_>>();`
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declare_lint! {
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pub UNUSED_COLLECT,
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Warn,
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"`collect()`ing an iterator without using the result; this is usually better \
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written as a for loop"
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}
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/// **What it does:** This lint checks for loops over ranges `x..y` where both `x` and `y` are constant and `x` is greater or equal to `y`, unless the range is reversed or has a negative `.step_by(_)`.
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///
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/// **Why is it bad?** Such loops will either be skipped or loop until wrap-around (in debug code, this may `panic!()`). Both options are probably not intended.
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///
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/// **Known problems:** The lint cannot catch loops over dynamically defined ranges. Doing this would require simulating all possible inputs and code paths through the program, which would be complex and error-prone.
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///
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/// **Examples**: `for x in 5..10-5 { .. }` (oops, stray `-`)
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declare_lint! {
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pub REVERSE_RANGE_LOOP,
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Warn,
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"Iterating over an empty range, such as `10..0` or `5..5`"
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}
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/// **What it does:** This lint checks `for` loops over slices with an explicit counter and suggests the use of `.enumerate()`.
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///
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/// **Why is it bad?** Not only is the version using `.enumerate()` more readable, the compiler is able to remove bounds checks which can lead to faster code in some instances.
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///
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/// **Known problems:** None.
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///
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/// **Example:** `for i in 0..v.len() { foo(v[i]); }` or `for i in 0..v.len() { bar(i, v[i]); }`
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declare_lint! {
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pub EXPLICIT_COUNTER_LOOP,
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Warn,
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"for-looping with an explicit counter when `_.enumerate()` would do"
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}
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/// **What it does:** This lint checks for empty `loop` expressions.
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///
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/// **Why is this bad?** Those busy loops burn CPU cycles without doing anything. Think of the environment and either block on something or at least make the thread sleep for some microseconds.
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///
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/// **Known problems:** None
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///
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/// **Example:** `loop {}`
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declare_lint! {
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pub EMPTY_LOOP,
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Warn,
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"empty `loop {}` detected"
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}
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/// **What it does:** This lint checks for `while let` expressions on iterators.
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///
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/// **Why is this bad?** Readability. A simple `for` loop is shorter and conveys the intent better.
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///
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/// **Known problems:** None
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///
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/// **Example:** `while let Some(val) = iter() { .. }`
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declare_lint! {
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pub WHILE_LET_ON_ITERATOR,
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Warn,
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"using a while-let loop instead of a for loop on an iterator"
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}
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/// **What it does:** This warns when you iterate on a map (`HashMap` or `BTreeMap`) and ignore
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/// either the keys or values.
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///
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/// **Why is this bad?** Readability. There are `keys` and `values` methods that can be used to
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/// express that don't need the values or keys.
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///
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/// **Known problems:** None
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||
///
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/// **Example:**
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/// ```rust
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/// for (k, _) in &map { .. }
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/// ```
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/// could be replaced by
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/// ```rust
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/// for k in map.keys() { .. }
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/// ```
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declare_lint! {
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pub FOR_KV_MAP,
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Warn,
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"looping on a map using `iter` when `keys` or `values` would do"
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}
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#[derive(Copy, Clone)]
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pub struct LoopsPass;
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impl LintPass for LoopsPass {
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fn get_lints(&self) -> LintArray {
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lint_array!(NEEDLESS_RANGE_LOOP,
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EXPLICIT_ITER_LOOP,
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ITER_NEXT_LOOP,
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WHILE_LET_LOOP,
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UNUSED_COLLECT,
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REVERSE_RANGE_LOOP,
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EXPLICIT_COUNTER_LOOP,
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EMPTY_LOOP,
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WHILE_LET_ON_ITERATOR,
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FOR_KV_MAP)
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}
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}
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impl LateLintPass for LoopsPass {
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fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
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if let Some((pat, arg, body)) = recover_for_loop(expr) {
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check_for_loop(cx, pat, arg, body, expr);
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}
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// check for `loop { if let {} else break }` that could be `while let`
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// (also matches an explicit "match" instead of "if let")
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// (even if the "match" or "if let" is used for declaration)
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if let ExprLoop(ref block, _) = expr.node {
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// also check for empty `loop {}` statements
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if block.stmts.is_empty() && block.expr.is_none() {
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span_lint(cx,
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EMPTY_LOOP,
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expr.span,
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"empty `loop {}` detected. You may want to either use `panic!()` or add \
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`std::thread::sleep(..);` to the loop body.");
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}
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||
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||
// extract the expression from the first statement (if any) in a block
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let inner_stmt_expr = extract_expr_from_first_stmt(block);
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||
// or extract the first expression (if any) from the block
|
||
if let Some(inner) = inner_stmt_expr.or_else(|| extract_first_expr(block)) {
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||
if let ExprMatch(ref matchexpr, ref arms, ref source) = inner.node {
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||
// ensure "if let" compatible match structure
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match *source {
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MatchSource::Normal | MatchSource::IfLetDesugar{..} => {
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if arms.len() == 2 && arms[0].pats.len() == 1 && arms[0].guard.is_none() &&
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arms[1].pats.len() == 1 && arms[1].guard.is_none() &&
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is_break_expr(&arms[1].body) {
|
||
if in_external_macro(cx, expr.span) {
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||
return;
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||
}
|
||
|
||
// NOTE: we used to make build a body here instead of using
|
||
// ellipsis, this was removed because:
|
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// 1) it was ugly with big bodies;
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||
// 2) it was not indented properly;
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||
// 3) it wasn’t very smart (see #675).
