[Version 9.0] Feature support for attributes on local functions #1466
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BillWagner
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Nov 11, 2025
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I reviewed the existing edits, made a couple small wording changes. This is ready for committee review for V9. |
jskeet
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Jan 14, 2026
| For invocations that occur within declarations of instance constructors, static constructors, finalizers and operators the member name used is implementation-dependent. | ||
| For an invocation that occurs within a local function, the name of the member method that calls that local function is used. Consider the following: if member method `M` calls local function `F1`, which in turn calls local function `F2`, and `F2` has a parameter marked with this attribute, the method name passed to `F2` is `M`, because a local function is *not* a function member! |
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We should separate out the normative and informative here (and remove the exclamation mark preferrably...) Showing this as actual example code would be useful too.
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Agreed! My original PR (#994) had a version of this text in an example, but that appears to have been lost. I'll work with Bill to restore it.
| A static local function may be made conditional in the same sense as a conditional method ([§23.5.3.2](attributes.md#23532-conditional-methods)). | ||
| A compile time error ocurrs if a non-static local function is made conditional. |
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I'm interested in why this is the case - and maybe readers would be too?
jnm2
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Jan 15, 2026
| #### 23.5.3.1 General | ||
| The attribute `Conditional` enables the definition of ***conditional method***s and ***conditional attribute class***es. | ||
| The attribute `Conditional` enables the definition of ***conditional methods***, ***conditional local function***s, and ***conditional attribute class***es. |
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Since the original style continues to be followed with the last two items:
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| The attribute `Conditional` enables the definition of ***conditional methods***, ***conditional local function***s, and ***conditional attribute class***es. | |
| The attribute `Conditional` enables the definition of ***conditional method***s, ***conditional local function***s, and ***conditional attribute class***es. |
| A static local function may be made conditional in the same sense as a conditional method ([§23.5.3.2](attributes.md#23532-conditional-methods)). | ||
| A compile time error ocurrs if a non-static local function is made conditional. |
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Suggested change
| A compile time error ocurrs if a non-static local function is made conditional. | |
| A compile time error occurs if a non-static local function is made conditional. |
| For invocations that occur within declarations of instance constructors, static constructors, finalizers and operators the member name used is implementation-dependent. | ||
| For an invocation that occurs within a local function, the name of the member method that calls that local function is used. Consider the following: if member method `M` calls local function `F1`, which in turn calls local function `F2`, and `F2` has a parameter marked with this attribute, the method name passed to `F2` is `M`, because a local function is *not* a function member! |
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Lambdas and anonymous methods are in the same boat as local functions.
Add support for attributes and extern on local functions fix md formatting
This is now ready for committee review.
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Update the C# standard for the feature of applying attributes on local functions.
Note that this also includes specifying
externon a static local function.This contains all commits from #994. Subsequent edits also made.