42 lines
1.4 KiB
Rust
42 lines
1.4 KiB
Rust
use crate::utils::usage::mutated_variables;
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use crate::utils::{expr_or_init, is_trait_method, span_lint_and_help};
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use if_chain::if_chain;
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use rustc_hir as hir;
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use rustc_lint::LateContext;
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use rustc_span::sym;
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use super::SUSPICIOUS_MAP;
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pub fn check<'tcx>(
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cx: &LateContext<'tcx>,
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expr: &hir::Expr<'_>,
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map_args: &[hir::Expr<'_>],
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count_args: &[hir::Expr<'_>],
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) {
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if_chain! {
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if let [count_recv] = count_args;
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if let [_, map_arg] = map_args;
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if is_trait_method(cx, count_recv, sym::Iterator);
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let closure = expr_or_init(cx, map_arg);
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if let Some(body_id) = cx.tcx.hir().maybe_body_owned_by(closure.hir_id);
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let closure_body = cx.tcx.hir().body(body_id);
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if !cx.typeck_results().expr_ty(&closure_body.value).is_unit();
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then {
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if let Some(map_mutated_vars) = mutated_variables(&closure_body.value, cx) {
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// A variable is used mutably inside of the closure. Suppress the lint.
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if !map_mutated_vars.is_empty() {
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return;
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}
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}
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span_lint_and_help(
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cx,
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SUSPICIOUS_MAP,
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expr.span,
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"this call to `map()` won't have an effect on the call to `count()`",
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None,
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"make sure you did not confuse `map` with `filter` or `for_each`",
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);
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}
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}
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}
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