Make no-body function declaration implicitly global

These were the intended semantics of #57311 (and matches what it
used to do in 1.11). Note however that this differs from the
body-ful form, which now always tries to extend. Fixes #57546.

Author: Keno

src/julia-syntax.scm

@@ -1181,7 +1181,9 @@
     (cond ((and (length= e 2) (or (symbol? name) (globalref? name)))
            (if (not (valid-name? name))
                (error (string "invalid function name \"" name "\"")))
-           `(method ,name))
+           (if (globalref? name)
+            `(block (global ,name) (method ,name))
+            `(method ,name)))
           ((not (pair? name))  e)
           ((eq? (car name) 'call)
            (let* ((raw-typevars (or where '()))

test/syntax.jl

@@ -4110,3 +4110,11 @@ end
 # Issue #56904 - lambda linearized twice
 @test (let; try 3; finally try 1; f(() -> x); catch x; end; end; x = 7; end) === 7
 @test (let; try 3; finally try 4; finally try 1; f(() -> x); catch x; end; end; end; x = 7; end) === 7
+
+# Issue #57546 - explicit function declaration should create new global
+module FuncDecl57546
+    using Test
+    @test_nowarn @eval function Any end
+    @test isa(Any, Function)
+    @test isempty(methods(Any))
+end