make .= return its right hand side. fixes #25954

src/julia-syntax.scm

@@ -1921,7 +1921,12 @@
 
    '.=
    (lambda (e)
-     (expand-fuse-broadcast (cadr e) (caddr e)))
+     `(ifvalue
+       ,(let ((temp (make-ssavalue)))
+          `(block ,(expand-forms `(= ,temp ,(caddr e)))
+                  ,(expand-fuse-broadcast (cadr e) temp)
+                  ,temp))
+       ,(expand-fuse-broadcast (cadr e) (caddr e))))
 
    '|<:|
    (lambda (e) (expand-forms `(call |<:| ,@(cdr e))))
@@ -3679,6 +3684,8 @@ f(x) = yt(x)
              (if value
                  (compile (cadr e) break-labels value tail)
                  #f))
+            ((ifvalue)
+             (compile (if value (cadr e) (caddr e)) break-labels value tail))
             ((if elseif)
              (let ((test `(gotoifnot ,(compile-cond (cadr e) break-labels) _))
                    (end-jump `(goto _))

test/broadcast.jl

@@ -612,3 +612,15 @@ let n = 1
     @test ceil.(Int, n ./ (1,)) == (1,)
     @test ceil.(Int, 1 ./ (1,)) == (1,)
 end
+
+# issue #25954, value of `.=`
+let a = zeros(2, 3), b = zeros(4, 5)
+    a .= b .= 1
+    @test a == ones(2, 3)
+    @test b == ones(4, 5)
+    @test (b .= 1) === 1
+    c = [6, 7]; d = [8, 9]
+    x = (a .= c.+d)
+    @test a == [14 14 14; 16 16 16]
+    @test x == [14, 16]
+end