Closure construction from raw pointers

std_shims/closures.nim

@@ -0,0 +1,27 @@
+proc init*[ClosureType: proc](T: type ClosureType; p, env: pointer): T =
+  {.emit: "`result`->ClP_0 = `p`; `result`->ClE_0 = `env`;".}
+
+when isMainModule:
+  type
+    SomeClosure = proc(y: string): int
+
+  proc makeClosure(x: int): SomeClosure =
+    result = proc(y: string): int =
+      return x + y.len + 10
+
+  var f1 = makeClosure(20)
+  doAssert f1("test") == 34
+
+  type
+    CustomEnvironment = object
+      captured: int
+
+  proc rawClosureProc(y: string, env: pointer): int =
+    return cast[ptr CustomEnvironment](env).captured + y.len + 10
+
+  var env = create CustomEnvironment
+  env.captured = 10
+
+  var f2: SomeClosure = SomeClosure.init(rawClosureProc, cast[pointer](env))
+  doAssert f2("test") == 24
+