//! Check that functions don't accept an "excessive" number of arguments. 

use syntax::ast::{Block, FnDecl, NodeId};
use syntax::codemap::Span;
use syntax::visit::FnKind;
use rustc::lint::{Context, LintArray, LintPass};

const MAX_ARGS_DEFAULT: usize = 6;
const MAX_ARGS_FOR_CLOSURE: usize = 4;

declare_lint!(FN_ARG_LIST_LENGTH, Warn, "Warn about long argument lists");

pub struct Pass;

fn get_max_args_allowed(kind: &FnKind) -> usize {
    if let &FnKind::FkFnBlock = kind {
        MAX_ARGS_FOR_CLOSURE
    } else {
        MAX_ARGS_DEFAULT
    }
}

impl LintPass for Pass {
    fn get_lints(&self) -> LintArray {
        lint_array!(FN_ARG_LIST_LENGTH)
    }

    fn check_fn(&mut self, cx: &Context, kind: FnKind, decl: &FnDecl, _: &Block,
                span: Span, _: NodeId) {
        if decl.inputs.len() > get_max_args_allowed(&kind) {
            cx.span_lint(FN_ARG_LIST_LENGTH, span, 
                            "function has an excessive number of arguments");
        }
    }
}

//! Check that functions don't accept an "excessive" number of arguments. 

use syntax::ast::{Block, FnDecl, NodeId};
use syntax::codemap::Span;
use syntax::visit::FnKind;
use rustc::lint::{Context, LintArray, LintPass};

const MAX_ARGS_DEFAULT: usize = 6;
const MAX_ARGS_FOR_CLOSURE: usize = 4;

declare_lint!(FN_ARG_LIST_LENGTH, Warn, "Warn about long argument lists");

pub struct Pass;

fn get_max_args_allowed(kind: &FnKind) -> usize {
    match kind {
        &FnKind::FkFnBlock => MAX_ARGS_FOR_CLOSURE,
        _ => MAX_ARGS_DEFAULT
    }
}

impl LintPass for Pass {
    fn get_lints(&self) -> LintArray {
        lint_array!(FN_ARG_LIST_LENGTH)
    }

    fn check_fn(&mut self, cx: &Context, kind: FnKind, decl: &FnDecl, _: &Block,
                span: Span, _: NodeId) {
        if decl.inputs.len() > get_max_args_allowed(&kind) {
            cx.span_lint(FN_ARG_LIST_LENGTH, span, 
                            "function has an excessive number of arguments");
        }
    }
}

--- 
+++ 
@@ -13,9 +13,10 @@
 pub struct Pass;
 
 fn get_max_args_allowed(kind: &FnKind) -> usize {
-    match kind {
-        &FnKind::FkFnBlock => MAX_ARGS_FOR_CLOSURE,
-        _ => MAX_ARGS_DEFAULT
+    if let &FnKind::FkFnBlock = kind {
+        MAX_ARGS_FOR_CLOSURE
+    } else {
+        MAX_ARGS_DEFAULT
     }
 }
 
Use if-let as we only have a binary match
