From ae108f7a567a87188b144d3fe4f99ddf808750de Mon Sep 17 00:00:00 2001
From: Joey Yakimowich-Payne <jyakimowich-payne@dotdash.com>
Date: Thu, 13 Feb 2020 08:02:20 -0700
Subject: [PATCH] WIP 4

---
 lib/pure/collections/hashcommon.nim |  2 +-
 lib/pure/hashes.nim                 | 14 +++++++-------
 tests/collections/thashsets.nim     | 12 +++++++++++-
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/lib/pure/collections/hashcommon.nim b/lib/pure/collections/hashcommon.nim
index ce5ab5809..6281074af 100644
--- a/lib/pure/collections/hashcommon.nim
+++ b/lib/pure/collections/hashcommon.nim
@@ -52,7 +52,7 @@ proc rawGetKnownHC[X, A](t: X, key: A, hc: Hash): int {.inline.} =
   rawGetKnownHCImpl()
 
 template genHashImpl(key, hc: typed) =
-  hc = hash(key, targetBits=lastSetBit(maxHash(t)))
+  hc = hash(key, targetBits=lastSetBit(maxHash(t).uint))
   if hc == 0: # This almost never taken branch should be very predictable.
     hc = 314159265 # Value doesn't matter; Any non-zero favorite is fine.
 
diff --git a/lib/pure/hashes.nim b/lib/pure/hashes.nim
index 111e25382..9a511ce9d 100644
--- a/lib/pure/hashes.nim
+++ b/lib/pure/hashes.nim
@@ -117,11 +117,11 @@ const
   defaultSeedB = (1734880652122947187'u64).uint
 
 template computeIntegerHash(x, numBits, seedA, seedB): Hash =
-  cast[Hash]((seedA*cast[uint](x) + seedB) shr (sizeof(x)*8 - targetBits*8))
+  cast[Hash]((seedA*cast[uint](x) + seedB) shr (sizeof(x)*8 - numBits*8))
 
 proc hash*(
   x: int,
-  targetBits = sizeof(uint).uint32,
+  targetBits: SomeUnsignedInt = sizeof(uint),
   seedA = defaultSeedA,
   seedB = defaultSeedB
 ): Hash {.inline.} =
@@ -130,7 +130,7 @@ proc hash*(
 
 proc hash*(
   x: int64,
-  targetBits = sizeof(uint).uint32,
+  targetBits: SomeUnsignedInt = sizeof(uint),
   seedA = defaultSeedA,
   seedB = defaultSeedB
 ): Hash {.inline.} =
@@ -139,7 +139,7 @@ proc hash*(
 
 proc hash*(
   x: uint,
-  targetBits = sizeof(uint).uint32,
+  targetBits: SomeUnsignedInt = sizeof(uint),
   seedA = defaultSeedA,
   seedB = defaultSeedB
 ): Hash {.inline.} =
@@ -148,7 +148,7 @@ proc hash*(
 
 proc hash*(
   x: uint64,
-  targetBits = sizeof(uint).uint32,
+  targetBits: SomeUnsignedInt = sizeof(uint),
   seedA = defaultSeedA,
   seedB = defaultSeedB
 ): Hash {.inline.} =
@@ -157,7 +157,7 @@ proc hash*(
 
 proc hash*(
   x: char,
-  targetBits = sizeof(uint).uint32,
+  targetBits: SomeUnsignedInt = sizeof(uint),
   seedA = defaultSeedA,
   seedB = defaultSeedB
 ): Hash {.inline.} =
@@ -166,7 +166,7 @@ proc hash*(
 
 proc hash*[T: Ordinal](
   x: T,
-  targetBits = sizeof(uint).uint32,
+  targetBits: SomeUnsignedInt = sizeof(uint),
   seedA = defaultSeedA,
   seedB = defaultSeedB
 ): Hash {.inline.} =
diff --git a/tests/collections/thashsets.nim b/tests/collections/thashsets.nim
index cd4401511..bccf4654f 100644
--- a/tests/collections/thashsets.nim
+++ b/tests/collections/thashsets.nim
@@ -1,4 +1,4 @@
-import sets, hashes, algorithm
+import sets, hashes, algorithm, bitops
 
 
 block setEquality:
@@ -120,3 +120,13 @@ block hashForOrderdSet:
   reversed = !$reversed
   doAssert hash(r) == reversed
   doAssert hash(s1) != reversed
+
+block hashDoesntHaveLowerBitsCleared:
+  let num32 = 0xFFFF.uint32
+  let bits = num32.lastBitSet
+
+  let h1 = hash(0xFFFFFFFF00000000'u64, targetBits=bits)
+  let h2 = hash(0x2345123400000000'u64, targetBits=bits)
+
+
+  doAssert (h1 and num32) != (h2 and num32)