Consider GetEnumerator when computing foreach variable escape

dotnet · Sep 27, 2022 · ae8e2c2 · ae8e2c2
1 parent 784a29c
commit ae8e2c2
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diff --git a/src/Compilers/CSharp/Portable/Binder/ForEachLoopBinder.cs b/src/Compilers/CSharp/Portable/Binder/ForEachLoopBinder.cs
@@ -255,7 +255,10 @@ private BoundForEachStatement BindForEachPartsWorker(BindingDiagnosticBag diagno
             bool hasNameConflicts = false;
             BoundForEachDeconstructStep deconstructStep = null;
             BoundExpression iterationErrorExpression = null;
-            uint collectionEscape = GetValEscape(collectionExpr, this.LocalScopeDepth);
+            uint collectionEscape = getEnumeratorMethod != null
+                // Get escape of `collection.GetEnumerator()` call if possible.
+                ? GetValEscape(BoundCall.Synthesized(_syntax, collectionExpr, getEnumeratorMethod), this.LocalScopeDepth)
+                : GetValEscape(collectionExpr, this.LocalScopeDepth);
             switch (_syntax.Kind())
             {
                 case SyntaxKind.ForEachStatement:

diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/RefFieldTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/RefFieldTests.cs
@@ -11532,6 +11532,57 @@ ref struct Enumerator1
                 );
         }
 
+        [Fact]
+        [WorkItem(64218, "https://github.com/dotnet/roslyn/issues/64218")]
+        public void LocalScope_12_Foreach_04()
+        {
+            var source =
+@"class Program
+{
+    static void Main()
+    {
+        int i0 = 0;
+        S s0 = new S(ref i0);
+        {
+            int i1 = 1;
+            foreach (S s1 in Enumerable1.Create(ref i1)) {
+                s0 = s1;
+                break;
+            }
+        }
+        {
+            int i2 = 1;
+            foreach (S s2 in Enumerable2.Create(ref i2)) {
+                s0 = s2;
+                break;
+            }
+        }
+    }
+}
+ref struct S
+{
+    public S(ref int i) { }
+}
+ref struct Enumerable1
+{
+    public static Enumerable1 Create(ref int p) => default;
+    public Enumerator1 GetEnumerator() => default;
+}
+class Enumerable2
+{
+    public static Enumerable2 Create(ref int p) => default;
+    public Enumerator1 GetEnumerator() => default;
+}
+class Enumerator1
+{
+    public S Current => throw null;
+    public bool MoveNext() => false;
+}
+";
+            var comp = CreateCompilation(source);
+            comp.VerifyDiagnostics();
+        }
+
         [Fact]
         public void ScopedRefAndRefStructOnly_06_Foreach()
         {