Allow expression variables in lambdas within constructor and field initializers.

Fixes #16935.

src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs

@@ -2200,7 +2200,7 @@ private BoundExpression BindOutVariableArgument(DeclarationExpressionSyntax decl
             SourceLocalSymbol localSymbol = this.LookupLocal(designation.Identifier);
             if ((object)localSymbol != null)
             {
-                if (InConstructorInitializer || InFieldInitializer)
+                if ((InConstructorInitializer || InFieldInitializer) && ContainingMemberOrLambda.ContainingSymbol.Kind == SymbolKind.NamedType)
                 {
                     Error(diagnostics, ErrorCode.ERR_ExpressionVariableInConstructorOrFieldInitializer, declarationExpression);
                 }

src/Compilers/CSharp/Portable/Binder/Binder_Patterns.cs

@@ -292,7 +292,7 @@ internal BoundExpression ConvertPatternExpression(TypeSymbol inputType, CSharpSy
 
             if (localSymbol != (object)null)
             {
-                if (InConstructorInitializer || InFieldInitializer)
+                if ((InConstructorInitializer || InFieldInitializer) && ContainingMemberOrLambda.ContainingSymbol.Kind == SymbolKind.NamedType)
                 {
                     Error(diagnostics, ErrorCode.ERR_ExpressionVariableInConstructorOrFieldInitializer, node);
                 }

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

@@ -5273,6 +5273,39 @@ static bool TakeOutParam(int y, out int x)
 #endif
         }
 
+        [Fact]
+        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
+        public void FieldInitializers_04()
+        {
+            var source =
+@"
+public class X
+{
+    public static void Main()
+    {
+        System.Console.WriteLine(Test1());
+    }
+
+    static System.Func<bool> Test1 = () => TakeOutParam(1, out int x1) && Dummy(x1); 
+
+    static bool Dummy(int x) 
+    {
+        System.Console.WriteLine(x);
+        return true;
+    }
+
+    static bool TakeOutParam(int y, out int x) 
+    {
+        x = y;
+        return true;
+    }
+}
+";
+            var compilation = CreateCompilationWithMscorlib45(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
+            CompileAndVerify(compilation, expectedOutput: @"1
+True");
+        }
+
         [Fact]
         public void Scope_Fixed_01()
         {
@@ -10688,6 +10721,39 @@ static bool TakeOutParam(int y, out int x)
 #endif
         }
 
+        [Fact]
+        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
+        public void PropertyInitializers_02()
+        {
+            var source =
+@"
+public class X
+{
+    public static void Main()
+    {
+        System.Console.WriteLine(Test1());
+    }
+
+    static System.Func<bool> Test1 {get;} = () => TakeOutParam(1, out int x1) && Dummy(x1); 
+
+    static bool Dummy(int x) 
+    {
+        System.Console.WriteLine(x);
+        return true;
+    }
+
+    static bool TakeOutParam(int y, out int x) 
+    {
+        x = y;
+        return true;
+    }
+}
+";
+            var compilation = CreateCompilationWithMscorlib45(source, options: TestOptions.DebugExe, parseOptions: TestOptions.Regular);
+            CompileAndVerify(compilation, expectedOutput: @"1
+True");
+        }
+
         [Fact]
         public void Scope_Query_01()
         {
@@ -17720,6 +17786,56 @@ class Test3 : Test2
             VerifyModelForOutVar(model, x1Decl);
         }
 
