[nem-bug] [Nemerle 0000642]: Error if list declared without initialisation

[feedback at nemerle.org]

A NOTE has been added to this issue.
======================================================================
<http://nemerle.org/bugs/view.php?id=642> 
======================================================================
Reported By:                VladD2
Assigned To:                nazgul
======================================================================
Project:                    Nemerle
Issue ID:                   642
Category:                   Compiler
Reproducibility:            always
Severity:                   minor
Priority:                   normal
Status:                     resolved
Resolution:                 fixed
Fixed in Version:           
======================================================================
Date Submitted:             04-01-2006 19:09 CEST
Last Modified:              05-03-2006 13:24 CEST
======================================================================
Summary:                    Error if list declared without initialisation
Description: 
Error reported for this code:
mutable seq : list[int];
seq = [3];
WriteLine(seq.Head);

Error message:
test-016.n:8:20:8:23: error: parse error near identifier `int': unexpected
end of token sequence
test-016.n:8:20:8:23: error: expected assignment operator =

======================================================================

----------------------------------------------------------------------
 nazgul - 04-05-06 21:12 
----------------------------------------------------------------------
BTW, this is our design from the beginning. We do not want any
uninitialized local variable flying around. Usually you can just do 

mutable seq = null;
seq = [3];

it will work fine. And as for value types, you can always use their
parameterless constructor:

mutable x = int();
x = 4;

I'm against, but maybe we should change this design - it creates
additional problems, because we must then perform complex flow control to
prevent usage of uninitialized variables.

----------------------------------------------------------------------
 nazgul - 05-03-06 13:22 
----------------------------------------------------------------------
Fixed on trunk (r6217).
We decided to use the simplest approach - we now allow lack of initializer
when declaring mutable variables, but we generate the "DefaultValue(T)"
expression. Interesting point is that generated IL looks identical :)

----------------------------------------------------------------------
 nazgul - 05-03-06 13:24 
----------------------------------------------------------------------
Also, in Nemerle it is now even more convenient to use:

mutable a,b,c,d;
a = 1;
b = "a";
c = 32.3;
d = System.DataTime.Now;

while in C#:

int a;
string b;
double c;
System.DateTime d;
a = 1;
b = "a";
c = 32.3;
d = System.DataTime.Now;

Issue History
Date Modified  Username       Field                    Change              
======================================================================
04-01-06 19:09 VladD2         New Issue                                    
04-05-06 21:12 nazgul         Note Added: 0001163                          
05-03-06 13:22 nazgul         Status                   new => resolved     
05-03-06 13:22 nazgul         Resolution               open => fixed       
05-03-06 13:22 nazgul         Assigned To               => nazgul          
05-03-06 13:22 nazgul         Note Added: 0001219                          
05-03-06 13:22 nazgul         Description Updated                          
05-03-06 13:24 nazgul         Note Added: 0001220                          
======================================================================