[Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array #38474

Closed
#39198
Closed
[Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array#38474
#39198
Assignees
gewarren
Labels
🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change

Description

@jkotas
jkotas
opened on Nov 29, 2023

Description

The type of array instance returned by RuntimeHelpers.GetSubArray is changed to match the source array. RuntimeHelpers.GetSubArray is used by C# compiler to implement range operator for arrays.

This behavior change can be only observable by code that uses covariant array conversions.

Version

.NET 9 Preview 1

Previous behavior

RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of type T[].

For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is object[]

New behavior

RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of the same type as array argument.

For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is string[].

Type of breaking change

  • Binary incompatible: Existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
  • Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.
  • Behavioral change: Existing binaries may behave differently at run time.

Reason for change

The design of C# pattern matching features assume that the type of array instance returned RuntimeHelpers.GetSubArray match the source array. The previous behavior led to unexpected behavior of certain complex pattern expressions that used slicing of co-variant arrays. See dotnet/roslyn#69053 for details.

Recommended action

The recommended action is to remove dependency of the affected code on array co-variance.

For example, change:

object[] arr = new string[1];
M(arr[1..2]);

to

string[] arr = new string[1];
M(arr[1..2]);

Feature area

Core .NET libraries

Affected APIs

System.Runtme.CompilerServices.RuntimeHelpers.GetSubArray

Associated WorkItem - 196551

Metadata

Metadata

Assignees

Labels

🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change

Type

No type

Projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions

    , 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
     blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

    Skip to content
    [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array #38474
    Closed
    #39198
    Closed
    [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array#38474
    #39198
    Assignees
    gewarren
    Labels
    🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
    Description
    @jkotas
    jkotas
    opened on Nov 29, 2023
    Description
    The type of array instance returned by RuntimeHelpers.GetSubArray is changed to match the source array. RuntimeHelpers.GetSubArray is used by C# compiler to implement range operator for arrays.
    This behavior change can be only observable by code that uses covariant array conversions.
    Version
    .NET 9 Preview 1
    Previous behavior
    RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of type T[].
    For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is object[]
    New behavior
    RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of the same type as array argument.
    For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is string[].
    Type of breaking change
    • Binary incompatible: Existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
    • Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.
    • Behavioral change: Existing binaries may behave differently at run time.
    Reason for change
    The design of C# pattern matching features assume that the type of array instance returned RuntimeHelpers.GetSubArray match the source array. The previous behavior led to unexpected behavior of certain complex pattern expressions that used slicing of co-variant arrays. See dotnet/roslyn#69053 for details.
    Recommended action
    The recommended action is to remove dependency of the affected code on array co-variance.
    For example, change:
    object[] arr = new string[1];
M(arr[1..2]);

    to
    string[] arr = new string[1];
M(arr[1..2]);

    Feature area
    Core .NET libraries
    Affected APIs
    System.Runtme.CompilerServices.RuntimeHelpers.GetSubArray
    Associated WorkItem - 196551
    Metadata
    Metadata
    Assignees
    Labels
    🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
    Type
    No type
    Projects
      Milestone
      No milestone
      Relationships
      None yet
      Development
      No branches or pull requests
      Issue actions
      
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

      Skip to content
      [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array #38474
      Closed
      #39198
      Closed
      [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array#38474
      #39198
      Assignees
      gewarren
      Labels
      🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
      Description
      @jkotas
      jkotas
      opened on Nov 29, 2023
      Description
      The type of array instance returned by RuntimeHelpers.GetSubArray is changed to match the source array. RuntimeHelpers.GetSubArray is used by C# compiler to implement range operator for arrays.
      This behavior change can be only observable by code that uses covariant array conversions.
      Version
      .NET 9 Preview 1
      Previous behavior
      RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of type T[].
      For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is object[]
      New behavior
      RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of the same type as array argument.
      For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is string[].
      Type of breaking change
      • Binary incompatible: Existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
      • Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.
      • Behavioral change: Existing binaries may behave differently at run time.
      Reason for change
      The design of C# pattern matching features assume that the type of array instance returned RuntimeHelpers.GetSubArray match the source array. The previous behavior led to unexpected behavior of certain complex pattern expressions that used slicing of co-variant arrays. See dotnet/roslyn#69053 for details.
      Recommended action
      The recommended action is to remove dependency of the affected code on array co-variance.
      For example, change:
      object[] arr = new string[1];
M(arr[1..2]);

      to
      string[] arr = new string[1];
M(arr[1..2]);

