rust-clippy/clippy_lints/src/redundant_pub_crate.rs

use crate::utils::span_lint_and_help;
use rustc_hir::{Item, ItemKind, VisibilityKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_tool_lint, impl_lint_pass};

declare_clippy_lint! {
    /// **What it does:** Checks for items declared `pub(crate)` that are not crate visible because they
    /// are inside a private module.
    ///
    /// **Why is this bad?** Writing `pub(crate)` is misleading when it's redundant due to the parent
    /// module's visibility.
    ///
    /// **Known problems:** None.
    ///
    /// **Example:**
    ///
    /// ```rust
    /// mod internal {
    ///     pub(crate) fn internal_fn() { }
    /// }
    /// ```
    /// This function is not visible outside the module and it can be declared with `pub` or
    /// private visibility
    /// ```rust
    /// mod internal {
    ///     pub fn internal_fn() { }
    /// }
    /// ```
    pub REDUNDANT_PUB_CRATE,
    nursery,
    "Using `pub(crate)` visibility on items that are not crate visible due to the visibility of the module that contains them."
}

#[derive(Default)]
pub struct RedundantPubCrate {
    is_exported: Vec<bool>,
}

impl_lint_pass!(RedundantPubCrate => [REDUNDANT_PUB_CRATE]);

impl<'a, 'tcx> LateLintPass<'a, 'tcx> for RedundantPubCrate {
    fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'tcx>) {
        if let VisibilityKind::Crate { .. } = item.vis.node {
            if !cx.access_levels.is_exported(item.hir_id) {
                if let Some(false) = self.is_exported.last() {
                    span_lint_and_help(
                        cx,
                        REDUNDANT_PUB_CRATE,
                        item.span,
                        &format!("pub(crate) {} inside private module", item.kind.descr()),
                        "consider using `pub` instead of `pub(crate)`",
                    )
                }
            }
        }

        if let ItemKind::Mod { .. } = item.kind {
            self.is_exported.push(cx.access_levels.is_exported(item.hir_id));
        }
    }

    fn check_item_post(&mut self, _cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'tcx>) {
        if let ItemKind::Mod { .. } = item.kind {
            self.is_exported.pop().expect("unbalanced check_item/check_item_post");
        }
    }
}