Arity warnings for def

CHANGELOG.md

@@ -18,6 +18,7 @@ For a list of breaking changes, check [here](#breaking-changes).
 ## Unreleased
 
 - [#1976](https://github.com/clj-kondo/clj-kondo/issues/1976): warn about using multiple bindings after varargs (`&`) symbol in fn syntax
+- Add arity checks for code `def`
 - [#1971](https://github.com/clj-kondo/clj-kondo/issues/1971): false positive `:redundant-fn-wrapper` with syntax-quoted body
 - [#1984](https://github.com/clj-kondo/clj-kondo/issues/1984): lint java constructor calls as unresolved-symbol when using dot notation.
 - [#1970](https://github.com/clj-kondo/clj-kondo/issues/1970): `:dynamic-var-not-earmuffed` should be opt-in

src/clj_kondo/impl/analyzer.clj

@@ -1093,12 +1093,14 @@
         children (next children)
         docstring (when (> (count children) 1)
                     (string-from-token (first children)))
-
         defmulti? (or (= 'clojure.core/defmulti defined-by)
                       (= 'cljs.core/defmulti defined-by))
         doc-node (when docstring
                    (first children))
         [child & children] (if docstring (next children) children)
+        core-def? (one-of (first (:callstack ctx)) [[clojure.core def] [cljs.core def]])
+        _ (when (and core-def? children)
+            (findings/reg-finding! ctx (utils/node->line (:filename ctx) expr :invalid-arity "Too many arguments to def")))
         [extra-meta extra-meta-node children] (if (and defmulti?
                                                        child
                                                        (identical? :map (utils/tag child)))
@@ -1118,8 +1120,7 @@
         children (if (:analyze-var-defs-shallowly? ctx)
                    []
                    children)
-        def-init (when (and (or (= 'clojure.core/def defined-by)
-                                (= 'cljs.core/def defined-by))
+        def-init (when (and core-def?
                             (= 1 (count children)))
                    (or (analyze-expression** ctx (first children))
                        ;; prevent analysis of only child more than once

test/clj_kondo/invalid_arity_test.clj

@@ -1,7 +1,7 @@
 (ns clj-kondo.invalid-arity-test
   (:require
    [clj-kondo.test-utils :refer
-    [lint! assert-submaps]]
+    [lint! assert-submaps assert-submaps2]]
    [clojure.java.io :as io]
    [clojure.string :as str]
    [clojure.test :as t :refer [deftest is testing]]
@@ -181,3 +181,13 @@
    '({:file "corpus/def_fn.clj", :row 12, :col 1, :level :error,
       :message "def-fn/cons is called with 3 args but expects 2"})
    (lint! (io/file "corpus/def_fn.clj"))))
+
+(deftest def-test
+  (assert-submaps2
+   [{:row 1,
+     :col 1,
+     :level :error,
+     :message "Too many arguments to def"}]
+   (lint! "(def x 1 2)"))
+  (is (empty? (lint! "(def x)")))
+  (is (empty? (lint! "(def x \"foo\" 1)"))))