Merge pull request #20058 from VSadov/spanDetect2

Fix detection of Span types 

src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.cs

@@ -2061,7 +2061,10 @@ internal override bool IsByRefLikeType
 
                     if (this.TypeKind == TypeKind.Struct)
                     {
-                        if (IsWellknownSpans())
+                        //PROTOTYPE(span): Span and ReadOnlySpan should have ByRefLike attribute, eventually.
+                        //                 For now assume that any "System.Span" and "System.ReadOnlySpan" structs 
+                        //                 are ByRefLike
+                        if (this.IsSpanType())
                         {
                             isByRefLike = ThreeState.True;
                         }
@@ -2108,27 +2111,6 @@ internal override bool IsReadOnly
             }
         }
 
-        //PROTOTYPE(span): Span and ReadonlySpan should have spanLike marker.
-        //                 For now assume that any "System.Span" and "System.ReadOnlySpan" structs 
-        //                 are span-like
-        private bool IsWellknownSpans()
-        {
-            var originalDef = this.OriginalDefinition;
-
-            if (originalDef.Name != "Span" && originalDef.Name != "ReadonlySpan")
-            {
-                return false;
-            }
-
-            var ns = originalDef.ContainingSymbol as NamespaceSymbol;
-            if (ns?.Name != "System")
-            {
-                return false;
-            }
-
-            return ns.IsGlobalNamespace;
-        }
-
         internal override bool HasDeclarativeSecurity
         {
             get { return (_flags & TypeAttributes.HasSecurity) != 0; }

src/Compilers/CSharp/Portable/Symbols/TypeSymbolExtensions.cs

@@ -1278,6 +1278,31 @@ private static bool HasNamespaceName(NamespaceSymbol @namespace, string namespac
             return (name.Length == length) && (string.Compare(name, 0, namespaceName, offset, length, comparison) == 0);
         }
 
+        internal static bool IsSpanType(this TypeSymbol type)
+        {
+            if ((type as NamedTypeSymbol)?.Arity != 1)
+            {
+                // must be a generic type of arity '1'
+                return false;
+            }
+
+            if (type.Name != "Span" && type.Name != "ReadOnlySpan")
+            {
+                // must be called "Span" or "ReadOnlySpan"
+                return false;
+            }
+
+            var ns = type.ContainingSymbol as NamespaceSymbol;
+            if (ns?.Name != "System")
+            {
+                // must be in "System" namespace
+                return false;
+            }
+
+            // the "System" must be in the global namespace
+            return ns.ContainingNamespace.IsGlobalNamespace;
+        }
+
         internal static bool IsNonGenericTaskType(this TypeSymbol type, CSharpCompilation compilation)
         {
             var namedType = type as NamedTypeSymbol;

src/Compilers/CSharp/Test/Semantic/Semantics/SpanStackSafetyTests.cs

@@ -28,7 +28,7 @@ namespace System
         public override int GetHashCode() => 1;
     }
 
