Use SelectAsArray instead of LINQ

Author: sharwell

src/Compilers/Core/Portable/InternalUtilities/EnumerableExtensions.cs

@@ -305,7 +305,10 @@ public static ImmutableArray<TResult> SelectAsArray<TSource, TResult>(this IEnum
                 return ImmutableArray<TResult>.Empty;
             }
 
-            var builder = ArrayBuilder<TResult>.GetInstance();
+            var builder = source is ICollection<TSource> collection
+                ? ArrayBuilder<TResult>.GetInstance(collection.Count)
+                : ArrayBuilder<TResult>.GetInstance();
+
             builder.AddRange(source.Select(selector));
 
             return builder.ToImmutableAndFree();

src/Compilers/Core/Portable/InternalUtilities/OneOrMany.cs

@@ -137,7 +137,7 @@ public OneOrMany<TResult> Select<TResult>(Func<T, TResult> selector)
         {
             return HasOne ?
                 OneOrMany.Create(selector(_one)) :
-                OneOrMany.Create(_many.SelectAsArray(selector));
+                OneOrMany.Create(Microsoft.CodeAnalysis.ImmutableArrayExtensions.SelectAsArray(_many, selector));
         }
 
         public OneOrMany<TResult> Select<TResult, TArg>(Func<T, TArg, TResult> selector, TArg arg)

src/VisualStudio/Core/Def/Implementation/ProjectSystem/FileChangeWatcher.cs

@@ -422,7 +422,7 @@ public async ValueTask ApplyAsync(IVsAsyncFileChangeEx service, CancellationToke
 
                     case Kind.UnwatchFiles:
                         Contract.ThrowIfFalse(_tokens is not null);
-                        await service.UnadviseFileChangesAsync(_tokens.Select(token => token.Cookie!.Value).ToArray(), cancellationToken).ConfigureAwait(false);
+                        await service.UnadviseFileChangesAsync(_tokens.SelectAsArray(token => token.Cookie!.Value), cancellationToken).ConfigureAwait(false);
                         return;
 
                     default: