fix bug in let when a global var is both shadowed and used in an RHS (

JuliaLang#39570)

src/julia-syntax.scm

@@ -1221,41 +1221,25 @@
  (decl? (cadar binds)))
  (let ((vname (decl-var (cadar binds))))
  (loop (cdr binds)
- (if (expr-contains-eq vname (caddar binds))
- (let ((tmp (make-ssavalue)))
- `(scope-block
- (block ,@hs
- (= ,tmp ,(caddar binds))
- (scope-block
- (block
- (local-def ,(cadar binds))
- (= ,vname ,tmp)
- ,blk)))))
- `(scope-block
- (block ,@hs
- (local-def ,(cadar binds))
- (= ,vname ,(caddar binds))
- ,blk))))))
+ (let ((tmp (make-ssavalue)))
+ `(block (= ,tmp ,(caddar binds))
+ (scope-block
+ (block ,@hs
+ (local-def ,(cadar binds))
+ (= ,vname ,tmp)
+ ,blk)))))))
  ;; (a, b, c, ...) = rhs
  ((and (pair? (cadar binds))
  (eq? (caadar binds) 'tuple))
  (let ((vars (lhs-vars (cadar binds))))
  (loop (cdr binds)
- (if (expr-contains-p (lambda (x) (memq x vars)) (caddr (car binds)))
- ;; use more careful lowering if there are name conflicts. issue #25652
- (let ((temp (make-ssavalue)))
- `(block
- (= ,temp ,(caddr (car binds)))
- (scope-block
- (block ,@hs
- ,@(map (lambda (v) `(local-def ,v)) vars)
- (= ,(cadr (car binds)) ,temp)
- ,blk))))
- `(scope-block
- (block ,@hs
- ,@(map (lambda (v) `(local-def ,v)) vars)
- ,(car binds)
- ,blk))))))
+ (let ((tmp (make-ssavalue)))
+ `(block (= ,tmp ,(caddar binds))
+ (scope-block
+ (block ,@hs
+ ,@(map (lambda (v) `(local-def ,v)) vars)
+ (= ,(cadar binds) ,tmp)
+ ,blk)))))))
  (else (error "invalid let syntax"))))
  (else (error "invalid let syntax")))))))))
 

test/core.jl

@@ -4124,15 +4124,6 @@ let ex = quote
  @test ex.args[2] == :test
 end
 
-# issue #25652
-x25652 = 1
-x25652_2 = let (x25652, _) = (x25652, nothing)
- x25652 = x25652 + 1
- x25652
-end
-@test x25652_2 == 2
-@test x25652 == 1
-
 # issue #15180
 function f15180(x::T) where T
  X = Vector{T}(undef, 1)

test/syntax.jl

@@ -2678,3 +2678,21 @@ end
  @test f((b=3, c=2, a=4)) == (4, 3)
  @test_throws ErrorException f((;))
 end
+
+# issue #25652
+x25652 = 1
+x25652_2 = let (x25652, _) = (x25652, nothing)
+ x25652 = x25652 + 1
+ x25652
+end
+@test x25652_2 == 2
+@test x25652 == 1
+
+@test let x = x25652
+ x25652 = x+3
+ x25652
+end == 4
+@test let (x,) = (x25652,)
+ x25652 = x+3
+ x25652
+end == 4