fix #43960, evaluation order of splat inside ref

Author: JeffBezanson

src/julia-syntax.scm

@@ -130,31 +130,29 @@
 ;; returns (values index-list stmts) where stmts are statements that need
 ;; to execute first.
 (define (process-indices a i)
-  (let loop ((lst i)
-             (n   1)
-             (stmts '())
-             (tuples '())
-             (ret '()))
-    (if (null? lst)
-        (values (reverse ret) (reverse stmts))
-        (let ((idx  (car lst))
-              (last (null? (cdr lst))))
-          (if (and (pair? idx) (eq? (car idx) '...))
-              (if (symbol-like? (cadr idx))
-                  (loop (cdr lst) (+ n 1)
-                        stmts
-                        (cons (cadr idx) tuples)
-                        (cons `(... ,(replace-beginend (cadr idx) a n tuples last))
-                              ret))
-                  (let ((g (make-ssavalue)))
-                    (loop (cdr lst) (+ n 1)
-                          (cons `(= ,g ,(replace-beginend (cadr idx) a n tuples last))
-                                stmts)
-                          (cons g tuples)
-                          (cons `(... ,g) ret))))
-              (loop (cdr lst) (+ n 1)
-                    stmts tuples
-                    (cons (replace-beginend idx a n tuples last) ret)))))))
+  (let* ((ex `(ref ,a ,@i))
+         (r-a-s-e (if (any vararg? i)
+                      (remove-argument-side-effects ex)
+                      (cons ex '())))
+         (a (cadr (car r-a-s-e)))
+         (i (cddr (car r-a-s-e)))
+         (stmts (cdr r-a-s-e)))
+    (let loop ((lst i)
+               (n   1)
+               (tuples '())
+               (ret '()))
+      (if (null? lst)
+          (values (reverse ret) stmts)
+          (let ((idx  (car lst))
+                (last (null? (cdr lst))))
+            (if (vararg? idx)
+                (loop (cdr lst) (+ n 1)
+                      (cons (cadr idx) tuples)
+                      (cons `(... ,(replace-beginend (cadr idx) a n tuples last))
+                            ret))
+                (loop (cdr lst) (+ n 1)
+                      tuples
+                      (cons (replace-beginend idx a n tuples last) ret))))))))
 
 ;; GF method does not need to keep decl expressions on lambda args
 ;; except for rest arg

test/syntax.jl

@@ -1204,6 +1204,14 @@ end
 @test [(0,0)... 1] == [0 0 1]
 @test Float32[(0,0)... 1] == Float32[0 0 1]
 
+# issue #43960, evaluation order of splatting in `ref`
+let a = [], b = [4,3,2,1]
+    f() = (push!(a, 1); 2)
+    g() = (push!(a, 2); ())
+    @test b[f(), g()...] == 3
+    @test a == [1,2]
+end
+
 @testset "raw_str macro" begin
     @test raw"$" == "\$"
     @test raw"\n" == "\\n"