-    public ref struct ReadonlySpan<T>
+    public ref struct ReadOnlySpan<T>
     {
         public ref readonly T this[int i] => throw null;
         public override int GetHashCode() => 2;
@@ -40,6 +40,7 @@ namespace System
     }
 }
 ";
+
         //PROTOTYPE(span): this will be updated when rules for defining span are implemented
         //                 most likely we would just pick the actual binary/corlib where
         //                 span lives.
@@ -83,7 +84,7 @@ class Program
     static void Main()
     {
         object x = new Span<int>();
-        object y = new ReadonlySpan<byte>();
+        object y = new ReadOnlySpan<byte>();
         object z = new SpanLike<int>();
     }
 }
@@ -95,9 +96,9 @@ static void Main()
                 // (8,20): error CS0029: Cannot implicitly convert type 'System.Span<int>' to 'object'
                 //         object x = new Span<int>();
                 Diagnostic(ErrorCode.ERR_NoImplicitConv, "new Span<int>()").WithArguments("System.Span<int>", "object").WithLocation(8, 20),
-                // (9,20): error CS0029: Cannot implicitly convert type 'System.ReadonlySpan<byte>' to 'object'
-                //         object y = new ReadonlySpan<byte>();
-                Diagnostic(ErrorCode.ERR_NoImplicitConv, "new ReadonlySpan<byte>()").WithArguments("System.ReadonlySpan<byte>", "object").WithLocation(9, 20),
+                // (9,20): error CS0029: Cannot implicitly convert type 'System.ReadOnlySpan<byte>' to 'object'
+                //         object y = new ReadOnlySpan<byte>();
+                Diagnostic(ErrorCode.ERR_NoImplicitConv, "new ReadOnlySpan<byte>()").WithArguments("System.ReadOnlySpan<byte>", "object").WithLocation(9, 20),
                 // (10,20): error CS0029: Cannot implicitly convert type 'System.SpanLike<int>' to 'object'
                 //         object z = new SpanLike<int>();
                 Diagnostic(ErrorCode.ERR_NoImplicitConv, "new SpanLike<int>()").WithArguments("System.SpanLike<int>", "object")
@@ -109,9 +110,9 @@ static void Main()
                 // (8,20): error CS0029: Cannot implicitly convert type 'System.Span<int>' to 'object'
                 //         object x = new Span<int>();
                 Diagnostic(ErrorCode.ERR_NoImplicitConv, "new Span<int>()").WithArguments("System.Span<int>", "object").WithLocation(8, 20),
-                // (9,20): error CS0029: Cannot implicitly convert type 'System.ReadonlySpan<byte>' to 'object'
-                //         object y = new ReadonlySpan<byte>();
-                Diagnostic(ErrorCode.ERR_NoImplicitConv, "new ReadonlySpan<byte>()").WithArguments("System.ReadonlySpan<byte>", "object").WithLocation(9, 20),
+                // (9,20): error CS0029: Cannot implicitly convert type 'System.ReadOnlySpan<byte>' to 'object'
+                //         object y = new ReadOnlySpan<byte>();
+                Diagnostic(ErrorCode.ERR_NoImplicitConv, "new ReadOnlySpan<byte>()").WithArguments("System.ReadOnlySpan<byte>", "object").WithLocation(9, 20),
                 // (10,20): error CS0029: Cannot implicitly convert type 'System.SpanLike<int>' to 'object'
                 //         object z = new SpanLike<int>();
                 Diagnostic(ErrorCode.ERR_NoImplicitConv, "new SpanLike<int>()").WithArguments("System.SpanLike<int>", "object")
@@ -743,5 +744,101 @@ static void Main()
                 Diagnostic(ErrorCode.ERR_MethDelegateMismatch, "ToString").WithArguments("ToString", "System.Func<string>").WithLocation(16, 46)
             );
         }
+
+        //PROTOTYPE(span): Span and ReadOnlySpan should have ByRefLike attribute, eventually.
+        //                 For now assume that any "System.Span" and "System.ReadOnlySpan" structs 
+        //                 are ByRefLike
+        [Fact]
+        public void SpanDetect()
+        {
+
+            //span structs are not marked as "ref"
+            string spanSourceNoRefs = @"
+namespace System
+{
+    public struct Span<T> 
+    {
+        public ref T this[int i] => throw null;
+        public override int GetHashCode() => 1;
+    }
+
+    public struct ReadOnlySpan<T>
+    {
+        public ref readonly T this[int i] => throw null;
+        public override int GetHashCode() => 2;
+    }
+
+    public struct RegularStruct<T>
+    {
+    }
+
+    // arity 0 - not a span
+    public struct Span 
+    {
+    }
+
+    // arity 2 - not a span
+    public struct Span<T, U> 
+    {
+        public ref T this[int i] => throw null;
+        public override int GetHashCode() => 1;
+    }
+}
+
+// nested
+public struct S1
+{
+    public struct Span<T> 
+    {
+        public ref T this[int i] => throw null;
+        public override int GetHashCode() => 1;
+    }
+}
+
+public struct Span<T> 
+{
+    public ref T this[int i] => throw null;
+    public override int GetHashCode() => 1;
+}
+
+";
+            var reference = CreateCompilation(
+                spanSourceNoRefs,
+                references: new List<MetadataReference>() { MscorlibRef_v4_0_30316_17626, SystemCoreRef, CSharpRef },
+                options: TestOptions.ReleaseDll);
+
+            reference.VerifyDiagnostics();
+
+            var text = @"
+using System;
+
+class Program
+{
+    static void Main()
+    {
+        object x = new System.Span<int>();
+        object y = new ReadOnlySpan<byte>();
+
+        object z1 = new Span();
+        object z2 = new Span<int, int>();
+        object z3 = new S1.Span<int>();
+        object z4 = new Span<int>();
+    }
+}
+";
+            var comp = CreateCompilation(
+                text,
+                references: new List<MetadataReference>() { MscorlibRef_v4_0_30316_17626, SystemCoreRef, CSharpRef, reference.EmitToImageReference() },
+                options: TestOptions.ReleaseExe);
+
+            comp.VerifyDiagnostics(
+                // (8,20): error CS0029: Cannot implicitly convert type 'System.Span<int>' to 'object'
+                //         object x = new System.Span<int>();
+                Diagnostic(ErrorCode.ERR_NoImplicitConv, "new System.Span<int>()").WithArguments("System.Span<int>", "object").WithLocation(8, 20),
+                // (9,20): error CS0029: Cannot implicitly convert type 'System.ReadOnlySpan<byte>' to 'object'
+                //         object y = new ReadOnlySpan<byte>();
+                Diagnostic(ErrorCode.ERR_NoImplicitConv, "new ReadOnlySpan<byte>()").WithArguments("System.ReadOnlySpan<byte>", "object").WithLocation(9, 20)
+            );
+        }
     }
 }