Designing Nullable Reference Types in F#
summary
F# 5 adds nullable reference types aligned with C# 8 but preserves backwards compatibility by emitting warnings not errors and encoding nullability as metadata attributes. The compiler uses pattern-matching helpers, a new generics constraint for non-null, and attributes like NullableAttribute with bool[] to represent nested nullability to other compilers. Experiments on real code show many surprising warnings (files with dozens of breakages, projects with hundreds of warnings). Oddly, options emit null and the design wrestles between oblivious semantics vs assume-nonnull.
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chapters (28)
- 0:00Introduction
- 2:42Knowability Assumptions
- 3:13Nothing
- 3:39Implicit
- 10:48Design Goals
- 17:05Pattern Matching
- 19:58Fsharp Rules
- 25:25Noble Value Types
- 26:18Type Relations
- 27:20Knowable
- 28:43Not Null
- 30:20Nominal Types
- 31:45No Attribute Types
- 32:05FSharp
- 32:25Nullable Reference Types
- 33:13Difficult Design Choice
- 34:03No Reference Exceptions
- 34:32Knowable Assumption
- 35:23Two Paths
- 36:47F Sharp
- 37:24Default Values
- 38:18ClineMutable
- 39:18OptionType
- 41:34Why is it important
- 43:51Links
- 46:53Interrupt
- 47:04ByRef
- 48:11Code Base
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