+        [Fact]
+        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
+        public void ConstructorInitializers_05()
+        {
+            var text = @"
+public class Cls
+{
+    public static void Main()
+    {
+        Do(new Test2());
+    }
+
+    static void Do(object x){}
+
+    public static object Test1(out int x)
+    {
+        x = 123;
+        return null;
+    }
+
+    class Test2
+    {
+        Test2(System.Func<object> x)
+        {
+            System.Console.WriteLine(x());
+        }
+
+        public Test2()
+        : this(() =>
+               {
+                    Test1(out var x1);
+                    return x1;
+               })
+        {}
+    }
+}";
+            var compilation = CreateCompilationWithMscorlib(text,
+                                                            options: TestOptions.ReleaseExe,
+                                                            parseOptions: TestOptions.Regular);
+
+            CompileAndVerify(compilation, expectedOutput: @"123").VerifyDiagnostics();
+
+            var tree = compilation.SyntaxTrees.Single();
+            var model = compilation.GetSemanticModel(tree);
+
+            var x1Decl = GetOutVarDeclaration(tree, "x1");
+            var x1Ref = GetReference(tree, "x1");
+            VerifyModelForOutVar(model, x1Decl, x1Ref);
+        }
+
         [Fact]
         public void SimpleVar_14()
         {
@@ -22658,7 +22774,7 @@ static bool TakeOutParam(bool y, out bool x)
             }
         }
 
-        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/16935")]
+        [Fact]
         [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
         public void GlobalCode_Lambda_02()
         {

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

@@ -1088,6 +1088,33 @@ static bool Dummy(System.Func<int> x)
 #endif
         }
 
+        [Fact]
+        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
+        public void FieldInitializers_04()
+        {
+            var source =
+@"
+public class X
+{
+    public static void Main()
+    {
+        System.Console.WriteLine(Test1());
+    }
+
+    static System.Func<bool> Test1 = () => 1 is int x1 && Dummy(x1); 
+
+    static bool Dummy(int x) 
+    {
+        System.Console.WriteLine(x);
+        return true;
+    }
+}
+";
+            var compilation = CreateCompilationWithMscorlib45(source, options: TestOptions.DebugExe);
+            CompileAndVerify(compilation, expectedOutput: @"1
+True");
+        }
+
         [Fact]
         public void PropertyInitializers_01()
         {
@@ -1121,6 +1148,34 @@ static bool Dummy(int x)
                 );
 #endif
         }
+
+        [Fact]
+        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
+        public void PropertyInitializers_02()
+        {
+            var source =
+@"
+public class X
+{
+    public static void Main()
+    {
+        System.Console.WriteLine(Test1());
+    }
+
+    static System.Func<bool> Test1 {get;} = () => 1 is int x1 && Dummy(x1); 
+
+    static bool Dummy(int x) 
+    {
+        System.Console.WriteLine(x);
+        return true;
+    }
+}
+";
+            var compilation = CreateCompilationWithMscorlib45(source, options: TestOptions.DebugExe);
+            CompileAndVerify(compilation, expectedOutput: @"1
+True");
+        }
+
         [Fact]
         public void ConstructorInitializers_01()
         {
@@ -1179,6 +1234,54 @@ public C(object b)
 #endif
         }
 
+        [Fact]
+        [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
+        public void ConstructorInitializers_02()
+        {
+            var source =
+@"
+public class X
+{
+    public static void Main()
+    {
+        var x = new D();
+    }
+}
+
+class D : C
+{
+    public D(System.Func<bool> o) : base(() => 2 is int x1 && Dummy(x1)) 
+    {
+        System.Console.WriteLine(o());
+    }
+
+    public D() : this(() => 1 is int x1 && Dummy(x1)) 
+    {
+    }
+
+    static bool Dummy(int x) 
+    {
+        System.Console.WriteLine(x);
+        return true;
+    }
+}
+
+class C
+{
+    public C(System.Func<bool> b) 
+    { 
+        System.Console.WriteLine(b());
+    }
+}
+";
+            var compilation = CreateCompilationWithMscorlib45(source, options: TestOptions.DebugExe);
+            CompileAndVerify(compilation, expectedOutput:
+@"2
+True
+1
+True");
+        }
+
         [Fact]
         public void Switch_01()
         {

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

@@ -7196,7 +7196,7 @@ public void GlobalCode_Lambda_01()
             }
         }
 
-        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/16935")]
+        [Fact]
         [WorkItem(16935, "https://github.com/dotnet/roslyn/issues/16935")]
         public void GlobalCode_Lambda_02()
         {