Can someone please tell me how #_ reader macro is implemented? Searching through http://github.com/clojure/clojure, I can't seem to find it.

@ag It's probably in LispReader.java.

It is, right in clojure.lang.LispReader.DiscardReader.

Thank you!

https://github.com/clojure/clojure/blob/5ffe3833508495ca7c635d47ad7a1c8b820eab76/src/jvm/clojure/lang/LispReader.java#L118

Is ( a symbol?

no

these are all symbols that sometimes are namespaced/symbols

( is just a token for the lisp reader that is not reified anywhere I’m assuming?

/ % + <!! also symbols

I don't understand how the spec error can be so clear and yet i don't see the same thing. What i see is that the :refere-clojure is correctly using :exlude (first code block) but the spec error (second block) is very clear that it think it's an ":as" could the way i got to the library be not taking me to the real code? I just hovered over the import in my app and did a lsp-find-defination.

(ns clojure.core.async
  "Facilities for async programming and communication.

go blocks are dispatched over an internal thread pool, which
defaults to 8 threads. The size of this pool can be modified using
the Java system property `clojure.core.async.pool-size`."
  (:refer-clojure :exclude [reduce transduce into merge map take partition ;; <--------------- looks fine to me
                            partition-by bounded-count])
  (:require [clojure.core.async.impl.protocols :as impl]
            [clojure.core.async.impl.channels :as channels]
            [clojure.core.async.impl.buffers :as buffers]
            [clojure.core.async.impl.timers :as timers]
            [clojure.core.async.impl.dispatch :as dispatch]
            [clojure.core.async.impl.ioc-macros :as ioc]
            [clojure.core.async.impl.mutex :as mutex]
            [clojure.core.async.impl.concurrent :as conc]
            )
  (:import [java.util.concurrent.locks Lock]
           [java.util.concurrent Executors Executor ThreadLocalRandom]
           [java.util ArrayList]))

aused by: clojure.lang.ExceptionInfo: Call to clojure.core/refer-clojure did not conform to spec:
-- Spec failed --------------------

  (... ... ':as ...)
           ^^^^

should be one of: :exclude, :only, :rename

-- Spec failed --------------------

  (... ... (... :as) ...)
                ^^^

should be one of: :exclude, :only, :rename

-------------------------
Detected 2 errors
 {:clojure.spec.alpha/problems ({:path [:args :exclude :op :spec], :pred #{:exclude}, :val (quote :as), :via [], :in [2]} {:path [:args :exclude :op :quoted-spec :spec], :pred #{:exclude}, :val :as, :via [], :in [2 1]} {:path [:args :only :op :spec], :pred #{:only}, :val (quote :as), :via [], :in [2]} {:path [:args :only :op :quoted-spec :spec], :pred #{:only}, :val :as, :via [], :in [2 1]} {:path [:args :rename :op :spec], :pred #{:rename}, :val (quote :as), :via [], :in [2]} {:path [:args :rename :op :quoted-spec :spec], :pred #{:rename}, :val :as, :via [], :in [2 1]}), :clojure.spec.alpha/spec #object[clojure.spec.alpha$regex_spec_impl$reify__2436 0x1cb9ef52 "clojure.spec.alpha$regex_spec_impl$reify__2436@1cb9ef52"], :clojure.spec.alpha/value ((quote :exclude) (quote [reduce transduce into merge map take partition partition-by bounded-count]) (quote :as) (quote core)), :clojure.spec.alpha/args ((quote :exclude) (quote [reduce transduce into merge map take partition partition-by bounded-count]) (quote :as) (quote core))}