Add :safe declarations

Context: #495 (comment)

clj-refactor.el

@@ -55,12 +55,14 @@
 (defcustom cljr-add-ns-to-blank-clj-files t
   "If t, automatically add a ns form to new .clj files."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-auto-sort-ns t
   "If t, sort ns form after any command that changes it."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-magic-requires t
   "Whether to automatically require common namespaces when they are used.
@@ -85,64 +87,75 @@ Any other non-nil value means to add the form without asking."
   "Alist of aliases and namespaces used by `cljr-slash'."
   :type '(repeat (cons (string :tag "Short alias")
                        (string :tag "Full namespace")))
+  :safe #'listp
   :group 'cljr)
 
 (defcustom cljr-project-clean-prompt t
   "If t, `cljr-project-clean' asks before doing anything.
 If nil, the project clean functions are run without warning."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-project-clean-functions
   (list #'cljr-clean-ns)
   "List of functions called by `cljr-project-clean'.
 These are called on all .clj files in the project."
   :group 'cljr
-  :type '(repeat function))
+  :type '(repeat function)
+  :safe #'listp)
 
 (defcustom cljr-project-clean-exceptions '("dev/user.clj" "project.clj" "boot.clj")
   "A list of files that `cljr-project-clean' should avoid."
   :group 'cljr
-  :type '(repeat string))
+  :type '(repeat string)
+  :safe #'listp)
 
 (defcustom cljr-hotload-dependencies nil
   "If t, newly added dependencies are also hotloaded into the repl.
 This only applies to dependencies added by `cljr-add-project-dependency'."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-favor-private-functions t
   "If t, refactorings insert private function declarations."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-favor-prefix-notation nil
   "If t, `cljr-clean-ns' favors prefix notation in the ns form."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-insert-newline-after-require t
   "If t, `cljr-clean-ns' will place a newline after the `:require` and `:import` tokens."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-use-multiple-cursors t
   "If t, some refactorings use the `multiple-cursors' package.
 This improves interactivity of the commands.  If nil, those
 refactorings will use regular prompts instead."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-auto-clean-ns t
   "If t, call `cljr-clean-ns' after commands that change the ns."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-populate-artifact-cache-on-startup t
   "If t, the middleware will eagerly populate the artifact cache.
 This makes `cljr-add-project-dependency' as snappy as can be."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-warn-on-eval t
   "If t, warn the user before running any op that requires ASTs to be built
@@ -151,26 +164,30 @@ This makes `cljr-add-project-dependency' as snappy as can be."
    so if this is on the AST cache is not warmed at startup or after certain
    operations."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-eagerly-build-asts-on-startup t
   "If t, the middleware will eagerly populate the ast cache.
 This makes `cljr-find-usages' and `cljr-rename-symbol' as snappy
 as can be."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-suppress-middleware-warnings nil
   "If t, no middleware warnings are printed to the repl."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-suppress-no-project-warning nil
   "If t, no warning is printed when starting a REPL outside a project.
 By default, a warning is printed in this case since clj-refactor
 will not work as expected in such REPLs."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-ignore-analyzer-errors nil
   "If t, `cljr-find-usages' `cljr-inline-symbol' `cljr-rename-symbol'
@@ -182,58 +199,68 @@ namespaces which can be analyzed.
 If nil, `cljr-find-usages'  `cljr-inline-symbol' `cljr-rename-symbol'
 won't run if there is a broken namespace in the project."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (define-obsolete-variable-alias 'cljr-find-usages-ignore-analyzer-errors 'cljr-ignore-analyzer-errors "2.3.0")
 
 (defcustom cljr-auto-eval-ns-form t
   "When true refactorings which change the ns form also trigger
   its re-evaluation."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-midje-test-declaration "[midje.sweet :as midje]"
   "The require form to use when midje is in use."
   :group 'cljr
-  :type 'string)
+  :type 'string
+  :safe #'stringp)
 
 (defcustom cljr-expectations-test-declaration "[expectations :as e]"
   "The require form to use when expectations is in use."
   :group 'cljr
-  :type 'string)
+  :type 'string
+  :safe #'stringp)
 
 (defcustom cljr-cljc-clojure-test-declaration "#?(:clj [clojure.test :as t]
 :cljs [cljs.test :as t :include-macros true])"
   "The require form to use when clojure.test and cljs.test is in use in a cljc file."
   :group 'cljr
-  :type 'string)
+  :type 'string
+  :safe #'stringp)
 
 (defcustom cljr-cljs-clojure-test-declaration "[cljs.test :as t :include-macros true]"
   "The require form to use when cljs.test is in use in a cljs file."
   :group 'cljr
-  :type 'string)
+  :type 'string
+  :safe #'stringp)
 
 (defcustom cljr-clojure-test-declaration "[clojure.test :as t]"
   "The require form to use when clojure.test is in use in a clj file."
   :group 'cljr
-  :type 'string)
+  :type 'string
+  :safe #'stringp)
 
 (defcustom cljr-clojure-test-namespace-under-test-alias  "sut"
   "The package alias to use for the namespace under test."
   :group 'cljr
-  :type 'string)
+  :type 'string
+  :safe #'stringp)
 
 (defcustom cljr-inject-dependencies-at-jack-in t
   "When nil, do not inject repl dependencies (most likely nREPL middlewares) at `cider-jack-in' time."
   :group 'cljr
-  :type 'boolean)
+  :type 'boolean
+  :safe #'booleanp)
 
 (defcustom cljr-assume-language-context nil
   "If set to 'clj' or 'cljs', clj-refactor will use that value in situations
   where the language context is ambiguous. If set to nil, a popup will be
   created in each ambiguous case asking user to choose language context."
   :group 'cljr
-  :type 'string)
+  :type 'string
+  :safe #'stringp)
 
 (defcustom cljr-libspec-whitelist
   '("^cljsns" "^slingshot.test" "^monger.joda-time" "^monger.json")
@@ -242,7 +269,8 @@ won't run if there is a broken namespace in the project."
 This is useful when `clean-ns' should leave a libspec alone even
 if it appears to be unused."
   :group 'cljr
-  :type '(repeat string))
+  :type '(repeat string)
+  :safe #'listp)
 
 (defvar cljr-minimum-clojure-version "1.8.0"
   "The oldest Clojure version supported by our middleware.")
@@ -290,7 +318,8 @@ if it appears to be unused."
   "List of (Java style) regexes to paths that should be ignored
   by the middleware."
   :group 'cljr
-  :type '(repeat string))
+  :type '(repeat string)
+  :safe #'listp)
 
 ;;; Buffer Local Declarations
 
@@ -3258,6 +3287,7 @@ If customizing it, you most likely should `(setq cljr-suppress-middleware-warnin
 for avoiding a warning that would be irrelevant for this case."
   :group 'cljr
   :type 'string
+  :safe #'stringp
   :package-version "3.0.0")
 
 (defun cljr--middleware-version ()