Prefer return collection abstraction instead of implementation

Rule ND2303 .NET Framework Usage / System.Collections

Matches methods returning a collection implementation (List<T>, HashSet<T>, Dictionary<TKey,TValue>). Clients rarely need the exact implementation: prefer returning an interface like IList<T>, ICollection<T>, IEnumerable<T> or IDictionary<TKey,TValue>.

Not a rule, since the interface isn't preferable in all cases.

CQLinq source

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// <Name>Prefer return collection abstraction instead of implementation</Name>
// <Id>ND2303:PreferReturnCollectionAbstractionInsteadOfImplementation</Id>

// warnif count > 0  // This query is not a rule per default

let implTypes = ThirdParty.Types.WithFullNameIn(
   "System.Collections.Generic.List<T>",
   "System.Collections.Generic.HashSet<T>",
   "System.Collections.Generic.Dictionary<TKey,TValue>")

from m in Application.Methods.WithReturnTypeIn(implTypes) 
select new { 
   m, 
   m.ReturnType,
   Debt = 5.ToMinutes().ToDebt(),
   Severity = Severity.Low
}

//<Expl>
// The *{0}* should return a collection abstraction like *IList<T>* 
// instead of returning the concrete *{1}*.
//</Expl>

//<Desc>
// Matches methods returning a collection implementation (*List<T>*,
// *HashSet<T>*, *Dictionary<TKey,TValue>*). Clients rarely need the exact
// implementation: prefer returning an interface like *IList<T>*,
// *ICollection<T>*, *IEnumerable<T>* or *IDictionary<TKey,TValue>*.
//
// Not a rule, since the interface isn't preferable in all cases.
//</Desc>

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.NET Framework Usage / System.Collections: all 4 items