fix #25020, syntax error for using X() (#25836)

Author: JeffBezanson

Diff for: src/julia-parser.scm

@@ -1058,7 +1058,9 @@
            (and (not (number? t))    ;; disallow "x.3" and "sqrt(2)2"
                 (not (eqv? t #\@))   ;; disallow "x@time"
                 ;; issue #16427, disallow juxtaposition with block forms
-                (not (and (pair? expr) (block-form? (car expr)))))
+                (not (and (pair? expr) (or (block-form? (car expr))
+                                           (syntactic-unary-op? (car expr))
+                                           (initial-reserved-word? (car expr))))))
            ;; to allow x'y as a special case
            #;(and (pair? expr) (memq (car expr) '(|'| |.'|))
                 (not (memv t '(#\( #\[ #\{))))
@@ -1071,7 +1073,6 @@
            ;; issue #20575
            (error "cannot juxtapose string literal"))
        (not (initial-reserved-word? t))
-       (not (and (pair? expr) (syntactic-unary-op? (car expr))))
        ;; TODO: this would disallow juxtaposition with 0, which is ambiguous
        ;; with e.g. hex literals `0x...`. however this is used for `0im`, which
        ;; we might not want to break.

Diff for: test/syntax.jl

@@ -1265,3 +1265,6 @@ function bar16239()
     f()
 end
 @test bar16239() == 0
+
+# issue #25020
+@test_throws ParseError Meta.parse("using Colors()")