Arc global (#20768)

* temp

* unsure

* fix condition

* port macro arc runable examples to one file

* trigger doc ci

* fix

Co-authored-by: ringabout <43030857+ringabout@users.noreply.github.com>

tests/arc/tarc_macro.nim

@@ -0,0 +1,46 @@
+import macros
+
+var destroyCalled = false
+macro bar() =
+  let s = newTree(nnkAccQuoted, ident"=destroy")
+  # let s = ident"`=destroy`" # this would not work
+  result = quote do:
+    type Foo = object
+    # proc `=destroy`(a: var Foo) = destroyCalled = true # this would not work
+    proc `s`(a: var Foo) = destroyCalled = true
+    block:
+      let a = Foo()
+bar()
+doAssert destroyCalled
+
+# custom `op`
+var destroyCalled2 = false
+macro bar(ident) =
+  var x = 1.5
+  result = quote("@") do:
+    type Foo = object
+    let `@ident` = 0 # custom op interpolated symbols need quoted (``)
+    proc `=destroy`(a: var Foo) =
+      doAssert @x == 1.5
+      doAssert compiles(@x == 1.5)
+      let b1 = @[1,2]
+      let b2 = @@[1,2]
+      doAssert $b1 == "[1, 2]"
+      doAssert $b2 == "@[1, 2]"
+      destroyCalled2 = true
+    block:
+      let a = Foo()
+bar(someident)
+doAssert destroyCalled2
+
+proc `&%`(x: int): int = 1
+proc `&%`(x, y: int): int = 2
+
+macro bar2() =
+  var x = 3
+  result = quote("&%") do:
+    var y = &%x # quoting operator
+    doAssert &%&%y == 1 # unary operator => need to escape
+    doAssert y &% y == 2 # binary operator => no need to escape
+    doAssert y == 3
+bar2()