Disallow span conversions between spans which are not structs (#74587)

* Disallow span conversions between spans which are not structs * Require ref struct
dotnet · Aug 2, 2024 · 3e83e7b · 3e83e7b
1 parent 4ba990b
commit 3e83e7b
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Showing 2 changed files with 26 additions and 0 deletions.
diff --git a/src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs b/src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs
@@ -1343,6 +1343,8 @@ internal static bool IsSpan(this TypeSymbol type)
             return type is NamedTypeSymbol
             {
                 Name: "Span",
+                IsValueType: true,
+                IsRefLikeType: true,
                 Arity: 1,
                 ContainingType: null,
                 ContainingNamespace: { Name: nameof(System), ContainingNamespace.IsGlobalNamespace: true },
@@ -1354,6 +1356,8 @@ internal static bool IsReadOnlySpan(this TypeSymbol type)
             return type is NamedTypeSymbol
             {
                 Name: "ReadOnlySpan",
+                IsValueType: true,
+                IsRefLikeType: true,
                 Arity: 1,
                 ContainingType: null,
                 ContainingNamespace: { Name: nameof(System), ContainingNamespace.IsGlobalNamespace: true },

diff --git a/src/Compilers/CSharp/Test/Emit3/FirstClassSpanTests.cs b/src/Compilers/CSharp/Test/Emit3/FirstClassSpanTests.cs
@@ -331,6 +331,28 @@ public readonly ref struct Span<T>
             Diagnostic(ErrorCode.ERR_MissingPredefinedMember, "arr()").WithArguments("System.Span<T>", "op_Implicit").WithLocation(2, 15));
     }
 
+    [Theory, CombinatorialData]
+    public void Conversion_Array_Span_Implicit_SpanNotRefStruct(
+        [CombinatorialValues("class", "struct", "readonly struct", "record", "record struct", "readonly record struct")] string kind,
+        [CombinatorialValues("Span", "ReadOnlySpan")] string type)
+    {
+        var source = $$"""
+            using System;
+            {{type}}<int> s =
+                arr();
+            static int[] arr() => new int[] { 1, 2, 3 };
+
+            namespace System
+            {
+                public {{kind}} {{type}}<T>;
+            }
+            """;
+        CreateCompilation(source).VerifyDiagnostics(
+            // (3,5): error CS0029: Cannot implicitly convert type 'int[]' to 'System.Span<int>'
+            //     arr();
+            Diagnostic(ErrorCode.ERR_NoImplicitConv, "arr()").WithArguments("int[]", $"System.{type}<int>").WithLocation(3, 5));
+    }
+
     [Theory, CombinatorialData]
     public void Conversion_Array_Span_Implicit_DifferentOperator(
         [CombinatorialValues("int[]", "T[][]")] string parameterType)