up

Author: psfinaki

docs/fsharp/language-reference/generics/constraints.md

@@ -21,7 +21,7 @@ There are several different constraints you can apply to limit the types that ca
 |----------|------|-----------|
 |Type Constraint|*type-parameter* :> *type*|The provided type must be equal to or derived from the type specified, or, if the type is an interface, the provided type must implement the interface.|
 |Null Constraint|*type-parameter* : null|The provided type must support the null literal. This includes all .NET object types but not F# list, tuple, function, class, record, or union types.|
-|Not Null Constraint|*type-parameter* : not null|The provided type must not support the null literal. This includes both `null` annotated types and types which have null as their representation value (such as the option type).|
+|Not Null Constraint|*type-parameter* : not null|The provided type must not support the null literal. This disallows both `null` annotated types and types which have null as their representation value (such as the option type). This does allow value types, since those can never be null.|
 |Explicit Member Constraint|[(]*type-parameter* [or ... or *type-parameter*)] : (*member-signature*)|At least one of the type arguments provided must have a member that has the specified signature; not intended for common use. Members must be either explicitly defined on the type or part of an implicit type extension to be valid targets for an Explicit Member Constraint.|
 |Constructor Constraint|*type-parameter* : ( new : unit -> 'a )|The provided type must have a parameterless constructor.|
 |Value Type Constraint|*type-parameter* : struct|The provided type must be a .NET value type.|

docs/fsharp/language-reference/values/null-values.md

@@ -93,7 +93,7 @@ match x with
 | null -> ...
 ```
 
-Note that all these capabilities were added to the language for the interoperability purposes. Using `| null` within F# code is not considered idiomatic for denoting missing information - for that purpose use options, as described above.
+Note that the extra null related capabilities were added to the language for the interoperability purposes. Using `| null` within F# code is not considered idiomatic for denoting missing information - for that purpose, use options (as described above). Read more about null-related [conventions](../../style-guide/conventions.md#nulls-and-default-values) in the style guide.
 
 ## See also
 

docs/fsharp/style-guide/conventions.md

@@ -709,7 +709,7 @@ let getLineFromStream (stream: System.IO.StreamReader) : string | null =
     stream.ReadLine()
 ```
 
-Instead, use idiomatic F# means (e.g., options):
+**Instead**, use idiomatic F# means (e.g., options):
 ```fsharp
 let getLineFromStream (stream: System.IO.StreamReader) : string option =
     match stream.ReadLine() with