[mcs] Initial by ref returns and variables support

40 files changed, 539 insertions, 1 deletions

diff --git a/mcs/errors/cs0131-6.cs b/mcs/errors/cs0131-6.cs
new file mode 100644
index 00000000000..8af3e939fbf
--- /dev/null
+++ b/mcs/errors/cs0131-6.cs
@@ -0,0 +1,15 @@
+// CS0131: The left-hand side of an assignment must be a variable, a property or an indexer
+// Line: 8
+
+class X
+{
+	void Test ()
+	{
+		Foo () = 1;
+	}
+
+	static int Foo ()
+	{
+		return 1;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs0199-2.cs b/mcs/errors/cs0199-2.cs
new file mode 100644
index 00000000000..efad7c89367
--- /dev/null
+++ b/mcs/errors/cs0199-2.cs
@@ -0,0 +1,12 @@
+// CS0199: A static readonly field `X.f' cannot be passed ref or out (except in a static constructor)
+// Line: 10
+
+class X
+{
+	static readonly int f = 0;
+
+	public static void Main ()
+	{
+		ref int j = ref f;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs0206-5.cs b/mcs/errors/cs0206-5.cs
new file mode 100644
index 00000000000..bd9691ffbc5
--- /dev/null
+++ b/mcs/errors/cs0206-5.cs
@@ -0,0 +1,12 @@
+// CS0206: A property, indexer or dynamic member access may not be passed as `ref' or `out' parameter
+// Line: 10
+
+class X
+{
+	static int P { get; set; }
+
+	static void Main ()
+	{
+		ref int rl = ref P;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs1503-17.cs b/mcs/errors/cs1503-17.cs
new file mode 100644
index 00000000000..23921edc939
--- /dev/null
+++ b/mcs/errors/cs1503-17.cs
@@ -0,0 +1,31 @@
+// CS1503: Argument `#1' cannot convert `ref long' expression to type `ref int'
+// Line: 18
+
+using System;
+
+class X
+{
+	long field;
+
+	static void Main ()
+	{
+		var x = new X ();
+		x.Run ();
+	}
+
+	void Run ()
+	{
+		Test (ref Prop);
+	}
+
+	static int Test (ref int y)
+	{
+		return y;
+	}
+
+	ref long Prop {
+		get {
+			return ref field;
+		}
+	}
+}
diff --git a/mcs/errors/cs1547-13.cs b/mcs/errors/cs1547-13.cs
new file mode 100644
index 00000000000..1b3f8e1c14b
--- /dev/null
+++ b/mcs/errors/cs1547-13.cs
@@ -0,0 +1,7 @@
+// CS1547: Keyword `void' cannot be used in this context
+// Line: 6
+
+interface IA
+{
+	ref void Foo ();
+}
diff --git a/mcs/errors/cs1644-55.cs b/mcs/errors/cs1644-55.cs
new file mode 100644
index 00000000000..58384a6f289
--- /dev/null
+++ b/mcs/errors/cs1644-55.cs
@@ -0,0 +1,11 @@
+// CS1644: Feature `byref locals and returns' cannot be used because it is not part of the C# 6.0 language specification
+// Line: 9
+// Compiler options: -langversion:6
+
+class Text
+{
+	static ref long Foo ()
+	{
+		throw new System.NotImplementedException ();
+	}
+}
diff --git a/mcs/errors/cs1715-3.cs b/mcs/errors/cs1715-3.cs
new file mode 100644
index 00000000000..d3cd5dab0f7
--- /dev/null
+++ b/mcs/errors/cs1715-3.cs
@@ -0,0 +1,16 @@
+// CS1715: `B.Foo': type must be `int' to match overridden member `A.Foo'
+// Line: 11
+
+public abstract class A
+{
+	public abstract ref int Foo { get; }
+}
+
+public class B : A
+{
+	public override ref long Foo {
+		get {
+			throw null;
+		}
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs1764.cs b/mcs/errors/cs1764.cs
index f8a89b25659..a1dd2e36d15 100644
--- a/mcs/errors/cs1764.cs
+++ b/mcs/errors/cs1764.cs
@@ -1,4 +1,4 @@
