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Auto merge of #6313 - giraffate:fix_fp_needless_collect, r=ebroto

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Fix FP in indirect `needless_collect` when used multiple times

Fix https://github.com/rust-lang/rust-clippy/issues/5991
Fix https://github.com/rust-lang/rust-clippy/issues/6297

changelog: Fix FP in indirect `needless_collect` when used multiple times
This commit is contained in:
bors 2020-11-23 22:26:45 +00:00
commit 295fe28057
2 changed files with 53 additions and 1 deletions
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34
clippy_lints/src/loops.rs
View file

@ -2950,7 +2950,7 @@ fn check_needless_collect_indirect_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateCo
for ref stmt in block.stmts {
if_chain! {
if let StmtKind::Local(
Local { pat: Pat { kind: PatKind::Binding(_, _, ident, .. ), .. },
Local { pat: Pat { hir_id: pat_id, kind: PatKind::Binding(_, _, ident, .. ), .. },
init: Some(ref init_expr), .. }
) = stmt.kind;
if let ExprKind::MethodCall(ref method_name, _, &[ref iter_source], ..) = init_expr.kind;
@ -2964,6 +2964,16 @@ fn check_needless_collect_indirect_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateCo
if let Some(iter_calls) = detect_iter_and_into_iters(block, *ident);
if iter_calls.len() == 1;
then {
let mut used_count_visitor = UsedCountVisitor {
cx,
id: *pat_id,
count: 0,
};
walk_block(&mut used_count_visitor, block);
if used_count_visitor.count > 1 {
return;
}
// Suggest replacing iter_call with iter_replacement, and removing stmt
let iter_call = &iter_calls[0];
span_lint_and_then(
@ -3087,6 +3097,28 @@ impl<'tcx> Visitor<'tcx> for IterFunctionVisitor {
}
}
struct UsedCountVisitor<'a, 'tcx> {
cx: &'a LateContext<'tcx>,
id: HirId,
count: usize,
}
impl<'a, 'tcx> Visitor<'tcx> for UsedCountVisitor<'a, 'tcx> {
type Map = Map<'tcx>;
fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
if same_var(self.cx, expr, self.id) {
self.count += 1;
} else {
walk_expr(self, expr);
}
}
fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
NestedVisitorMap::OnlyBodies(self.cx.tcx.hir())
}
}
/// Detect the occurrences of calls to `iter` or `into_iter` for the
/// given identifier
fn detect_iter_and_into_iters<'tcx>(block: &'tcx Block<'tcx>, identifier: Ident) -> Option<Vec<IterFunction>> {