mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-22 11:03:16 +00:00
391 lines
13 KiB
Rust
391 lines
13 KiB
Rust
use crate::utils::{
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get_parent_expr, higher, in_macro_or_desugar, same_tys, snippet, span_lint_and_then, span_note_and_lint,
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};
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use crate::utils::{SpanlessEq, SpanlessHash};
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::ty::Ty;
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use rustc::{declare_lint_pass, declare_tool_lint};
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use rustc_data_structures::fx::FxHashMap;
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use smallvec::SmallVec;
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use std::collections::hash_map::Entry;
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use std::hash::BuildHasherDefault;
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use syntax::symbol::LocalInternedString;
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declare_clippy_lint! {
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/// **What it does:** Checks for consecutive `if`s with the same condition.
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///
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/// **Why is this bad?** This is probably a copy & paste error.
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///
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/// **Known problems:** Hopefully none.
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///
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/// **Example:**
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/// ```ignore
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/// if a == b {
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/// …
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/// } else if a == b {
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/// …
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/// }
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/// ```
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///
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/// Note that this lint ignores all conditions with a function call as it could
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/// have side effects:
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///
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/// ```ignore
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/// if foo() {
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/// …
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/// } else if foo() { // not linted
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/// …
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/// }
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/// ```
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pub IFS_SAME_COND,
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correctness,
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"consecutive `ifs` with the same condition"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for `if/else` with the same body as the *then* part
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/// and the *else* part.
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///
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/// **Why is this bad?** This is probably a copy & paste error.
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///
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/// **Known problems:** Hopefully none.
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///
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/// **Example:**
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/// ```ignore
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/// let foo = if … {
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/// 42
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/// } else {
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/// 42
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/// };
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/// ```
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pub IF_SAME_THEN_ELSE,
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correctness,
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"if with the same *then* and *else* blocks"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for `match` with identical arm bodies.
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///
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/// **Why is this bad?** This is probably a copy & paste error. If arm bodies
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/// are the same on purpose, you can factor them
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/// [using `|`](https://doc.rust-lang.org/book/patterns.html#multiple-patterns).
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///
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/// **Known problems:** False positive possible with order dependent `match`
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/// (see issue
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/// [#860](https://github.com/rust-lang/rust-clippy/issues/860)).
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///
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/// **Example:**
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/// ```rust,ignore
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/// match foo {
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/// Bar => bar(),
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/// Quz => quz(),
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/// Baz => bar(), // <= oops
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/// }
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/// ```
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///
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/// This should probably be
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/// ```rust,ignore
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/// match foo {
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/// Bar => bar(),
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/// Quz => quz(),
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/// Baz => baz(), // <= fixed
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/// }
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/// ```
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///
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/// or if the original code was not a typo:
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/// ```rust,ignore
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/// match foo {
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/// Bar | Baz => bar(), // <= shows the intent better
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/// Quz => quz(),
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/// }
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/// ```
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pub MATCH_SAME_ARMS,
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pedantic,
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"`match` with identical arm bodies"
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}
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declare_lint_pass!(CopyAndPaste => [IFS_SAME_COND, IF_SAME_THEN_ELSE, MATCH_SAME_ARMS]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CopyAndPaste {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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if !in_macro_or_desugar(expr.span) {
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// skip ifs directly in else, it will be checked in the parent if
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if let Some(expr) = get_parent_expr(cx, expr) {
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if let Some((_, _, Some(ref else_expr))) = higher::if_block(&expr) {
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if else_expr.hir_id == expr.hir_id {
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return;
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}
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}
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}
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let (conds, blocks) = if_sequence(expr);
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lint_same_then_else(cx, &blocks);
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lint_same_cond(cx, &conds);
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lint_match_arms(cx, expr);
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}
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}
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}
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/// Implementation of `IF_SAME_THEN_ELSE`.
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fn lint_same_then_else(cx: &LateContext<'_, '_>, blocks: &[&Block]) {
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let eq: &dyn Fn(&&Block, &&Block) -> bool = &|&lhs, &rhs| -> bool { SpanlessEq::new(cx).eq_block(lhs, rhs) };
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if let Some((i, j)) = search_same_sequenced(blocks, eq) {
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span_note_and_lint(
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cx,
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IF_SAME_THEN_ELSE,
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j.span,
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"this `if` has identical blocks",
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i.span,
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"same as this",
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);
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}
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}
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/// Implementation of `IFS_SAME_COND`.
