admin管理员组文章数量:1025512
I have a function with following signature
State MoveForward(in Path path);
Path is a ref struct
State is also a ref struct with just integer.
Now I have another helper function
bool TryMoveForward(in Path path, ref State state)
{
// which does something like:
state = MoveForward(path); // "line A"
return !state.IsEnd(); // IsEnd determined by integer != -1
}
At the "line A" I am getting the error CS8347: Cannot use a result of 'MoveForward' in this context because it may expose variables referenced by parameter 'path' outside of their declaration scope.
But I think this shouldn't be the case or atleast compiler can be smart enough to avoid throwing this error for few reasons:
- State is created just with integers (Compiler can look into the usage of
path). There is no reference exposed from "path" - "State" is a ref struct which doesn't carry any "ref" to escape with.
How can I make compiler not complain about this?
I don't understand whether it is a problem of assigning something to ref State state or passing the path to in parameter.
If I remove in in MoveForward the error goes away. I want to keep the "in"
If I split the line, I don't have any way to avoid the error. eg:
var result = MoveForward(path); // "line A"
state = result;
return !state.IsEnd(); // IsEnd determined by integer != -1
Getting CS8352: Cannot use variable 'result' in this context because it may expose referenced variables outside of their declaration scope.
state has its own memory in stack and result should be able to be copied to state similar to single line statement.
I have a function with following signature
State MoveForward(in Path path);
Path is a ref struct
State is also a ref struct with just integer.
Now I have another helper function
bool TryMoveForward(in Path path, ref State state)
{
// which does something like:
state = MoveForward(path); // "line A"
return !state.IsEnd(); // IsEnd determined by integer != -1
}
At the "line A" I am getting the error CS8347: Cannot use a result of 'MoveForward' in this context because it may expose variables referenced by parameter 'path' outside of their declaration scope.
But I think this shouldn't be the case or atleast compiler can be smart enough to avoid throwing this error for few reasons:
- State is created just with integers (Compiler can look into the usage of
path). There is no reference exposed from "path" - "State" is a ref struct which doesn't carry any "ref" to escape with.
How can I make compiler not complain about this?
I don't understand whether it is a problem of assigning something to ref State state or passing the path to in parameter.
If I remove in in MoveForward the error goes away. I want to keep the "in"
If I split the line, I don't have any way to avoid the error. eg:
var result = MoveForward(path); // "line A"
state = result;
return !state.IsEnd(); // IsEnd determined by integer != -1
Getting CS8352: Cannot use variable 'result' in this context because it may expose referenced variables outside of their declaration scope.
state has its own memory in stack and result should be able to be copied to state similar to single line statement.
1 Answer
Reset to default 2Based on this explanations https://github/dotnet/csharplang/blob/main/proposals/csharp-11.0/low-level-struct-improvements.md#keywords-vs-attributes
Opt out is a keyword (scoped) but the opt in is an attribute ([UnscopedRef]). So in your case you must defined it as scoped:
State MoveForward(scoped in Path path)
I have a function with following signature
State MoveForward(in Path path);
Path is a ref struct
State is also a ref struct with just integer.
Now I have another helper function
bool TryMoveForward(in Path path, ref State state)
{
// which does something like:
state = MoveForward(path); // "line A"
return !state.IsEnd(); // IsEnd determined by integer != -1
}
At the "line A" I am getting the error CS8347: Cannot use a result of 'MoveForward' in this context because it may expose variables referenced by parameter 'path' outside of their declaration scope.
But I think this shouldn't be the case or atleast compiler can be smart enough to avoid throwing this error for few reasons:
- State is created just with integers (Compiler can look into the usage of
path). There is no reference exposed from "path" - "State" is a ref struct which doesn't carry any "ref" to escape with.
How can I make compiler not complain about this?
I don't understand whether it is a problem of assigning something to ref State state or passing the path to in parameter.
If I remove in in MoveForward the error goes away. I want to keep the "in"
If I split the line, I don't have any way to avoid the error. eg:
var result = MoveForward(path); // "line A"
state = result;
return !state.IsEnd(); // IsEnd determined by integer != -1
Getting CS8352: Cannot use variable 'result' in this context because it may expose referenced variables outside of their declaration scope.
state has its own memory in stack and result should be able to be copied to state similar to single line statement.
I have a function with following signature
State MoveForward(in Path path);
Path is a ref struct
State is also a ref struct with just integer.
Now I have another helper function
bool TryMoveForward(in Path path, ref State state)
{
// which does something like:
state = MoveForward(path); // "line A"
return !state.IsEnd(); // IsEnd determined by integer != -1
}
At the "line A" I am getting the error CS8347: Cannot use a result of 'MoveForward' in this context because it may expose variables referenced by parameter 'path' outside of their declaration scope.
But I think this shouldn't be the case or atleast compiler can be smart enough to avoid throwing this error for few reasons:
- State is created just with integers (Compiler can look into the usage of
path). There is no reference exposed from "path" - "State" is a ref struct which doesn't carry any "ref" to escape with.
How can I make compiler not complain about this?
I don't understand whether it is a problem of assigning something to ref State state or passing the path to in parameter.
If I remove in in MoveForward the error goes away. I want to keep the "in"
If I split the line, I don't have any way to avoid the error. eg:
var result = MoveForward(path); // "line A"
state = result;
return !state.IsEnd(); // IsEnd determined by integer != -1
Getting CS8352: Cannot use variable 'result' in this context because it may expose referenced variables outside of their declaration scope.
state has its own memory in stack and result should be able to be copied to state similar to single line statement.
- 1 I cannot reproduce this. Did I misunderstand something? – Sweeper Commented Nov 18, 2024 at 10:01
- @Sweeper, made a small change in your code to use "state" to update after calling MoveForward – Vivek MVK Commented Nov 18, 2024 at 10:22
-
Statelooks like anoutrather than arefinTryMoveForward()– Jimi Commented Nov 18, 2024 at 11:20 -
@Jimi, some code are redacted.
TryMoveForwardalso uses input fromstate– Vivek MVK Commented Nov 18, 2024 at 12:14 -
The State returned from
MoveForward()is then what? Based on the code posted here, I assumebool TryMoveForward(in Path path, out State state)would compile. Maybe something actually relevant is missing? – Jimi Commented Nov 18, 2024 at 13:36
1 Answer
Reset to default 2Based on this explanations https://github/dotnet/csharplang/blob/main/proposals/csharp-11.0/low-level-struct-improvements.md#keywords-vs-attributes
Opt out is a keyword (scoped) but the opt in is an attribute ([UnscopedRef]). So in your case you must defined it as scoped:
State MoveForward(scoped in Path path)
本文标签： cCS8347CS8352 with quotref structquot and quotinquotquotrefquot parameterStack Overflow
版权声明：本文标题：c# - CS8347CS8352 with "ref struct" and "in""ref" parameter - Stack Overfl 内容由热心网友自发贡献，该文观点仅代表作者本人， 转载请联系作者并注明出处：http://it.en369.cn/questions/1745628673a2160023.html， 本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌抄袭侵权/违法违规的内容，一经查实，本站将立刻删除。
Statelooks like anoutrather than arefinTryMoveForward()– Jimi Commented Nov 18, 2024 at 11:20TryMoveForwardalso uses input fromstate– Vivek MVK Commented Nov 18, 2024 at 12:14MoveForward()is then what? Based on the code posted here, I assumebool TryMoveForward(in Path path, out State state)would compile. Maybe something actually relevant is missing? – Jimi Commented Nov 18, 2024 at 13:36