Add 49 polyfills across System, System.Collections.Generic, System.IO, and System.Linq by Copilot · Pull Request #91 · Tyrrrz/PolyShim

Copilot · 2026-03-22T17:19:36Z

Adds 49 missing polyfill APIs across four major namespaces, identified from analysis of the existing codebase. Each group adds related polyfills and corresponding tests.

Changes

`System` — `ArgumentOutOfRangeException` throw helpers (.NET 8.0)

ThrowIfNegative<T>, ThrowIfNegativeOrZero<T>, ThrowIfZero<T> (using IComparable<T> constraint)
ThrowIfGreaterThan<T>, ThrowIfGreaterThanOrEqual<T>, ThrowIfLessThan<T>, ThrowIfLessThanOrEqual<T>
ThrowIfEqual<T>, ThrowIfNotEqual<T>

`System` — `ObjectDisposedException.ThrowIf` (.NET 8.0)

ThrowIf(bool, object) and ThrowIf(bool, Type)

`System` — `Random` Span overloads (.NET 8.0)

GetItems<T>(ReadOnlySpan<T>, int), GetItems<T>(ReadOnlySpan<T>, Span<T>), Shuffle<T>(Span<T>)

`System` — `Convert` Span overloads (.NET 5.0 / .NET 9.0)

FromHexString(ReadOnlySpan<char>), ToHexString(ReadOnlySpan<byte>) (.NET 5.0)
ToHexStringLower(ReadOnlySpan<byte>) (.NET 9.0)

`System` — `TimeSpan` factory overloads (.NET 7.0 / .NET 9.0)

TimeSpan.FromMicroseconds(double) (.NET 7.0)
TimeSpan.FromSeconds(long, ...), FromMinutes(long, ...), FromHours(long, ...), FromDays(long, ...) (.NET 9.0)

`System` — `string.IndexOf(char, StringComparison)` (.NET 5.0)

Related to existing Contains(char, StringComparison) polyfill

`System` — Numeric `TryParse(ReadOnlySpan<char>, IFormatProvider?, out T)` (.NET 7.0)

Added for all 13 types that already have TryParse(string, IFormatProvider?, out T) polyfills: byte, short, int, long, sbyte, ushort, uint, ulong, float, double, decimal, IntPtr, UIntPtr
Also added for DateTime and DateTimeOffset

`System.Collections.Generic` — `Stack<T>.TryPeek` / `TryPop` (.NET Core 2.0)

Matches existing pattern from Queue<T>.TryDequeue / TryPeek polyfill

`System.Collections.Generic` — `EnsureCapacity` (.NET 5.0 / .NET 6.0)

Dictionary<TKey,TValue>.EnsureCapacity(int) (.NET 5.0)
HashSet<T>.EnsureCapacity(int), Queue<T>.EnsureCapacity(int), Stack<T>.EnsureCapacity(int) (.NET 6.0)
Note: best-effort stub since these types don't expose writable Capacity on older frameworks

`System.IO` — `Path.Exists` (.NET 7.0)

bool Path.Exists(string?) — implemented as File.Exists || Directory.Exists

`System.IO` — `File.AppendAllBytes` Span/Memory overloads (.NET 9.0)

AppendAllBytes(string, ReadOnlySpan<byte>) and AppendAllBytesAsync(string, ReadOnlyMemory<byte>, CancellationToken)

`System.Linq` — `Enumerable.Zip` 3-sequence overload (.NET 6.0)

IEnumerable<(TFirst, TSecond, TThird)> Zip<TFirst, TSecond, TThird>(IEnumerable<TSecond>, IEnumerable<TThird>)

Security Summary

No security vulnerabilities were identified or introduced by these changes (confirmed by CodeQL scan).

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Tyrrrz · 2026-03-22T18:09:01Z

@copilot rename the PR title, replace the number of sections with the number of new APIs, and also highlight major namespaces

Copilot · 2026-03-22T18:13:49Z

@copilot rename the PR title, replace the number of sections with the number of new APIs, and also highlight major namespaces

Counted 49 new APIs total across four namespaces:

System (39): ArgumentOutOfRangeException ×9, ObjectDisposedException ×2, Random ×3, Convert ×3, TimeSpan ×6, string ×1, numeric TryParse(ReadOnlySpan<char>) ×15
System.Collections.Generic (6): Stack.TryPeek/TryPop ×2, EnsureCapacity ×4 types
System.IO (3): Path.Exists ×1, File.AppendAllBytes/AppendAllBytesAsync span overloads ×2
System.Linq (1): Enumerable.Zip 3-sequence overload

Suggested title: "Add 49 polyfills across System, System.Collections.Generic, System.IO, and System.Linq"

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Pull request overview

Adds a new batch of PolyShim polyfills to backport newer BCL APIs (NET 5–9 era) onto older TFMs, along with corresponding unit tests in PolyShim.Tests.