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span_lint_and_then(cx,
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WHILE_LET_LOOP,
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expr.span,
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"this loop could be written as a `while let` loop",
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|db| {
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let sug = format!("while let {} = {} {{ .. }}",
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snippet(cx, arms[0].pats[0].span, ".."),
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||
snippet(cx, matchexpr.span, ".."));
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||
db.span_suggestion(expr.span, "try", sug);
|
||
});
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||
}
|
||
}
|
||
_ => (),
|
||
}
|
||
}
|
||
}
|
||
}
|
||
if let ExprMatch(ref match_expr, ref arms, MatchSource::WhileLetDesugar) = expr.node {
|
||
let pat = &arms[0].pats[0].node;
|
||
if let (&PatKind::TupleStruct(ref path, Some(ref pat_args)),
|
||
&ExprMethodCall(method_name, _, ref method_args)) = (pat, &match_expr.node) {
|
||
let iter_expr = &method_args[0];
|
||
if let Some(lhs_constructor) = path.segments.last() {
|
||
if method_name.node.as_str() == "next" &&
|
||
match_trait_method(cx, match_expr, &["core", "iter", "Iterator"]) &&
|
||
lhs_constructor.identifier.name.as_str() == "Some" &&
|
||
!is_iterator_used_after_while_let(cx, iter_expr) {
|
||
let iterator = snippet(cx, method_args[0].span, "_");
|
||
let loop_var = snippet(cx, pat_args[0].span, "_");
|
||
span_help_and_lint(cx,
|
||
WHILE_LET_ON_ITERATOR,
|
||
expr.span,
|
||
"this loop could be written as a `for` loop",
|
||
&format!("try\nfor {} in {} {{...}}", loop_var, iterator));
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
fn check_stmt(&mut self, cx: &LateContext, stmt: &Stmt) {
|
||
if let StmtSemi(ref expr, _) = stmt.node {
|
||
if let ExprMethodCall(ref method, _, ref args) = expr.node {
|
||
if args.len() == 1 && method.node.as_str() == "collect" &&
|
||
match_trait_method(cx, expr, &["core", "iter", "Iterator"]) {
|
||
span_lint(cx,
|
||
UNUSED_COLLECT,
|
||
expr.span,
|
||
"you are collect()ing an iterator and throwing away the result. \
|
||
Consider using an explicit for loop to exhaust the iterator");
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
fn check_for_loop(cx: &LateContext, pat: &Pat, arg: &Expr, body: &Expr, expr: &Expr) {
|
||
check_for_loop_range(cx, pat, arg, body, expr);
|
||
check_for_loop_reverse_range(cx, arg, expr);
|
||
check_for_loop_arg(cx, pat, arg, expr);
|
||
check_for_loop_explicit_counter(cx, arg, body, expr);
|
||
check_for_loop_over_map_kv(cx, pat, arg, body, expr);
|
||
}
|
||
|
||
/// Check for looping over a range and then indexing a sequence with it.
|
||
/// The iteratee must be a range literal.
