From 272bc81f51b59ccde9c91818816f40a88266cd32 Mon Sep 17 00:00:00 2001
From: Bung <crc32@qq.com>
Date: Thu, 12 Nov 2020 01:41:49 +0800
Subject: [PATCH] Fix 14127 js from int to int casting (#15918)

* fix #14127 from int to int casting

* add test for #14127

* use template for test, also test uint2int

* move to tests/types/t14127_cast_number.nim targets:c cpp js

(cherry picked from commit a81434a890d70e7146c440c59caadc701c6099b3)
---
 compiler/jsgen.nim                 |  3 +--
 tests/types/t14127_cast_number.nim | 30 ++++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 tests/types/t14127_cast_number.nim

diff --git a/compiler/jsgen.nim b/compiler/jsgen.nim
index ba43610980..708c1cad7e 100644
--- a/compiler/jsgen.nim
+++ b/compiler/jsgen.nim
@@ -2406,8 +2406,7 @@ proc genCast(p: PProc, n: PNode, r: var TCompRes) =
     r.res = "($1 $2)" % [r.res, trimmer]
   elif toInt:
     if fromInt:
-      let trimmer = unsignedTrimmer(dest.size)
-      r.res = "($1 $2)" % [r.res, trimmer]
+      return
     elif fromUint:
       if src.size == 4 and dest.size == 4:
         # XXX prevent multi evaluations
diff --git a/tests/types/t14127_cast_number.nim b/tests/types/t14127_cast_number.nim
new file mode 100644
index 0000000000..4bb23f22fe
--- /dev/null
+++ b/tests/types/t14127_cast_number.nim
@@ -0,0 +1,30 @@
+discard """
+  targets: "c cpp js"
+"""
+block: # bug #14127
+  template int2uint(T) =
+    var a = -1
+    let b = cast[T](a)
+    doAssert b < 0
+    let c = b + 1
+    doAssert c is T
+    doAssert c == 0
+
+  int2uint(int8)
+  int2uint(int16)
+  int2uint(int32)
+  int2uint(int64)
+
+block: # maybe related
+  template uint2int(T) =
+    var a = 3
+    let b = cast[T](a)
+    doAssert b > 0
+    let c = b - 1
+    doAssert c is T
+    doAssert c == 2
+
+  uint2int(uint8)
+  uint2int(uint16)
+  uint2int(uint32)
+  uint2int(uint64)