new and operator ++

[Kerneltrap]

Hi,

I have a type:

public struct Value
{
public static Value operator ++(Value v)
{
return new Value();
}

public static Value New()
{
return new Value();
}
}

This code

Value v1 = Value.New()++;

compiles successfully, but i get InvalidProgramException.

The same for

Value v = new Value()++;

Changing from struct to class doesn't help.

Microsoft (R) Visual C# 2005 Compiler version 8.00.50727.42
Win XP SP2.

[Nicholas Paldino [.NET/C# MVP]]

This is pretty interesting, as I get the same thing (and one would
assume that the C# compiler wouldn't produce invalid code).

I would submit this to Microsoft Connect as a bug.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Kerneltrap" <Sh******@gmail.comwrote in message
news:11*********************@q69g2000hsb.googlegro ups.com...

Hi,

I have a type:

public struct Value
{
public static Value operator ++(Value v)
{
return new Value();
}

public static Value New()
{
return new Value();
}
}

This code

Value v1 = Value.New()++;

compiles successfully, but i get InvalidProgramException.

The same for

Value v = new Value()++;

Changing from struct to class doesn't help.

Microsoft (R) Visual C# 2005 Compiler version 8.00.50727.42
Win XP SP2.

[Tom Spink]

Kerneltrap wrote:

Hi,

I have a type:

public struct Value
{
public static Value operator ++(Value v)
{
return new Value();
}

public static Value New()
{
return new Value();
}
}

This code

Value v1 = Value.New()++;

compiles successfully, but i get InvalidProgramException.

The same for

Value v = new Value()++;

Changing from struct to class doesn't help.

Microsoft (R) Visual C# 2005 Compiler version 8.00.50727.42
Win XP SP2.

Hi

JOOI, the Mono C# Compiler yields a compilation error:

"error CS0131: The left-hand side of an assignment must be a variable, a
property or an indexer"

Interesting.

--
Tom Spink
University of Edinburgh

[Willy Denoyette [MVP]]

"Tom Spink" <ts****@gmail.comwrote in message
news:%2***************@TK2MSFTNGP02.phx.gbl...

Kerneltrap wrote:

>Hi,

I have a type:

public struct Value
{
public static Value operator ++(Value v)
{
return new Value();
}

public static Value New()
{
return new Value();
}
}

This code

Value v1 = Value.New()++;

compiles successfully, but i get InvalidProgramException.

The same for

Value v = new Value()++;

Changing from struct to class doesn't help.

Microsoft (R) Visual C# 2005 Compiler version 8.00.50727.42
Win XP SP2.

Hi

JOOI, the Mono C# Compiler yields a compilation error:

"error CS0131: The left-hand side of an assignment must be a variable, a
property or an indexer"

Interesting.

--
Tom Spink
University of Edinburgh

This is actually what the C# compiler should do as well, this is a compiler
error that is corrected in Orcas version of the compiler.

Willy.

[Peter Duniho]

On Mon, 18 Jun 2007 16:42:45 -0700, Willy Denoyette [MVP]
<wi*************@telenet.bewrote:

"Tom Spink" <ts****@gmail.comwrote in message
news:%2***************@TK2MSFTNGP02.phx.gbl...

>Kerneltrap wrote:

>>[...]
This code

Value v1 = Value.New()++;

compiles successfully, but i get InvalidProgramException.

The same for

Value v = new Value()++;

JOOI, the Mono C# Compiler yields a compilation error:

"error CS0131: The left-hand side of an assignment must be a variable, a
property or an indexer"

This is actually what the C# compiler should do as well, this is a
compiler error that is corrected in Orcas version of the compiler.

Okay, I'll bite.

Why is "Value v1" and "Value v" not considered a "variable, a property or
an indexer"? Specifically, sure looks like a variable to me. What am I
missing?

Pete

[Ben Voigt [C++ MVP]]

"Peter Duniho" <Np*********@nnowslpianmk.comwrote in message
news:op***************@petes-computer.local...
On Mon, 18 Jun 2007 16:42:45 -0700, Willy Denoyette [MVP]
<wi*************@telenet.bewrote:

"Tom Spink" <ts****@gmail.comwrote in message
news:%2***************@TK2MSFTNGP02.phx.gbl...

>Kerneltrap wrote:

>>[...]
This code

Value v1 = Value.New()++;

compiles successfully, but i get InvalidProgramException.

The same for

Value v = new Value()++;

JOOI, the Mono C# Compiler yields a compilation error:

"error CS0131: The left-hand side of an assignment must be a variable, a
property or an indexer"

This is actually what the C# compiler should do as well, this is a
compiler error that is corrected in Orcas version of the compiler.

Okay, I'll bite.

Why is "Value v1" and "Value v" not considered a "variable, a property or
an indexer"? Specifically, sure looks like a variable to me. What am I
missing?

Pete
You're missing operator binding: The code reads as:

Value v = ((new Value())++);

The postincrement operator is buried within the right-hand side of the
assignment.

Does

Value v; (v = new Value())++;

work?

[Kerneltrap]

On Jun 19, 4:25 am, "Ben Voigt [C++ MVP]" <[e-mail]:

"Peter Duniho" <[e-mail] in message

news:op***************@petes-computer.local...
On Mon, 18 Jun 2007 16:42:45 -0700, Willy Denoyette [MVP]

<[e-mail]:

"Tom Spink" <[e-mail] in message
news:%2***************@TK2MSFTNGP02.phx.gbl...