|
||
fn check_for_loop_range(cx: &LateContext, pat: &Pat, arg: &Expr, body: &Expr, expr: &Expr) {
|
||
if let Some(UnsugaredRange { start: Some(ref start), ref end, .. }) = unsugar_range(&arg) {
|
||
// the var must be a single name
|
||
if let PatKind::Ident(_, ref ident, _) = pat.node {
|
||
let mut visitor = VarVisitor {
|
||
cx: cx,
|
||
var: ident.node.name,
|
||
indexed: HashMap::new(),
|
||
nonindex: false,
|
||
};
|
||
walk_expr(&mut visitor, body);
|
||
|
||
// linting condition: we only indexed one variable
|
||
if visitor.indexed.len() == 1 {
|
||
let (indexed, indexed_extent) = visitor.indexed
|
||
.into_iter()
|
||
.next()
|
||
.unwrap_or_else(|| unreachable!() /* len == 1 */);
|
||
|
||
// ensure that the indexed variable was declared before the loop, see #601
|
||
if let Some(indexed_extent) = indexed_extent {
|
||
let pat_extent = cx.tcx.region_maps.var_scope(pat.id);
|
||
if cx.tcx.region_maps.is_subscope_of(indexed_extent, pat_extent) {
|
||
return;
|
||
}
|
||
}
|
||
|
||
let starts_at_zero = is_integer_literal(start, 0);
|
||
|
||
let skip: Cow<_> = if starts_at_zero {
|
||
"".into()
|
||
} else {
|
||
format!(".skip({})", snippet(cx, start.span, "..")).into()
|
||
};
|
||
|
||
let take: Cow<_> = if let Some(ref end) = *end {
|
||
if is_len_call(&end, &indexed) {
|
||
"".into()
|
||
} else {
|
||
format!(".take({})", snippet(cx, end.span, "..")).into()
|
||
}
|
||
} else {
|
||
"".into()
|
||
};
|
||
|
||
if visitor.nonindex {
|
||
span_lint(cx,
|
||
NEEDLESS_RANGE_LOOP,
|
||
expr.span,
|
||
&format!("the loop variable `{}` is used to index `{}`. Consider using `for ({}, \
|
||
item) in {}.iter().enumerate(){}{}` or similar iterators",
|
||
ident.node.name,
|
||
indexed,
|
||
ident.node.name,
|
||
indexed,
|
||
take,
|
||
skip));
|
||
} else {
|
||
let repl = if starts_at_zero && take.is_empty() {
|
||
format!("&{}", indexed)
|
||
} else {
|
||
format!("{}.iter(){}{}", indexed, take, skip)
|
||
};
|
||
|
||
span_lint(cx,
|
||
NEEDLESS_RANGE_LOOP,
|
||
expr.span,
|
||
&format!("the loop variable `{}` is only used to index `{}`. \
|
||
Consider using `for item in {}` or similar iterators",
|
||
ident.node.name,
|
||
indexed,
|
||
repl));
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
fn is_len_call(expr: &Expr, var: &Name) -> bool {
|
||
if_let_chain! {[
|
||
let ExprMethodCall(method, _, ref len_args) = expr.node,
|
||
len_args.len() == 1,
|
||
method.node.as_str() == "len",
|
||
let ExprPath(_, ref path) = len_args[0].node,
|
||
path.segments.len() == 1,
|
||
&path.segments[0].identifier.name == var
|
||
], {
|
||
return true;
|
||
}}
|
||
|
||
false
|
||
}
|
||
|
||
fn check_for_loop_reverse_range(cx: &LateContext, arg: &Expr, expr: &Expr) {
|
||
// if this for loop is iterating over a two-sided range...
|
||
if let Some(UnsugaredRange { start: Some(ref start), end: Some(ref end), limits }) = unsugar_range(&arg) {
|
||
// ...and both sides are compile-time constant integers...
|
||
if let Ok(start_idx) = eval_const_expr_partial(&cx.tcx, start, ExprTypeChecked, None) {
|
||
if let Ok(end_idx) = eval_const_expr_partial(&cx.tcx, end, ExprTypeChecked, None) {
|
||
// ...and the start index is greater than the end index,
|
||
// this loop will never run. This is often confusing for developers
|
||
// who think that this will iterate from the larger value to the
|
||
// smaller value.
