Add polyfills for System.Collections.Generic.CollectionExtensions

[Copilot]

Adds polyfills covering the missing members of CollectionExtensions across .NET versions.

New polyfills

.NET Core 2.0 (NetCore20/CollectionExtensions.cs)

• IDictionary<TKey,TValue>.TryAdd(key, value)
• IDictionary<TKey,TValue>.Remove(key, out value)

.NET 5.0 (Net50/IReadOnlySet.cs)

• IReadOnlySet<T> interface

.NET 7.0 (Net70/CollectionExtensions.cs)

• IList<T>.AsReadOnly() → ReadOnlyCollection<T>
• IDictionary<TKey,TValue>.AsReadOnly() → ReadOnlyDictionary<TKey,TValue>

.NET 8.0 (Net80/CollectionExtensions.cs)

• List<T>.AddRange(ReadOnlySpan<T>)
• List<T>.InsertRange(int, ReadOnlySpan<T>) — delegates to List<T>.InsertRange(IEnumerable<T>) for O(n) complexity
• List<T>.CopyTo(Span<T>)

.NET 9.0 (Net90/ReadOnlySet.cs)

• ReadOnlySet<T> — wraps ISet<T>, implements IReadOnlySet<T>

.NET 10.0 (Net100/CollectionExtensions.cs)

• ISet<T>.AsReadOnly() → ReadOnlySet<T>

[Tyrrrz]

@copilot getting build errors

[Copilot]

@copilot getting build errors

Fixed in 75889a5 — [ExcludeFromCodeCoverage] is not valid on interface declarations in older C# language versions (CS0592). Removed it from IReadOnlySet<T>, matching the pattern used by other interface polyfills in the repo (e.g. IAsyncDisposable, IValueTaskSource).

[Copilot]

Pull request overview

Adds new polyfills for missing System.Collections.Generic.CollectionExtensions members across older TFMs, including span-based List<T> helpers, AsReadOnly() helpers, and ReadOnlySet<T> / IReadOnlySet<T> support (plus a C# 14 extension-resolution bridge for .NET 5–9).

Changes:

• Add IDictionary<TKey,TValue>.TryAdd() and Remove(key, out value) polyfills for older TFMs.
• Add .NET 5-era AsReadOnly() polyfills for IList<T> / IDictionary<TKey,TValue> and introduce IReadOnlySet<T>.
• Add .NET 8-era span-based List<T> polyfills and .NET 9/10 ReadOnlySet<T> + ISet<T>.AsReadOnly() polyfills (with a C# 14 bridge on .NET 5+).

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
PolyShim/NetCore20/CollectionExtensions.cs	Adds TryAdd and Remove(key, out value) extension member polyfills for IDictionary.
PolyShim/Net80/CollectionExtensions.cs	Adds span-based List<T> extension member polyfills (AddRange, InsertRange, CopyTo).
PolyShim/Net50/IReadOnlySet.cs	Introduces IReadOnlySet<T> polyfill for non-.NET 5+ TFMs.
PolyShim/Net50/CollectionExtensions.cs	Adds AsReadOnly() polyfills for IList<T> and IDictionary<TKey,TValue>.
PolyShim/Net90/ReadOnlySet.cs	Adds ReadOnlySet<T> implementation for pre-.NET 9 TFMs.
PolyShim/Net100/CollectionExtensions.cs	Adds ISet<T>.AsReadOnly() and C# 14 resolution bridge for AsReadOnly() overloads on .NET 5+.
PolyShim.Tests/NetCore20/CollectionExtensionsTests.cs	Adds tests for TryAdd/Remove(key, out) behavior.
PolyShim.Tests/Net80/CollectionExtensionsTests.cs	Adds tests for span-based List<T> polyfills.
PolyShim.Tests/Net50/CollectionExtensionsTests.cs	Adds tests for AsReadOnly() on IList<T>/IDictionary<TKey,TValue>.
PolyShim.Tests/Net100/CollectionExtensionsTests.cs	Adds tests for ISet<T>.AsReadOnly() / ReadOnlySet<T> behavior.

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[codecov]

Codecov Report

❌ Patch coverage is 95.08197% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.66%. Comparing base (8ff8470) to head (f3fa29e).
⚠️ Report is 1 commits behind head on prime.

Files with missing lines	Patch %	Lines
PolyShim/Net90/ReadOnlySet.cs	45.45%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            prime     #113      +/-   ##
==========================================
+ Coverage   90.64%   90.66%   +0.02%     
==========================================
  Files         275      282       +7     
  Lines        4776     4898     +122     
  Branches      394      401       +7     
==========================================
+ Hits         4329     4441     +112     
- Misses        358      367       +9     
- Partials       89       90       +1     

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[Copilot]

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I tried to connect to the following addresses, but was blocked by firewall rules:

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  • Triggering command: /usr/share/dotnet/dotnet /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/PolyShim/PolyShim/PolyShim.Tests/bin/Debug/net10.0/PolyShim.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/PolyShim/PolyShim/PolyShim.Tests/bin/Debug/net10.0/PolyShim.Tests.deps.json /home/REDACTED/work/PolyShim/PolyShim/PolyShim.Tests/bin/Debug/net10.0/testhost.dll --port 35633 --endpoint 127.0.0.1:035633 --role client --parentprocessid 4154 --datacollectionport 0 --telemetryoptedin false (dns block)
  • Triggering command: /usr/share/dotnet/dotnet /usr/share/dotnet/dotnet exec --runtimeconfig /home/REDACTED/work/PolyShim/PolyShim/PolyShim.Tests/bin/Debug/net10.0/PolyShim.Tests.runtimeconfig.json --depsfile /home/REDACTED/work/PolyShim/PolyShim/PolyShim.Tests/bin/Debug/net10.0/PolyShim.Tests.deps.json /home/REDACTED/work/PolyShim/PolyShim/PolyShim.Tests/bin/Debug/net10.0/testhost.dll --port 36239 --endpoint 127.0.0.1:036239 --role client --parentprocessid 4372 --datacollectionport 0 --telemetryoptedin false (dns block)

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