Replace short preconditions in the main package

source/tanya/math/package.d

@@ -562,7 +562,11 @@ if (isFloatingPoint!F)
  */
 H pow(I, G, H)(in auto ref I x, in auto ref G y, in auto ref H z)
 if (isIntegral!I && isIntegral!G && isIntegral!H)
-in (z > 0, "Division by zero")
+in
+{
+    assert(z > 0, "Division by zero");
+}
+do
 {
     G mask = G.max / 2 + 1;
     H result;

source/tanya/math/random.d

@@ -92,7 +92,10 @@ abstract class EntropySource
      *                $(D_PARAM output) length.
      */
     Nullable!ubyte poll(out ubyte[maxGather] output) @nogc
-    out (length; length.isNull || length.get <= maxGather);
+    out (length)
+    {
+        assert(length.isNull || length.get <= maxGather);
+    }
 }
 
 version (CRuntime_Bionic)