Description
Type of issue
Missing information
Description
I'm working on the Ecma C# spec with lambda/anonymous function parameters [where I'm adding scoped], and my tests generated two CS errors, CS1677 and CS1661, from the same code. While I'll document the issue here, it likely will require tweaking the description for CS1661 as well.
Basically, the explanation and example you currently provide does not handle my situation.
Consider the following:
Action<int> lam3a = (in int i) => Mz2(in i); // CS1677 on `i` in `in int i`, and CS1661 on `=>`
var lam3b = (in int i) => Mz2(in i); // no errors, and call below works fine.
int xx = 123;
lam3b(in xx);
public static void Mz2(in int v) { Console.WriteLine("In Mz2"); }
The CS1677 message I get is
Parameter 1 should not be declared with the 'in' keyword
The CS1661 message I get is
Cannot convert lambda expression to type 'Action<int>' because the parameter types do not match the delegate parameter types.
It appears that the explicit declaration type of lam3a is the problem, yet I don't see any way to change that (you can't include in in the type parameter), but when I let the compiler figure out the delegate type by using var, it works. This suggests that var can allow code that cannot be expressed directly using explicit types.
It seems there are multiple scenarios that can result in CS1661, as the message I got in the test above does not match the one in your Help entry, which states,
Cannot convert anonymous method block to delegate type 'delegate type' because the specified block's parameter types do not match the delegate parameter types
Page URL
https://learn.microsoft.com/en-us/dotnet/csharp/misc/cs1677?f1url=%3FappId%3Droslyn%26k%3Dk(CS1677)
Content source URL
https://github.com/dotnet/docs/blob/main/docs/csharp/misc/cs1677.md
Document Version Independent Id
9f888ae8-1183-8c38-f6d2-0dc075026016
Article author
Metadata
- ID: 802df120-d60d-3838-0ad6-e1437197950a
- Service: dotnet-csharp
- Sub-service: errors-warnings