PLEDGE008: Constant argument violates a precondition

Severity: Warning.

A call passes constants that a Pledge.Requires of the callee rejects. The precondition would throw on every run, so the bug is visible at compile time.

account.Withdraw(-5m);   // PLEDGE008: Argument amount: -5 violates the precondition 'amount > 0' of 'Account.Withdraw'

The analyzer substitutes constant arguments (including omitted optional parameters) into each precondition and evaluates it with three-valued logic. It understands literals, comparisons, &&, ||, !, ??, the conditional operator, is with constant, relational, and/or/not patterns, string.Length, string.IsNullOrEmpty and string.IsNullOrWhiteSpace. Anything else, including a member read such as Balance, is unknown, and a precondition whose outcome depends on an unknown is not reported. Only preconditions of methods declared in the same compilation are read; reading them from referenced assemblies' metadata attributes comes in v1.0.

Tests that break a contract on purpose can disable the rule for the file:

#pragma warning disable PLEDGE008