Kerneltrap wrote:

>[...]
This code

>Value v1 = Value.New()++;

>compiles successfully, but i get InvalidProgramException.

>The same for

>Value v = new Value()++;

JOOI, the Mono C# Compiler yields a compilation error:

"error CS0131: The left-hand side of an assignment must be a variable, a
property or an indexer"

This is actually what the C# compiler should do as well, this is a
compiler error that is corrected in Orcas version of the compiler.

Okay, I'll bite.

Why is "Value v1" and "Value v" not considered a "variable, a property or
an indexer"? Specifically, sure looks like a variable to me. What am I
missing?

Pete

You're missing operator binding: The code reads as:

Value v = ((new Value())++);

The postincrement operator is buried within the right-hand side of the
assignment.

Does

Value v; (v = new Value())++;

work?

It doesn't. Same effect.

[Christof Nordiek]

"Peter Duniho" <Np*********@nnowslpianmk.comschrieb im Newsbeitrag
news:op***************@petes-computer.local...

>>>
Value v1 = Value.New()++;

compiles successfully, but i get InvalidProgramException.

JOOI, the Mono C# Compiler yields a compilation error:

"error CS0131: The left-hand side of an assignment must be a variable, a
property or an indexer"

Okay, I'll bite.

Why is "Value v1" and "Value v" not considered a "variable, a property or
an indexer"? Specifically, sure looks like a variable to me. What am I
missing?

What you're missing is, that exp++ contains an assignment to exp. So this
should be "a varialbe, a property or an indexer".

What actually do you wan't to do?

Christof

[Willy Denoyette [MVP]]

"Peter Duniho" <Np*********@nnowslpianmk.comwrote in message
news:op***************@petes-computer.local...
On Mon, 18 Jun 2007 16:42:45 -0700, Willy Denoyette [MVP]
<wi*************@telenet.bewrote:

"Tom Spink" <ts****@gmail.comwrote in message
news:%2***************@TK2MSFTNGP02.phx.gbl...

>Kerneltrap wrote:

>>[...]
This code

Value v1 = Value.New()++;

compiles successfully, but i get InvalidProgramException.

The same for

Value v = new Value()++;

JOOI, the Mono C# Compiler yields a compilation error:

"error CS0131: The left-hand side of an assignment must be a variable, a
property or an indexer"

This is actually what the C# compiler should do as well, this is a
compiler error that is corrected in Orcas version of the compiler.

Okay, I'll bite.

Why is "Value v1" and "Value v" not considered a "variable, a property or
an indexer"? Specifically, sure looks like a variable to me. What am I
missing?

Pete

Pete, In top of what others said, the Mono compiler's error CS0131: is
somewhat misleading.
Orcas C# compiler error message:
[error CS1059: The operand of an increment or decrement operator must be a
variable, property or indexer]
is IMO more clear and accurate.
Willy.

[Peter Duniho]

On Tue, 19 Jun 2007 04:11:52 -0700, Willy Denoyette [MVP]
<wi*************@telenet.bewrote:

Pete, In top of what others said, the Mono compiler's error CS0131: is
somewhat misleading.
Orcas C# compiler error message:
[error CS1059: The operand of an increment or decrement operator must be
a variable, property or indexer] is IMO more clear and accurate.

Ah, okay. Since ++ has an implicit assignment, the result has to be able
to be assigned back to the original source, which isn't possible in this
case.

Thanks everyone. Makes sense now.

Pete

[Tom Spink]

Willy Denoyette [MVP] wrote:

"Tom Spink" <ts****@gmail.comwrote in message
news:%2***************@TK2MSFTNGP02.phx.gbl...

>Kerneltrap wrote:

>>Hi,

I have a type:

public struct Value
{
public static Value operator ++(Value v)
{
return new Value();
}

public static Value New()
{
return new Value();
}
}

This code

Value v1 = Value.New()++;

compiles successfully, but i get InvalidProgramException.

The same for

Value v = new Value()++;

Changing from struct to class doesn't help.

Microsoft (R) Visual C# 2005 Compiler version 8.00.50727.42
Win XP SP2.

Hi

JOOI, the Mono C# Compiler yields a compilation error:

"error CS0131: The left-hand side of an assignment must be a variable, a
property or an indexer"

Interesting.

--
Tom Spink
University of Edinburgh

This is actually what the C# compiler should do as well, this is a
compiler error that is corrected in Orcas version of the compiler.

Willy.

Nice. I figured as much, because of postfix increment's implicit
assignment. It's a shame it's worded a bit funny in gmcs.

--
Tom Spink
University of Edinburgh

[cody]

Nicholas Paldino [.NET/C# MVP] wrote:

This is pretty interesting, as I get the same thing (and one would
assume that the C# compiler wouldn't produce invalid code).

I would submit this to Microsoft Connect as a bug.

Strange.

Decimal d = New Decimal()++;

or even

Decimal d = 0m++;

Produces just a compilation error as it should. What is the difference?
Decimal is just a struct like any other or is it treated special by the
compiler as it is with System.String?