Test plan for "custom fixed"

[jcouv]

Specification

• [ ] Specification checked in to csharplang

Tests

• [x] Resolution of GetPinnableReference method (blocking)
  • [x] instance method wins over extensions SimpleCaseOfCustomFixed
  • [x] GPR with optional or params arguments (ignored) CustomFixedStructVariousErr07_Optional
  • [x] GetPinnableReference marked as ObsoleteCustomFixedStructVariousErr05_Obsolete`
  • [x] GetPinnableReference with use-site error CustomFixedStructVariousErr06_UseSite
  • [x] inaccessible GetPinnableReference (CustomFixedStructVariousErr01)
  • [x] GetPinnableReference<T>() (ignored) CustomFixedStructVariousErr04
  • [x] GetPinnableReference<T>() (instance) and GetPinnableReference() (extension), the extension is picked SimpleCaseOfCustomFixedExt
  • [x] Extension method on array or string (they are ignored, for compat) FixStringArrayExtensionHelpersIgnored
  • [x] missing old helper (GetOffsetToStartOf…), missing new helper FixStringMissingAllHelpers
  • [x] instance GPR on sSystem.String (used), on System.Array (ignored) - FixedHelpersOnStringAndArray

  • [x] GPR on System.Object (ignored on String/Array, used on others) FixedHelperOnObject

• [x] fixed (int* ptr = nullableArray) // with GetPinnableExtension on NullableArray (ok) (CustomFixedStructNullable)
• [x] fixed (int* ptr = nullableArray) (error because operator doesn't lift) (CustomFixedStructNullableErr)
• [ ] integration with unmanaged constraint: void M<T>(ImmutableArray<T> tArray) where T : unmanaged { fixed(T* x = tArray) ... } (ok)
• [ ] VB doesn't have fixed, notify F#
• [x] langver (SimpleCaseOfCustomFixed_oldVersion)
• [x] two extension methods named GetPinnableReference should produce ambiguity (CustomFixedErrAmbiguous)
• [x] test GetPinnableReference that returns a nullptr (SimpleCaseOfCustomFixedNull)
• [ ] fixed (int* ptr = immutableArray) { ... /* write to the array */ ... } even though ref readonly int GetPinnableRefererence()
• [x] fixed (int* ptr = (C)null) // get a nullptr (SimpleCaseOfCustomFixedNull)
• [x] fixed (int* ptr = someStruct) (avoid copying the struct) (SimpleCaseOfCustomFixedStruct)
• [x] fixed (int* ptr = someClass) (must copy the reference)
• [x] fixed (int* ptr = tWithPinnable) (ok, check for struct, then don't copy, but if ref type, then do copy) (SimpleCaseOfCustomFixedGeneric)
• [x] GetPinnableReference is not exposed in semantic model or IOperation
• [x] fixed (int* ptr = (dynamic)immutableArray) (fails, no dynamic dispatch) (CustomFixedErrDynamic)
• [x] Verify evaluation order, and side-effects on structs (didn't copy) (CustomFixedStructSideeffects, CustomFixedClassSideeffects, CustomFixedGenericSideeffects)
• [ ] Conversions are not considered
• [ ] fixed (int* ptr = await e) ... (unsafe and async don't work together)
• [ ] Scenarios with struct, using this struct fixed (int* ptr = this) // in a struct or readonly struct (should copy, depending on instance or extension method)
• [ ] test with fixed buffer
• [x] PROTOTYPE markers removed

IDE

• [x] FAR on GetPinnableReference should the usage in fixed (requires some semantic model changes) (filed https://github.com/dotnet/roslyn/issues/25610)

Spec

• [ ] Update the spec with new method name and also move out the portions for alternatives
• [ ] Arrays and strings are already fixable

Language proposal https://github.com/dotnet/csharplang/blob/master/proposals/csharp-7.3/pattern-based-fixed.md PR https://github.com/dotnet/roslyn/pull/24469

[jcouv]

@VSadov I checked the boxes which I could verify. Take a look at the remaining ones. Feel free to update the list above with test names.