From 91746828de019efb053bcb2b2c285d9ca720a99f Mon Sep 17 00:00:00 2001
From: Sam Schweigel <sam.schweigel@juliahub.com>
Date: Tue, 7 Oct 2025 16:38:01 -0700
Subject: [PATCH] Make `=` and `const` toplevel-preserving syntax

Previously, `map-cl-convert` would keep the toplevel flag only when the
containing expression was toplevel and each element of the list passed to it
satisfied `toplevel-preserving?`.  Instead, make it so `toplevel-preserving?`
expressions are those where the toplevel flag should be propagated to the
children during closure conversion.

Fixes #59755.
---
 src/julia-syntax.scm |  8 +++-----
 test/syntax.jl       | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/src/julia-syntax.scm b/src/julia-syntax.scm
index 6bfb3ff5a7a7e..f3a57c6699c08 100644
--- a/src/julia-syntax.scm
+++ b/src/julia-syntax.scm
@@ -4063,14 +4063,12 @@ f(x) = yt(x)
     (and vi (vinfo:nospecialize vi))))
 
 (define (toplevel-preserving? e)
-  (and (pair? e) (memq (car e) '(if elseif block trycatch tryfinally trycatchelse))))
+  (and (pair? e) (memq (car e) '(if elseif block trycatch tryfinally trycatchelse = const))))
 
 (define (map-cl-convert exprs fname lam namemap defined toplevel interp opaq toplevel-pure parsed-method-stack (globals (table)) (locals (table)))
   (if toplevel
       (map (lambda (x)
-             (let ((tl (lift-toplevel (cl-convert x fname lam namemap defined
-                                                  (and toplevel (toplevel-preserving? x))
-                                                  interp opaq toplevel-pure parsed-method-stack globals locals))))
+             (let ((tl (lift-toplevel (cl-convert x fname lam namemap defined toplevel interp opaq toplevel-pure parsed-method-stack globals locals))))
                (if (null? (cdr tl))
                    (car tl)
                    `(block ,@(cdr tl) ,(car tl)))))
@@ -4473,7 +4471,7 @@ f(x) = yt(x)
            (cl-convert (cadr e) fname lam namemap defined toplevel interp opaq toplevel-pure parsed-method-stack globals locals))
           (else
            (cons (car e)
-                 (map-cl-convert (cdr e) fname lam namemap defined toplevel interp opaq toplevel-pure parsed-method-stack globals locals))))))))
+                 (map-cl-convert (cdr e) fname lam namemap defined (and toplevel (toplevel-preserving? e)) interp opaq toplevel-pure parsed-method-stack globals locals))))))))
 
 ;; wrapper for `cl-convert-`
 (define (cl-convert e fname lam namemap defined toplevel interp opaq toplevel-pure (parsed-method-stack '()) (globals (table)) (locals (table)))
diff --git a/test/syntax.jl b/test/syntax.jl
index af5d7ce5e50e8..cec389be057ad 100644
--- a/test/syntax.jl
+++ b/test/syntax.jl
@@ -4617,3 +4617,47 @@ end
     @test_throws UndefVarError macroexpand(@__MODULE__, :(@undefined_macro(x)))
     @test_throws UndefVarError macroexpand!(@__MODULE__, :(@undefined_macro(x)))
 end
+
+# #59755 - Don't hoist global declarations out of toplevel-preserving syntax
+module M59755 end
+@testset "toplevel-preserving syntax" begin
+    Core.eval(M59755, :(if true
+                            global v1::Bool
+                        else
+                            const v1 = 1
+                        end))
+    @test !isdefined(M59755, :v1)
+    @test Base.binding_kind(M59755, :v1) == Base.PARTITION_KIND_GLOBAL
+    @test Core.get_binding_type(M59755, :v1) == Bool
+
+    Core.eval(M59755, :(if false
+                            global v2::Bool
+                        else
+                            const v2 = 2
+                        end))
+    @test M59755.v2 === 2
+    @test Base.binding_kind(M59755, :v2) == Base.PARTITION_KIND_CONST
+
+    Core.eval(M59755, :(v3 = if true
+                            global v4::Bool
+                            4
+                        else
+                            const v4 = 5
+                            6
+                        end))
+    @test M59755.v3 == 4
+    @test !isdefined(M59755, :v4)
+    @test Base.binding_kind(M59755, :v4) == Base.PARTITION_KIND_GLOBAL
+    @test Core.get_binding_type(M59755, :v4) == Bool
+
+    Core.eval(M59755, :(v5 = if false
+                            global v6::Bool
+                            4
+                        else
+                            const v6 = 5
+                            6
+                        end))
+    @test M59755.v5 === 6
+    @test M59755.v6 === 5
+    @test Base.binding_kind(M59755, :v6) == Base.PARTITION_KIND_CONST
+end