From c3daaae95b15b25084083dddc3ec16850386a40f Mon Sep 17 00:00:00 2001
From: Rikki Gibson <rigibson@microsoft.com>
Date: Tue, 26 Feb 2019 13:23:48 -0800
Subject: [PATCH] Allow readonly modifier on property decls in general. Add
 more tests.

---
 .../Symbols/Source/SourcePropertySymbol.cs    | 10 ---
 .../Semantics/ReadOnlyStructsTests.cs         | 62 ++++++++++++++++---
 2 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbol.cs b/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbol.cs
index f2169f1457c99..033e0bfda6d28 100644
--- a/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbol.cs
+++ b/src/Compilers/CSharp/Portable/Symbols/Source/SourcePropertySymbol.cs
@@ -115,11 +115,6 @@ private SourcePropertySymbol(
                 : ((IndexerDeclarationSyntax)syntax).ExpressionBody;
             bool hasExpressionBody = arrowExpression != null;
 
-            if (!hasExpressionBody && HasReadOnlyModifier)
-            {
-                diagnostics.Add(ErrorCode.ERR_BadMemberFlag, location, SyntaxFacts.GetText(SyntaxKind.ReadOnlyKeyword));
-            }
-
             bool hasInitializer = !isIndexer && propertySyntax.Initializer != null;
 
             bool notRegularProperty = (!IsAbstract && !IsExtern && !isIndexer && hasAccessorList);
@@ -633,11 +628,6 @@ internal bool IsNew
             get { return (_modifiers & DeclarationModifiers.New) != 0; }
         }
 
-        private bool HasReadOnlyModifier
-        {
-            get { return (_modifiers & DeclarationModifiers.ReadOnly) != 0; }
-        }
-
         public override MethodSymbol GetMethod
         {
             get { return _getMethod; }
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/ReadOnlyStructsTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/ReadOnlyStructsTests.cs
index df424c947c140..d5d6bc0b60dbb 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/ReadOnlyStructsTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/ReadOnlyStructsTests.cs
@@ -420,10 +420,7 @@ public struct S
 }
 ";
             var comp = CreateCompilation(csharp);
-            comp.VerifyDiagnostics(
-                // (5,25): error CS0106: The modifier 'readonly' is not valid for this item
-                //     public readonly int P { get { return i; } }
-                Diagnostic(ErrorCode.ERR_BadMemberFlag, "P").WithArguments("readonly").WithLocation(5, 25));
+            comp.VerifyDiagnostics();
         }
 
         [Fact]
@@ -433,8 +430,10 @@ public void ReadOnlyAutoProperty()
 public struct S
 {
     public int P1 { readonly get; }
-    public int P2 { readonly get; set; }
-    public int P3 { readonly get; readonly set; } // PROTOTYPE: readonly set on an auto-property should give an error
+    public readonly int P2 { get; }
+    public int P3 { readonly get; set; }
+    public int P4 { readonly get; readonly set; } // PROTOTYPE: readonly set on an auto-property should give an error
+    public readonly int P5 { get; set; } // PROTOTYPE: readonly set on an auto-property should give an error
 }
 ";
             var comp = CreateCompilation(csharp);
@@ -453,7 +452,7 @@ public struct S
     public readonly ref int M1() => ref f1;
 
     private static readonly int f2;
-    public readonly ref readonly int M2() => ref f1;
+    public readonly ref readonly int M2() => ref f2;
 
     private static readonly int f3;
     public ref readonly int M3()
@@ -466,5 +465,54 @@ public ref readonly int M3()
             var comp = CreateCompilation(csharp);
             comp.VerifyDiagnostics();
         }
+
+        [Fact]
+        public void ReadOnlyConstructor()
+        {
+            var csharp = @"
+public struct S
+{
+    public readonly S(int i) { }
+}
+";
+            var comp = CreateCompilation(csharp);
+            comp.VerifyDiagnostics(
+                // (4,21): error CS0106: The modifier 'readonly' is not valid for this item
+                //     public readonly S(int i) { }
+                Diagnostic(ErrorCode.ERR_BadMemberFlag, "S").WithArguments("readonly").WithLocation(4, 21));
+        }
+
+        [Fact]
+        public void ReadOnlyOperator()
+        {
+            var csharp = @"
+public struct S
+{
+    public static readonly S operator +(S lhs, S rhs) => lhs;
+    public static readonly explicit operator int(S s) => 42;
+}
+";
+            var comp = CreateCompilation(csharp);
+            comp.VerifyDiagnostics(
+                // (4,39): error CS0106: The modifier 'readonly' is not valid for this item
+                //     public static readonly S operator +(S lhs, S rhs) => lhs;
+                Diagnostic(ErrorCode.ERR_BadMemberFlag, "+").WithArguments("readonly").WithLocation(4, 39),
+                // (5,46): error CS0106: The modifier 'readonly' is not valid for this item
+                //     public static readonly explicit operator int(S s) => 42;
+                Diagnostic(ErrorCode.ERR_BadMemberFlag, "int").WithArguments("readonly").WithLocation(5, 46));
+        }
+
+        [Fact]
+        public void ReadOnlyDelegate()
+        {
+            var csharp = @"
+public readonly delegate int Del();
+";
+            var comp = CreateCompilation(csharp);
+            comp.VerifyDiagnostics(
+                // (2,30): error CS0106: The modifier 'readonly' is not valid for this item
+                // public readonly delegate int Del();
+                Diagnostic(ErrorCode.ERR_BadMemberFlag, "Del").WithArguments("readonly").WithLocation(2, 30));
+        }
     }
 }