null default value for non-nullable parameter should warn #26626
Description
public class C
{
public void M(string x = null)
{
}
}For comparison, a local declaration does warn:
public class C
{
public void M()
{
string x = null; // warning CS8600: Converting null literal or possible null value to non-nullable type.
}
}Found in nullable dogfood.
Tagging @cston
Note: there are some IDE tests (in CSharpDeclareAsNullableCodeFixTests) for this bug, which should be unskipped.