|
||
let (sup, eq) = match (start_idx, end_idx) {
|
||
(ConstVal::Integral(start_idx), ConstVal::Integral(end_idx)) => {
|
||
(start_idx > end_idx, start_idx == end_idx)
|
||
}
|
||
_ => (false, false),
|
||
};
|
||
|
||
if sup {
|
||
let start_snippet = snippet(cx, start.span, "_");
|
||
let end_snippet = snippet(cx, end.span, "_");
|
||
|
||
span_lint_and_then(cx,
|
||
REVERSE_RANGE_LOOP,
|
||
expr.span,
|
||
"this range is empty so this for loop will never run",
|
||
|db| {
|
||
db.span_suggestion(expr.span,
|
||
"consider using the following if \
|
||
you are attempting to iterate \
|
||
over this range in reverse",
|
||
format!("({}..{}).rev()` ", end_snippet, start_snippet));
|
||
});
|
||
} else if eq && limits != ast::RangeLimits::Closed {
|
||
// if they are equal, it's also problematic - this loop
|
||
// will never run.
|
||
span_lint(cx,
|
||
REVERSE_RANGE_LOOP,
|
||
expr.span,
|
||
"this range is empty so this for loop will never run");
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
fn check_for_loop_arg(cx: &LateContext, pat: &Pat, arg: &Expr, expr: &Expr) {
|
||
let mut next_loop_linted = false; // whether or not ITER_NEXT_LOOP lint was used
|
||
if let ExprMethodCall(ref method, _, ref args) = arg.node {
|
||
// just the receiver, no arguments
|
||
if args.len() == 1 {
|
||
let method_name = method.node;
|
||
// check for looping over x.iter() or x.iter_mut(), could use &x or &mut x
|
||
if method_name.as_str() == "iter" || method_name.as_str() == "iter_mut" {
|
||
if is_ref_iterable_type(cx, &args[0]) {
|
||
let object = snippet(cx, args[0].span, "_");
|
||
span_lint(cx,
|
||
EXPLICIT_ITER_LOOP,
|
||
expr.span,
|
||
&format!("it is more idiomatic to loop over `&{}{}` instead of `{}.{}()`",
|
||
if method_name.as_str() == "iter_mut" {
|
||
"mut "
|
||
} else {
|
||
""
|
||
},
|
||
object,
|
||
object,
|
||
method_name));
|
||
}
|
||
} else if method_name.as_str() == "next" && match_trait_method(cx, arg, &["core", "iter", "Iterator"]) {
|
||
span_lint(cx,
|
||
ITER_NEXT_LOOP,
|
||
expr.span,
|
||
"you are iterating over `Iterator::next()` which is an Option; this will compile but is \
|
||
probably not what you want");
|
||
next_loop_linted = true;
|
||
}
|
||
}
|
||
}
|
||
if !next_loop_linted {
|
||
check_arg_type(cx, pat, arg);
|
||
}
|
||
}
|
||
|
||
/// Check for `for` loops over `Option`s and `Results`
|
||
fn check_arg_type(cx: &LateContext, pat: &Pat, arg: &Expr) {
|
||
let ty = cx.tcx.expr_ty(arg);
|
||
if match_type(cx, ty, &OPTION_PATH) {
|
||
span_help_and_lint(cx,
|
||
FOR_LOOP_OVER_OPTION,
|
||
arg.span,
|
||
&format!("for loop over `{0}`, which is an `Option`. This is more readably written as an \
|
||
`if let` statement.",
|
||
snippet(cx, arg.span, "_")),
|
||
&format!("consider replacing `for {0} in {1}` with `if let Some({0}) = {1}`",
|
||
snippet(cx, pat.span, "_"),
|
||
snippet(cx, arg.span, "_")));
|
||
} else if match_type(cx, ty, &RESULT_PATH) {
|
||
span_help_and_lint(cx,
|
||
FOR_LOOP_OVER_RESULT,
|
||
arg.span,
|
||
&format!("for loop over `{0}`, which is a `Result`. This is more readably written as an \
|
||
`if let` statement.",
|
||
snippet(cx, arg.span, "_")),
|
||
&format!("consider replacing `for {0} in {1}` with `if let Ok({0}) = {1}`",
|
||
snippet(cx, pat.span, "_"),
|
||
snippet(cx, arg.span, "_")));
|
||
}
|
||
}
|
||
|
||
fn check_for_loop_explicit_counter(cx: &LateContext, arg: &Expr, body: &Expr, expr: &Expr) {
|
||
// Look for variables that are incremented once per loop iteration.
|
||
let mut visitor = IncrementVisitor {
|
||
cx: cx,
|
||
states: HashMap::new(),
|
||
depth: 0,
|
||
done: false,
|
||
};
|
||
walk_expr(&mut visitor, body);
|
||
|
||
// For each candidate, check the parent block to see if
|
||
// it's initialized to zero at the start of the loop.
