clojure.core/*warn-on-reflection*

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Type: var Added: Clojure 1.0 Examples: 3 Runnable: 2

()

When set to true, the compiler will emit warnings when reflection is needed to resolve Java method calls or field accesses.

Defaults to false.

Examples

by shockbob on 2011-08-21 . May have evaluation errors. ▶

;; define two variables then set *warn-on-reflection* to true and try to call ;; one of their Java methods. Warnings are generated in both cases ;; set *warn-on-reflection* to false and note that you can call both functions ;; without a warning (def i 23) #'user/i (def s "123") #'user/s (set! *warn-on-reflection* true) true (.toString i) Reflection warning, NO_SOURCE_PATH:4 - reference to field toString can't be resolved. "23" (.toString s) Reflection warning, NO_SOURCE_PATH:5 - reference to field toString can't be resolved. "123" ;; Reflection (and hence reflection warnings) could be removed by giving type hints: (.toString ^String s) "123" (set! *warn-on-reflection* false) false (.toString i) "23" (.toString s) "123"

by randomizedthinking on 2022-12-31 ▶

(set! *warn-on-reflection* true) ;; turn on *warn-on-reflection* (def s "abc") ;; define s (.toString s) ;; => "abc"; WARN: type of s is unknown (.toString ^String s) ;; => "abc"; no warn given the type hint (let [s "abc"] (.toString s)) ;; => "abc"; no warn since Clojure can infer ;; type for the local binding (set! *warn-on-reflection* false) ;; turn off *warn-on-reflection*

by randomizedthinking on 2022-12-31 ▶

;; Important to note *warn-on-reflection* take its effect at compile time, ;; so binding the option won't work... even with a set! inside. ;; - binding creates a new env to evaluate subsequent statements ;; - yet, compiler still lives in the current env, so it won't see the value (binding [*warn-on-reflection* true] (set! *warn-on-reflection* true) (def s "abc") (.toString s)) ;; => "abc", no warning (println *warn-on-reflection*) ;; => false

See also

• clojure.core/*unchecked-math*

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