Proposal: dotnet/csharplang#287
Spec: https://github.com/dotnet/csharplang/blob/main/proposals/csharp-10.0/caller-argument-expression.md

General Concerns

• LangVersion - No lang version impact for caller info attributes.
• VB Interop
  • VB does case-insensitive identifier matching
  • VB emits correct casing, regardless of user's casing in source
• Update spec with implicit conversion rules
• Remove feature flag after Aleksey reviews.

Semantics

• Syntax is reflected exactly
  • Leading comments ignored
  • Trailing comments ignored
  • Middle comments included
  • Leading pragmas ignored
  • Trailing pragmas ignored
  • Middle pragmas included
• Parameter remapping
  • Extension methods
    • Info of this parameter
    • Info of non-this parameter
  • Delegate Invoke
  • Delegate BeginInvoke
  • Delegate EndInvoke
• Overridden by existing caller info attributes
  • CallerFilePathAttribute
  • CallerLineNumberAttribute
  • CallerMemberNameAttribute
• Self-referential attribute
• Explicit argument reordering
• Applied multiple times
• Invalid parameter name
• No default value provided for parameter
• Referenced parameter uses default value
• Attribute added to overridden method
• Attribute removed from overridden method
• Attribute applied to type with implicit conversion from string
  • Reference conversion
  • User-defined conversion
  • No conversion
• Compiler generated calls with user-written code
  • Extension GetEnumerator
  • Extension Deconstruct
  • Implicit Index/Slice (should be default)
  • Extension GetAwaiter
• Ref/out parameters
  • Out variable declarations
  • Out discards
• Implicit base constructor calls (should be ignored, like other Caller info attributes)

Open issues:

• could we add CallerArgumentExpression to Debug.Assert and have that new overload get picked?

FYI @Youssef1313