Rationale behind constraining default parameters as compile-time constants

Question

I am wondering why this would not compile:

public static void SomeFunction(Guid someGuid = Guid.NewGuid()) { // Do stuff }

with the message

"Default parameter value for 'someGuid' must be a compile-time constant"

while the overloaded version would compile:

 public static void SomeFunction() { SomeFunction(Guid.NewGuid()); } public static void SomeFunction(Guid someGuid) { // Do stuff }

In other words, why doesn't the compiler translate the first situation in the second? What lies behind this design choice?

SLaks · Accepted Answer · 2012-12-05 20:30:38Z

Default parameter values are compiled to CIL metadata (like attributes) which can only hold literal values.

The C# compiler does some magic there to allow decimals as well.

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