|
||
let map = &cx.tcx.map;
|
||
let parent_scope = map.get_enclosing_scope(expr.id).and_then(|id| map.get_enclosing_scope(id));
|
||
if let Some(parent_id) = parent_scope {
|
||
if let NodeBlock(block) = map.get(parent_id) {
|
||
for (id, _) in visitor.states.iter().filter(|&(_, v)| *v == VarState::IncrOnce) {
|
||
let mut visitor2 = InitializeVisitor {
|
||
cx: cx,
|
||
end_expr: expr,
|
||
var_id: *id,
|
||
state: VarState::IncrOnce,
|
||
name: None,
|
||
depth: 0,
|
||
past_loop: false,
|
||
};
|
||
walk_block(&mut visitor2, block);
|
||
|
||
if visitor2.state == VarState::Warn {
|
||
if let Some(name) = visitor2.name {
|
||
span_lint(cx,
|
||
EXPLICIT_COUNTER_LOOP,
|
||
expr.span,
|
||
&format!("the variable `{0}` is used as a loop counter. Consider using `for ({0}, \
|
||
item) in {1}.enumerate()` or similar iterators",
|
||
name,
|
||
snippet(cx, arg.span, "_")));
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Check for the `FOR_KV_MAP` lint.
|
||
fn check_for_loop_over_map_kv(cx: &LateContext, pat: &Pat, arg: &Expr, body: &Expr, expr: &Expr) {
|
||
if let PatKind::Tup(ref pat) = pat.node {
|
||
if pat.len() == 2 {
|
||
let (pat_span, kind) = match (&pat[0].node, &pat[1].node) {
|
||
(key, _) if pat_is_wild(key, body) => (&pat[1].span, "values"),
|
||
(_, value) if pat_is_wild(value, body) => (&pat[0].span, "keys"),
|
||
_ => return,
|
||
};
|
||
|
||
let arg_span = match arg.node {
|
||
ExprAddrOf(MutImmutable, ref expr) => expr.span,
|
||
ExprAddrOf(MutMutable, _) => return, // for _ in &mut _, there is no {values,keys}_mut method
|
||
_ => arg.span,
|
||
};
|
||
|
||
let ty = walk_ptrs_ty(cx.tcx.expr_ty(arg));
|
||
if match_type(cx, ty, &HASHMAP_PATH) || match_type(cx, ty, &BTREEMAP_PATH) {
|
||
span_lint_and_then(cx,
|
||
FOR_KV_MAP,
|
||
expr.span,
|
||
&format!("you seem to want to iterate on a map's {}", kind),
|
||
|db| {
|
||
db.span_suggestion(expr.span,
|
||
"use the corresponding method",
|
||
format!("for {} in {}.{}() {{...}}",
|
||
snippet(cx, *pat_span, ".."),
|
||
snippet(cx, arg_span, ".."),
|
||
kind));
|
||
});
|
||
}
|
||
}
|
||
}
|
||
|
||
}
|
||
|
||
/// Return true if the pattern is a `PatWild` or an ident prefixed with `'_'`.
|
||
fn pat_is_wild(pat: &PatKind, body: &Expr) -> bool {
|
||
match *pat {
|
||
PatKind::Wild => true,
|
||
PatKind::Ident(_, ident, None) if ident.node.name.as_str().starts_with('_') => {
|
||
let mut visitor = UsedVisitor {
|
||
var: ident.node,
|
||
used: false,
|
||
};
|
||
walk_expr(&mut visitor, body);
|
||
!visitor.used
|
||
}
|
||
_ => false,
|
||
}
|
||
}
|
||
|
||
struct UsedVisitor {
|
||
var: Ident, // var to look for
|
||
used: bool, // has the var been used otherwise?
|
||
}
|
||
|
||
impl<'a> Visitor<'a> for UsedVisitor {
|
||
fn visit_expr(&mut self, expr: &Expr) {
|
||
if let ExprPath(None, ref path) = expr.node {
|
||
if path.segments.len() == 1 && path.segments[0].identifier == self.var {
|
||
self.used = true;
|
||
return;
|
||
}
|
||
}
|
||
|
||
walk_expr(self, expr);
|
||
}
|
||
}
|
||
|
||
struct VarVisitor<'v, 't: 'v> {
|
||
cx: &'v LateContext<'v, 't>, // context reference
|
||
var: Name, // var name to look for as index
|
||
indexed: HashMap<Name, Option<CodeExtent>>, // indexed variables, the extent is None for global
|
||
nonindex: bool, // has the var been used otherwise?
