build.clj

(ns build
  (:require [clojure.tools.build.api :as b]))

(def class-dir "target/classes")
(def java-src-dirs ["src/java"])
(def clj-src-dirs ["src/clj"])

(defn- basis [opts]
  (b/create-basis {:aliases (:aliases opts)}))

(defn clean [_]
  (b/delete {:path class-dir}))

(defn compile-java
  [opts]
  (b/javac {:src-dirs java-src-dirs
            :class-dir class-dir
            :basis (basis opts)
            :javac-opts ["--release" "11"]}))

(defn compile-clj
  [opts]
  (b/compile-clj {:basis (basis opts)
                   :class-dir class-dir
                   :src-dirs clj-src-dirs
                   :ns-compile '[isf.genned]}))

(defn compile-all
  [opts]
  (compile-java opts)
  (compile-clj opts))

CLJTestInterface.java

package isf;

public interface CLJTestInterface {
    public static String staticGreet(String s) {
        return "static:" + s;
    }

    public static String staticGreetToAlias(String s) {
        return "static with alias:" + s;
    }
}

deps.edn

{:paths ["src/clj" "target/classes"]

 :aliases
 {:prepatch {:override-deps {org.clojure/clojure {:mvn/version "1.12.5"}}}

  :patched {:override-deps {org.clojure/clojure {:mvn/version "1.12.6-alpha1"}}}

  :build {:deps {io.github.clojure/tools.build {:mvn/version "0.10.10"}}
          :ns-default build}}}

genned.clj

(ns isf.genned
  (:gen-class :name isf.Genned
              :implements [isf.CLJTestInterface]
              :prefix "-"
              :methods [
                        ^{:static true} [staticGreetToAlias [String] void]
                        ]))

(defn -staticGreetToAlias [s]
  (println "forwarded! " s))

scratch.clj

(import 'isf.CLJTestInterface)
(CLJTestInterface/staticGreet "foo")
(CLJTestInterface/staticGreetToAlias "foo")

(import 'isf.Genned)
(def g (Genned.))

(.staticGreet g "bar")

;; PREPATCH YOU"LL SEE
;;   java.lang.NoSuchFieldError:
;;     Class isf.Genned does not have member field
;;     'clojure.lang.Var staticGreet__var'
;;
;;   WHY: gen-class's var-field-generation pass (`non-private-methods`)
;;   filters OUT static methods when deciding which `__var` fields to
;;   declare on the class, but the forwarder-generation pass
;;   doesn't filter them out. The emitted staticGreet method body
;;   still does `getstatic staticGreet__var`, referencing a field that
;;   was never declared. The class is internally inconsistent.

;; POST-PATCH YOU'LL SEE
;;   java.lang.IllegalArgumentException:
;;     No matching method staticGreet found taking 1 args for class isf.Genned


(.staticGreetToAlias g "bar")

;; PREPATCH YOU"LL SEE
;; Unhandled clojure.lang.ArityException
;;   Wrong number of args (2) passed to: isf.genned/-staticGreetToAlias

;; POST-PATCH YOU'LL SEE
;;   java.lang.IllegalArgumentException:
;;     No matching method staticGreetToAlias found taking 1 args for class isf.Genned


(Genned/staticGreet "bar")

;; BOTH
;; java.lang.IllegalArgumentException
;; No matching method staticGreet found taking 1 args for class isf.Genned

(Genned/staticGreetToAlias "bar")

;; BOTH pre and patched
;; forwarded!  bar