68 lines
2.7 KiB
Rust
68 lines
2.7 KiB
Rust
use clippy_utils::diagnostics::span_lint_and_then;
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use clippy_utils::source::snippet;
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use clippy_utils::ty::is_type_diagnostic_item;
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use clippy_utils::{eager_or_lazy, usage};
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use rustc_errors::Applicability;
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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::UNNECESSARY_LAZY_EVALUATIONS;
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/// lint use of `<fn>_else(simple closure)` for `Option`s and `Result`s that can be
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/// replaced with `<fn>(return value of simple closure)`
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pub(super) fn check<'tcx>(
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cx: &LateContext<'tcx>,
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expr: &'tcx hir::Expr<'_>,
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recv: &'tcx hir::Expr<'_>,
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arg: &'tcx hir::Expr<'_>,
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simplify_using: &str,
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) {
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let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Option);
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let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result);
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if is_option || is_result {
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if let hir::ExprKind::Closure(_, _, eid, _, _) = arg.kind {
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let body = cx.tcx.hir().body(eid);
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let body_expr = &body.value;
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if usage::BindingUsageFinder::are_params_used(cx, body) {
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return;
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}
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if eager_or_lazy::switch_to_eager_eval(cx, body_expr) {
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let msg = if is_option {
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"unnecessary closure used to substitute value for `Option::None`"
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} else {
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"unnecessary closure used to substitute value for `Result::Err`"
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};
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let applicability = if body
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.params
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.iter()
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// bindings are checked to be unused above
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.all(|param| matches!(param.pat.kind, hir::PatKind::Binding(..) | hir::PatKind::Wild))
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{
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Applicability::MachineApplicable
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} else {
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// replacing the lambda may break type inference
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Applicability::MaybeIncorrect
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};
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// This is a duplicate of what's happening in clippy_lints::methods::method_call,
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// which isn't ideal, We want to get the method call span,
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// but prefer to avoid changing the signature of the function itself.
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if let hir::ExprKind::MethodCall(_, _, span) = expr.kind {
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span_lint_and_then(cx, UNNECESSARY_LAZY_EVALUATIONS, expr.span, msg, |diag| {
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diag.span_suggestion(
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span,
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&format!("use `{}(..)` instead", simplify_using),
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format!("{}({})", simplify_using, snippet(cx, body_expr.span, "..")),
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applicability,
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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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