fix iterator equality + add test for proc equality + fix sameType (#21707)

* fix iterator equality + add test also for procs

fixes #21706

* all targets

* and isNil and repr

* separate overloads, fix sameType

* more restricted sameType?

* merge overloads again??

* remove sametype change for now

* fix sameType anyway (CI failure was not related)

---------

Co-authored-by: ringabout <43030857+ringabout@users.noreply.github.com>
(cherry picked from commit 380dafcc32)

lib/system.nim

@@ -1619,7 +1619,7 @@ proc isNil*[T](x: ref T): bool {.noSideEffect, magic: "IsNil".}
 proc isNil*[T](x: ptr T): bool {.noSideEffect, magic: "IsNil".}
 proc isNil*(x: pointer): bool {.noSideEffect, magic: "IsNil".}
 proc isNil*(x: cstring): bool {.noSideEffect, magic: "IsNil".}
-proc isNil*[T: proc](x: T): bool {.noSideEffect, magic: "IsNil".}
+proc isNil*[T: proc | iterator {.closure.}](x: T): bool {.noSideEffect, magic: "IsNil".}
   ## Fast check whether `x` is nil. This is sometimes more efficient than
   ## `== nil`.
 

lib/system/comparisons.nim

@@ -35,7 +35,7 @@ proc `==`*[T](x, y: ref T): bool {.magic: "EqRef", noSideEffect.}
   ## Checks that two `ref` variables refer to the same item.
 proc `==`*[T](x, y: ptr T): bool {.magic: "EqRef", noSideEffect.}
   ## Checks that two `ptr` variables refer to the same item.
-proc `==`*[T: proc](x, y: T): bool {.magic: "EqProc", noSideEffect.}
+proc `==`*[T: proc | iterator](x, y: T): bool {.magic: "EqProc", noSideEffect.}
   ## Checks that two `proc` variables refer to the same procedure.
 
 proc `<=`*[Enum: enum](x, y: Enum): bool {.magic: "LeEnum", noSideEffect.}

lib/system/repr_v2.nim

@@ -88,7 +88,7 @@ proc repr*(p: pointer): string =
         result[j] = HexChars[n and 0xF]
         n = n shr 4
 
-proc repr*(p: proc): string =
+proc repr*(p: proc | iterator {.closure.}): string =
   ## repr of a proc as its address
   repr(cast[ptr pointer](unsafeAddr p)[])