|
||
}
|
||
|
||
impl<'v, 't> Visitor<'v> for VarVisitor<'v, 't> {
|
||
fn visit_expr(&mut self, expr: &'v Expr) {
|
||
if let ExprPath(None, ref path) = expr.node {
|
||
if path.segments.len() == 1 && path.segments[0].identifier.name == self.var {
|
||
// we are referencing our variable! now check if it's as an index
|
||
if_let_chain! {
|
||
[
|
||
let Some(parexpr) = get_parent_expr(self.cx, expr),
|
||
let ExprIndex(ref seqexpr, _) = parexpr.node,
|
||
let ExprPath(None, ref seqvar) = seqexpr.node,
|
||
seqvar.segments.len() == 1
|
||
], {
|
||
let def_map = self.cx.tcx.def_map.borrow();
|
||
if let Some(def) = def_map.get(&seqexpr.id) {
|
||
match def.base_def {
|
||
Def::Local(..) | Def::Upvar(..) => {
|
||
let extent = self.cx.tcx.region_maps.var_scope(def.base_def.var_id());
|
||
self.indexed.insert(seqvar.segments[0].identifier.name, Some(extent));
|
||
return; // no need to walk further
|
||
}
|
||
Def::Static(..) | Def::Const(..) => {
|
||
self.indexed.insert(seqvar.segments[0].identifier.name, None);
|
||
return; // no need to walk further
|
||
}
|
||
_ => (),
|
||
}
|
||
}
|
||
}
|
||
}
|
||
// we are not indexing anything, record that
|
||
self.nonindex = true;
|
||
return;
|
||
}
|
||
}
|
||
walk_expr(self, expr);
|
||
}
|
||
}
|
||
|
||
fn is_iterator_used_after_while_let(cx: &LateContext, iter_expr: &Expr) -> bool {
|
||
let def_id = match var_def_id(cx, iter_expr) {
|
||
Some(id) => id,
|
||
None => return false,
|
||
};
|
||
let mut visitor = VarUsedAfterLoopVisitor {
|
||
cx: cx,
|
||
def_id: def_id,
|
||
iter_expr_id: iter_expr.id,
|
||
past_while_let: false,
|
||
var_used_after_while_let: false,
|
||
};
|
||
if let Some(enclosing_block) = get_enclosing_block(cx, def_id) {
|
||
walk_block(&mut visitor, enclosing_block);
|
||
}
|
||
visitor.var_used_after_while_let
|
||
}
|
||
|
||
struct VarUsedAfterLoopVisitor<'v, 't: 'v> {
|
||
cx: &'v LateContext<'v, 't>,
|
||
def_id: NodeId,
|
||
iter_expr_id: NodeId,
|
||
past_while_let: bool,
|
||
var_used_after_while_let: bool,
|
||
}
|
||
|
||
impl<'v, 't> Visitor<'v> for VarUsedAfterLoopVisitor<'v, 't> {
|
||
fn visit_expr(&mut self, expr: &'v Expr) {
|
||
if self.past_while_let {
|
||
if Some(self.def_id) == var_def_id(self.cx, expr) {
|
||
self.var_used_after_while_let = true;
|
||
}
|
||
} else if self.iter_expr_id == expr.id {
|
||
self.past_while_let = true;
|
||
}
|
||
walk_expr(self, expr);
|
||
}
|
||
}
|
||
|
||
|
||
/// Return true if the type of expr is one that provides `IntoIterator` impls
|
||
/// for `&T` and `&mut T`, such as `Vec`.
|
||
#[cfg_attr(rustfmt, rustfmt_skip)]
|
||
fn is_ref_iterable_type(cx: &LateContext, e: &Expr) -> bool {
|
||
// no walk_ptrs_ty: calling iter() on a reference can make sense because it
|
||
// will allow further borrows afterwards
|
||
let ty = cx.tcx.expr_ty(e);
|
||
is_iterable_array(ty) ||
|
||
match_type(cx, ty, &VEC_PATH) ||
|
||
match_type(cx, ty, &LL_PATH) ||
|
||
match_type(cx, ty, &HASHMAP_PATH) ||
|
||
match_type(cx, ty, &["std", "collections", "hash", "set", "HashSet"]) ||
|
||
match_type(cx, ty, &["collections", "vec_deque", "VecDeque"]) ||
|
||
match_type(cx, ty, &["collections", "binary_heap", "BinaryHeap"]) ||
|
||
match_type(cx, ty, &BTREEMAP_PATH) ||
|
||
match_type(cx, ty, &["collections", "btree", "set", "BTreeSet"])
|
||
}
|
||
|
||
fn is_iterable_array(ty: ty::Ty) -> bool {
|
||
// IntoIterator is currently only implemented for array sizes <= 32 in rustc
|
||
match ty.sty {
|
||
ty::TyArray(_, 0...32) => true,
|
||
_ => false,
|
||
}
|
||
}
|
||
|
||
/// If a block begins with a statement (possibly a `let` binding) and has an expression, return it.
