From c07807bedf1749fa9d3e826d3d736907fefbe568 Mon Sep 17 00:00:00 2001
From: Bung <crc32@qq.com>
Date: Sat, 7 Nov 2020 16:00:41 +0800
Subject: [PATCH] Fix #15706 (#15846)

* fix #15706 Underflow not detected when using dec on distinct ranges

* fix #15846 first, jsgen even doesn't care of range in this op
---
 compiler/ccgexprs.nim             | 2 +-
 tests/overflw/tdistinct_range.nim | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)
 create mode 100644 tests/overflw/tdistinct_range.nim

diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index 1eb6caeb3..a3fbeca5f 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -2269,7 +2269,7 @@ proc genMagicExpr(p: BProc, e: PNode, d: var TLoc, op: TMagic) =
       initLocExpr(p, e[1], a)
       initLocExpr(p, e[2], b)
 
-      let ranged = skipTypes(e[1].typ, {tyGenericInst, tyAlias, tySink, tyVar, tyLent})
+      let ranged = skipTypes(e[1].typ, {tyGenericInst, tyAlias, tySink, tyVar, tyLent, tyDistinct})
       let res = binaryArithOverflowRaw(p, ranged, a, b,
         if underlying.kind == tyInt64: fun64[op] else: fun[op])
 
diff --git a/tests/overflw/tdistinct_range.nim b/tests/overflw/tdistinct_range.nim
new file mode 100644
index 000000000..f53515d45
--- /dev/null
+++ b/tests/overflw/tdistinct_range.nim
@@ -0,0 +1,6 @@
+discard """
+  outputsub: "Error: unhandled exception: over- or underflow [OverflowDefect]"
+  exitcode: "1"
+"""
+var x: distinct range[0..5]
+dec(x)
\ No newline at end of file