Fix remove-argument-side-effects with keyword call (#60195)

Fix #60152, which impacted both lowering implementations.
      `remove-argument-side-effects` assumed all `kw` arguments from a
`parameters` block had already been dumped into the argument list, which
is
     not true in some cases.  In addition:

- JuliaLowering hit a MethodError in the dumped-`kw` case regardless.
There are other issues with `kw` which I'm ignoring in this PR (see
#60162)

- Delete some ancient history: `&` [used to be a valid
argument](a378b75#diff-5d79463faae0f7f19454c7f9888498d9f876082e258ab3efdca36a0ee64b0c87L72)
head sometime in 2012 apparently!

Author: mlechu

JuliaLowering/src/desugaring.jl

@@ -539,7 +539,11 @@ function _arg_to_temp(ctx, stmts, ex, eq_is_kw=false)
     elseif k == K"..."
         @ast ctx ex [k _arg_to_temp(ctx, stmts, ex[1])]
     elseif k == K"=" && eq_is_kw
-        @ast ctx ex [K"=" ex[1] _arg_to_temp(ex[2])]
+        @ast ctx ex [K"=" ex[1] _arg_to_temp(ctx, stmts, ex[2], false)]
+    elseif k == K"parameters"
+        mapchildren(ctx, ex) do e
+            _arg_to_temp(ctx, stmts, e, true)
+        end
     else
         emit_assign_tmp(stmts, ctx, ex)
     end

JuliaLowering/test/assignments.jl

@@ -95,4 +95,18 @@ let
 end
 """) == 3
 
+# removing argument side effect in kwcall lhs
+@eval test_mod f60152(v, pa; kw) = copy(v)
+@test JuliaLowering.include_string(test_mod, """
+    f60152([1, 2, 3], 0; kw=0) .*= 2
+""") == [2,4,6]
+@test JuliaLowering.include_string(test_mod, """
+let
+    pa_execs = 0
+    kw_execs = 0
+    out = f60152([1, 2, 3], (pa_execs+=1); kw=(kw_execs+=1)) .*= 2
+    (out, pa_execs, kw_execs)
+end
+""") == ([2,4,6], 1, 1)
+
 end

src/julia-syntax.scm

@@ -1809,11 +1809,13 @@
       (cons e '())
       (let ((a '()))
         (define (arg-to-temp x)
-          (cond ((effect-free? x)  x)
-                ((or (eq? (car x) '...) (eq? (car x) '&))
-                 `(,(car x) ,(arg-to-temp (cadr x))))
+          (cond ((effect-free? x) x)
+                ((eq? (car x) '...)
+                 `(... ,(arg-to-temp (cadr x))))
                 ((eq? (car x) 'kw)
-                 `(,(car x) ,(cadr x) ,(arg-to-temp (caddr x))))
+                 `(kw ,(cadr x) ,(arg-to-temp (caddr x))))
+                ((eq? (car x) 'parameters)
+                 `(parameters ,@(map arg-to-temp (cdr x))))
                 (else
                  (let ((g (make-ssavalue)))
                    (begin (set! a (cons `(= ,g ,x) a))

test/syntax.jl

@@ -3730,7 +3730,7 @@ end
     @test p("public() = 6") == Expr(:(=), Expr(:call, :public), Expr(:block, 6))
 end
 
-@testset "removing argument sideeffects" begin
+@testset "removing argument side effects" begin
     # Allow let blocks in broadcasted LHSes, but only evaluate them once:
     execs = 0
     array = [1]
@@ -3746,6 +3746,15 @@ end
     let; execs += 1; array; end::Vector{Int} .= 7
     @test array == [7]
     @test execs == 4
+
+    # remove argument side effects on lhs kwcall
+    pa_execs = 0
+    kw_execs = 0
+    f60152(v, pa; kw) = copy(v)
+    @test (f60152([1, 2, 3], 0; kw=0) .*= 2) == [2,4,6]
+    @test (f60152([1, 2, 3], (pa_execs+=1); kw=(kw_execs+=1)) .*= 2) == [2,4,6]
+    @test pa_execs === 1
+    @test kw_execs === 1
 end
 
 # Allow GlobalRefs in macro definition