-// CS1764: Cannot use fixed local `p' inside an anonymous method, lambda expression or query expression
+// CS1764: Cannot use fixed variable `p' inside an anonymous method, lambda expression or query expression
 // Line: 10
 // Compiler options: -unsafe
 
diff --git a/mcs/errors/cs8145.cs b/mcs/errors/cs8145.cs
new file mode 100644
index 00000000000..cf3c5084722
--- /dev/null
+++ b/mcs/errors/cs8145.cs
@@ -0,0 +1,7 @@
+// CS8145: Auto-implemented properties cannot return by reference
+// Line: 6
+
+public class X
+{
+	ref string TestProp { get; }
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8146.cs b/mcs/errors/cs8146.cs
new file mode 100644
index 00000000000..758804c1df6
--- /dev/null
+++ b/mcs/errors/cs8146.cs
@@ -0,0 +1,7 @@
+// CS8146: `X.TestProp': property and indexer which return by reference must have a get accessor
+// Line: 6
+
+public class X
+{
+	ref string TestProp { set; }
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8147-2.cs b/mcs/errors/cs8147-2.cs
new file mode 100644
index 00000000000..a4375d2d1a5
--- /dev/null
+++ b/mcs/errors/cs8147-2.cs
@@ -0,0 +1,14 @@
+// CS8147: `X.this[int]': property and indexer which return by reference cannot have set accessors
+// Line: 6
+
+public class X
+{
+	ref string this [int arg] { 
+		set {
+
+		}
+		get {
+
+		}
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8147.cs b/mcs/errors/cs8147.cs
new file mode 100644
index 00000000000..a006a4d9727
--- /dev/null
+++ b/mcs/errors/cs8147.cs
@@ -0,0 +1,14 @@
+// CS8147: `X.TestProp': property and indexer which return by reference cannot have set accessors
+// Line: 6
+
+public class X
+{
+	ref string TestProp { 
+		set {
+
+		}
+		get {
+
+		}
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8148-2.cs b/mcs/errors/cs8148-2.cs
new file mode 100644
index 00000000000..1961026d0d2
--- /dev/null
+++ b/mcs/errors/cs8148-2.cs
@@ -0,0 +1,16 @@
+// CS8148: `B.Foo': must return by reference to match overridden member `A.Foo'
+// Line: 11
+
+public abstract class A
+{
+	public abstract ref int Foo { get; }
+}
+
+public class B : A
+{
+	public override long Foo {
+		get {
+			throw null;
+		}
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8148.cs b/mcs/errors/cs8148.cs
new file mode 100644
index 00000000000..1e9178945c0
--- /dev/null
+++ b/mcs/errors/cs8148.cs
@@ -0,0 +1,15 @@
+// CS8148: `B.Foo()': must not return by reference to match overridden member `A.Foo()'
+// Line: 11
+
+public abstract class A
+{
+	public abstract int Foo ();
+}
+
+public class B : A
+{
+	public override ref int Foo ()
+	{
+
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8149-2.cs b/mcs/errors/cs8149-2.cs
new file mode 100644
index 00000000000..3514769c702
--- /dev/null
+++ b/mcs/errors/cs8149-2.cs
@@ -0,0 +1,14 @@
+// CS8149: By-reference returns can only be used in lambda expressions that return by reference
+// Line: 12
+
+using System;
+
+class A
+{
+	int p;
+	
+	void Test ()
+	{
+		Action a = () => ref p;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8149.cs b/mcs/errors/cs8149.cs
new file mode 100644
index 00000000000..351dd54235b
--- /dev/null
+++ b/mcs/errors/cs8149.cs
@@ -0,0 +1,12 @@
+// CS8149: By-reference returns can only be used in methods that return by reference
+// Line: 10
+
+class A
+{
+	int p;
+
+	int Test ()
+	{