Changes:

Added new polyfills across multiple TFMs (e.g., Stack<T>.TryPeek/TryPop, EnsureCapacity stubs, Path.Exists, new TimeSpan factories, span-based Random overloads, and span-based TryParse overloads).
Added/updated tests to validate the added polyfills across the test target frameworks.
Expanded Convert and File polyfills with span/memory overloads for hex and append operations.

Reviewed changes

Copilot reviewed 48 out of 48 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
PolyShim/NetCore20/Stack.cs	Adds `Stack<T>.TryPeek` / `TryPop` polyfills for older TFMs.
PolyShim/Net90/TimeSpan.cs	Adds .NET 9-style `TimeSpan` long-based factory overloads.
PolyShim/Net90/File.cs	Adds `File.AppendAllBytes` span/memory overload polyfills.
PolyShim/Net90/Convert.cs	Adds `Convert.ToHexStringLower(ReadOnlySpan<byte>)` polyfill.
PolyShim/Net80/Random.cs	Adds `Random.GetItems` span overloads and `Shuffle(Span<T>)`.
PolyShim/Net80/ObjectDisposedException.cs	Adds `ObjectDisposedException.ThrowIf` polyfills.
PolyShim/Net80/ArgumentOutOfRangeException.cs	Adds `ArgumentOutOfRangeException.ThrowIf*` helper polyfills.
PolyShim/Net70/Byte.cs	Adds `byte.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/Int16.cs	Adds `short.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/Int32.cs	Adds `int.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/Int64.cs	Adds `long.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/SByte.cs	Adds `sbyte.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/UInt16.cs	Adds `ushort.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/UInt32.cs	Adds `uint.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/UInt64.cs	Adds `ulong.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/Single.cs	Adds `float.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/Double.cs	Adds `double.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/Decimal.cs	Adds `decimal.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/IntPtr.cs	Adds `IntPtr.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/UIntPtr.cs	Adds `UIntPtr.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/DateTime.cs	Adds `DateTime.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/DateTimeOffset.cs	Adds `DateTimeOffset.TryParse(ReadOnlySpan<char>, ...)` polyfill.
PolyShim/Net70/TimeSpan.cs	Adds `TimeSpan.FromMicroseconds(double)` polyfill.
PolyShim/Net70/Path.cs	Adds `Path.Exists(string?)` polyfill (file/dir existence).
PolyShim/Net60/Stack.cs	Adds `Stack<T>.EnsureCapacity(int)` stub polyfill.
PolyShim/Net60/Queue.cs	Adds `Queue<T>.EnsureCapacity(int)` stub polyfill.
PolyShim/Net60/HashSet.cs	Adds `HashSet<T>.EnsureCapacity(int)` stub polyfill.
PolyShim/Net60/EnumerableExtensions.cs	Adds 3-sequence `Enumerable.Zip` polyfill.
PolyShim/Net50/String.cs	Adds `string.IndexOf(char, StringComparison)` polyfill.
PolyShim/Net50/Dictionary.cs	Adds `Dictionary<TKey,TValue>.EnsureCapacity(int)` stub polyfill.
PolyShim/Net50/Convert.cs	Adds span overloads for hex encode/decode polyfills.
PolyShim.Tests/NetCore20/StackTests.cs	Tests `Stack<T>.TryPeek` / `TryPop`.
PolyShim.Tests/Net90/TimeSpanTests.cs	Tests the new `TimeSpan` factory overloads.
PolyShim.Tests/Net90/FileTests.cs	Tests `AppendAllBytes` array/span and async array/memory overloads.
PolyShim.Tests/Net90/ConvertTests.cs	Tests `ToHexStringLower` array/span overloads.
PolyShim.Tests/Net80/RandomTests.cs	Tests `Random.GetItems` span overloads and `Shuffle(Span<T>)`.
PolyShim.Tests/Net80/ObjectDisposedExceptionTests.cs	Tests `ObjectDisposedException.ThrowIf` overloads.
PolyShim.Tests/Net80/ArgumentOutOfRangeExceptionTests.cs	Tests `ArgumentOutOfRangeException.ThrowIf*` helpers.
PolyShim.Tests/Net70/TimeSpanTests.cs	Tests `TimeSpan.FromMicroseconds`.
PolyShim.Tests/Net70/PathTests.cs	Tests `Path.Exists` behavior for file/dir/null/empty.
PolyShim.Tests/Net70/NumericTryParseSpanTests.cs	Tests `TryParse(ReadOnlySpan<char>, ...)` polyfills across numeric/date pointer types.
PolyShim.Tests/Net60/StackTests.cs	Tests `Stack<T>.EnsureCapacity` stub behavior.
PolyShim.Tests/Net60/QueueTests.cs	Tests `Queue<T>.EnsureCapacity` stub behavior.
PolyShim.Tests/Net60/HashSetTests.cs	Tests `HashSet<T>.EnsureCapacity` stub behavior.
PolyShim.Tests/Net60/EnumerableExtensionsTests.cs	Tests 3-sequence `Zip` polyfill behavior.
PolyShim.Tests/Net50/StringTests.cs	Tests `string.IndexOf(char, StringComparison)` polyfill.
PolyShim.Tests/Net50/DictionaryTests.cs	Tests `Dictionary<TKey,TValue>.EnsureCapacity` stub behavior.
PolyShim.Tests/Net50/ConvertTests.cs	Tests span/string overloads for hex encode/decode polyfills.