|
||
fn extract_expr_from_first_stmt(block: &Block) -> Option<&Expr> {
|
||
if block.stmts.is_empty() {
|
||
return None;
|
||
}
|
||
if let StmtDecl(ref decl, _) = block.stmts[0].node {
|
||
if let DeclLocal(ref local) = decl.node {
|
||
if let Some(ref expr) = local.init {
|
||
Some(expr)
|
||
} else {
|
||
None
|
||
}
|
||
} else {
|
||
None
|
||
}
|
||
} else {
|
||
None
|
||
}
|
||
}
|
||
|
||
/// If a block begins with an expression (with or without semicolon), return it.
|
||
fn extract_first_expr(block: &Block) -> Option<&Expr> {
|
||
match block.expr {
|
||
Some(ref expr) => Some(expr),
|
||
None if !block.stmts.is_empty() => {
|
||
match block.stmts[0].node {
|
||
StmtExpr(ref expr, _) | StmtSemi(ref expr, _) => Some(expr),
|
||
_ => None,
|
||
}
|
||
}
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
/// Return true if expr contains a single break expr (maybe within a block).
|
||
fn is_break_expr(expr: &Expr) -> bool {
|
||
match expr.node {
|
||
ExprBreak(None) => true,
|
||
// there won't be a `let <pat> = break` and so we can safely ignore the StmtDecl case
|
||
ExprBlock(ref b) => {
|
||
match extract_first_expr(b) {
|
||
Some(ref subexpr) => is_break_expr(subexpr),
|
||
None => false,
|
||
}
|
||
}
|
||
_ => false,
|
||
}
|
||
}
|
||
|
||
// To trigger the EXPLICIT_COUNTER_LOOP lint, a variable must be
|
||
// incremented exactly once in the loop body, and initialized to zero
|
||
// at the start of the loop.
|
||
#[derive(PartialEq)]
|
||
enum VarState {
|
||
Initial, // Not examined yet
|
||
IncrOnce, // Incremented exactly once, may be a loop counter
|
||
Declared, // Declared but not (yet) initialized to zero
|
||
Warn,
|
||
DontWarn,
|
||
}
|
||
|
||
/// Scan a for loop for variables that are incremented exactly once.
|
||
struct IncrementVisitor<'v, 't: 'v> {
|
||
cx: &'v LateContext<'v, 't>, // context reference
|
||
states: HashMap<NodeId, VarState>, // incremented variables
|
||
depth: u32, // depth of conditional expressions
|
||
done: bool,
|
||
}
|
||
|
||
impl<'v, 't> Visitor<'v> for IncrementVisitor<'v, 't> {
|
||
fn visit_expr(&mut self, expr: &'v Expr) {
|
||
if self.done {
|
||
return;
|
||
}
|
||
|
||
// If node is a variable
|
||
if let Some(def_id) = var_def_id(self.cx, expr) {
|
||
if let Some(parent) = get_parent_expr(self.cx, expr) {
|
||
let state = self.states.entry(def_id).or_insert(VarState::Initial);
|
||
|
||
match parent.node {
|
||
ExprAssignOp(op, ref lhs, ref rhs) => {
|
||
if lhs.id == expr.id {
|
||
if op.node == BiAdd && is_integer_literal(rhs, 1) {
|
||
*state = match *state {
|
||
VarState::Initial if self.depth == 0 => VarState::IncrOnce,
|
||
_ => VarState::DontWarn,
|
||
};
|
||
} else {
|
||
// Assigned some other value
|
||
*state = VarState::DontWarn;
|
||
}
|
||
}
|
||
}
|
||
ExprAssign(ref lhs, _) if lhs.id == expr.id => *state = VarState::DontWarn,
|
||
ExprAddrOf(mutability, _) if mutability == MutMutable => *state = VarState::DontWarn,
|
||
_ => (),
|
||
}
|
||
}
|
||
} else if is_loop(expr) {
|
||
self.states.clear();
|
||
self.done = true;
|
||
return;
|
||
} else if is_conditional(expr) {
|
||
self.depth += 1;
|
||
walk_expr(self, expr);
|
||
self.depth -= 1;
|
||
return;
|
||
}
|
||
walk_expr(self, expr);
|
||
}
|
||
}
|
||
|
||
/// Check whether a variable is initialized to zero at the start of a loop.