      Feature area
      Core .NET libraries
      Affected APIs
      System.Runtme.CompilerServices.RuntimeHelpers.GetSubArray
      Associated WorkItem - 196551
      Metadata
      Metadata
      Assignees
      Labels
      🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
      Type
      No type
      Projects
        Milestone
        No milestone
        Relationships
        None yet
        Development
        No branches or pull requests
        Issue actions
        
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

        Skip to content
        [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array #38474
        Closed
        #39198
        Closed
        [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array#38474
        #39198
        Assignees
        gewarren
        Labels
        🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
        Description
        @jkotas
        jkotas
        opened on Nov 29, 2023
        Description
        The type of array instance returned by RuntimeHelpers.GetSubArray is changed to match the source array. RuntimeHelpers.GetSubArray is used by C# compiler to implement range operator for arrays.
        This behavior change can be only observable by code that uses covariant array conversions.
        Version
        .NET 9 Preview 1
        Previous behavior
        RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of type T[].
        For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is object[]
        New behavior
        RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of the same type as array argument.
        For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is string[].
        Type of breaking change
        • Binary incompatible: Existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
        • Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.
        • Behavioral change: Existing binaries may behave differently at run time.
        Reason for change
        The design of C# pattern matching features assume that the type of array instance returned RuntimeHelpers.GetSubArray match the source array. The previous behavior led to unexpected behavior of certain complex pattern expressions that used slicing of co-variant arrays. See dotnet/roslyn#69053 for details.
        Recommended action
        The recommended action is to remove dependency of the affected code on array co-variance.
        For example, change:
        object[] arr = new string[1];
M(arr[1..2]);

        to
        string[] arr = new string[1];
M(arr[1..2]);

        Feature area
        Core .NET libraries
        Affected APIs
        System.Runtme.CompilerServices.RuntimeHelpers.GetSubArray
        Associated WorkItem - 196551
        Metadata
        Metadata
        Assignees
        Labels
        🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
        Type
        No type
        Projects
          Milestone
          No milestone
          Relationships
          None yet
          Development
          No branches or pull requests
          Issue actions
          
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

          Skip to content
          [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array #38474
          Closed
          #39198
          Closed
          [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array#38474
          #39198
          Assignees
          gewarren
          Labels
          🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
          Description
          @jkotas
          jkotas
          opened on Nov 29, 2023
          Description
          The type of array instance returned by RuntimeHelpers.GetSubArray is changed to match the source array. RuntimeHelpers.GetSubArray is used by C# compiler to implement range operator for arrays.
          This behavior change can be only observable by code that uses covariant array conversions.
          Version
          .NET 9 Preview 1
          Previous behavior
          RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of type T[].
          For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is object[]
          New behavior
          RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of the same type as array argument.
          For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is string[].
          Type of breaking change
          • Binary incompatible: Existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
          • Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.
          • Behavioral change: Existing binaries may behave differently at run time.
          Reason for change
          The design of C# pattern matching features assume that the type of array instance returned RuntimeHelpers.GetSubArray match the source array. The previous behavior led to unexpected behavior of certain complex pattern expressions that used slicing of co-variant arrays. See dotnet/roslyn#69053 for details.
          Recommended action
          The recommended action is to remove dependency of the affected code on array co-variance.
          For example, change:
          object[] arr = new string[1];
M(arr[1..2]);

          to
          string[] arr = new string[1];
M(arr[1..2]);

          Feature area
          Core .NET libraries
          Affected APIs
          System.Runtme.CompilerServices.RuntimeHelpers.GetSubArray
          Associated WorkItem - 196551
          Metadata
          Metadata
          Assignees
          Labels
          🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
          Type
          No type
          Projects
            Milestone
            No milestone
            Relationships
            None yet
            Development
            No branches or pull requests
            Issue actions
            
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

            Skip to content
            [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array #38474
            Closed
            #39198
            Closed
            [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array#38474
            #39198
            Assignees
            gewarren
            Labels
            🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
            Description
            @jkotas
            jkotas
            opened on Nov 29, 2023
            Description
            The type of array instance returned by RuntimeHelpers.GetSubArray is changed to match the source array. RuntimeHelpers.GetSubArray is used by C# compiler to implement range operator for arrays.
            This behavior change can be only observable by code that uses covariant array conversions.
            Version
            .NET 9 Preview 1
            Previous behavior
            RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of type T[].
            For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is object[]
            New behavior
            RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of the same type as array argument.
            For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is string[].
            Type of breaking change
            • Binary incompatible: Existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
            • Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.
            • Behavioral change: Existing binaries may behave differently at run time.
            Reason for change
            The design of C# pattern matching features assume that the type of array instance returned RuntimeHelpers.GetSubArray match the source array. The previous behavior led to unexpected behavior of certain complex pattern expressions that used slicing of co-variant arrays. See dotnet/roslyn#69053 for details.
            Recommended action
            The recommended action is to remove dependency of the affected code on array co-variance.
            For example, change:
            object[] arr = new string[1];
M(arr[1..2]);

            to
            string[] arr = new string[1];
M(arr[1..2]);