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PolyShim/Net60/Queue.cs

PolyShim/Net90/TimeSpan.cs

PolyShim/Net80/ObjectDisposedException.cs

PolyShim/Net80/ArgumentOutOfRangeException.cs

PolyShim/Net70/TimeSpan.cs

PolyShim/Net80/ObjectDisposedException.cs

PolyShim/Net80/ArgumentOutOfRangeException.cs

PolyShim/Net60/Stack.cs

Tyrrrz

@copilot

PolyShim.Tests/Net50/DictionaryTests.cs

PolyShim.Tests/Net70/NumericTryParseSpanTests.cs

PolyShim/Net50/Convert.cs

Tyrrrz · 2026-03-22T23:11:46Z

@copilot can you identify why the build is failing?

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Copilot · 2026-03-22T23:17:28Z

@copilot can you identify why the build is failing?

The build fails on net462 because FEATURE_MEMORY is false (no System.Memory package reference in the test project). This means the TryParse(ReadOnlySpan<char>, ...) polyfills aren't compiled (they're guarded with #if FEATURE_MEMORY in source), but the test methods try to call them.

Fixed in c2abeb1 by adding System.Memory as a package reference to the test project. This makes FEATURE_MEMORY true on net462, so the span-based polyfills compile and the tests work without needing #if FEATURE_MEMORY guards.

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Tyrrrz · 2026-03-23T10:48:06Z

@copilot the new build is failing too

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Copilot · 2026-03-23T10:59:25Z

@copilot the new build is failing too

The build was crashing because commit c2abeb1 added System.Memory as a package reference to the test project. This triggered a Roslyn compiler bug — NullReferenceException in TryEmitOptimizedReadonlySpanCreation when compiling for net462. The compiler tries to optimize ReadOnlySpan<byte> creation from u8 string literals but crashes because the type comes from the System.Memory NuGet package rather than the runtime.

Fixed in 2b1651a by:

Removing System.Memory from the test csproj
Adding #if !NETFRAMEWORK guards around the 16 span-based test methods (TryParse_Span_Test and FromHexString_Span_Test) since the underlying polyfills are guarded with #if FEATURE_MEMORY and don't exist on net462

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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 43355 --endpoint 127.0.0.1:043355 --role client --parentprocessid 4585 --datacollectionport 0 --telemetryoptedin false (dns block)

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Tyrrrz · 2026-03-23T11:26:35Z

@copilot build no longer crashing but the tests are failing

…iseconds(0.5) which rounds on net462 Co-authored-by: Tyrrrz <1935960+Tyrrrz@users.noreply.github.com> Agent-Logs-Url: https://github.com/Tyrrrz/PolyShim/sessions/47c6c53b-a628-46cd-a630-feea931231e7

Copilot · 2026-03-23T11:30:23Z

@copilot build no longer crashing but the tests are failing

Fixed in 617d1f3. The FromMicroseconds_Test was failing because TimeSpan.FromMilliseconds(0.5) rounds to 1ms on .NET Framework (it rounds to the nearest millisecond). Replaced with TimeSpan.FromTicks(5_000) which is exact on all platforms.

@copilot the new build is failing too

The test failure was in TimeSpan.FromMicroseconds_Test on net462 — TimeSpan.FromMilliseconds(0.5) rounds to 1ms on .NET Framework. Fixed in 617d1f3 by using TimeSpan.FromTicks(5_000) instead.

codecov · 2026-03-23T11:38:54Z

Codecov Report

❌ Patch coverage is 99.21415% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.32%. Comparing base (c02cb80) to head (617d1f3).
⚠️ Report is 2 commits behind head on prime.

Files with missing lines	Patch %	Lines
PolyShim.Tests/Net90/FileTests.cs	84.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            prime      #91      +/-   ##
==========================================
+ Coverage   85.48%   87.32%   +1.84%     
==========================================
  Files         220      255      +35     
  Lines        3630     4135     +505     
  Branches      315      345      +30     
==========================================
+ Hits         3103     3611     +508     
+ Misses        456      455       -1     
+ Partials       71       69       -2

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Copilot

Pull request overview

Copilot reviewed 63 out of 63 changed files in this pull request and generated 9 comments.