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fn lint_same_cond(cx: &LateContext<'_, '_>, conds: &[&Expr]) {
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let hash: &dyn Fn(&&Expr) -> u64 = &|expr| -> u64 {
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let mut h = SpanlessHash::new(cx, cx.tables);
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h.hash_expr(expr);
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h.finish()
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};
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let eq: &dyn Fn(&&Expr, &&Expr) -> bool =
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&|&lhs, &rhs| -> bool { SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, rhs) };
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for (i, j) in search_same(conds, hash, eq) {
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span_note_and_lint(
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cx,
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IFS_SAME_COND,
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j.span,
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"this `if` has the same condition as a previous if",
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i.span,
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"same as this",
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);
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}
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}
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/// Implementation of `MATCH_SAME_ARMS`.
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fn lint_match_arms<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr) {
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fn same_bindings<'tcx>(
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cx: &LateContext<'_, 'tcx>,
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lhs: &FxHashMap<LocalInternedString, Ty<'tcx>>,
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rhs: &FxHashMap<LocalInternedString, Ty<'tcx>>,
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) -> bool {
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lhs.len() == rhs.len()
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&& lhs
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.iter()
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.all(|(name, l_ty)| rhs.get(name).map_or(false, |r_ty| same_tys(cx, l_ty, r_ty)))
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}
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if let ExprKind::Match(_, ref arms, MatchSource::Normal) = expr.node {
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let hash = |&(_, arm): &(usize, &Arm)| -> u64 {
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let mut h = SpanlessHash::new(cx, cx.tables);
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h.hash_expr(&arm.body);
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h.finish()
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};
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let eq = |&(lindex, lhs): &(usize, &Arm), &(rindex, rhs): &(usize, &Arm)| -> bool {
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let min_index = usize::min(lindex, rindex);
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let max_index = usize::max(lindex, rindex);
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// Arms with a guard are ignored, those can’t always be merged together
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// This is also the case for arms in-between each there is an arm with a guard
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(min_index..=max_index).all(|index| arms[index].guard.is_none()) &&
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SpanlessEq::new(cx).eq_expr(&lhs.body, &rhs.body) &&
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// all patterns should have the same bindings
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same_bindings(cx, &bindings(cx, &lhs.pats[0]), &bindings(cx, &rhs.pats[0]))
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};
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let indexed_arms: Vec<(usize, &Arm)> = arms.iter().enumerate().collect();
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for (&(_, i), &(_, j)) in search_same(&indexed_arms, hash, eq) {
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span_lint_and_then(
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cx,
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MATCH_SAME_ARMS,
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j.body.span,
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"this `match` has identical arm bodies",
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|db| {
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db.span_note(i.body.span, "same as this");
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// Note: this does not use `span_suggestion` on purpose:
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// there is no clean way
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// to remove the other arm. Building a span and suggest to replace it to ""
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// makes an even more confusing error message. Also in order not to make up a
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// span for the whole pattern, the suggestion is only shown when there is only
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// one pattern. The user should know about `|` if they are already using it…
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if i.pats.len() == 1 && j.pats.len() == 1 {
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let lhs = snippet(cx, i.pats[0].span, "<pat1>");
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let rhs = snippet(cx, j.pats[0].span, "<pat2>");
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if let PatKind::Wild = j.pats[0].node {
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// if the last arm is _, then i could be integrated into _
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// note that i.pats[0] cannot be _, because that would mean that we're
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// hiding all the subsequent arms, and rust won't compile
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db.span_note(
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i.body.span,
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&format!(
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"`{}` has the same arm body as the `_` wildcard, consider removing it`",
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lhs
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),
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);
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} else {
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db.span_help(
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i.pats[0].span,
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&format!("consider refactoring into `{} | {}`", lhs, rhs),
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);
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}
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}
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},
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);
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}
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}
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}
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/// Returns the list of condition expressions and the list of blocks in a
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/// sequence of `if/else`.
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/// E.g., this returns `([a, b], [c, d, e])` for the expression
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/// `if a { c } else if b { d } else { e }`.
