add tests for recently closed issues (#10722)

tests/misc/tsizeof3.nim

@@ -0,0 +1,19 @@
+discard """
+output: '''
+[0, 0, 0, 0, 0, 0, 48, 57]
+'''
+"""
+# bug #7238
+
+type ByteArrayBE*[N: static[int]] = array[N, byte]
+  ## A byte array that stores bytes in big-endian order
+
+proc toByteArrayBE*[T: SomeInteger](num: T): ByteArrayBE[sizeof(T)]=
+  ## Convert an integer (in native host endianness) to a big-endian byte array
+  ## Notice the result type
+  const N = T.sizeof
+  for i in 0 ..< N:
+    result[i] = byte(num shr ((N-1-i) * 8))
+
+let a = 12345.toByteArrayBE
+echo a

tests/misc/tunsignedconv.nim

@@ -39,3 +39,7 @@ var n32 = ar[v32]
 var n64 = ar[v64]
 
 
+block t4176:
+  var yyy: uint8 = 0
+  yyy = yyy - 127
+  doAssert type(yyy) is uint8

tests/misc/tunsignedinc.nim

@@ -26,3 +26,9 @@ block:
   var x = 123'u16
   x -= 125
   doAssert(x == 65534'u16)
+
+block t4175:
+  let i = 0u - 1u
+  const j = 0u - 1u
+  doAssert i == j
+  doAssert j + 1u == 0u