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PolyShim/Net60/Stack.cs

PolyShim/Net60/HashSet.cs

PolyShim/Net80/Random.cs

PolyShim/Net90/Convert.cs

PolyShim/Net80/ObjectDisposedException.cs

PolyShim/Net60/Queue.cs

PolyShim/Net50/Dictionary.cs

PolyShim/Net50/Convert.cs

Copilot AI and others added 13 commits March 22, 2026 17:03

Add ArgumentOutOfRangeException throw helper polyfills (.NET 8.0)

087f473

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Add ObjectDisposedException.ThrowIf polyfills (.NET 8.0)

303aaf3

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Add Random Span overloads polyfills (.NET 8.0)

570dfbc

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Add Convert Span overloads polyfills (.NET 5.0 / .NET 9.0)

bdb9c02

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Add Stack<T>.TryPeek / TryPop polyfills (.NET Core 2.0)

8b27e29

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Add EnsureCapacity polyfills for Dictionary, HashSet, Queue, …

0b15172

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Add Enumerable.Zip 3-sequence overload polyfill (.NET 6.0)

f364c44

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Add TimeSpan factory overloads polyfills (.NET 7.0 / .NET 9.0)

0cf3d6e

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Add Path.Exists polyfill (.NET 7.0)

9abb34a

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Add File.AppendAllBytes Span/Memory overloads (.NET 9.0)

1aa5a29

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Add string.IndexOf(char, StringComparison) polyfill (.NET 5.0)

aa027dc

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Copilot AI assigned Copilot and Tyrrrz Mar 22, 2026

Copilot created this pull request from a session on behalf of Tyrrrz March 22, 2026 17:20 View session

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Tyrrrz added the enhancement New feature or request label Mar 22, 2026

Tyrrrz marked this pull request as ready for review March 22, 2026 18:08

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Copilot AI changed the title ~~Add missing polyfills: 12 new sections~~ Add 49 polyfills across System, System.Collections.Generic, System.IO, and System.Linq Mar 22, 2026

Copilot finished work on behalf of Tyrrrz March 22, 2026 18:14

Copilot AI reviewed Mar 22, 2026

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Add System.Memory package reference to test project to fix net462 build

c2abeb1

Co-authored-by: Tyrrrz <1935960+Tyrrrz@users.noreply.github.com> Agent-Logs-Url: https://github.com/Tyrrrz/PolyShim/sessions/2dbe3380-ee64-4405-9997-94647c7ea5cf

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Tyrrrz merged commit 3f239a7 into prime Mar 23, 2026
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Tyrrrz deleted the copilot/identify-missing-polyfills branch March 23, 2026 12:49

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Changes

System — ArgumentOutOfRangeException throw helpers (.NET 8.0)

System — ObjectDisposedException.ThrowIf (.NET 8.0)

System — Random Span overloads (.NET 8.0)

System — Convert Span overloads (.NET 5.0 / .NET 9.0)

System — TimeSpan factory overloads (.NET 7.0 / .NET 9.0)

System — string.IndexOf(char, StringComparison) (.NET 5.0)

System — Numeric TryParse(ReadOnlySpan<char>, IFormatProvider?, out T) (.NET 7.0)

System.Collections.Generic — Stack<T>.TryPeek / TryPop (.NET Core 2.0)

System.Collections.Generic — EnsureCapacity (.NET 5.0 / .NET 6.0)

System.IO — Path.Exists (.NET 7.0)

System.IO — File.AppendAllBytes Span/Memory overloads (.NET 9.0)

System.Linq — Enumerable.Zip 3-sequence overload (.NET 6.0)

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Copilot AI commented Mar 22, 2026 •

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`System` — `ArgumentOutOfRangeException` throw helpers (.NET 8.0)

`System` — `ObjectDisposedException.ThrowIf` (.NET 8.0)

`System` — `Random` Span overloads (.NET 8.0)

`System` — `Convert` Span overloads (.NET 5.0 / .NET 9.0)

`System` — `TimeSpan` factory overloads (.NET 7.0 / .NET 9.0)

`System` — `string.IndexOf(char, StringComparison)` (.NET 5.0)

`System` — Numeric `TryParse(ReadOnlySpan<char>, IFormatProvider?, out T)` (.NET 7.0)

`System.Collections.Generic` — `Stack<T>.TryPeek` / `TryPop` (.NET Core 2.0)

`System.Collections.Generic` — `EnsureCapacity` (.NET 5.0 / .NET 6.0)

`System.IO` — `Path.Exists` (.NET 7.0)

`System.IO` — `File.AppendAllBytes` Span/Memory overloads (.NET 9.0)

`System.Linq` — `Enumerable.Zip` 3-sequence overload (.NET 6.0)

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