Issue description

Similar to #17720, it would be great to have ranges of : and not for SynTypeConstraint.WhereTyparNotSupportsNull.

in

type C<'T when 
                'T
                    : // comment 1 
                    not // comment 2
                        null> = class end

We cannot piece back the comments to : and not.

Choose one or more from the following categories of impact

• Unexpected nullness warning (false positive in nullness checking, code uses --checknulls and langversion:preview).
• Missing nullness warning in a case which can produce nulls (false negative, code uses --checknulls and langversion:preview).
• Breaking change related to older null constructs in code not using the checknulls switch.
• Breaking change related to generic code and explicit type constraints (null, not null).
• Type inference issue (i.e. code worked without type annotations before, and applying the --checknulls enforces type annotations).
• C#/F# interop issue related to nullness metadata.
• Other (none of the categories above apply).

Operating System

Windows (Default)

What .NET runtime/SDK kind are you seeing the issue on

.NET SDK (.NET Core, .NET 5+)

.NET Runtime/SDK version

FCS 43.9.100-preview.24422.2

Reproducible code snippet and actual behavior

type C<'T when 
                'T
                    : // comment 1 
                    not // comment 2
                        null> = class end

Possible workarounds

No response