From 3f256a7c9e3058c58d3b45d1abeb3fd85bb71434 Mon Sep 17 00:00:00 2001
From: Omar Tawfik <OmarTawfik@users.noreply.github.com>
Date: Tue, 6 Mar 2018 00:13:57 +0200
Subject: [PATCH] Support PointerElementAccess in value escape rules (#24909)

---
 .../Portable/Binder/Binder.ValueChecks.cs     | 15 +++++-
 .../Semantic/Semantics/RefEscapingTests.cs    | 51 +++++++++++++++++++
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs b/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
index e499285c84a..f71d73a8a76 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
@@ -2185,6 +2185,11 @@ internal static uint GetValEscape(BoundExpression expr, uint scopeOfTheContainin
                     // just say it does not escape anywhere, so that we do not get false errors.
                     return scopeOfTheContainingExpression;
 
+                case BoundKind.PointerElementAccess:
+                case BoundKind.PointerIndirectionOperator:
+                    // Unsafe code will always be allowed to escape.
+                    return Binder.ExternalScope;
+
                 default:
                     throw ExceptionUtilities.UnexpectedValue($"{expr.Kind} expression of {expr.Type} type");
             }
@@ -2492,13 +2497,19 @@ internal static bool CheckValEscape(SyntaxNode node, BoundExpression expr, uint
                     var colElement = (BoundCollectionElementInitializer)expr;
                     return CheckValEscape(colElement.Arguments, escapeFrom, escapeTo, diagnostics);
 
+                case BoundKind.PointerElementAccess:
+                    var accessedExpression = ((BoundPointerElementAccess)expr).Expression;
+                    return CheckValEscape(accessedExpression.Syntax, accessedExpression, escapeFrom, escapeTo, checkingReceiver, diagnostics);
+
+                case BoundKind.PointerIndirectionOperator:
+                    var operandExpression = ((BoundPointerIndirectionOperator)expr).Operand;
+                    return CheckValEscape(operandExpression.Syntax, operandExpression, escapeFrom, escapeTo, checkingReceiver, diagnostics);
+
                 default:
                     throw ExceptionUtilities.UnexpectedValue($"{expr.Kind} expression of {expr.Type} type");
 
                 #region "cannot produce ref-like values"
 //                case BoundKind.ThrowExpression:
-//                case BoundKind.PointerIndirectionOperator:
-//                case BoundKind.PointerElementAccess:
 //                case BoundKind.ArgListOperator:
 //                case BoundKind.ArgList:
 //                case BoundKind.RefTypeOperator:
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/RefEscapingTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/RefEscapingTests.cs
index 065d96e616b..55c95f2dc96 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/RefEscapingTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/RefEscapingTests.cs
@@ -3201,5 +3201,56 @@ public class C
 ";
             CreateCompilationWithMscorlibAndSpan(text).VerifyDiagnostics();
         }
+
+        [Fact]
+        [WorkItem(24776, "https://github.com/dotnet/roslyn/issues/24776")]
+        public void PointerElementAccess_RefStructPointer()
+        {
+            CreateCompilation(@"
+public ref struct TestStruct
+{
+    public void M() { }
+}
+public class C
+{
+    public static unsafe void Test(TestStruct[] ar)
+    {
+        fixed (TestStruct* p = ar)
+        {
+            for (int i = 0; i < ar.Length; i++)
+            {
+                p[i].M();
+            }
+        }
+    }
+}", options: TestOptions.UnsafeReleaseDll).VerifyDiagnostics(
+                // (8,36): error CS0611: Array elements cannot be of type 'TestStruct'
+                //     public static unsafe void Test(TestStruct[] ar)
+                Diagnostic(ErrorCode.ERR_ArrayElementCantBeRefAny, "TestStruct").WithArguments("TestStruct").WithLocation(8, 36));
+        }
+
+        [Fact]
+        [WorkItem(24776, "https://github.com/dotnet/roslyn/issues/24776")]
+        public void PointerIndirectionOperator_RefStructPointer()
+        {
+            CreateCompilation(@"
+public ref struct TestStruct
+{
+    public void M() { }
+}
+public class C
+{
+    public static unsafe void Test(TestStruct[] ar)
+    {
+        fixed (TestStruct* p = ar)
+        {
+            var x = *p;
+        }
+    }
+}", options: TestOptions.UnsafeReleaseDll).VerifyDiagnostics(
+                // (8,36): error CS0611: Array elements cannot be of type 'TestStruct'
+                //     public static unsafe void Test(TestStruct[] ar)
+                Diagnostic(ErrorCode.ERR_ArrayElementCantBeRefAny, "TestStruct").WithArguments("TestStruct").WithLocation(8, 36));
+        }
     }
 }
-- 
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