From 339ebe958dad77caa04c50161a00288da8c3cab3 Mon Sep 17 00:00:00 2001
From: flywind <43030857+xflywind@users.noreply.github.com>
Date: Mon, 15 Feb 2021 07:22:46 -0600
Subject: [PATCH] JS: fix div uint64 no truncation (#16899)

---
 compiler/jsgen.nim    |  5 ++++-
 tests/arithm/tdiv.nim | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 tests/arithm/tdiv.nim

diff --git a/compiler/jsgen.nim b/compiler/jsgen.nim
index 04009250e8..5d96907b56 100644
--- a/compiler/jsgen.nim
+++ b/compiler/jsgen.nim
@@ -671,7 +671,10 @@ proc arith(p: PProc, n: PNode, r: var TCompRes, op: TMagic) =
   of mAddU: binaryUintExpr(p, n, r, "+")
   of mSubU: binaryUintExpr(p, n, r, "-")
   of mMulU: binaryUintExpr(p, n, r, "*")
-  of mDivU: binaryUintExpr(p, n, r, "/")
+  of mDivU:
+    binaryUintExpr(p, n, r, "/")
+    if n[1].typ.skipTypes(abstractRange).size == 8:
+      r.res = "Math.trunc($1)" % [r.res]
   of mDivI:
     arithAux(p, n, r, op)
   of mModI:
diff --git a/tests/arithm/tdiv.nim b/tests/arithm/tdiv.nim
new file mode 100644
index 0000000000..5d8eed84dc
--- /dev/null
+++ b/tests/arithm/tdiv.nim
@@ -0,0 +1,19 @@
+discard """
+  targets: "c js"
+"""
+
+
+block divUint64:
+  proc divTest() =
+    let x1 = 12'u16
+    let y = x1 div 5'u16
+    let x2 = 1345567'u32
+    let z = x2 div 5'u32
+    let a = 1345567'u64 div uint64(x1)
+    doAssert y == 2
+    doAssert z == 269113
+    doAssert a == 112130
+
+  static: divTest()
+  divTest()
+