Consider the following code:
(definterface Test
(^void fail (link: )))
(deftype TestImpl
(link: ^{:unsynchronized-mutable true :tag int} x)
Test
(fail (link: this)
(set! x (dec x))))
Its compilation fails with the following message:
CompilerException java.lang.VerifyError: (class: test/TestImpl, method: fail signature: ()V) Expecting to find integer on stack, compiling:(.../test.clj:27)
The following code works:
(definterface Test
(^void fail (link: )))
(deftype TestImpl
(link: ^{:unsynchronized-mutable true :tag int} x)
Test
(fail (link: this)
(set! x (int (dec x)))))
The only change here is that I have wrapped (dec x) form into (int) call.
I understand that in fact the former code should not work anyway (or at least should not work as I have expected) because (dec) is defined as a call to clojure.lang.Numbers.dec(), which is overloaded for double, long and Object only (in fact, changing :tag int to :tag long in the first example allows the program to compile). However, the error message is completely uninformative and misleading; it also looks like that it is a consequence of compiler error. It is also not a problem of this concrete example; I found this error in more complex interface method implementation where (set!) call was right in the middle of its body.
I'm using Clojure 1.4.0 and have experienced this problem on Archlinux x86_64 and Windows 7 x86_64.
Full stack trace of the error, in case it would be helpful:
java.lang.VerifyError: (class: test/TestImpl, method: fail signature: ()V) Expecting to find integer on stack, compiling:(.../test.clj:27)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6462)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyze(Compiler.java:6223)
at clojure.lang.Compiler$BodyExpr$Parser.parse(Compiler.java:5618)
at clojure.lang.Compiler$FnMethod.parse(Compiler.java:5054)
at clojure.lang.Compiler$FnExpr.parse(Compiler.java:3674)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6453)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6443)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.access$100(Compiler.java:37)
at clojure.lang.Compiler$DefExpr$Parser.parse(Compiler.java:518)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6455)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6443)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyze(Compiler.java:6223)
at clojure.lang.Compiler$BodyExpr$Parser.parse(Compiler.java:5618)
at clojure.lang.Compiler$LetExpr$Parser.parse(Compiler.java:5919)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6455)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.analyze(Compiler.java:6223)
at clojure.lang.Compiler$BodyExpr$Parser.parse(Compiler.java:5618)
at clojure.lang.Compiler$FnMethod.parse(Compiler.java:5054)
at clojure.lang.Compiler$FnExpr.parse(Compiler.java:3674)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6453)
at clojure.lang.Compiler.analyze(Compiler.java:6262)
at clojure.lang.Compiler.eval(Compiler.java:6508)
at clojure.lang.Compiler.load(Compiler.java:6952)
at clojure.lang.Compiler.loadFile(Compiler.java:6912)
at clojure.lang.RT$3.invoke(RT.java:307)
at test$eval3224.invoke(NO_SOURCE_FILE:43)
at clojure.lang.Compiler.eval(Compiler.java:6511)
at clojure.lang.Compiler.eval(Compiler.java:6477)
at clojure.core$eval.invoke(core.clj:2797)
at clojure.main$repl$read_eval_print__6405.invoke(main.clj:245)
at clojure.main$repl$fn__6410.invoke(main.clj:266)
at clojure.main$repl.doInvoke(main.clj:266)
at clojure.lang.RestFn.invoke(RestFn.java:421)
at clojure.main$repl_opt.invoke(main.clj:332)
at clojure.main$main.doInvoke(main.clj:428)
at clojure.lang.RestFn.invoke(RestFn.java:397)
at clojure.lang.Var.invoke(Var.java:411)
at clojure.lang.AFn.applyToHelper(AFn.java:159)
at clojure.lang.Var.applyTo(Var.java:532)
at clojure.main.main(main.java:37)
Caused by: java.lang.VerifyError: (class: test/TestImpl, method: fail signature: ()V) Expecting to find integer on stack
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at clojure.lang.RT.classForName(RT.java:2039)
at clojure.lang.Compiler$HostExpr.maybeClass(Compiler.java:957)
at clojure.lang.Compiler$HostExpr.access$400(Compiler.java:736)
at clojure.lang.Compiler$NewExpr$Parser.parse(Compiler.java:2473)
at clojure.lang.Compiler.analyzeSeq(Compiler.java:6455)
... 45 more
