From dc2befcffc7412768097c2a2a6819724a4745aeb Mon Sep 17 00:00:00 2001
From: Jeff Bezanson <jeff.bezanson@gmail.com>
Date: Fri, 18 Jun 2021 14:18:45 -0400
Subject: [PATCH] fix #41253, parse error in `function (::T{})` (#41259)

---
 src/julia-parser.scm | 7 +++++--
 test/syntax.jl       | 3 +++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/julia-parser.scm b/src/julia-parser.scm
index 70912c4272c8c..3a5dfad9293bd 100644
--- a/src/julia-parser.scm
+++ b/src/julia-parser.scm
@@ -1329,7 +1329,8 @@
 (define (valid-1arg-func-sig? sig)
   (or (symbol? sig)
       (and (pair? sig) (eq? (car sig) '|::|)
-           (symbol? (cadr sig)))))
+           (or (symbol? (cadr sig))
+               (length= sig 2)))))
 
 (define (unwrap-where x)
   (if (and (pair? x) (eq? (car x) 'where))
@@ -1469,7 +1470,9 @@
                                    ;; function foo  =>  syntax error
                                    (error (string "expected \"(\" in " word " definition")))
                                (if (not (valid-func-sig? paren sig))
-                                   (error (string "expected \"(\" in " word " definition"))
+                                   (if paren
+                                       (error (string "ambiguous signature in " word " definition. Try adding a comma if this is a 1-argument anonymous function."))
+                                       (error (string "expected \"(\" in " word " definition")))
                                    sig)))
                      (body (parse-block s)))
                 (expect-end s word)
diff --git a/test/syntax.jl b/test/syntax.jl
index 7cee3c0755f65..6e3ec82ca3e81 100644
--- a/test/syntax.jl
+++ b/test/syntax.jl
@@ -2927,3 +2927,6 @@ b'` == `$("a\\\nb")`
           \\
           ``` == `'\'`
 end
+
+# issue #41253
+@test (function (::Dict{}); end)(Dict()) === nothing