+		return ref p;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8150.cs b/mcs/errors/cs8150.cs
new file mode 100644
index 00000000000..fd4ef7a2db0
--- /dev/null
+++ b/mcs/errors/cs8150.cs
@@ -0,0 +1,12 @@
+// CS8150: By-reference return is required when method returns by reference
+// Line: 10
+
+class A
+{
+	int p;
+
+	ref int Test ()
+	{
+		return p;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8151.cs b/mcs/errors/cs8151.cs
new file mode 100644
index 00000000000..934faefff7c
--- /dev/null
+++ b/mcs/errors/cs8151.cs
@@ -0,0 +1,12 @@
+// CS8151: The return by reference expression must be of type `string' because this method returns by reference
+// Line: 10
+
+public class X
+{
+	int field;
+
+	ref string TestMethod ()
+	{
+		return ref field;
+	}
+}
diff --git a/mcs/errors/cs8152.cs b/mcs/errors/cs8152.cs
new file mode 100644
index 00000000000..45546ad9d9a
--- /dev/null
+++ b/mcs/errors/cs8152.cs
@@ -0,0 +1,14 @@
+// CS8152: `C' does not implement interface member `IA.Foo()' and the best implementing candidate `C.Foo()' return type `void' does not return by reference
+// Line: 11
+
+interface IA
+{
+	ref char Foo ();
+}
+
+public class C : IA
+{
+	public void Foo ()
+	{
+	}
+}
diff --git a/mcs/errors/cs8153.cs b/mcs/errors/cs8153.cs
new file mode 100644
index 00000000000..d36f110208f
--- /dev/null
+++ b/mcs/errors/cs8153.cs
@@ -0,0 +1,24 @@
+// CS8153: An expression tree lambda cannot contain a call to a method, property, or indexer that returns by reference
+// Line: 11
+
+using System;
+using System.Linq.Expressions;
+
+class X
+{
+	void Foo ()
+	{
+		Expression<Func<int>> e = () => Test (ref this[0]);
+	}
+
+	static int Test (ref int y)
+	{
+		return y;
+	}
+
+	ref int this [int y] {
+		get {
+			throw null;
+		}
+	}
+}
diff --git a/mcs/errors/cs8154.cs b/mcs/errors/cs8154.cs
new file mode 100644
index 00000000000..ed98513e65e
--- /dev/null
+++ b/mcs/errors/cs8154.cs
@@ -0,0 +1,12 @@
+// CS8154: The body of `TestClass.TestFunction()' cannot be an iterator block because the method returns by reference
+// Line: 10
+
+class TestClass
+{
+    int x;
+
+    ref int TestFunction()
+    {
+        yield return x;
+    }
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8155.cs b/mcs/errors/cs8155.cs
new file mode 100644
index 00000000000..45d8b4e414a
--- /dev/null
+++ b/mcs/errors/cs8155.cs
@@ -0,0 +1,16 @@
+// CS8155: Lambda expressions that return by reference cannot be converted to expression trees
+// Line: 14
+
+using System.Linq.Expressions;
+
+class TestClass
+{
+    static int x;
+
+    delegate ref int D ();
+
+    static void Main ()
+    {
+        Expression<D> e = () => ref x;
+    }
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8156-2.cs b/mcs/errors/cs8156-2.cs
new file mode 100644
index 00000000000..7507ec475c3
--- /dev/null
+++ b/mcs/errors/cs8156-2.cs
@@ -0,0 +1,16 @@
+// CS8156: An expression cannot be used in this context because it may not be returned by reference
+// Line: 8
+
+class X
+{
+	int Prop {
+		get {
+			return 1;
+		}
+	}
+
+	ref int Test ()
+	{
+		return ref Prop;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8156.cs b/mcs/errors/cs8156.cs
new file mode 100644
index 00000000000..fe3f6b7c987
--- /dev/null
+++ b/mcs/errors/cs8156.cs
