equality and hashing for closures

lib/pure/hashes.nim

@@ -67,6 +67,13 @@ proc hash*(x: Pointer): THash {.inline.} =
   else:
     result = (cast[THash](x)) shr 3 # skip the alignment
   
+proc hash*[T: proc](x: T): THash {.inline.} =
+  ## efficient hashing of proc vars; closures are supported too.
+  when T is "closure":
+    result = hash(rawProc(x)) !& hash(rawEnv(x))
+  else:
+    result = hash(pointer(x))
+  
 proc hash*(x: int): THash {.inline.} = 
   ## efficient hashing of integers
   result = x

lib/system.nim

@@ -1348,6 +1348,7 @@ proc isNil*(x: string): 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".}
   ## Fast check whether `x` is nil. This is sometimes more efficient than
   ## ``== nil``.