|
||
struct InitializeVisitor<'v, 't: 'v> {
|
||
cx: &'v LateContext<'v, 't>, // context reference
|
||
end_expr: &'v Expr, // the for loop. Stop scanning here.
|
||
var_id: NodeId,
|
||
state: VarState,
|
||
name: Option<Name>,
|
||
depth: u32, // depth of conditional expressions
|
||
past_loop: bool,
|
||
}
|
||
|
||
impl<'v, 't> Visitor<'v> for InitializeVisitor<'v, 't> {
|
||
fn visit_decl(&mut self, decl: &'v Decl) {
|
||
// Look for declarations of the variable
|
||
if let DeclLocal(ref local) = decl.node {
|
||
if local.pat.id == self.var_id {
|
||
if let PatKind::Ident(_, ref ident, _) = local.pat.node {
|
||
self.name = Some(ident.node.name);
|
||
|
||
self.state = if let Some(ref init) = local.init {
|
||
if is_integer_literal(init, 0) {
|
||
VarState::Warn
|
||
} else {
|
||
VarState::Declared
|
||
}
|
||
} else {
|
||
VarState::Declared
|
||
}
|
||
}
|
||
}
|
||
}
|
||
walk_decl(self, decl);
|
||
}
|
||
|
||
fn visit_expr(&mut self, expr: &'v Expr) {
|
||
if self.state == VarState::DontWarn {
|
||
return;
|
||
}
|
||
if expr == self.end_expr {
|
||
self.past_loop = true;
|
||
return;
|
||
}
|
||
// No need to visit expressions before the variable is
|
||
// declared
|
||
if self.state == VarState::IncrOnce {
|
||
return;
|
||
}
|
||
|
||
// If node is the desired variable, see how it's used
|
||
if var_def_id(self.cx, expr) == Some(self.var_id) {
|
||
if let Some(parent) = get_parent_expr(self.cx, expr) {
|
||
match parent.node {
|
||
ExprAssignOp(_, ref lhs, _) if lhs.id == expr.id => {
|
||
self.state = VarState::DontWarn;
|
||
}
|
||
ExprAssign(ref lhs, ref rhs) if lhs.id == expr.id => {
|
||
self.state = if is_integer_literal(rhs, 0) && self.depth == 0 {
|
||
VarState::Warn
|
||
} else {
|
||
VarState::DontWarn
|
||
}
|
||
}
|
||
ExprAddrOf(mutability, _) if mutability == MutMutable => self.state = VarState::DontWarn,
|
||
_ => (),
|
||
}
|
||
}
|
||
|
||
if self.past_loop {
|
||
self.state = VarState::DontWarn;
|
||
return;
|
||
}
|
||
} else if !self.past_loop && is_loop(expr) {
|
||
self.state = VarState::DontWarn;
|
||
return;
|
||
} else if is_conditional(expr) {
|
||
self.depth += 1;
|
||
walk_expr(self, expr);
|
||
self.depth -= 1;
|
||
return;
|
||
}
|
||
walk_expr(self, expr);
|
||
}
|
||
}
|
||
|
||
fn var_def_id(cx: &LateContext, expr: &Expr) -> Option<NodeId> {
|
||
if let Some(path_res) = cx.tcx.def_map.borrow().get(&expr.id) {
|
||
if let Def::Local(_, node_id) = path_res.base_def {
|
||
return Some(node_id);
|
||
}
|
||
}
|
||
None
|
||
}
|
||
|
||
fn is_loop(expr: &Expr) -> bool {
|
||
match expr.node {
|
||
ExprLoop(..) | ExprWhile(..) => true,
|
||
_ => false,
|
||
}
|
||
}
|
||
|
||
fn is_conditional(expr: &Expr) -> bool {
|
||
match expr.node {
|
||
ExprIf(..) | ExprMatch(..) => true,
|
||
_ => false,
|
||
}
|
||
}
|