rust-clippy/clippy_lints/src/functions/too_many_arguments.rs

use rustc_hir::{self as hir, intravisit};
use rustc_lint::LateContext;
use rustc_span::Span;
use rustc_target::spec::abi::Abi;

use clippy_utils::diagnostics::span_lint;
use clippy_utils::is_trait_impl_item;

use super::TOO_MANY_ARGUMENTS;

pub(super) fn check_fn(
    cx: &LateContext<'tcx>,
    kind: intravisit::FnKind<'tcx>,
    decl: &'tcx hir::FnDecl<'_>,
    span: Span,
    hir_id: hir::HirId,
    too_many_arguments_threshold: u64,
) {
    // don't warn for implementations, it's not their fault
    if !is_trait_impl_item(cx, hir_id) {
        // don't lint extern functions decls, it's not their fault either
        match kind {
            intravisit::FnKind::Method(
                _,
                &hir::FnSig {
                    header: hir::FnHeader { abi: Abi::Rust, .. },
                    ..
                },
                _,
            )
            | intravisit::FnKind::ItemFn(_, _, hir::FnHeader { abi: Abi::Rust, .. }, _) => check_arg_number(
                cx,
                decl,
                span.with_hi(decl.output.span().hi()),
                too_many_arguments_threshold,
            ),
            _ => {},
        }
    }
}

pub(super) fn check_trait_item(
    cx: &LateContext<'tcx>,
    item: &'tcx hir::TraitItem<'_>,
    too_many_arguments_threshold: u64,
) {
    if let hir::TraitItemKind::Fn(ref sig, _) = item.kind {
        // don't lint extern functions decls, it's not their fault
        if sig.header.abi == Abi::Rust {
            check_arg_number(
                cx,
                sig.decl,
                item.span.with_hi(sig.decl.output.span().hi()),
                too_many_arguments_threshold,
            );
        }
    }
}

fn check_arg_number(cx: &LateContext<'_>, decl: &hir::FnDecl<'_>, fn_span: Span, too_many_arguments_threshold: u64) {
    let args = decl.inputs.len() as u64;
    if args > too_many_arguments_threshold {
        span_lint(
            cx,
            TOO_MANY_ARGUMENTS,
            fn_span,
            &format!(
                "this function has too many arguments ({}/{})",
                args, too_many_arguments_threshold
            ),
        );
    }
}