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Readonly Local Variable Cannot Be Used As An Assignment Target

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HaloFour commented Oct 29, 2015 @alrz The scoping would be entirely different, though. is ... Yes No Additional feedback? 1500 characters remaining Submit Skip this Thank you! Unfortunately @mattwar 's suggestion works for tuples only, while this proposal works for any type that can be used in pattern-matching. http://rss4medics.com/cannot-be/readonly-property-cannot-be-used-as-an-assignment-target.php

I'll look it up in my annotated spec tonight... Yes, is is for incomplete patterns, hence returns a bool. gafter changed the title from Proposal: Destructuring assignment for tuples and other types to Proposal: Destructuring assignment statement Oct 29, 2015 .NET Foundation member gafter commented Oct 29, 2015 .Select(t => I think it is a bit confusing to have a statement (other than an expression-statement) start with an expression. http://stackoverflow.com/questions/11251855/readonly-local-variable-cannot-be-used-as-an-assignment-target

Readonly Property Cannot Be Used As An Assignment Target

My proposal would permit let Point(int x, int y) = computePoint() ?? I'm asking, not because C# should be just like F#, but because these problems have already been solved in F#, and, as far as I know there have been no complaints throw null; // Helpful compiletime error! Join them; it only takes a minute: Sign up Readonly local variable cannot be used as an assignment target up vote 9 down vote favorite If I have: var myObjects =

The pattern variables don't escape their case in a match expression. public static bool operator is(Point p, out double x, out double y) { x = p.X; y = p.Y; return true; } Without this operator Point(x, y) wouldn't even be a alrz commented Oct 29, 2015 Are you suggesting that case be a pattern-matching operator? alrz referenced this issue Jan 16, 2016 Closed Allow using on non disposable and skip using when object is null #8004 .NET Foundation member gafter commented Jan 18, 2016 @Thaina Problem

In that case, let rules is applied and an optional else would be permitted. Linq Readonly Property Cannot Be Used As An Assignment Target And, on the other hand, the proposed let else appears at first glance to be a variable declaration statement, but it becomes a conditional statement, too. My first solution above runs into race conditions in multithreaded scenarios (the very and only reson for using a ConcurrentBag). This entry was posted in Uncategorized.

I'm saying that instead of supporting ALL PATTERNS just support a subset of them but with, for example, better type inference like var x,y = tuple; or var RGB(r,g,b) = color; I attended an Austin Technology Council talk calle... Its purpose is easily served by existing constructs. Can Trump undo the UN climate change agreement?

Linq Readonly Property Cannot Be Used As An Assignment Target

Join them; it only takes a minute: Sign up Why is The Iteration Variable in a C# foreach statement read-only? https://msdn.microsoft.com/en-us/library/zshzt6s3.aspx Can you at least confirm that in the current proposal, you intend to allow both let Point(int x, int y) = computePoint() ?? Readonly Property Cannot Be Used As An Assignment Target The standard possible way would be using match in this context which I think can be simplified to the 4th line. FunctionalFirst commented Oct 29, 2015 @gafter IMO, that's good enough.

You're welcome to discuss the expression form there. More about the author last of the Murder They Wrote notes I attended once more the Agile Austin UX SIG. It therefore does not introduce a dangling-else ambiguity. The Polar example shows one reason you might want these to be able to fail.

And as I said. Your proposed throw unless construct appears at first glance to be a throw statement, but that is not necessarily its purpose, nor does it necessarily throw. The let statement is specifically useful with single-case complete patterns. check my blog Please enable JavaScript to view the comments powered by Disqus.

Join them; it only takes a minute: Sign up Readonly local variable cannot be used as an assignment target up vote 9 down vote favorite If I have: var myObjects = x, int? What does "there lived here then" mean?

let Destination { Place is Coordinates { Longitude is var longitude } } = d; ...

Inspired by an F# feature and a conversation on github, we could support decomposition like this: block-statement : let-statement ; let-statement : 'let' identifier '=' expression ';' | 'let' complex-pattern '=' It like value keyword that never been used and will not be used outside set { } of properties (sometimes we can make variable named value in other places) let too throw; by itself in C# does not reset the stack tr... HaloFour commented Oct 29, 2015 @gafter Oo, ok, that does make sense then.

as even-shorter shorthand for ?? The problem is to asign, but internal changes of objects don't present a problem: using System; using System.Collections.Generic; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { List colection HaloFour commented Jan 18, 2016 @Thaina It is normal, right up until a new keyword is added. news Using that construct you could write your first example like this: .Select(t => t match (case (var x, var y): x + y)) orthoxerox commented Oct 29, 2015 @gafter why would

Not the beholder. const is best of all IMHO. Is adding the ‘tbl’ prefix to table names really a problem? share|improve this answer edited Sep 4 '14 at 10:39 SAM 377313 answered Jun 28 '12 at 19:52 Marc Gravell♦ 634k14817662235 add a comment| up vote 6 down vote If you want

Problem solve Please don't add any new keyword so casually HaloFour commented Jan 13, 2016 @Thaina They're not, they're repurposing the existing let keyword to function for pattern destructuring. p : new Point(0,0); or even var point = computePoint() ?? What if it was generic? Having two ways to declare a variable using the same keyword but with two different semantics would be quite confusing.

FunctionalFirst commented Oct 29, 2015 @gafter In F#, using let with an ADT produces the warning: Incomplete pattern matches on this expression, and potentially throws a MatchFailureException at run-time. You do not need unsafe code to break readonly, and yet the effect is the same as with an unverifiable program that writes to a readonly field: struct S1 { public Actually in F#, type of the target object inferred from cases in match e.g. As does the following example.

I have to be honest that I believe this is a CIL verification hole, and should produce unverifiable MSIL much like when you try to overlay structs containing overlapping GC references. That's it.