@@ -0,0 +1,10 @@
+// CS8156: An expression cannot be used in this context because it may not be returned by reference
+// Line: 8
+
+class Test
+{
+	ref int Foo ()
+	{
+		return ref 2;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8157.cs b/mcs/errors/cs8157.cs
new file mode 100644
index 00000000000..35d700f19c4
--- /dev/null
+++ b/mcs/errors/cs8157.cs
@@ -0,0 +1,13 @@
+// CS8157: Cannot return `r' by reference because it was initialized to a value that cannot be returned by reference
+// Line: 11
+
+struct S
+{
+	int i;
+
+	ref int M ()
+	{
+		ref int r = ref i;
+		return ref r;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8160.cs b/mcs/errors/cs8160.cs
new file mode 100644
index 00000000000..2b4ea42c5ab
--- /dev/null
+++ b/mcs/errors/cs8160.cs
@@ -0,0 +1,12 @@
+// CS8160: A readonly field cannot be returned by reference
+// Line: 10
+
+class X
+{
+	readonly int f = 0;
+
+	ref int Test ()
+	{
+		return ref f;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8161.cs b/mcs/errors/cs8161.cs
new file mode 100644
index 00000000000..0d028a116ed
--- /dev/null
+++ b/mcs/errors/cs8161.cs
@@ -0,0 +1,12 @@
+// CS8161: A static readonly field cannot be returned by reference
+// Line: 10
+
+class X
+{
+	static readonly int f;
+
+	static ref int Test ()
+	{
+		return ref f;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8170-2.cs b/mcs/errors/cs8170-2.cs
new file mode 100644
index 00000000000..dbd76a4da36
--- /dev/null
+++ b/mcs/errors/cs8170-2.cs
@@ -0,0 +1,12 @@
+// CS8170:
+// Line: 10
+
+public struct S
+{
+	int f;
+
+	public ref S Foo ()
+	{
+		return ref f;
+	}
+}
diff --git a/mcs/errors/cs8170.cs b/mcs/errors/cs8170.cs
new file mode 100644
index 00000000000..142e1a1943f
--- /dev/null
+++ b/mcs/errors/cs8170.cs
@@ -0,0 +1,10 @@
+// CS8170:
+// Line: 8
+
+public struct S
+{
+	public ref S Foo ()
+	{
+		return ref this;
+	}
+}
diff --git a/mcs/errors/cs8171.cs b/mcs/errors/cs8171.cs
new file mode 100644
index 00000000000..36eae2c65a4
--- /dev/null
+++ b/mcs/errors/cs8171.cs
@@ -0,0 +1,12 @@
+// CS8171: Cannot initialize a by-value variable `l' with a reference expression
+// Line: 10
+
+class Test
+{
+	int field;
+
+	void Foo ()
+	{
+		int l = ref field;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8172.cs b/mcs/errors/cs8172.cs
new file mode 100644
index 00000000000..7ddd3833e8c
--- /dev/null
+++ b/mcs/errors/cs8172.cs
@@ -0,0 +1,12 @@
+// CS8172: Cannot initialize a by-reference variable `j' with a value
+// Line: 10
+
+class X
+{
+	static int f;
+
+	public static void Main ()
+	{
+		ref int j = f;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8173.cs b/mcs/errors/cs8173.cs
new file mode 100644
index 00000000000..7c7d894ad6e
--- /dev/null
+++ b/mcs/errors/cs8173.cs
@@ -0,0 +1,13 @@
+// CS8173: The expression must be of type `long' because it is being assigned by reference
+// Line: 11
+
+public class X
+{
+	int field;
+
+	public static void Main ()
+	{
+		int i = 5;
+		ref long j = ref i;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8174.cs b/mcs/errors/cs8174.cs
new file mode 100644
index 00000000000..888711a0626
--- /dev/null
+++ b/mcs/errors/cs8174.cs
@@ -0,0 +1,10 @@
+// CS8174: A declaration of a by-reference variable must have an initializer
+// Line: 8
+
+class X
