improve PosMap

Cargo.lock

@@ -145,6 +145,12 @@ dependencies = [
  "windows-sys",
 ]
 
+[[package]]
+name = "const_for"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9c50fcfdf972929aff202c16b80086aa3cfc6a3a820af714096c58c7c1d0582"
+
 [[package]]
 name = "criterion"
 version = "0.5.1"
@@ -443,6 +449,7 @@ dependencies = [
  "allocative",
  "arrayvec",
  "console",
+ "const_for",
  "criterion",
  "crossbeam-channel",
  "either",