            Feature area
            Core .NET libraries
            Affected APIs
            System.Runtme.CompilerServices.RuntimeHelpers.GetSubArray
            Associated WorkItem - 196551
            Metadata
            Metadata
            Assignees
            Labels
            🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
            Type
            No type
            Projects
              Milestone
              No milestone
              Relationships
              None yet
              Development
              No branches or pull requests
              Issue actions
              
, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

              Skip to content
              [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array #38474
              Closed
              #39198
              Closed
              [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array#38474
              #39198
              Assignees
              gewarren
              Labels
              🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
              Description
              @jkotas
              jkotas
              opened on Nov 29, 2023
              Description
              The type of array instance returned by RuntimeHelpers.GetSubArray is changed to match the source array. RuntimeHelpers.GetSubArray is used by C# compiler to implement range operator for arrays.
              This behavior change can be only observable by code that uses covariant array conversions.
              Version
              .NET 9 Preview 1
              Previous behavior
              RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of type T[].
              For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is object[]
              New behavior
              RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of the same type as array argument.
              For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is string[].
              Type of breaking change
              • Binary incompatible: Existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
              • Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.
              • Behavioral change: Existing binaries may behave differently at run time.
              Reason for change
              The design of C# pattern matching features assume that the type of array instance returned RuntimeHelpers.GetSubArray match the source array. The previous behavior led to unexpected behavior of certain complex pattern expressions that used slicing of co-variant arrays. See dotnet/roslyn#69053 for details.
              Recommended action
              The recommended action is to remove dependency of the affected code on array co-variance.
              For example, change:
              object[] arr = new string[1];
M(arr[1..2]);

              to
              string[] arr = new string[1];
M(arr[1..2]);

              Feature area
              Core .NET libraries
              Affected APIs
              System.Runtme.CompilerServices.RuntimeHelpers.GetSubArray
              Associated WorkItem - 196551
              Metadata
              Metadata
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              Labels
              🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
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              No type
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                No milestone
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                None yet
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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                [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array #38474
                Closed
                #39198
                Closed
                [Breaking change]: Change the type of array instance returned RuntimeHelpers.GetSubArray to match the source array#38474
                #39198
                Assignees
                gewarren
                Labels
                🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
                Description
                @jkotas
                jkotas
                opened on Nov 29, 2023
                Description
                The type of array instance returned by RuntimeHelpers.GetSubArray is changed to match the source array. RuntimeHelpers.GetSubArray is used by C# compiler to implement range operator for arrays.
                This behavior change can be only observable by code that uses covariant array conversions.
                Version
                .NET 9 Preview 1
                Previous behavior
                RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of type T[].
                For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is object[]
                New behavior
                RuntimeHelpers.GetSubArray<T>(T[] array, Range range) method returns an array instance of the same type as array argument.
                For example, the type of array instance returned by RuntimeHelpers.GetSubArray<object>(new string[1], ...) is string[].
                Type of breaking change
                • Binary incompatible: Existing binaries may encounter a breaking change in behavior, such as failure to load or execute, and if so, require recompilation.
                • Source incompatible: When recompiled using the new SDK or component or to target the new runtime, existing source code may require source changes to compile successfully.
                • Behavioral change: Existing binaries may behave differently at run time.
                Reason for change
                The design of C# pattern matching features assume that the type of array instance returned RuntimeHelpers.GetSubArray match the source array. The previous behavior led to unexpected behavior of certain complex pattern expressions that used slicing of co-variant arrays. See dotnet/roslyn#69053 for details.
                Recommended action
                The recommended action is to remove dependency of the affected code on array co-variance.
                For example, change:
                object[] arr = new string[1];
M(arr[1..2]);

                to
                string[] arr = new string[1];
M(arr[1..2]);

                Feature area
                Core .NET libraries
                Affected APIs
                System.Runtme.CompilerServices.RuntimeHelpers.GetSubArray
                Associated WorkItem - 196551
                Metadata
                Metadata
                Assignees
                Labels
                🏁 Release: .NET 9Work items for the .NET 9 release📌 seQUESTeredIdentifies that an issue has been imported into Quest.breaking-changeIndicates a .NET Core breaking change
                Type
                No type
                Projects
                  Milestone
                  No milestone
                  Relationships
                  None yet
                  Development
                  No branches or pull requests
                  Issue actions