How is null + true a string?

Question

Since true is not a string type, how is null + true a string ?

string s = true;  //Cannot implicitly convert type 'bool' to 'string'   
bool b = null + true; //Cannot implicitly convert type 'string' to 'bool'

What is the reason behind this?

Answer 1

Interestingly, using Reflector to inspect what is generated, the following code:

string b = null + true;
Console.WriteLine(b);

is transformed into this by the compiler:

Console.WriteLine(true);

The reasoning behind this "optimization" is a bit weird I must say, and does not rhyme with the operator selection I would expect.

Also, the following code:

var b = null + true; 
var sb = new StringBuilder(b);

is transformed into

string b = true; 
StringBuilder sb = new StringBuilder(b);

where string b = true; is actually not accepted by the compiler.