A more general question is, that where should I put a type hint to avoid coercing to (int ...) explicitly?

(defn get-some-results ^long [] 1) ?

0 and 1 are longs here, not ints

ah, right! thank you Alex!

but not sure if your warning was from clojure or linter?

it's from Clojure when I reload a namespace

Performance warning, /home/foo/Bar/xxx/api/src/model/foo.clj:77:11 - case has int tests, but tested expression is not primitive.

but yes, ^long solves the problem

> (defn get-some-results ^long [] 1) Fairly sure that a defn cannot return a primitive type - primitives don't survive across clojure function call boundaries Likewise you cannot simply:

(let [^long result (get-some-result)])

(let [result (long (get-some-result))])

Well, this works fine:

(defn get-foo ^long [] 42)

(let [result (get-foo)]
    (case result
      1 :boo
      2 :baa
      42 :lol))

:lol

Functions have limited support for primitive arguments and return type: type hints for long and double (only these) generate primitive-typed overloads. Note that this capability is restricted to functions of arity no greater than 4.

> Fairly sure that a defn cannot return a primitive type it does for ^long or ^double

TIL then!

I believe, here is a list of all the possible types combination: https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/IFn.java#L97

yes, all combinations of ^long or ^double up to arity 4

Here's the surprising (to me!) repl session. This is running in an empty folder:

~/temp$ % clj -Sdeps '{:paths ["src" "target"]}'
Clojure 1.11.1
user=> (slurp ( "file.txt"))
Execution error (IllegalArgumentException) at user/eval1 (REPL:1).
Cannot open <nil> as a Reader.
user=> (clojure.java.shell/sh "mkdir" "-p" "target")
{:exit 0, :out "", :err ""}
user=> (spit "target/file.txt" "hi")
nil
user=> (slurp ( "file.txt"))
Execution error (IllegalArgumentException) at user/eval7 (REPL:1).
Cannot open <nil> as a Reader.
user=>
~/temp$ % clj -Sdeps '{:paths ["src" "target"]}'
Clojure 1.11.1
user=> (slurp ( "file.txt"))
"hi"

As you can see, resource doesn't find file.txt until I restart the clojure process. I'm wondering if this is a java or tools.deps behavior, and if people have found a good workaround for "non-existent (at startup) folders containing resources"

not really an answer to the question, but I sometimes use a target/.gitkeep file to avoid errors like this. Then I check it in with git add -f target/.gitkeep && git commit.

I believe it's a JVM thing. Adding class files to an existing classpath is relatively dynamic on the JVM. Adding new paths to a running JVM is often requires a custom class loader (similar to web servers like tomcat). The easiest approach is to create the necessary directories before running the repl (or restart the repl after adding a new path). Not sure if the new hot loading tools on Clojure 1.12 support paths. I think hot loading jars is more amenable that paths in the JVM (but it's been a decade since I last did that sort of thing)

You can do something like this:

(def funny-addition fm/funny-addition)
(alter-var-meta #'funny-addition #(merge % (select-keys (meta #'fm/funny-addition) [:doc :arglists])))

The library potemkin does this for you, although I believe it's usually considered unidiomatic these days, mostly because it means that any kind of "go to definition" functionality will give you confusing results.

The honeysql 1 library has a util you could use or reference: https://github.com/seancorfield/honeysql/blob/v1.0.461/src/honeysql/util.clj#L3

ahhhh very interesting, appreciate the inputs! maybe it'd just be preferred to copy over the :arglists and :doc, I think thats all I'd want to "forward" over

and that shouldn't mess up the go-to-defs

In case it helps, cider-nrepl latest detects the (def funny-addition fm/funny-addition) pattern and reflects all relevant metadata, in a non-intrusive way (nothing is mutated). If you use other tooling, it's a sensible feature to request.

What about :refer in :require?

that does not add the var to ns-publics of the current ns which means it's unavailable to consumers of the referring namespace.

Ah, right.