src/tools/clippy/clippy_lints/src/create_dir.rs

use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;

declare_clippy_lint! {
    /// ### What it does
    /// Checks usage of `std::fs::create_dir` and suggest using `std::fs::create_dir_all` instead.
    ///
    /// ### Why is this bad?
    /// Sometimes `std::fs::create_dir` is mistakenly chosen over `std::fs::create_dir_all`.
    ///
    /// ### Example
    /// ```rust,ignore
    /// std::fs::create_dir("foo");
    /// ```
    ///
    /// Use instead:
    /// ```rust,ignore
    /// std::fs::create_dir_all("foo");
    /// ```
    #[clippy::version = "1.48.0"]
    pub CREATE_DIR,
    restriction,
    "calling `std::fs::create_dir` instead of `std::fs::create_dir_all`"
}

declare_lint_pass!(CreateDir => [CREATE_DIR]);

impl LateLintPass<'_> for CreateDir {
    fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
        if_chain! {
            if let ExprKind::Call(func, [arg, ..]) = expr.kind;
            if let ExprKind::Path(ref path) = func.kind;
            if let Some(def_id) = cx.qpath_res(path, func.hir_id).opt_def_id();
            if cx.tcx.is_diagnostic_item(sym::fs_create_dir, def_id);
            then {
                span_lint_and_sugg(
                    cx,
                    CREATE_DIR,
                    expr.span,
                    "calling `std::fs::create_dir` where there may be a better way",
                    "consider calling `std::fs::create_dir_all` instead",
                    format!("create_dir_all({})", snippet(cx, arg.span, "..")),
                    Applicability::MaybeIncorrect,
                )
            }
        }
    }
}