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fn if_sequence(mut expr: &Expr) -> (SmallVec<[&Expr; 1]>, SmallVec<[&Block; 1]>) {
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let mut conds = SmallVec::new();
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let mut blocks: SmallVec<[&Block; 1]> = SmallVec::new();
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while let Some((ref cond, ref then_expr, ref else_expr)) = higher::if_block(&expr) {
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conds.push(&**cond);
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if let ExprKind::Block(ref block, _) = then_expr.node {
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blocks.push(block);
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} else {
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panic!("ExprKind::If node is not an ExprKind::Block");
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}
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if let Some(ref else_expr) = *else_expr {
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expr = else_expr;
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} else {
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break;
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}
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}
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// final `else {..}`
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if !blocks.is_empty() {
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if let ExprKind::Block(ref block, _) = expr.node {
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blocks.push(&**block);
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}
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}
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(conds, blocks)
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}
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/// Returns the list of bindings in a pattern.
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fn bindings<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, pat: &Pat) -> FxHashMap<LocalInternedString, Ty<'tcx>> {
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fn bindings_impl<'a, 'tcx>(
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cx: &LateContext<'a, 'tcx>,
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pat: &Pat,
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map: &mut FxHashMap<LocalInternedString, Ty<'tcx>>,
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) {
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match pat.node {
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PatKind::Box(ref pat) | PatKind::Ref(ref pat, _) => bindings_impl(cx, pat, map),
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PatKind::TupleStruct(_, ref pats, _) => {
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for pat in pats {
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bindings_impl(cx, pat, map);
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}
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},
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PatKind::Binding(.., ident, ref as_pat) => {
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if let Entry::Vacant(v) = map.entry(ident.as_str()) {
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v.insert(cx.tables.pat_ty(pat));
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}
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if let Some(ref as_pat) = *as_pat {
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bindings_impl(cx, as_pat, map);
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}
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},
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PatKind::Struct(_, ref fields, _) => {
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for pat in fields {
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bindings_impl(cx, &pat.node.pat, map);
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}
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},
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PatKind::Tuple(ref fields, _) => {
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for pat in fields {
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bindings_impl(cx, pat, map);
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}
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},
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PatKind::Slice(ref lhs, ref mid, ref rhs) => {
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for pat in lhs {
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bindings_impl(cx, pat, map);
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}
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if let Some(ref mid) = *mid {
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bindings_impl(cx, mid, map);
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}
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for pat in rhs {
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bindings_impl(cx, pat, map);
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}
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},
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PatKind::Lit(..) | PatKind::Range(..) | PatKind::Wild | PatKind::Path(..) => (),
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}
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}
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let mut result = FxHashMap::default();
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bindings_impl(cx, pat, &mut result);
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result
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}
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fn search_same_sequenced<T, Eq>(exprs: &[T], eq: Eq) -> Option<(&T, &T)>
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where
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Eq: Fn(&T, &T) -> bool,
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{
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for win in exprs.windows(2) {
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if eq(&win[0], &win[1]) {
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return Some((&win[0], &win[1]));
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}
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}
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None
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}
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fn search_common_cases<'a, T, Eq>(exprs: &'a [T], eq: &Eq) -> Option<(&'a T, &'a T)>
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where
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Eq: Fn(&T, &T) -> bool,
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{
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if exprs.len() < 2 {
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None
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} else if exprs.len() == 2 {
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if eq(&exprs[0], &exprs[1]) {
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Some((&exprs[0], &exprs[1]))
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} else {
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None
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}
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} else {
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None
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}
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}
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fn search_same<T, Hash, Eq>(exprs: &[T], hash: Hash, eq: Eq) -> Vec<(&T, &T)>
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where
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Hash: Fn(&T) -> u64,
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Eq: Fn(&T, &T) -> bool,
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{
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if let Some(expr) = search_common_cases(&exprs, &eq) {
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return vec![expr];
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}
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let mut match_expr_list: Vec<(&T, &T)> = Vec::new();
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let mut map: FxHashMap<_, Vec<&_>> =
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FxHashMap::with_capacity_and_hasher(exprs.len(), BuildHasherDefault::default());
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for expr in exprs {
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match map.entry(hash(expr)) {
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Entry::Occupied(mut o) => {
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for o in o.get() {
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if eq(o, expr) {
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match_expr_list.push((o, expr));
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}
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}
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o.get_mut().push(expr);
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},
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Entry::Vacant(v) => {
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v.insert(vec![expr]);
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},
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}
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}
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match_expr_list
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}
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