Display argument that is duplicated in function calls (#35857)

Author: ssikdar1

src/julia-syntax.scm

@@ -335,11 +335,11 @@
          (optional-positional-defs name sparams req opt dfl body
                                    (append req opt vararg) rett)))))
    ;; no optional positional args
-   (let ((names (map car sparams))
-         (anames (map (lambda (x) (if (underscore-symbol? x) UNUSED x))
-                      (llist-vars argl))))
-     (if (has-dups (filter (lambda (x) (not (eq? x UNUSED))) anames))
-         (error "function argument names not unique"))
+   (let* ((names (map car sparams))
+          (anames (map (lambda (x) (if (underscore-symbol? x) UNUSED x)) (llist-vars argl)))
+          (unused_anames (filter (lambda (x) (not (eq? x UNUSED))) anames)))
+     (if (has-dups unused_anames)
+         (error (string "function argument name not unique: \"" (car (has-dups unused_anames)) "\"")))
      (if (has-dups names)
          (error "function static parameter names not unique"))
      (if (any (lambda (x) (and (not (eq? x UNUSED)) (memq x names))) anames)

test/syntax.jl

@@ -2192,7 +2192,7 @@ end
 
 # Syntax desugaring pass errors contain line numbers
 @test Meta.lower(@__MODULE__, Expr(:block, LineNumberNode(101, :some_file), :(f(x,x)=1))) ==
-    Expr(:error, "function argument names not unique around some_file:101")
+    Expr(:error, "function argument name not unique: \"x\" around some_file:101")
 
 # Ensure file names don't leak between `eval`s
 eval(LineNumberNode(11, :incorrect_file))