+{
+	public static void Main ()
+	{
+		ref int j;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8175.cs b/mcs/errors/cs8175.cs
new file mode 100644
index 00000000000..4ef39db696d
--- /dev/null
+++ b/mcs/errors/cs8175.cs
@@ -0,0 +1,17 @@
+// CS8175: Cannot use by-reference variable `v' inside an anonymous method, lambda expression, or query expression
+// Line: 14
+
+using System;
+
+public class Test
+{
+	public static void Main()
+	{
+		var arr = new int [1];
+		ref var v = ref arr [0];
+
+		Action a = delegate {
+			ref var v2 = ref v;
+		};
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8176.cs b/mcs/errors/cs8176.cs
new file mode 100644
index 00000000000..514c0b2b554
--- /dev/null
+++ b/mcs/errors/cs8176.cs
@@ -0,0 +1,15 @@
+// CS8176: Iterators cannot use by-reference variables
+// Line: 12
+
+using System.Collections.Generic;
+
+class X
+{
+	int x;
+
+	IEnumerable<int> Test ()
+	{
+		ref int y = ref x;
+		yield break;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8177.cs b/mcs/errors/cs8177.cs
new file mode 100644
index 00000000000..414ece1b4be
--- /dev/null
+++ b/mcs/errors/cs8177.cs
@@ -0,0 +1,15 @@
+// CS8177: Async methods cannot use by-reference variables
+// Line: 12
+
+using System.Threading.Tasks;
+
+class X
+{
+	int x;
+
+	async Task Test ()
+	{
+		ref int y = ref x;
+		await Task.Yield ();
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8178-2.cs b/mcs/errors/cs8178-2.cs
new file mode 100644
index 00000000000..e61b7d9eb5c
--- /dev/null
+++ b/mcs/errors/cs8178-2.cs
@@ -0,0 +1,20 @@
+// CS8178: `await' cannot be used in an expression containing a call to `X.this[int]' because it returns by reference
+// Line: 12
+
+using System.Threading.Tasks;
+
+class X
+{
+	int x;
+
+	async Task Test ()
+	{
+		Foo (ref this [await Task.FromResult (1)]);
+	}
+
+	ref int this [int arg] => ref x;
+
+	static void Foo (ref int arg)
+	{
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8178.cs b/mcs/errors/cs8178.cs
new file mode 100644
index 00000000000..6f779621570
--- /dev/null
+++ b/mcs/errors/cs8178.cs
@@ -0,0 +1,24 @@
+// CS8178: `await' cannot be used in an expression containing a call to `X.Wrap(int)' because it returns by reference
+// Line: 12
+
+using System.Threading.Tasks;
+
+class X
+{
+	int x;
+
+	async Task Test ()
+	{
+		Foo (ref Wrap (await Task.FromResult (1))) = 4;
+	}
+
+	ref int Wrap (int arg)
+	{
+		return ref x;
+	}
+
+	static ref int Foo (ref int arg)
+	{
+		return ref arg;
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/cs8189.cs b/mcs/errors/cs8189.cs
new file mode 100644
index 00000000000..909ec3b4fcf
--- /dev/null
+++ b/mcs/errors/cs8189.cs
@@ -0,0 +1,17 @@
+// CS8189: By reference return delegate does not match `C.D()' return type
+// Line: 15
+
+class C
+{
+	delegate ref int D ();
+
+	static int M ()
+	{
+		return 1;
+	}
+
+	static void Main ()
+	{
+		D d = new D (M);
+	}
+}
\ No newline at end of file
diff --git a/mcs/errors/known-issues-net_4_x b/mcs/errors/known-issues-net_4_x
index 40f81ded970..c9ed9317350 100644
--- a/mcs/errors/known-issues-net_4_x
+++ b/mcs/errors/known-issues-net_4_x
@@ -22,3 +22,8 @@ cs8129.cs NO ERROR
 cs8141.cs
 cs8141-2.cs
 cs8144.cs
+cs8157.cs NO ERROR
+cs8160.cs
+cs8161.cs
+cs8170.cs NO ERROR
+cs8170-2.cs