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static private AllTestValuesMustHaveSameType ( string paramName ) : |
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/// <summary>
/// Creates a <see cref="SwitchExpression"/>.
/// </summary>
/// <param name="type">The result type of the switch.</param>
/// <param name="switchValue">The value to be tested against each case.</param>
/// <param name="defaultBody">The result of the switch if no cases are matched.</param>
/// <param name="comparison">The equality comparison method to use.</param>
/// <param name="cases">The valid cases for this switch.</param>
/// <returns>The created <see cref="SwitchExpression"/>.</returns>
public static SwitchExpression Switch(Type type, Expression switchValue, Expression defaultBody, MethodInfo comparison, IEnumerable <SwitchCase> cases)
{
ExpressionUtils.RequiresCanRead(switchValue, nameof(switchValue));
if (switchValue.Type == typeof(void))
{
throw Error.ArgumentCannotBeOfTypeVoid(nameof(switchValue));
}
ReadOnlyCollection <SwitchCase> caseList = cases.ToReadOnly();
ContractUtils.RequiresNotNullItems(caseList, nameof(cases));
// Type of the result. Either provided, or it is type of the branches.
Type resultType;
if (type != null)
{
resultType = type;
}
else if (caseList.Count != 0)
{
resultType = caseList[0].Body.Type;
}
else if (defaultBody != null)
{
resultType = defaultBody.Type;
}
else
{
resultType = typeof(void);
}
bool customType = type != null;
if (comparison != null)
{
ValidateMethodInfo(comparison, nameof(comparison));
ParameterInfo[] pms = comparison.GetParametersCached();
if (pms.Length != 2)
{
throw Error.IncorrectNumberOfMethodCallArguments(comparison, nameof(comparison));
}
// Validate that the switch value's type matches the comparison method's
// left hand side parameter type.
ParameterInfo leftParam = pms[0];
bool liftedCall = false;
if (!ParameterIsAssignable(leftParam, switchValue.Type))
{
liftedCall = ParameterIsAssignable(leftParam, switchValue.Type.GetNonNullableType());
if (!liftedCall)
{
throw Error.SwitchValueTypeDoesNotMatchComparisonMethodParameter(switchValue.Type, leftParam.ParameterType);
}
}
ParameterInfo rightParam = pms[1];
foreach (SwitchCase c in caseList)
{
ContractUtils.RequiresNotNull(c, nameof(cases));
ValidateSwitchCaseType(c.Body, customType, resultType, nameof(cases));
for (int i = 0, n = c.TestValues.Count; i < n; i++)
{
// When a comparison method is provided, test values can have different type but have to
// be reference assignable to the right hand side parameter of the method.
Type rightOperandType = c.TestValues[i].Type;
if (liftedCall)
{
if (!rightOperandType.IsNullableType())
{
throw Error.TestValueTypeDoesNotMatchComparisonMethodParameter(rightOperandType, rightParam.ParameterType);
}
rightOperandType = rightOperandType.GetNonNullableType();
}
if (!ParameterIsAssignable(rightParam, rightOperandType))
{
throw Error.TestValueTypeDoesNotMatchComparisonMethodParameter(rightOperandType, rightParam.ParameterType);
}
}
}
// if we have a non-boolean user-defined equals, we don't want it.
if (comparison.ReturnType != typeof(bool))
{
throw Error.EqualityMustReturnBoolean(comparison, nameof(comparison));
}
}
else if (caseList.Count != 0)
{
// When comparison method is not present, all the test values must have
// the same type. Use the first test value's type as the baseline.
Expression firstTestValue = caseList[0].TestValues[0];
foreach (SwitchCase c in caseList)
{
ContractUtils.RequiresNotNull(c, nameof(cases));
ValidateSwitchCaseType(c.Body, customType, resultType, nameof(cases));
// When no comparison method is provided, require all test values to have the same type.
for (int i = 0, n = c.TestValues.Count; i < n; i++)
{
if (!TypeUtils.AreEquivalent(firstTestValue.Type, c.TestValues[i].Type))
{
throw Error.AllTestValuesMustHaveSameType(nameof(cases));
}
}
}
// Now we need to validate that switchValue.Type and testValueType
// make sense in an Equal node. Fortunately, Equal throws a
// reasonable error, so just call it.
BinaryExpression equal = Equal(switchValue, firstTestValue, false, comparison);
// Get the comparison function from equals node.
comparison = equal.Method;
}
if (defaultBody == null)
{
if (resultType != typeof(void))
{
throw Error.DefaultBodyMustBeSupplied(nameof(defaultBody));
}
}
else
{
ValidateSwitchCaseType(defaultBody, customType, resultType, nameof(defaultBody));
}
return(new SwitchExpression(resultType, switchValue, defaultBody, comparison, caseList));
}