fix Issue 8675 - Nothrow can't throw Errors

- fixed by checking whether the thrown exception is derived
  from Error before complaining about uncaught throws

dmd2/statement.c

@@ -5112,8 +5112,17 @@ Statement *ThrowStatement::semantic(Scope *sc)
 int ThrowStatement::blockExit(bool mustNotThrow)
 {
     if (mustNotThrow)
+    {
+        ClassDeclaration *cd = exp->type->toBasetype()->isClassHandle();
+        assert(cd);
+
+        // Bugzilla 8675
+        // Throwing Errors is allowed even if mustNotThrow
+        if (cd != ClassDeclaration::errorException &&
+            !ClassDeclaration::errorException->isBaseOf(cd, NULL))
             error("%s is thrown but not caught", exp->type->toChars());
-    return BEthrow;  // obviously
+    }
+    return BEthrow;
 }