From 7cce7803bbbaccf7b4b6b64e02635505e42f1ce0 Mon Sep 17 00:00:00 2001
From: Julien Couvreur <julien.couvreur@gmail.com>
Date: Wed, 22 Apr 2020 17:06:41 -0700
Subject: [PATCH] Address remaining feedback

---
 .../Portable/Binder/Binder.ValueChecks.cs     |  3 +-
 .../Symbols/Wrapped/WrappedMethodSymbol.cs    |  2 +-
 .../Semantic/Semantics/InitOnlyMemberTests.cs | 63 ++++++++++++++++++-
 .../MetadataReader/MetadataDecoder.cs         |  1 +
 .../Symbols/Metadata/PE/SymbolFactory.vb      |  2 +-
 5 files changed, 66 insertions(+), 5 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs b/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
index 26043c81a6ca1..94a08e8f123c3 100644
--- a/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
+++ b/src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs
@@ -756,8 +756,7 @@ bool isAssignedFromInitOnlySetterOnThis(BoundExpression receiver)
                     return false;
                 }
 
-                var containingMember = ContainingMemberOrLambda;
-                if (!(containingMember is MethodSymbol method))
+                if (!(ContainingMemberOrLambda is MethodSymbol method))
                 {
                     return false;
                 }
diff --git a/src/Compilers/CSharp/Portable/Symbols/Wrapped/WrappedMethodSymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Wrapped/WrappedMethodSymbol.cs
index 64b723146f2ff..abdeb67724e00 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Wrapped/WrappedMethodSymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Wrapped/WrappedMethodSymbol.cs
@@ -349,6 +349,6 @@ internal override bool GenerateDebugInfo
 
         internal override bool IsDeclaredReadOnly => UnderlyingMethod.IsDeclaredReadOnly;
 
-        internal sealed override bool IsInitOnly => UnderlyingMethod.IsInitOnly;
+        internal override bool IsInitOnly => UnderlyingMethod.IsInitOnly;
     }
 }
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/InitOnlyMemberTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/InitOnlyMemberTests.cs
index 0edbf1e93051d..4fee9d4b29047 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/InitOnlyMemberTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/InitOnlyMemberTests.cs
@@ -2128,7 +2128,7 @@ int P2
         }
 
         [Fact]
-        public void ModReqOnAccessorParameter()
+        public void ModReqOnSetAccessorParameter()
         {
             string il = @"
 .class public auto ansi beforefieldinit C extends System.Object
@@ -2184,6 +2184,67 @@ public class Derived2 : C
                 );
         }
 
+        [Fact]
+        public void ModReqOnGetAccessorReturnValue()
+        {
+            string il = @"
+.class public auto ansi beforefieldinit C extends System.Object
+{
+    .method public hidebysig specialname newslot virtual instance int32 modreq(System.Runtime.CompilerServices.IsExternalInit) get_Property () cil managed
+    {
+        IL_0000: ldnull
+        IL_0001: throw
+    }
+
+    .method public hidebysig specialname newslot virtual instance void set_Property ( int32 'value' ) cil managed
+    {
+        IL_0000: ldnull
+        IL_0001: throw
+    }
+
+    .method public hidebysig specialname rtspecialname instance void .ctor () cil managed
+    {
+        IL_0000: ldnull
+        IL_0001: throw
+    }
+
+    .property instance int32 Property()
+    {
+        .get instance int32 modreq(System.Runtime.CompilerServices.IsExternalInit) C::get_Property()
+        .set instance void C::set_Property(int32)
+    }
+}
+
+.class public auto ansi sealed beforefieldinit System.Runtime.CompilerServices.IsExternalInit extends System.Object
+{
+    .method public hidebysig specialname rtspecialname instance void .ctor () cil managed
+    {
+        IL_0000: ldnull
+        IL_0001: throw
+    }
+}
+";
+
+            string source = @"
+public class Derived : C
+{
+    public override int Property { get { throw null; } }
+}
+public class Derived2 : C
+{
+    public override int Property { get { throw null; } }
+}
+";
+
+            var reference = CreateMetadataReferenceFromIlSource(il);
+            var comp = CreateCompilation(source, references: new[] { reference }, parseOptions: TestOptions.RegularPreview);
+            comp.VerifyDiagnostics();
+
+            var property = (PEPropertySymbol)comp.GlobalNamespace.GetMember("C.Property");
+            Assert.False(property.GetMethod.IsInitOnly);
+            Assert.False(property.SetMethod.IsInitOnly);
+        }
+
         [Fact]
         public void TestSyntaxFacts()
         {
diff --git a/src/Compilers/Core/Portable/MetadataReader/MetadataDecoder.cs b/src/Compilers/Core/Portable/MetadataReader/MetadataDecoder.cs
index f78e71e2d29d2..968bb29819016 100644
--- a/src/Compilers/Core/Portable/MetadataReader/MetadataDecoder.cs
+++ b/src/Compilers/Core/Portable/MetadataReader/MetadataDecoder.cs
@@ -1187,6 +1187,7 @@ private void DecodeParameterOrThrow(ref BlobReader signatureReader, /*out*/ ref
             var allowedRequiredModifiers = AllowedRequiredModifierType.System_Runtime_InteropServices_InAttribute;
             if (isReturn)
             {
+                // PROTOTYPE(init-only): can we make this more restrictive (ie. disallow aside from the return value of a setter)?
                 allowedRequiredModifiers |= AllowedRequiredModifierType.System_Runtime_CompilerServices_IsExternalInit;
             }
 
diff --git a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/SymbolFactory.vb b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/SymbolFactory.vb
index d154ca3221462..45d526b738f48 100644
--- a/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/SymbolFactory.vb
+++ b/src/Compilers/VisualBasic/Portable/Symbols/Metadata/PE/SymbolFactory.vb
@@ -62,7 +62,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols.Metadata.PE
         End Function
 
         Friend Overrides Function IsAcceptedIsExternalInitModifierType(type As TypeSymbol) As Boolean
-            ' VB doesn't deal with init-only members.
+            ' PROTOTYPE(init-only): VB doesn't deal with init-only members yet.
             Return False
         End Function