Local Function Status

This is a checklist for current and outstanding work on the local functions feature, as spec'd in local-functions.md.

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Known issues

Compiler:

• Parser builds nodes for local functions when feature not enabled (#9940)
• Compiler crash: base call to state machine method, in state machine method (#9872)
• Need custom warning for unused local function (#9661)
• Generate quick action does not offer to generate local (#9352)
• Parser ambiguity research (#10388)
• Dynamic support (#10389)
• Referring to local function in expression tree (#10390)
• Resolve definite assignment rules (#10391)
• Remove support for var return type (#10392)
• Update error messages (#10393)

IDE:

• Some selections around local functions fail extract method refactoring [ ] (#8719)
• Extracting local function passed to an Action introduces compiler error [ ] (#8718)
• Ctrl+. on a delegate invocation crashes VS (via Extract method) (#8717)
• Inline temp introduces compiler error (#8716)
• Call hierarchy search never terminates on local functions (#8654)
• Nav bar doesn't support local functions (#8648)
• No outlining for local functions (#8647)
• Squiggles all over the place when using an unsupported modifier (#8645)
• Peek definition errors out on local function (#8644)
• Void keyword not recommended while declaring local function (#8616)
• Change signature doesn't update the signature of the local function (#8539)

Feature Completeness Progress

• N-level nested local functions
• Capture
  • Works alongside lambdas and behaves very similarly in fallback cases
  • Has zero-allocation closures (struct frames by ref) on functions never converted to a delegate and are not an iterator/async
• Standard parameter features
  • params
  • ref/out
  • named/optional
• Visibility
  • May revisit design (currently shadows, may do overloads)
• Generics
  • Nongeneric local functions in generic methods (same as lambdas).
  • Generic local functions in nongeneric methods.
  • Generic local functions in generic methods.
  • Arbitrary nesting of generic local functions.
  • Generic local functions with constraints.
• Inferred return type
• Iterators
• Async